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Review

Neurovascular Dysfunction and Glymphatic Impairment: An Unexplored Therapeutic Frontier in Neurodegeneration

1
College of Pharmacy, Alfaisal University, Riyadh 11533, Saudi Arabia
2
College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2025, 26(24), 11843; https://doi.org/10.3390/ijms262411843
Submission received: 1 November 2025 / Revised: 20 November 2025 / Accepted: 29 November 2025 / Published: 8 December 2025
(This article belongs to the Section Molecular Neurobiology)

Abstract

Neurodegenerative diseases pose major clinical challenges partly due to the underappreciation of the brain’s vascular and clearance systems. Evidence suggests that neurovascular dysfunction and glymphatic impairment are early contributors to disease onset, preceding established markers such as protein aggregation. This review synthesizes recent advances in understanding how disruption of the neurovascular unit (NVU) and glymphatic pathways contributes to neurodegeneration. We analyzed published literature documenting the temporal relationship between vascular dysfunction, glymphatic clearance impairment, and subsequent neurodegenerative pathology, with a focus on identifying therapeutic targets within this axis. Current research demonstrates that blood-brain barrier BBB breakdown, pericyte dysfunction, and compromised cerebral perfusion precede protein aggregation in multiple neurodegenerative disorders. Glymphatic dysfunction, characterized by aquaporin-4 (AQP4) depolarization and abnormalities in meningeal lymphatic vessels, impairs the clearance of neurotoxic metabolites. Novel therapeutic opportunities include the preservation of pericyte function, restoration of AQP4 polarity, enhancement of meningeal lymphatic drainage via vascular endothelial growth factor-C (VEGF-C)/vascular endothelial growth factor receptor-3 VEGFR-3 signaling, and targeted modulation of microRNA and complement pathways that regulate neuroinflammation. By targeting the earliest vascular and glymphatic disruptions, emerging therapeutic strategies may halt or delay disease progression before irreversible neuronal loss occurs. This neurovascular-glymphatic approach represents an unexplored frontier that complements traditional protein-centric therapeutic paradigms, offering new possibilities for early intervention in neurodegenerative disorders.

1. Introduction

The conventional understanding of neurodegenerative disorders has predominantly focused on protein aggregation, neuronal death, and synaptic dysfunction as primary pathogenic mechanisms [1]. However, emerging evidence reveals a critical and underappreciated pathophysiological axis that precedes and potentially drives these classic hallmarks: the neurovascular-glymphatic dysfunction cascade [2]. This review presents a comprehensive analysis of an unexplored therapeutic frontier centered on the intricate relationship between cerebrovascular integrity, glymphatic clearance mechanisms, and the inflammatory cascade that culminates in neurodegeneration.
The blood-brain barrier (BBB), once considered a static protective barrier, is now recognized as a dynamic interface critically involved in the pathogenesis of multiple neurodegenerative conditions [3]. The earliest indicators of multiple neurodegenerative disorders in humans and animal models include impaired BBB stability, regional cerebral blood flow shortfalls, and vascular inflammation associated with BBB dysfunction [4]. Concurrently, the recently discovered glymphatic system represents a fundamental brain waste clearance mechanism whose dysfunction may precede classical pathological changes in Alzheimer’s disease and other neurodegenerative disorders [2]. The convergence of BBB dysfunction, glymphatic impairment, and neuroinflammation creates a self-perpetuating cycle that accelerates neurodegeneration through mechanisms that remain largely untargeted by current therapeutic approaches. This neurovascular dysfunction represents one of the earliest detectable changes in neurodegeneration, often preceding classical pathological markers by years or decades [5].
This review identifies three critical knowledge gaps that represent unprecedented therapeutic opportunities: (1) the role of pericyte dysfunction as a primary initiator of neurovascular NVU failure, (2) the therapeutic potential of targeting glymphatic-lymphatic interfaces, and (3) the development of precision medicine approaches that address the vascular-inflammatory axis in neurodegeneration. These interconnected pathways offer novel pharmacological targets that could potentially halt or reverse the neurodegenerative process before irreversible neuronal damage occurs.

2. Methodology of Literature Search

A comprehensive literature search was conducted to synthesize information for this narrative review, focusing on the intersection of neurovascular, glymphatic, and neuroinflammatory pathways in neurodegeneration. The search was performed using the PubMed, Scopus, and Web of Science databases.
Our search strategy employed a combination of keywords and MeSH (Medical Subject Headings) terms. The primary search terms included: (“neurovascular unit” OR “neurovascular dysfunction” OR “blood-brain barrier” OR “pericyte”) AND (“glymphatic system” OR “glymphatic impairment” OR “meningeal lymphatics” OR “aquaporin-4”) AND (“neurodegeneration” OR “Alzheimer’s disease” OR “neuroinflammation” OR “proteinopathy”).
This primary search was supplemented with more specific secondary searches to identify key mechanisms and therapeutic targets discussed in the review. These included combinations of the above terms with “complement system”, “C1q”, “microglia”, “synaptic pruning”, “VEGF-C”, “microRNA”, “miR-124”, “miR-155”, and “sPDGFRβ”.
The search was primarily focused on articles published between January 2015 and October 2025 to ensure the inclusion of the most recent advances in this rapidly evolving field. This timeframe was expanded to include highly cited, foundational papers published prior to 2015 that were essential for establishing key concepts (e.g., the discovery of the glymphatic system or the role of the complement in synaptic pruning).
Inclusion criteria for articles were: (1) original research articles (preclinical and clinical studies), (2) review articles, and (3) meta-analyses. All articles were required to be published in the English language. The selection process involved screening titles and abstracts for their direct relevance to the review’s central themes. Full texts of the selected articles were then assessed for their contribution to the understanding of neurovascular-glymphatic interactions, key biomarkers, and emerging therapeutic targets.

3. Pathophysiology of Neurovascular Unit Dysfunction

3.1. From Components to Pericyte-Driven Pathology

The NVU comprises endothelial cells, pericytes, astrocytes, microglia, and neurons, collectively maintaining cerebrovascular homeostasis and BBB integrity [6]. The persistent neurovascular unit dysfunction (NVUD) hypothesis proposes that continuous abnormalities in the NVU following initial insults serve as the pathophysiological substrate yielding chronic neuroinflammation, proteinopathies, and oxidative stress [7]. Figure 1 illustrates the progressive cascade of neurovascular dysfunction, from early pericyte injury and subtle BBB disruption to advanced neurodegeneration characterized by severe vascular damage, protein accumulation, and chronic neuroinflammation, highlighting how these changes precede and potentially drive classical disease manifestations.
This framework suggests that targeting NVUD could provide both treatment and prevention strategies for late-onset neurodegenerative diseases, representing a paradigm shift from protein-centric to vascular-centric therapeutic approaches. High metabolic demands and continuous exposure to systemic inflammatory mediators make the NVU vulnerable [8], establishing it as a critical target for early therapeutic intervention [5]. Recent evidence demonstrates that NVUD with BBB hyperpermeability contributes to major depressive disorder and various neurological conditions through oxidative stress and neuroinflammation mechanistically linked to neurovascular dysfunction [9].
Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to neurodegeneration pathophysiology may help identify novel therapeutic and preventative approaches [10]. The temporal relationship where BBB dysfunction and decreased cerebral blood flow are early pathophysiological changes in neurodegenerative disorders suggests that vascular-targeted therapies could potentially halt disease progression before irreversible neuronal damage occurs [11]. Table 1 summarizes the key biomarkers of neurovascular and glymphatic dysfunction that can be detected in cerebrospinal fluid (CSF), plasma, and brain tissue, providing critical diagnostic and monitoring tools for both clinical assessment and therapeutic development.
Within this integrated neurovascular framework, pericytes emerge as the critical cellular component whose dysfunction initiates the cascade leading to widespread NVU failure. Pericytes are contractile cells embedded within the capillary basement membrane that have emerged as central regulators of BBB integrity and cerebral blood flow [32]. Pericyte dysfunction, characterized by the release of soluble platelet-derived growth factor receptor-β (sPDGFRβ), serves as both a biomarker of BBB dysfunction and a potential therapeutic target [15]. The loss of pericytes has been associated with the development and progression of various diseases, such as diabetes, Alzheimer’s disease, stroke and traumatic brain injury [5,33].
CSF PDGFRβ levels increase in early neurodegenerative disorders [12,14,15]. These elevations correlate with both neuroinflammation and cognitive decline [13,34]. BBB alterations may contribute to Alzheimer’s disease pathology through various mechanisms, including impaired amyloid-β clearance and neuroinflammation, with soluble PDGFRβ emerging as a potential biomarker for BBB integrity [34].
The PDGF-BB/PDGFRβ signaling pathway maintains pericyte survival and vascular stability through activation of extracellular signal-regulated kinase ERK and phosphatidylinositol 3-kinase PI3K pathways [35]. Disruption of this signaling cascade leads to pericyte loss, BBB breakdown, and subsequent neuroinflammation [36]. Notably, pericyte dysfunction appears to be particularly pronounced in APOE4 carriers, where impaired APOE-mediated signaling accelerates pericyte injury and vascular regression. APOE4 promotes the cyclophilin A-nuclear factor B-matrix metalloproteinase 9 complex pathway, which directly increases pericyte injury and impairs the formation of basement membranes [37].
Pericyte loss is one of the earliest characteristics of cerebral amyloid angiopathy, and although pericyte loss correlates with neuronal loss, the molecular mechanisms by which pericyte loss contributes to neurodegeneration remain poorly understood. BBB disruption resulting from pericyte loss serves as an early pathological hallmark in cerebral amyloid angiopathy, promoting amyloid-β accumulation and neurodegeneration via MAPK-dependent pathways [38].

3.2. Vascular Endothelial Growth Factor as a Dual-Acting Therapeutic Target

Vascular endothelial growth factor (VEGF) represents a critical mediator of neurovascular coupling and brain clearance mechanisms with established neuroprotective properties. VEGF prevents neurons from death under critical conditions such as hypoxia and glucose deprivation through binding to specific receptors, which are also expressed on the surface of neuronal cells. The neuroprotective actions occur directly through the inhibition of programmed cell death or apoptosis and the stimulation of neurogenesis [39]. VEGF binding to VEGFR-2 receptors triggers the phosphatidylinositol 3-kinase/Akt signal transduction system and, in consequence, leads to the inhibition of programmed cell death by activating antiapoptotic proteins through the transcription factor NF-κB and inhibiting proapoptotic signaling [39]. Recent clinical evidence demonstrates that transcranial radiofrequency wave treatment increases VEGF levels in Alzheimer’s disease patients, correlating with enhanced clearance of tau and amyloid-β proteins from the brain through facilitation of meningeal lymphatic vessel flow and toxin clearance [40].
Exogenous application of VEGF can increase the permeability of the BBB without causing brain edema, and pretreatment with VEGF may be a feasible method to facilitate drug delivery into the CNS [41]. VEGF treatment at optimal concentrations significantly reduced brain weight loss and gross brain injury in neonatal hypoxic–ischemic brain injury models. The neuroprotective effects may be related to activation of the Akt/ERK signaling pathway, as VEGF increased phosphorylation of protein kinase B and extracellular-signal regulated kinase 1/2 in the cortex [42]. The temporal aspects of VEGF treatment are critical, as early inhibition of VEGF may have significant potential against cerebral ischemia, partly by regulating the expression of matrix metalloproteinases [43]. While pericyte dysfunction initiates neurovascular unit breakdown [32,35], the consequences extend beyond simple vascular permeability to fundamentally alter brain waste clearance mechanisms [44,45].

3.3. The Glymphatic-Lymphatic Interface

The glymphatic system’s role in human neurodegeneration remains contentious. While rodent studies consistently demonstrate AQP4-dependent clearance mechanisms, human evidence is more limited and conflicting. Despite growing interest in neurovascular-glymphatic dysfunction, several controversies persist in the field. The existence and functionality of the glymphatic system in humans remains debated, with some studies questioning whether findings from rodent models accurately translate to human pathophysiology [4]. Smith et al. demonstrated diffusive and AQP4-independent solute transport in rodent brain parenchyma, challenging the traditional glymphatic model [22]. Additionally, the temporal relationship between vascular dysfunction and protein aggregation varies across studies, with ongoing debate about whether vascular pathology is a cause or consequence of neurodegeneration. These knowledge gaps highlight the need for human-specific research and standardized methodologies to validate therapeutic targets identified in preclinical models.
The glymphatic system, a brain-wide network facilitating CSF-interstitial fluid exchange, represents a fundamental mechanism for clearing metabolic waste and pathological proteins [44]. This system functions through perivascular pathways, where AQP4 water channels on astrocytic endfeet facilitate fluid movement [45]. Dysfunction of this system has emerged as an early and predictive marker of neurodegeneration, often preceding amyloid pathology [2]. The glymphatic system was identified as a waste drainage system in the brain that promotes the elimination of amyloid-β and tau protein [46]. Regional variation in glymphatic function dictates tau accumulation in mouse models of Alzheimer’s disease tauopathy, with impaired CSF-interstitial fluid exchange and AQP4 polarization observed in affected regions [47]. The central role of AQP4 in the glymphatic clearance of tau from the brain has been established through studies showing marked impaired glymphatic CSF-interstitial fluid exchange and tau protein clearance using novel AQP4 inhibitors [47].
Impaired glymphatic clearance is an important cause of metabolite accumulation in Alzheimer’s disease, as the disease is characterized by the abnormal accumulation of amyloid-β protein creating neuritic plaques and hyperphosphorylated tau protein forming neurofibrillary tangles [48]. Multisensory gamma stimulation has been shown to promote glymphatic clearance, as glymphatic transport clears parenchymal metabolites, including pathogenic proteins such as amyloid-β [49]. The glymphatic system, critically dependent on astrocytic AQP4 water channels for CSF-interstitial fluid exchange [21,23], becomes compromised when neurovascular integrity fails [2,47].

3.4. Aquaporin-4 Polarity Loss: A Therapeutic Target

The polarized localization of AQP4 at perivascular astrocytic endfeet is essential for efficient glymphatic function [45]. In Alzheimer’s disease Loss of AQP4 polarity occurs when AQP4 expression is mislocalized within astrocytes, becoming broadly distributed rather than concentrated at the perivascular end feet, impairing its efficiency in fluid transport and waste clearance, which exacerbates the accumulation of amyloid-β, contributing to the progression of Alzheimer’s disease pathology. Studies have shown that various factors, such as APOE4 and amyloid-β, influence the structure and function of AQP4, thereby regulating glymphatic system flow and affecting cognitive function. AQP4 holds great potential as a therapeutic target for Alzheimer’s disease, with drug development and lifestyle interventions, such as aerobic exercise and dietary regulation, being promising approaches to restore AQP4 polarity and enhance its metabolic waste (i.e., β-amyloid) clearance capacity [50,51].
Recent research identifies calmodulin-dependent phosphorylation of AQP4 as leading to increased expression of AQP4 at the plasma membrane of astrocytes in hypoxia-induced edema. The mechanism involves transient receptor potential vanilloid type 4-facilitated calcium influx that activates calmodulin, leading to cAMP-dependent protein kinase A activation. The phosphorylation of AQP4 at Ser276 causes AQP4 to relocalize to the plasma membrane, and inhibition of calmodulin with trifluoperazine significantly reduced AQP4 translocation, CNS edema, and accelerated functional recovery compared with untreated animals [52]. Alterations in AQP4 expression and polarization occur in neurodegenerative diseases, with depolarized AQP4 expression observed to occur in line with disease progression. AQP4 depolarization may be a pathological factor associated with disease onset and progression, as sustained depolarization of AQP4 impairs the function of maintaining water balance in the spinal cord, leading to swelling and malformation of astrocytes and interfering with neuronal function [53].
The astrocyte AQP4 polarized distribution-mediated glymphatic system is essential for amyloid-β and abnormal tau clearance and represents a potential therapeutic target for Alzheimer’s disease. High-intensity interval training has been shown to ameliorate Alzheimer’s disease pathology through enhancement of the glymphatic system via restoration of AQP4 polarization [54]. Aerobic exercise improves clearance of amyloid-β via the glymphatic system, as previous studies have suggested that aquaporin-4-mediated glymphatic system is an important pathway to clear β-amyloid in the brain [50].

3.5. Meningeal Lymphatic Vessels: A Novel Drainage Target

Effective glymphatic clearance requires not only proper AQP4 function but also efficient downstream drainage pathways [44,45]. The recent discovery of meningeal lymphatic vessels has revealed a critical peripheral component of brain waste clearance that directly connects central nervous system drainage to systemic lymphatic circulation [55]. These vessels, which drain approximately 50% of CSF volume, represent a direct connection between CNS and peripheral lymphatic circulation [56]. Dysfunction of meningeal lymphatic vessels (mLVs) has been implicated in protein accumulation and cognitive decline, making them attractive targets for therapeutic intervention. VEGF-C and VEGFR3 signaling pathways control mLV development and maintenance, and pharmacological enhancement of this signaling can potentially restore drainage capacity in neurodegenerative conditions.
VEGF-C prophylaxis favors lymphatic drainage and improves neurological outcomes after ischemic stroke through enhanced CSF drainage to deep cervical lymph nodes [57]. Age-related changes in meningeal lymphatic function may contribute to the accumulation of neurotoxic proteins and the development of age-related neurodegenerative diseases [58].

4. Neuroinflammation and the Tripartite Synapse

4.1. Microglial Dysfunction and Synaptic Clearance

Microglial cells serve dual functions as brain immune sentinels and regulators of synaptic plasticity [59]. In neurodegenerative conditions, chronically activated microglia produce neurotoxic factors including tumor necrosis factor-α, nitric oxide, and reactive oxygen species, creating a self-perpetuating inflammatory cycle [59]. This chronic activation is maintained through reactive microgliosis, were neuronal damage signals further microglial activation, creating a feed-forward loop of neurodegeneration. Microglia can be categorized into two opposite types: classical (M1) or alternative (M2), though there’s a continuum of different intermediate phenotypes between M1 and M2, and microglia can transit from one phenotype to another. M1 microglia release inflammatory mediators and induce inflammation and neurotoxicity, while M2 microglia release anti-inflammatory mediators and induce anti-inflammatory effects and neuroprotection [60]. The balance between M1 (pro-inflammatory) and M2 (anti-inflammatory) microglial phenotypes is critically important for neurological recovery. In neurodegenerative diseases, activated microglia are excessively shifted toward the M1 or neurotoxic phenotype due to microRNA dysregulation, particularly involving miR-124 and miR-155 pathways that control neuroinflammatory processes [61]. M1-type microglia release diverse proinflammatory mediators and free radicals that inhibit brain repair and regeneration. Conversely, microglia of the M2 phenotype improve brain repair and regeneration by enhancing phagocytosis, releasing trophic factors, and reducing brain inflammation. Following stimulation with LPS or IFN-γ, M1 microglia express high levels of inducible nitric oxide synthase and pro-inflammatory cytokines/chemokines such as TNF-α, IL-1β, and CC chemokine ligand 2 [62].

4.2. Complement-Mediated Synaptic Pruning

The complement system, particularly C1q and C3 components, mediates synaptic pruning through microglial phagocytosis [63]. While essential for normal development, excessive complement activation in neurodegenerative conditions leads to pathological synapse loss [20]. In pathological conditions such as Alzheimer’s disease, virus infection, or radiation-induced injury, excessive complement-mediated synaptic pruning results in excessive elimination of synapses and is associated with cognitive impairment [63]. C1q localizes predominantly to presynaptic terminals, suggesting that complement-mediated pruning is initiated by presynaptic processes [64]. Recent evidence demonstrates that complement-mediated synaptic loss involves local apoptotic-like mechanisms within synapses, indicating that targeted anti-apoptotic therapies could preserve synaptic integrity [64].
Deletion or blockage of C1q, C3, or CR3 [65] in mouse models of Alzheimer’s disease has been shown to protect synapses and prevent cognitive impairments, highlighting the therapeutic potential of complement inhibition strategies [66]. The role of the complement system in synaptic pruning and neurodegeneration presents novel therapeutic opportunities for controlling excessive synaptic elimination [65]. TREM2, a microglial receptor, modulates complement-mediated synaptic pruning by regulating microglial phagocytic capacity and inflammatory responses [67]. The specific mechanism of TREM2 regulation of synaptic clearance involves modulation of microglial activation states and phagocytic function [67].

4.3. MicroRNA-Mediated Inflammation Control

MicroRNA-mediated regulation represents a critical control mechanism for neuroinflammation within the neurovascular-glymphatic dysfunction framework. miR-124 functions as a master regulator of microglial quiescence by targeting pro-inflammatory transcripts and promoting anti-inflammatory M2 polarization through the C/EBPα-PU.1 pathway [27,68]. Loss of miR-124 expression in neurodegenerative diseases contributes to sustained M1 microglial activation and chronic neuroinflammation.
Conversely, miR-155 acts as a pro-inflammatory amplifier, enhancing NF-κB signaling and promoting M1 microglial responses [28,29]. Elevated miR-155 levels correlate with disease severity in multiple sclerosis and Alzheimer’s disease, making it an attractive therapeutic target for anti-inflammatory interventions.
Therapeutic modulation of these microRNA pathways offers precision approaches to control neuroinflammation. miR-124 replacement therapy using lipid nanoparticles or viral vectors could restore anti-inflammatory signaling, while miR-155 inhibition through antagomirs or locked nucleic acid inhibitors could reduce pathological inflammation [61,69]. These microRNA-based therapeutics provide targeted approaches to rebalance microglial phenotypes and preserve neurovascular integrity [70].

5. Discussion

5.1. Inadequacy of Protein-Centric Approaches

Current therapeutic strategies for neurodegenerative disorders have predominantly focused on reducing pathological protein accumulation, particularly amyloid-β and tau in Alzheimer’s disease [11]. The vascular hypothesis of Alzheimer’s disease proposes that vascular risk factors result in dysregulation of the NVU and hypoxia, which may reduce amyloid-β clearance from the brain and increase its production, leading to both parenchymal and vascular accumulation [11]. Several protein-centric approaches have either been associated with inappropriate immune responses triggering inflammation or have failed to improve cognition, highlighting the need for alternative therapeutic targets beyond protein aggregation [11]. The failure of numerous clinical trials targeting amyloid-β underscores the limitations of protein-centric approaches and suggests that therapeutic interventions must address multiple pathophysiological mechanisms simultaneously. A systematic analysis of failed trials reveals that amyloid-targeted therapies consistently fail to improve cognition despite successfully reducing plaque burden, indicating that neurodegeneration has progressed beyond reversible stages by the time of intervention. In contrast, vascular-targeted approaches offer earlier intervention windows, potentially halting disease progression before irreversible neuronal damage occurs. For example, while aducanumab requires 18+ months to show amyloid reduction with questionable cognitive benefit, VEGF-C treatment demonstrates cognitive improvements within weeks in preclinical models through enhanced clearance mechanisms. This temporal advantage suggests that vascular interventions should be prioritized in early disease stages, while protein-centric approaches may require combination with vascular restoration to achieve clinical efficacy in established disease [11].
The neurovascular dysfunction hypothesis provides a framework for understanding how vascular pathology precedes and potentially drives protein aggregation, offering new avenues for early intervention [11]. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to neurodegeneration pathophysiology may help identify novel therapeutic and preventative approaches [9]. These approaches must consider the complex interplay between vascular dysfunction and neuroinflammation, where microglial phenotype balance critically influences therapeutic outcomes [71].

5.2. Blood–Brain Barrier Permeability as an Overlooked Target

This temporal relationship suggests that vascular-targeted therapies could potentially halt disease progression before irreversible neuronal damage occurs [5]. Blood-based biomarkers are quantitative, non-invasive diagnostic tools that can identify candidate biomarkers for Alzheimer’s disease using the hypothesis that with BBB dysfunction, brain-synthesized proteins can leak into plasma for detection [72]. Pericytes in Alzheimer’s disease are key players in disease pathogenesis, and transplanted neural stem cells have been shown to alleviate Alzheimer’s disease pathology and cognitive decline, partly by replenishing pericytes [73].

5.3. Inflammation-Mediated Neurovascular Damage

The majority of vascular transcriptional changes occur in pericytes, with SMAD3 upregulated in Alzheimer’s disease pericytes having the highest number of ligands including VEGFA, which is downregulated in Alzheimer’s disease astrocytes [74]. Microglia-mediated neuroinflammation is considered a double-edged sword, performing both harmful and helpful effects in neurodegenerative diseases [60,75]. Balancing microglia M1/M2 polarization has a promising therapeutic prospect in neurodegenerative diseases [60].

5.4. Precision Medicine Approaches to Neurovascular Dysfunction

Biomarker-guided approaches utilizing vascular dysfunction indicators such as CSF PDGFRβ levels could enable early identification of at-risk individuals before classical pathological changes occur [15]. As outlined in Table 2, these findings have informed the development of multiple promising therapeutic targets addressing various aspects of neurovascular and glymphatic dysfunction, each with distinct mechanisms of action and potential clinical applications based on preclinical evidence.
Models of precision medicine for neurodegeneration focus on developing personalized therapeutic strategies based on individual pathophysiological profiles [1]. The integration of multi-modal biomarker approaches including neuroimaging, fluid biomarkers, and genetic profiling could enable personalized therapeutic strategies targeting specific aspects of neurovascular dysfunction [76]. Biomarker discovery in Alzheimer’s and neurodegenerative diseases focuses on identifying novel targets for early intervention and personalized treatment approaches [77].
Table 2. Emerging Therapeutic Targets for Neurovascular-Glymphatic Dysfunction.
Table 2. Emerging Therapeutic Targets for Neurovascular-Glymphatic Dysfunction.
Therapeutic TargetMechanism of ActionPreclinical EvidenceProposed Therapeutic ApproachPotential BenefitsChallenges/ConsiderationsKey References
PDGF-BB/PDGFRβ SignalingMaintains pericyte survival and BBB integrity via ERK and PI3K pathwaysPDGFRβ ± mice show accelerated BBB breakdown and neurodegeneration; restoration protects against vascular damagePDGF-BB supplementation; prevention of PDGFRβ shedding; APOE4-targeted interventionsPreserves pericyte coverage; maintains BBB integrity; prevents early vascular damageTiming critical; systemic effects; optimal dosing unclear[35,78]
VEGF-C/VEGFR-3 SignalingEnhances meningeal lymphatic vessel function and promotes lymphangiogenesis for brain waste clearanceVEGF-C administration in AD mice increases mLV diameter, reduces CSF and brain Aβ, restores cognitionRecombinant VEGF-C (intrathecal or systemic); VEGFR-3 agonists; transcranial radiofrequency stimulationEnhances protein clearance; reduces tau and Aβ accumulation; improves cognitive functionDelivery route optimization; potential angiogenic effects; dose-finding needed[30,31]
AQP4 Polarization RestorationRestores proper localization of AQP4 at perivascular astrocytic endfeet to enhance glymphatic flowExercise and calmodulin inhibition restore AQP4 polarization and improve Aβ clearance in AD modelsHigh-intensity interval training; aerobic exercise; calmodulin inhibitors (trifluoperazine); pharmacological AQP4 modulatorsEnhances glymphatic clearance; reduces protein accumulation; improves waste removalExercise compliance; pharmacological specificity; avoiding edema[79,80,81]
Complement C1q InhibitionBlocks initiation of classical complement cascade; prevents C1q tagging of synapses for eliminationC1q deletion or neutralizing antibodies protect synapses and improve cognition in AD mouse modelsAnti-C1q monoclonal antibodies; C1q inhibitor peptides; selective C1q blockersPrevents excessive synaptic pruning; preserves cognitive function; reduces neuroinflammationBalancing physiological vs. pathological complement; immune surveillance concerns[19,82,83]
Complement C3 ModulationPrevents C3 cleavage and iC3b-mediated synaptic tagging; blocks complement amplificationC3 deficiency prevents age-related synapse loss and improves LTP in aged mice; protects against AD pathologyC3 inhibitors (compstatin analogs); C3 convertase inhibitorsReduces synaptic loss; improves cognitive outcomes; maintains neuronal networksTiming of intervention; systemic complement functions; infection risk[18,84,85]
CR3 (CD11b/CD18) BlockadePrevents microglial engulfment of iC3b-tagged synapsesCR3 knockout mice protected from Aβ-induced synapse loss; reduced microglial phagocytosisCR3 antagonists; CD11b-blocking antibodies; small molecule inhibitorsPreserves synapses; reduces microglial-mediated damage; maintains circuit functionMicroglial function preservation; specificity for pathological pruning[19,20]
C5aR1 (C5a Receptor) AntagonismBlocks C5a-mediated microglial activation; reduces excessive synaptic pruningC5aR1 deletion or PMX205 treatment reduces synapse loss and improves cognition in multiple AD modelsPMX205 or PMX53 (C5aR1 antagonists); small molecule C5aR1 inhibitorsReduces synaptic loss; improves behavior; modulates neuroinflammation without blocking upstream complementBetter therapeutic window than C1q/C3 inhibition; preserves beneficial complement functions[86,87,88]
miR-124 Replacement TherapyRestores anti-inflammatory signaling; promotes M2 microglial polarization; inhibits inflammatory mediatorsmiR-124 overexpression reduces neuroinflammation and promotes neuroprotection in injury modelsLipid nanoparticle-encapsulated miR-124; viral vector delivery; synthetic miR-124 mimicsShifts microglia to anti-inflammatory phenotype; reduces TNF-α; increases IL-10Delivery to CNS; off-target effects; stability of miRNA therapeutics[27]
miR-155 InhibitionReduces pro-inflammatory signaling; decreases NF-κB activation; attenuates M1 microglial responsesmiR-155 deletion improves outcomes in spinal cord injury and reduces neuroinflammation in MS modelsAntagomiR-155; locked nucleic acid (LNA) anti-miR-155; GapmeR inhibitorsReduces neuroinflammation; improves functional recovery; modulates TLR signalingDelivery challenges; dosing optimization; potential immune effects[29,89]
Meningeal Lymphatic EnhancementPhysical or pharmacological enhancement of mLV structure and functionExercise enhances mLV flow; VEGF-C expands mLV diameter and improves clearance in aged miceAerobic exercise protocols; VEGF-C administration; minimally invasive mLV stimulationEnhances brain-to-cervical lymph node drainage; improves clearance of proteins and immune cellsAge-related mLV degeneration; non-invasive enhancement methods needed[30,90]
TREM2 ModulationRegulates microglial phagocytic capacity and metabolic state; modulates complement-mediated pruningTREM2 deficiency alters microglial response to plaques; affects synaptic engulfmentTREM2 agonistic antibodies; TREM2 activity enhancers (context-dependent)Modulates microglial function; may enhance beneficial phagocytosis while reducing excessive pruningComplex role (protective vs. detrimental); stage-dependent effects[91,92,93]
CD200-CD200R Axis EnhancementMaintains microglial quiescence; promotes M2 polarization; reduces inflammatory activationCD200-Fc treatment shifts macrophages/microglia from M1 to M2; reduces pro-inflammatory cytokinesCD200-Fc fusion protein; CD200R agonistsReduces neuroinflammation; promotes neuroprotective microglial phenotype; decreases oxidative stressSystemic delivery; CNS penetration; long-term safety[94]
Abbreviations: PDGF-BB, platelet-derived growth factor-BB; PDGFRβ, platelet-derived growth factor receptor-β; BBB, blood–brain barrier; ERK, extracellular signal-regulated kinase; PI3K, phosphatidylinositol 3-kinase; VEGF-C, vascular endothelial growth factor-C; VEGFR-3, vascular endothelial growth factor receptor-3; mLV, meningeal lymphatic vessels; Aβ, amyloid-β; AD, Alzheimer’s disease; AQP4, aquaporin-4; CR3, complement receptor 3; C5aR1, C5a receptor 1; miR, microRNA; TNF-α, tumor necrosis factor-α; IL-10, interleukin-10; CNS, central nervous system; MS, multiple sclerosis; NF-κB, nuclear factor kappa B; TLR, Toll-like receptor; TREM2, triggering receptor expressed on myeloid cells 2; LTP, long-term potentiation.

5.5. Molecular Pathway-Based Therapeutic Targets

Clinical translation of VEGF-C therapies could involve various delivery approaches, including intrathecal administration or systemic delivery with brain-targeting strategies [57].
The prophylactic administration of VEGF-C has shown particular promise, promoting multiple vascular, immune, and neural responses that culminate in protection against neurological damage in acute ischemic stroke models [57]. Therapeutic approaches to central nervous system (CNS) diseases via the meningeal lymphatic system represent a novel frontier in neurodegenerative disease treatment [95]. The meningeal lymphatic drainage provides novel insights into CNS clearance mechanisms and offers new therapeutic targets [56].
Therapeutic targeting of the complement system represents a promising approach for controlling excessive synaptic pruning in neurodegenerative conditions [63]. The complement system in neurodegenerative and neuroinflammatory diseases presents novel therapeutic opportunities for controlling pathological complement activation [96]. Several preclinical complement-targeted therapeutics are in development, focusing on selective inhibition of complement components to preserve beneficial synaptic refinement while preventing pathological synapse loss [63].
MiR-124 and miR-155 serve as therapeutic targets in microglia-mediated neuroinflammation, offering novel approaches for modulating microglial polarization. Therapeutic strategies could involve miR-124 replacement therapy to restore anti-inflammatory signaling or miR-155 inhibition to reduce pro-inflammatory responses. These approaches could be delivered using various platforms including lipid nanoparticles, viral vectors, or conjugated oligonucleotides [61]. Regulation of MicroRNAs in Parkinson’s disease and their potential therapeutic applications demonstrate the broad applicability of microRNA-based therapies [97].

5.6. Comparative Therapeutic Efficacy and Intervention Windows

The therapeutic landscape for neurodegeneration requires strategic consideration of intervention timing and target selection [1,76,98]. Vascular-targeted therapies demonstrate optimal efficacy in pre-symptomatic and early symptomatic stages when BBB integrity can still be preserved or restored [5,13,16]. Early detection of BBB breakdown in aging human hippocampus [16] and elevated sPDGFRβ levels in pre-symptomatic individuals [12,14] provide critical windows for vascular intervention before irreversible damage occurs [5,10].
Protein-centric approaches, while potentially beneficial for established disease, show limited efficacy when initiated after significant neuronal loss has occurred [11]. The vascular hypothesis of Alzheimer’s disease proposes that addressing neurovascular unit dysfunction earlier in the disease cascade may be more effective than targeting downstream protein aggregation [11]. Failed amyloid-β trials underscore this temporal limitation, as cognitive benefits remain elusive even when plaque burden is successfully reduced [11].
Cost-effectiveness analyses suggest that early vascular interventions, despite higher upfront screening costs, may provide superior long-term outcomes compared to late-stage protein clearance strategies [76,99]. Biomarker-guided precision medicine approaches utilizing vascular dysfunction indicators such as CSF PDGFRβ levels [12,14,15], albumin quotient measurements [13,16], and complement activation markers [17,18,19] could enable early identification of at-risk individuals before classical pathological changes occur [76,77].

6. Future Directions and Research Priorities

6.1. Current and Planned Clinical Trials

Several clinical trials are advancing neurovascular-glymphatic therapeutic concepts toward human application. ANX005, a humanized anti-C1q antibody, is currently in Phase II trials for autoimmune diseases with planned expansion to neurodegenerative conditions [83]. VEGF-C enhancement strategies are entering early-phase human studies, building on promising preclinical stroke results [57]. Exercise intervention trials specifically targeting glymphatic function through AQP4 modulation are being developed by multiple research groups. Additionally, transcranial radiofrequency treatments that enhance VEGF expression and improve protein clearance have shown initial promise in small Alzheimer’s disease cohorts [40]. These ongoing efforts represent the first wave of clinical translation for neurovascular-glymphatic dysfunction concepts, with results expected within the next 3–5 years.

6.2. Neurovascular Unit-Targeted Drug Delivery

Successful translation of neurovascular-glymphatic therapeutics requires sophisticated delivery strategies that overcome blood–brain barrier limitations [100]. Focused ultrasound combined with microbubbles offers a non-invasive approach for transient BBB opening, enabling targeted delivery of large molecules like VEGF-C and complement inhibitors to specific brain regions [41,101]. Lipid nanoparticle systems, successfully employed for mRNA vaccines, show promise for delivering microRNA therapeutics (miR-124 mimics or miR-155 inhibitors) with minimal systemic toxicity [61,89].
Viral vector strategies, particularly adeno-associated virus serotypes with CNS tropism, provide sustained expression of therapeutic proteins but require careful safety monitoring for immunogenic responses [61]. Intranasal delivery represents an attractive non-invasive route for small molecule complement inhibitors, bypassing the BBB through olfactory pathways [95]. Intrathecal administration, while more invasive, offers direct CSF access for biologics targeting glymphatic enhancement [30,31,57]. Each delivery modality presents unique risk-benefit profiles that must be carefully matched to specific therapeutic targets and patient populations [100,102].

6.3. Combination Therapy Approaches

The complex nature of neurovascular dysfunction, glymphatic impairment, and neuroinflammation necessitates combination therapeutic strategies, though significant feasibility challenges remain [103]. While preclinical evidence suggests potential synergies, clinical translation faces substantial obstacles including drug–drug interactions, overlapping toxicities, and complex dosing optimization requirements.
Potential combinations include VEGF-C enhancement with complement modulation, though this approach raises concerns about excessive angiogenesis combined with compromised immune surveillance. AQP4 activation with microRNA-based anti-inflammatory therapy requires sophisticated delivery systems and carries risks of off-target gene silencing and unpredictable inflammatory rebound effects [104]. Pericyte protection strategies combined with glymphatic enhancement may produce conflicting vascular effects, as BBB stabilization could paradoxically impede therapeutic drug penetration.
Critical safety considerations include the long-term consequences of complement system inhibition, which may increase infection susceptibility and cancer risk over decades of treatment. VEGF pathway modulation has established associations with cardiovascular complications and hemorrhagic events, particularly concerning aging populations with pre-existing cerebrovascular disease. MicroRNA therapeutics face delivery challenges, immune activation risks, and unknown long-term genomic effects.
The microbiota–gut–brain axis [104] and gut–brain vascular axis [105] represent additional therapeutic opportunities, though mechanistic understanding remains limited and individual microbiome variability complicates standardized interventions. Rational combination design requires extensive phase I safety studies, pharmacokinetic modeling, and biomarker-guided dose optimization considering the temporal sequence of pathophysiological events [106].
Current limitations include lack of predictive biomarkers for treatment response, absence of standardized outcome measures, and insufficient understanding of optimal therapeutic windows. Long-term efficacy and safety profiles for these novel targets remain largely unknown, necessitating cautious clinical development with extensive safety monitoring and adaptive trial designs.

6.4. Translational Challenges and Biomarker Development

Translation to clinical applications faces challenges including development of appropriate biomarkers, establishing relevant trial endpoints, and addressing species differences in neurovascular anatomy [99]. The Global Neurodegeneration Proteomics Consortium represents an important initiative for addressing these challenges [99]. Future clinical trials should incorporate adaptive approaches allowing biomarker-guided dose optimization and patient stratification [98]. Advanced biomarkers for BBB dysfunction [15,72] are critical for precision medicine, with biofluid markers for Alzheimer’s disease focusing on vascular and inflammatory indicators [107]. MiRNA neuroinflammatory biomarkers offer novel approaches to monitoring therapeutic responses [108], while reference ranges for CSF PDGFRβ provide clinical assessment standards for pericyte dysfunction [109]. Associations between CSF PDGFRβ, aging, BBB dysfunction, and neuroinflammation provide mechanistic insights into vascular contributions to neurodegeneration [110].

7. Conclusions

Neurovascular dysfunction and glymphatic impairment constitute foundational yet underappreciated mechanisms driving the pathogenesis of neurodegenerative diseases. Therapeutic approaches that exclusively target protein aggregation have not sufficiently addressed the complex cascade of vascular and clearance deficits that initiate and perpetuate neuronal injury. This review highlights the critical importance of maintaining NVU integrity, preserving pericyte function, restoring AQP4 polarization, and enhancing meningeal lymphatic drainage as integral strategies to interrupt neurodegenerative progression. Furthermore, modulation of microglial inflammatory phenotypes and complement-mediated synaptic pruning offers additional avenues to mitigate neuroinflammation and synaptic loss. The integration of advanced biomarkers reflecting vascular and glymphatic dysfunction with precision medicine approaches promises to refine early diagnosis and enable tailored interventions. Fostering research and clinical translation targeting these interconnected vascular inflammatory pathways holds substantial potential to transform therapeutic paradigms and improve outcomes for patients with Alzheimer’s disease and related neurodegenerative disorders.

Author Contributions

G.K.M.: Investigation, Methodology, Resources, Formal analysis, Writing—original draft. O.B.: Conceptualization, Formal analysis, Methodology, Validation, Writing—original draft, Writing—review and editing. A.W.H.: Investigation, Methodology, Resources, Formal analysis, Writing—original draft, V.M.: Conceptualization, Methodology, Visualization, Resources, Validation, Writing—original draft, Writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

Amyloid-β
AktProtein Kinase B
APOE4Apolipoprotein Epsilon 4
AQP4Aquaporin-4
ARG-1Arginase 1
BBBBlood–Brain Barrier
C/EBPαCCAAT/Enhancer-Binding Protein alpha
C1qComplement component 1q
C3Complement component 3
C5aR1C5a Receptor 1
CD200-CD200RCD200-CD200 Receptor
CR3Complement Receptor 3
CREB1cAMP Response Element Binding Protein 1
CSFCerebrospinal Fluid
ERKExtracellular signal-Regulated Kinase
GFAPGlial Fibrillary Acidic Protein
IL-10Interleukin 10
IL-1βInterleukin 1 beta
LPSLipopolysaccharide
MAPKMitogen-Activated Protein Kinase
miR-124microRNA 124
miR-155microRNA 155
NF-κBNuclear Factor kappa B
PDGF-BBPlatelet-Derived Growth Factor-BB
PDGFRβPlatelet-Derived Growth Factor Receptor-β
PI3KPhosphatidylinositol 3-Kinase
PU.1PU.1 (also known as SPI1)
QalbCSF/Plasma Albumin Ratio
Ser276Serine at position 276
sPDGFRβsoluble Platelet-Derived Growth Factor Receptor-β
TLRToll-Like Receptor
TNF-αTumor Necrosis Factor-α
TREM2Triggering Receptor Expressed on Myeloid cells 2
VEGFVascular Endothelial Growth Factor

References

  1. Espay, A.J. Models of Precision Medicine for Neurodegeneration. Handb. Clin. Neurol. 2023, 192, 21–34. [Google Scholar] [CrossRef]
  2. Huang, S.-Y.; Zhang, Y.-R.; Guo, Y.; Du, J.; Ren, P.; Wu, B.-S.; Feng, J.-F.; Cheng, W.; Yu, J.-T. Glymphatic System Dysfunction Predicts Amyloid Deposition, Neurodegeneration, and Clinical Progression in Alzheimer’s Disease. Alzheimers Dement. 2024, 20, 3251–3269. [Google Scholar] [CrossRef]
  3. Sweeney, M.D.; Sagare, A.P.; Zlokovic, B.V. Blood-Brain Barrier Breakdown in Alzheimer Disease and Other Neurodegenerative Disorders. Nat. Rev. Neurol. 2018, 14, 133–150. [Google Scholar] [CrossRef]
  4. Chen, T.; Dai, Y.; Hu, C.; Lin, Z.; Wang, S.; Yang, J.; Zeng, L.; Li, S.; Li, W. Cellular and Molecular Mechanisms of the Blood-Brain Barrier Dysfunction in Neurodegenerative Diseases. Fluids Barriers CNS 2024, 21, 60. [Google Scholar] [CrossRef]
  5. Yu, X.; Ji, C.; Shao, A. Neurovascular Unit Dysfunction and Neurodegenerative Disorders. Front. Neurosci. 2020, 14, 334. [Google Scholar] [CrossRef] [PubMed]
  6. Kugler, E.C.; Greenwood, J.; MacDonald, R.B. The “Neuro-Glial-Vascular” Unit: The Role of Glia in Neurovascular Unit Formation and Dysfunction. Front. Cell Dev. Biol. 2021, 9, 732820. [Google Scholar] [CrossRef] [PubMed]
  7. Zhou, Y.; Chen, Q.; Wang, Y.; Wu, H.; Xu, W.; Pan, Y.; Gao, S.; Dong, X.; Zhang, J.H.; Shao, A. Persistent Neurovascular Unit Dysfunction: Pathophysiological Substrate and Trigger for Late-Onset Neurodegeneration After Traumatic Brain Injury. Front. Neurosci. 2020, 14, 581. [Google Scholar] [CrossRef] [PubMed]
  8. van Vliet, E.A.; Marchi, N. Neurovascular Unit Dysfunction as a Mechanism of Seizures and Epilepsy during Aging. Epilepsia 2022, 63, 1297–1313. [Google Scholar] [CrossRef]
  9. Najjar, S.; Pearlman, D.M.; Devinsky, O.; Najjar, A.; Zagzag, D. Neurovascular Unit Dysfunction with Blood-Brain Barrier Hyperpermeability Contributes to Major Depressive Disorder: A Review of Clinical and Experimental Evidence. J. Neuroinflamm. 2013, 10, 142. [Google Scholar] [CrossRef]
  10. Najjar, S.; Pahlajani, S.; De Sanctis, V.; Stern, J.N.H.; Najjar, A.; Chong, D. Neurovascular Unit Dysfunction and Blood-Brain Barrier Hyperpermeability Contribute to Schizophrenia Neurobiology: A Theoretical Integration of Clinical and Experimental Evidence. Front. Psychiatry 2017, 8, 83. [Google Scholar] [CrossRef]
  11. Soto-Rojas, L.O.; Pacheco-Herrero, M.; Martínez-Gómez, P.A.; Campa-Córdoba, B.B.; Apátiga-Pérez, R.; Villegas-Rojas, M.M.; Harrington, C.R.; de la Cruz, F.; Garcés-Ramírez, L.; Luna-Muñoz, J. The Neurovascular Unit Dysfunction in Alzheimer’s Disease. Int. J. Mol. Sci. 2021, 22, 2022. [Google Scholar] [CrossRef] [PubMed]
  12. Miners, J.S.; Kehoe, P.G.; Love, S.; Zetterberg, H.; Blennow, K. CSF Evidence of Pericyte Damage in Alzheimer’s Disease Is Associated with Markers of Blood-Brain Barrier Dysfunction and Disease Pathology. Alzheimers Res. Ther. 2019, 11, 81. [Google Scholar] [CrossRef]
  13. Nation, D.A.; Sweeney, M.D.; Montagne, A.; Sagare, A.P.; D’Orazio, L.M.; Pachicano, M.; Sepehrband, F.; Nelson, A.R.; Buennagel, D.P.; Harrington, M.G.; et al. Blood-Brain Barrier Breakdown Is an Early Biomarker of Human Cognitive Dysfunction. Nat. Med. 2019, 25, 270–276. [Google Scholar] [CrossRef] [PubMed]
  14. Sweeney, M.D.; Sagare, A.P.; Pachicano, M.; Harrington, M.G.; Joe, E.; Chui, H.C.; Schneider, L.S.; Montagne, A.; Ringman, J.M.; Fagan, A.M.; et al. A Novel Sensitive Assay for Detection of a Biomarker of Pericyte Injury in Cerebrospinal Fluid. Alzheimers Dement. 2020, 16, 821–830. [Google Scholar] [CrossRef]
  15. Vrillon, A.; Ashton, N.J.; Bouaziz-Amar, E.; Mouton-Liger, F.; Cognat, E.; Dumurgier, J.; Lilamand, M.; Karikari, T.K.; Prevot, V.; Zetterberg, H.; et al. Dissection of Blood-Brain Barrier Dysfunction through CSF PDGFRβ and Amyloid, Tau, Neuroinflammation, and Synaptic CSF Biomarkers in Neurodegenerative Disorders. EBioMedicine 2025, 115, 105694. [Google Scholar] [CrossRef] [PubMed]
  16. Montagne, A.; Barnes, S.R.; Sweeney, M.D.; Halliday, M.R.; Sagare, A.P.; Zhao, Z.; Toga, A.W.; Jacobs, R.E.; Liu, C.Y.; Amezcua, L.; et al. Blood-Brain Barrier Breakdown in the Aging Human Hippocampus. Neuron 2015, 85, 296–302. [Google Scholar] [CrossRef]
  17. Stephan, A.H.; Madison, D.V.; Mateos, J.M.; Fraser, D.A.; Lovelett, E.A.; Coutellier, L.; Kim, L.; Tsai, H.-H.; Huang, E.J.; Rowitch, D.H.; et al. A Dramatic Increase of C1q Protein in the CNS during Normal Aging. J. Neurosci. 2013, 33, 13460–13474. [Google Scholar] [CrossRef]
  18. Shi, Q.; Colodner, K.J.; Matousek, S.B.; Merry, K.; Hong, S.; Kenison, J.E.; Frost, J.L.; Le, K.X.; Li, S.; Dodart, J.-C.; et al. Complement C3-Deficient Mice Fail to Display Age-Related Hippocampal Decline. J. Neurosci. 2015, 35, 13029–13042. [Google Scholar] [CrossRef]
  19. Hong, S.; Beja-Glasser, V.F.; Nfonoyim, B.M.; Frouin, A.; Li, S.; Ramakrishnan, S.; Merry, K.M.; Shi, Q.; Rosenthal, A.; Barres, B.A.; et al. Complement and Microglia Mediate Early Synapse Loss in Alzheimer Mouse Models. Science 2016, 352, 712–716. [Google Scholar] [CrossRef]
  20. Presumey, J.; Bialas, A.R.; Carroll, M.C. Complement System in Neural Synapse Elimination in Development and Disease. Adv. Immunol. 2017, 135, 53–79. [Google Scholar] [CrossRef]
  21. Iliff, J.J.; Wang, M.; Liao, Y.; Plogg, B.A.; Peng, W.; Gundersen, G.A.; Benveniste, H.; Vates, G.E.; Deane, R.; Goldman, S.A.; et al. A Paravascular Pathway Facilitates CSF Flow through the Brain Parenchyma and the Clearance of Interstitial Solutes, Including Amyloid β. Sci. Transl. Med. 2012, 4, 147ra111. [Google Scholar] [CrossRef]
  22. Smith, A.J.; Yao, X.; Dix, J.A.; Jin, B.-J.; Verkman, A.S. Test of the “glymphatic” Hypothesis Demonstrates Diffusive and Aquaporin-4-Independent Solute Transport in Rodent Brain Parenchyma. Elife 2017, 6, e27679. [Google Scholar] [CrossRef]
  23. Mestre, H.; Hablitz, L.M.; Xavier, A.L.; Feng, W.; Zou, W.; Pu, T.; Monai, H.; Murlidharan, G.; Castellanos Rivera, R.M.; Simon, M.J.; et al. Aquaporin-4-Dependent Glymphatic Solute Transport in the Rodent Brain. Elife 2018, 7, e40070. [Google Scholar] [CrossRef] [PubMed]
  24. Craig-Schapiro, R.; Perrin, R.J.; Roe, C.M.; Xiong, C.; Carter, D.; Cairns, N.J.; Mintun, M.A.; Peskind, E.R.; Li, G.; Galasko, D.R.; et al. YKL-40: A Novel Prognostic Fluid Biomarker for Preclinical Alzheimer’s Disease. Biol. Psychiatry 2010, 68, 903–912. [Google Scholar] [CrossRef] [PubMed]
  25. Janelidze, S.; Mattsson, N.; Stomrud, E.; Lindberg, O.; Palmqvist, S.; Zetterberg, H.; Blennow, K.; Hansson, O. CSF Biomarkers of Neuroinflammation and Cerebrovascular Dysfunction in Early Alzheimer Disease. Neurology 2018, 91, e867–e877. [Google Scholar] [CrossRef]
  26. Benedet, A.L.; Milà-Alomà, M.; Vrillon, A.; Ashton, N.J.; Pascoal, T.A.; Lussier, F.; Karikari, T.K.; Hourregue, C.; Cognat, E.; Dumurgier, J.; et al. Differences Between Plasma and Cerebrospinal Fluid Glial Fibrillary Acidic Protein Levels Across the Alzheimer Disease Continuum. JAMA Neurol. 2021, 78, 1471–1483. [Google Scholar] [CrossRef]
  27. Ponomarev, E.D.; Veremeyko, T.; Barteneva, N.; Krichevsky, A.M.; Weiner, H.L. MicroRNA-124 Promotes Microglia Quiescence and Suppresses EAE by Deactivating Macrophages via the C/EBP-α-PU.1 Pathway. Nat. Med. 2011, 17, 64–70. [Google Scholar] [CrossRef] [PubMed]
  28. Guedes, J.R.; Custódia, C.M.; Silva, R.J.; de Almeida, L.P.; Pedroso de Lima, M.C.; Cardoso, A.L. Early miR-155 Upregulation Contributes to Neuroinflammation in Alzheimer’s Disease Triple Transgenic Mouse Model. Hum. Mol. Genet. 2014, 23, 6286–6301. [Google Scholar] [CrossRef]
  29. Butovsky, O.; Jedrychowski, M.P.; Cialic, R.; Krasemann, S.; Murugaiyan, G.; Fanek, Z.; Greco, D.J.; Wu, P.M.; Doykan, C.E.; Kiner, O.; et al. Targeting miR-155 Restores Abnormal Microglia and Attenuates Disease in SOD1 Mice. Ann. Neurol. 2015, 77, 75–99. [Google Scholar] [CrossRef]
  30. Da Mesquita, S.; Louveau, A.; Vaccari, A.; Smirnov, I.; Cornelison, R.C.; Kingsmore, K.M.; Contarino, C.; Onengut-Gumuscu, S.; Farber, E.; Raper, D.; et al. Functional Aspects of Meningeal Lymphatics in Ageing and Alzheimer’s Disease. Nature 2018, 560, 185–191. [Google Scholar] [CrossRef]
  31. Ahn, J.H.; Cho, H.; Kim, J.-H.; Kim, S.H.; Ham, J.-S.; Park, I.; Suh, S.H.; Hong, S.P.; Song, J.-H.; Hong, Y.-K.; et al. Meningeal Lymphatic Vessels at the Skull Base Drain Cerebrospinal Fluid. Nature 2019, 572, 62–66. [Google Scholar] [CrossRef] [PubMed]
  32. Brown, L.S.; Foster, C.G.; Courtney, J.-M.; King, N.E.; Howells, D.W.; Sutherland, B.A. Pericytes and Neurovascular Function in the Healthy and Diseased Brain. Front. Cell Neurosci. 2019, 13, 282. [Google Scholar] [CrossRef] [PubMed]
  33. Li, P.; Fan, H. Pericyte Loss in Diseases. Cells 2023, 12, 1931. [Google Scholar] [CrossRef] [PubMed]
  34. Preis, L.; Villringer, K.; Brosseron, F.; Düzel, E.; Jessen, F.; Petzold, G.C.; Ramirez, A.; Spottke, A.; Fiebach, J.B.; Peters, O. Assessing Blood-Brain Barrier Dysfunction and Its Association with Alzheimer’s Pathology, Cognitive Impairment and Neuroinflammation. Alzheimers Res. Ther. 2024, 16, 172. [Google Scholar] [CrossRef]
  35. Smyth, L.C.D.; Highet, B.; Jansson, D.; Wu, J.; Rustenhoven, J.; Aalderink, M.; Tan, A.; Li, S.; Johnson, R.; Coppieters, N.; et al. Characterisation of PDGF-BB:PDGFRβ Signalling Pathways in Human Brain Pericytes: Evidence of Disruption in Alzheimer’s Disease. Commun. Biol. 2022, 5, 235. [Google Scholar] [CrossRef]
  36. Shen, J.; Xu, G.; Zhu, R.; Yuan, J.; Ishii, Y.; Hamashima, T.; Matsushima, T.; Yamamoto, S.; Takatsuru, Y.; Nabekura, J.; et al. PDGFR-β Restores Blood-Brain Barrier Functions in a Mouse Model of Focal Cerebral Ischemia. J. Cereb. Blood Flow. Metab. 2019, 39, 1501–1515. [Google Scholar] [CrossRef]
  37. Cercy, S.P. Pericytes and the Neurovascular Unit: The Critical Nexus of Alzheimer Disease Pathogenesis? Explor. Res. Hypothesis Med. 2021, 6, 125–134. [Google Scholar] [CrossRef]
  38. Liu, T.; Guo, W.; Gong, M.; Zhu, L.; Cao, T.; Huang, Y.; Yang, Y.; Chen, J.; Yang, C.; Zhang, S.; et al. Pericyte Loss: A Key Factor Inducing Brain Aβ40 Accumulation and Neuronal Degeneration in Cerebral Amyloid Angiopathy. Exp. Brain Res. 2025, 243, 191. [Google Scholar] [CrossRef]
  39. Góra-Kupilas, K.; Jośko, J. The Neuroprotective Function of Vascular Endothelial Growth Factor (VEGF). Folia Neuropathol. 2005, 43, 31–39. [Google Scholar]
  40. Arendash, G.W.; Lin, X.; Cao, C. Enhanced Brain Clearance of Tau and Amyloid-β in Alzheimer’s Disease Patients by Transcranial Radiofrequency Wave Treatment: A Central Role of Vascular Endothelial Growth Factor (VEGF). J. Alzheimers Dis. 2024, 100, S223–S241. [Google Scholar] [CrossRef]
  41. Jiang, S.; Xia, R.; Jiang, Y.; Wang, L.; Gao, F. Vascular Endothelial Growth Factors Enhance the Permeability of the Mouse Blood-Brain Barrier. PLoS ONE 2014, 9, e86407. [Google Scholar] [CrossRef] [PubMed]
  42. Feng, Y.; Rhodes, P.G.; Bhatt, A.J. Neuroprotective Effects of Vascular Endothelial Growth Factor Following Hypoxic Ischemic Brain Injury in Neonatal Rats. Pediatr. Res. 2008, 64, 370–374. [Google Scholar] [CrossRef]
  43. Zhang, H.-T.; Zhang, P.; Gao, Y.; Li, C.-L.; Wang, H.-J.; Chen, L.-C.; Feng, Y.; Li, R.-Y.; Li, Y.-L.; Jiang, C.-L. Early VEGF Inhibition Attenuates Blood-Brain Barrier Disruption in Ischemic Rat Brains by Regulating the Expression of MMPs. Mol. Med. Rep. 2017, 15, 57–64. [Google Scholar] [CrossRef]
  44. Tarasoff-Conway, J.M.; Carare, R.O.; Osorio, R.S.; Glodzik, L.; Butler, T.; Fieremans, E.; Axel, L.; Rusinek, H.; Nicholson, C.; Zlokovic, B.V.; et al. Clearance Systems in the Brain-Implications for Alzheimer Disease. Nat. Rev. Neurol. 2015, 11, 457–470. [Google Scholar] [CrossRef]
  45. Gomolka, R.S.; Hablitz, L.M.; Mestre, H.; Giannetto, M.; Du, T.; Hauglund, N.L.; Xie, L.; Peng, W.; Martinez, P.M.; Nedergaard, M.; et al. Loss of Aquaporin-4 Results in Glymphatic System Dysfunction via Brain-Wide Interstitial Fluid Stagnation. Elife 2023, 12, e82232. [Google Scholar] [CrossRef]
  46. Ota, M.; Sato, N.; Nakaya, M.; Shigemoto, Y.; Kimura, Y.; Chiba, E.; Yokoi, Y.; Tsukamoto, T.; Matsuda, H. Relationships Between the Deposition of Amyloid-β and Tau Protein and Glymphatic System Activity in Alzheimer’s Disease: Diffusion Tensor Image Study. J. Alzheimers Dis. 2022, 90, 295–303. [Google Scholar] [CrossRef]
  47. Harrison, I.F.; Ismail, O.; Machhada, A.; Colgan, N.; Ohene, Y.; Nahavandi, P.; Ahmed, Z.; Fisher, A.; Meftah, S.; Murray, T.K.; et al. Impaired Glymphatic Function and Clearance of Tau in an Alzheimer’s Disease Model. Brain 2020, 143, 2576–2593. [Google Scholar] [CrossRef] [PubMed]
  48. Hazzard, I.; Batiste, M.; Luo, T.; Cheung, C.; Lui, F. Impaired Glymphatic Clearance Is an Important Cause of Alzheimer’s Disease. Explor. Neuroprot. Ther. 2024, 4, 401–410. [Google Scholar] [CrossRef]
  49. Murdock, M.H.; Yang, C.-Y.; Sun, N.; Pao, P.-C.; Blanco-Duque, C.; Kahn, M.C.; Kim, T.; Lavoie, N.S.; Victor, M.B.; Islam, M.R.; et al. Multisensory Gamma Stimulation Promotes Glymphatic Clearance of Amyloid. Nature 2024, 627, 149–156. [Google Scholar] [CrossRef]
  50. Liang, S.; Liu, H.; Wang, X.; Lin, H.; Zheng, L.; Zhang, Y.; Peng, L.; Huang, S.; Chen, L. Aerobic Exercise Improves Clearance of Amyloid-β via the Glymphatic System in a Mouse Model of Alzheimer’s Disease. Brain Res. Bull. 2025, 222, 111263. [Google Scholar] [CrossRef]
  51. Qianqian, Y.; Li, H.; Liu, H.; Ye, Y.; Yu, C. Factors Affecting Aquaporin-4 and Its Regulatory Mechanisms in Alzheimer’s Disease. Neurol. Asia 2025, 30, 361–367. [Google Scholar] [CrossRef]
  52. Patabendige, A.; Chen, R. Astrocytic Aquaporin 4 Subcellular Translocation as a Therapeutic Target for Cytotoxic Edema in Ischemic Stroke. Neural Regen. Res. 2022, 17, 2666–2668. [Google Scholar] [CrossRef]
  53. Dai, J.; Lin, W.; Zheng, M.; Liu, Q.; He, B.; Luo, C.; Lu, X.; Pei, Z.; Su, H.; Yao, X. Alterations in AQP4 Expression and Polarization in the Course of Motor Neuron Degeneration in SOD1G93A Mice. Mol. Med. Rep. 2017, 16, 1739–1746. [Google Scholar] [CrossRef] [PubMed]
  54. Feng, S.; Wu, C.; Zou, P.; Deng, Q.; Chen, Z.; Li, M.; Zhu, L.; Li, F.; Liu, T.C.-Y.; Duan, R.; et al. High-Intensity Interval Training Ameliorates Alzheimer’s Disease-like Pathology by Regulating Astrocyte Phenotype-Associated AQP4 Polarization. Theranostics 2023, 13, 3434–3450. [Google Scholar] [CrossRef]
  55. Li, G.; Cao, Y.; Tang, X.; Huang, J.; Cai, L.; Zhou, L. The Meningeal Lymphatic Vessels and the Glymphatic System: Potential Therapeutic Targets in Neurological Disorders. J. Cereb. Blood Flow. Metab. 2022, 42, 1364–1382. [Google Scholar] [CrossRef]
  56. Zhang, Q.; Niu, Y.; Li, Y.; Xia, C.; Chen, Z.; Chen, Y.; Feng, H. Meningeal Lymphatic Drainage: Novel Insights into Central Nervous System Disease. Signal Transduct. Target. Ther. 2025, 10, 142. [Google Scholar] [CrossRef] [PubMed]
  57. Boisserand, L.S.B.; Geraldo, L.H.; Bouchart, J.; El Kamouh, M.-R.; Lee, S.; Sanganahalli, B.G.; Spajer, M.; Zhang, S.; Lee, S.; Parent, M.; et al. VEGF-C Prophylaxis Favors Lymphatic Drainage and Modulates Neuroinflammation in a Stroke Model. J. Exp. Med. 2024, 221, e20221983. [Google Scholar] [CrossRef]
  58. Liu, Q.; Wu, C.; Ding, Q.; Liu, X.-Y.; Zhang, N.; Shen, J.-H.; Ou, Z.-T.; Lin, T.; Zhu, H.-X.; Lan, Y.; et al. Age-Related Changes in Meningeal Lymphatic Function Are Closely Associated with Vascular Endothelial Growth Factor-C Expression. Brain Res. 2024, 1833, 148868. [Google Scholar] [CrossRef]
  59. Lull, M.E.; Block, M.L. Microglial Activation and Chronic Neurodegeneration. Neurotherapeutics 2010, 7, 354–365. [Google Scholar] [CrossRef]
  60. Guo, S.; Wang, H.; Yin, Y. Microglia Polarization From M1 to M2 in Neurodegenerative Diseases. Front. Aging Neurosci. 2022, 14, 815347. [Google Scholar] [CrossRef]
  61. Asl, E.R.; Hosseini, S.E.; Tahmasebi, F.; Bolandi, N.; Barati, S. MiR-124 and MiR-155 as Therapeutic Targets in Microglia-Mediated Inflammation in Multiple Sclerosis. Cell Mol. Neurobiol. 2025, 45, 63. [Google Scholar] [CrossRef]
  62. Song, G.J.; Suk, K. Pharmacological Modulation of Functional Phenotypes of Microglia in Neurodegenerative Diseases. Front. Aging Neurosci. 2017, 9, 139. [Google Scholar] [CrossRef]
  63. Gomez-Arboledas, A.; Acharya, M.M.; Tenner, A.J. The Role of Complement in Synaptic Pruning and Neurodegeneration. Immunotargets Ther. 2021, 10, 373–386. [Google Scholar] [CrossRef] [PubMed]
  64. Györffy, B.A.; Kun, J.; Török, G.; Bulyáki, É.; Borhegyi, Z.; Gulyássy, P.; Kis, V.; Szocsics, P.; Micsonai, A.; Matkó, J.; et al. Local Apoptotic-like Mechanisms Underlie Complement-Mediated Synaptic Pruning. Proc. Natl. Acad. Sci. USA 2018, 115, 6303–6308. [Google Scholar] [CrossRef]
  65. Liu, H.; Jiang, M.; Chen, Z.; Li, C.; Yin, X.; Zhang, X.; Wu, M. The Role of the Complement System in Synaptic Pruning after Stroke. Aging Dis. 2024, 16, 1452–1470. [Google Scholar] [CrossRef] [PubMed]
  66. Cho, K. Emerging Roles of Complement Protein C1q in Neurodegeneration. Aging Dis. 2019, 10, 652–663. [Google Scholar] [CrossRef]
  67. Qin, Q.; Wang, M.; Yin, Y.; Tang, Y. The Specific Mechanism of TREM2 Regulation of Synaptic Clearance in Alzheimer’s Disease. Front. Immunol. 2022, 13, 845897. [Google Scholar] [CrossRef] [PubMed]
  68. Zhao, J.; He, Z.; Wang, J. MicroRNA-124: A Key Player in Microglia-Mediated Inflammation in Neurological Diseases. Front. Cell Neurosci. 2021, 15, 771898. [Google Scholar] [CrossRef]
  69. Gaudet, A.D.; Fonken, L.K.; Watkins, L.R.; Nelson, R.J.; Popovich, P.G. MicroRNAs: Roles in Regulating Neuroinflammation. Neuroscientist 2018, 24, 221–245. [Google Scholar] [CrossRef]
  70. Sun, Y.; Li, Q.; Gui, H.; Xu, D.-P.; Yang, Y.-L.; Su, D.-F.; Liu, X. MicroRNA-124 Mediates the Cholinergic Anti-Inflammatory Action through Inhibiting the Production of pro-Inflammatory Cytokines. Cell Res. 2013, 23, 1270–1283. [Google Scholar] [CrossRef]
  71. Nagy, E.E.; Frigy, A.; Szász, J.A.; Horváth, E. Neuroinflammation and Microglia/Macrophage Phenotype Modulate the Molecular Background of Post-Stroke Depression: A Literature Review. Exp. Ther. Med. 2020, 20, 2510–2523. [Google Scholar] [CrossRef]
  72. Dan, Y.R.; Chiam, K.-H. Discovery of Plasma Biomarkers Related to Blood-Brain Barrier Dysregulation in Alzheimer’s Disease. Front. Bioinform. 2024, 4, 1463001. [Google Scholar] [CrossRef] [PubMed]
  73. Zhang, Y.; Mu, B.-R.; Ran, Z.; Zhu, T.; Huang, X.; Yang, X.; Wang, D.-M.; Ma, Q.-H.; Lu, M.-H. Pericytes in Alzheimer’s Disease: Key Players and Therapeutic Targets. Exp. Neurol. 2024, 379, 114825. [Google Scholar] [CrossRef] [PubMed]
  74. İş, Ö.; Wang, X.; Reddy, J.S.; Min, Y.; Yilmaz, E.; Bhattarai, P.; Patel, T.; Bergman, J.; Quicksall, Z.; Heckman, M.G.; et al. Gliovascular Transcriptional Perturbations in Alzheimer’s Disease Reveal Molecular Mechanisms of Blood Brain Barrier Dysfunction. Nat. Commun. 2024, 15, 4758. [Google Scholar] [CrossRef]
  75. Long, Y.; Li, X.-Q.; Deng, J.; Ye, Q.-B.; Li, D.; Ma, Y.; Wu, Y.-Y.; Hu, Y.; He, X.-F.; Wen, J.; et al. Modulating the Polarization Phenotype of Microglia—A Valuable Strategy for Central Nervous System Diseases. Ageing Res. Rev. 2024, 93, 102160. [Google Scholar] [CrossRef]
  76. Niotis, K.; Janney, C.; Helfman, S.; Hristov, H.; Clute-Reinig, N.; Angerbauer, D.; Saperia, C.; Murray, S.; Westine, J.; Seifan, A.; et al. A Blood Biomarker-Guided Precision Medicine Approach for Individualized Neurodegenerative Disease Risk Reduction and Treatment: The Future of Preventive Neurology? (P7-3.016). Neurology 2025, 104, 201. [Google Scholar] [CrossRef]
  77. Ashton, N.J.; Benedet, A.L.; Di Molfetta, G.; Pola, I.; Anastasi, F.; Fernández-Lebrero, A.; Puig-Pijoan, A.; Keshavan, A.; Schott, J.; Tan, K.; et al. Biomarker Discovery in Alzheimer’s and Neurodegenerative Diseases Using Nucleic Acid-Linked Immuno-Sandwich Assay. medRxiv 2024. [Google Scholar] [CrossRef]
  78. Armulik, A.; Genové, G.; Mäe, M.; Nisancioglu, M.H.; Wallgard, E.; Niaudet, C.; He, L.; Norlin, J.; Lindblom, P.; Strittmatter, K.; et al. Pericytes Regulate the Blood-Brain Barrier. Nature 2010, 468, 557–561. [Google Scholar] [CrossRef] [PubMed]
  79. Kitchen, P.; Day, R.E.; Taylor, L.H.J.; Salman, M.M.; Bill, R.M.; Conner, M.T.; Conner, A.C. Identification and Molecular Mechanisms of the Rapid Tonicity-Induced Relocalization of the Aquaporin 4 Channel. J. Biol. Chem. 2015, 290, 16873–16881. [Google Scholar] [CrossRef] [PubMed]
  80. Wang, M.; Ding, F.; Deng, S.; Guo, X.; Wang, W.; Iliff, J.J.; Nedergaard, M. Focal Solute Trapping and Global Glymphatic Pathway Impairment in a Murine Model of Multiple Microinfarcts. J. Neurosci. 2017, 37, 2870–2877. [Google Scholar] [CrossRef]
  81. Ding, X.-B.; Wang, X.-X.; Xia, D.-H.; Liu, H.; Tian, H.-Y.; Fu, Y.; Chen, Y.-K.; Qin, C.; Wang, J.-Q.; Xiang, Z.; et al. Impaired Meningeal Lymphatic Drainage in Patients with Idiopathic Parkinson’s Disease. Nat. Med. 2021, 27, 411–418. [Google Scholar] [CrossRef]
  82. Fonseca, M.I.; Chu, S.-H.; Hernandez, M.X.; Fang, M.J.; Modarresi, L.; Selvan, P.; MacGregor, G.R.; Tenner, A.J. Cell-Specific Deletion of C1qa Identifies Microglia as the Dominant Source of C1q in Mouse Brain. J. Neuroinflamm. 2017, 14, 48. [Google Scholar] [CrossRef]
  83. Lansita, J.A.; Mease, K.M.; Qiu, H.; Yednock, T.; Sankaranarayanan, S.; Kramer, S. Nonclinical Development of ANX005: A Humanized Anti-C1q Antibody for Treatment of Autoimmune and Neurodegenerative Diseases. Int. J. Toxicol. 2017, 36, 449–462. [Google Scholar] [CrossRef]
  84. Wyss-Coray, T.; Yan, F.; Lin, A.H.-T.; Lambris, J.D.; Alexander, J.J.; Quigg, R.J.; Masliah, E. Prominent Neurodegeneration and Increased Plaque Formation in Complement-Inhibited Alzheimer’s Mice. Proc. Natl. Acad. Sci. USA 2002, 99, 10837–10842. [Google Scholar] [CrossRef] [PubMed]
  85. Litvinchuk, A.; Wan, Y.-W.; Swartzlander, D.B.; Chen, F.; Cole, A.; Propson, N.E.; Wang, Q.; Zhang, B.; Liu, Z.; Zheng, H. Complement C3aR Inactivation Attenuates Tau Pathology and Reverses an Immune Network Deregulated in Tauopathy Models and Alzheimer’s Disease. Neuron 2018, 100, 1337–1353.e5. [Google Scholar] [CrossRef] [PubMed]
  86. Fonseca, M.I.; Ager, R.R.; Chu, S.-H.; Yazan, O.; Sanderson, S.D.; LaFerla, F.M.; Taylor, S.M.; Woodruff, T.M.; Tenner, A.J. Treatment with a C5aR Antagonist Decreases Pathology and Enhances Behavioral Performance in Murine Models of Alzheimer’s Disease. J. Immunol. 2009, 183, 1375–1383. [Google Scholar] [CrossRef] [PubMed]
  87. Hernandez, M.X.; Jiang, S.; Cole, T.A.; Chu, S.-H.; Fonseca, M.I.; Fang, M.J.; Hohsfield, L.A.; Torres, M.D.; Green, K.N.; Wetsel, R.A.; et al. Prevention of C5aR1 Signaling Delays Microglial Inflammatory Polarization, Favors Clearance Pathways and Suppresses Cognitive Loss. Mol. Neurodegener. 2017, 12, 66. [Google Scholar] [CrossRef]
  88. Propson, N.E.; Roy, E.R.; Litvinchuk, A.; Köhl, J.; Zheng, H. Endothelial C3a Receptor Mediates Vascular Inflammation and Blood-Brain Barrier Permeability during Aging. J. Clin. Investig. 2021, 131, 140966. [Google Scholar] [CrossRef]
  89. Lopez-Ramirez, M.A.; Wu, D.; Pryce, G.; Simpson, J.E.; Reijerkerk, A.; King-Robson, J.; Kay, O.; de Vries, H.E.; Hirst, M.C.; Sharrack, B.; et al. MicroRNA-155 Negatively Affects Blood-Brain Barrier Function during Neuroinflammation. FASEB J. 2014, 28, 2551–2565. [Google Scholar] [CrossRef]
  90. Hsu, M.; Rayasam, A.; Kijak, J.A.; Choi, Y.H.; Harding, J.S.; Marcus, S.A.; Karpus, W.J.; Sandor, M.; Fabry, Z. Neuroinflammation-Induced Lymphangiogenesis near the Cribriform Plate Contributes to Drainage of CNS-Derived Antigens and Immune Cells. Nat. Commun. 2019, 10, 229. [Google Scholar] [CrossRef]
  91. Wang, Y.; Cella, M.; Mallinson, K.; Ulrich, J.D.; Young, K.L.; Robinette, M.L.; Gilfillan, S.; Krishnan, G.M.; Sudhakar, S.; Zinselmeyer, B.H.; et al. TREM2 Lipid Sensing Sustains the Microglial Response in an Alzheimer’s Disease Model. Cell 2015, 160, 1061–1071. [Google Scholar] [CrossRef]
  92. Bemiller, S.M.; McCray, T.J.; Allan, K.; Formica, S.V.; Xu, G.; Wilson, G.; Kokiko-Cochran, O.N.; Crish, S.D.; Lasagna-Reeves, C.A.; Ransohoff, R.M.; et al. TREM2 Deficiency Exacerbates Tau Pathology through Dysregulated Kinase Signaling in a Mouse Model of Tauopathy. Mol. Neurodegener. 2017, 12, 74. [Google Scholar] [CrossRef]
  93. Filipello, F.; Morini, R.; Corradini, I.; Zerbi, V.; Canzi, A.; Michalski, B.; Erreni, M.; Markicevic, M.; Starvaggi-Cucuzza, C.; Otero, K.; et al. The Microglial Innate Immune Receptor TREM2 Is Required for Synapse Elimination and Normal Brain Connectivity. Immunity 2018, 48, 979–991.e8. [Google Scholar] [CrossRef] [PubMed]
  94. Walker, D.G.; McGeer, P.L. Complement Gene Expression in Human Brain: Comparison between Normal and Alzheimer Disease Cases. Brain Res. Mol. Brain Res. 1992, 14, 109–116. [Google Scholar] [CrossRef] [PubMed]
  95. Zhang, R.; Li, J.; Li, X.; Zhang, S. Therapeutic Approaches to CNS Diseases via the Meningeal Lymphatic and Glymphatic System: Prospects and Challenges. Front. Cell Dev. Biol. 2024, 12, 1467085. [Google Scholar] [CrossRef]
  96. Negro-Demontel, L.; Maleki, A.F.; Reich, D.S.; Kemper, C. The Complement System in Neurodegenerative and Inflammatory Diseases of the Central Nervous System. Front. Neurol. 2024, 15, 1396520. [Google Scholar] [CrossRef]
  97. Shaheen, N.; Shaheen, A.; Osama, M.; Nashwan, A.J.; Bharmauria, V.; Flouty, O. MicroRNAs Regulation in Parkinson’s Disease, and Their Potential Role as Diagnostic and Therapeutic Targets. NPJ Parkinsons Dis. 2024, 10, 186. [Google Scholar] [CrossRef]
  98. Antoniou, M.; Jorgensen, A.L.; Kolamunnage-Dona, R. Biomarker-Guided Adaptive Trial Designs in Phase II and Phase III: A Methodological Review. PLoS ONE 2016, 11, e0149803. [Google Scholar] [CrossRef] [PubMed]
  99. Imam, F.; Saloner, R.; Vogel, J.W.; Krish, V.; Abdel-Azim, G.; Ali, M.; An, L.; Anastasi, F.; Bennett, D.; Pichet Binette, A.; et al. The Global Neurodegeneration Proteomics Consortium: Biomarker and Drug Target Discovery for Common Neurodegenerative Diseases and Aging. Nat. Med. 2025, 31, 2556–2566. [Google Scholar] [CrossRef]
  100. He, Z.; Sun, J. The Role of the Neurovascular Unit in Vascular Cognitive Impairment: Current Evidence and Future Perspectives. Neurobiol. Dis. 2025, 204, 106772. [Google Scholar] [CrossRef]
  101. Thalgott, J.H.; Zucker, N.; Deffieux, T.; Koopman, M.S.; Dizeux, A.; Avramut, C.M.; Koning, R.I.; Mager, H.-J.; Rabelink, T.J.; Tanter, M.; et al. Non-Invasive Characterization of Pericyte Dysfunction in Mouse Brain Using Functional Ultrasound Localization Microscopy. Nat. Biomed. Eng. 2025, ahead of print. Erratum in Nat. Biomed. Eng. 2025, ahead of print. https: //doi.org/10.1038/s41551-025-01494-6. [Google Scholar] [CrossRef]
  102. Qi, L.; Wang, F.; Sun, X.; Li, H.; Zhang, K.; Li, J. Recent Advances in Tissue Repair of the Blood-Brain Barrier after Stroke. J. Tissue Eng. 2024, 15, 20417314241226551. [Google Scholar] [CrossRef]
  103. Zhao, K.; Li, Z.; Sun, T.; Liu, Q.; Cheng, Y.; Barreto, G.; Li, Z.; Liu, R. Editorial: Novel Therapeutic Target and Drug Discovery for Neurological Diseases, Volume II. Front. Pharmacol. 2025, 16, 1566950. [Google Scholar] [CrossRef]
  104. Loh, J.S.; Mak, W.Q.; Tan, L.K.S.; Ng, C.X.; Chan, H.H.; Yeow, S.H.; Foo, J.B.; Ong, Y.S.; How, C.W.; Khaw, K.Y. Microbiota-Gut-Brain Axis and Its Therapeutic Applications in Neurodegenerative Diseases. Signal Transduct. Target. Ther. 2024, 9, 37. [Google Scholar] [CrossRef]
  105. Carloni, S.; Rescigno, M. The Gut-Brain Vascular Axis in Neuroinflammation. Semin. Immunol. 2023, 69, 101802. [Google Scholar] [CrossRef]
  106. Wasan, K.M.; Iqtadar, S.; Mudogo, C.N.; Chávez-Fumagalli, M.A. Editorial: Novel Pharmacological Targets and Strategies to Treat Neglected Global Diseases (NGDs): An LMIC Perspective. Front. Pharmacol. 2025, 15, 7705. [Google Scholar] [CrossRef] [PubMed]
  107. Wang, S.; Xie, S.; Zheng, Q.; Zhang, Z.; Wang, T.; Zhang, G. Biofluid Biomarkers for Alzheimer’s Disease. Front. Aging Neurosci. 2024, 16, 1380237. [Google Scholar] [CrossRef] [PubMed]
  108. Keikha, R.; Hashemi-Shahri, S.M.; Jebali, A. The miRNA Neuroinflammatory Biomarkers in COVID-19 Patients with Different Severity of Illness. Neurologia 2023, 38, e41–e51. [Google Scholar] [CrossRef] [PubMed]
  109. De Kort, A.M.; Kuiperij, H.B.; Kersten, I.; Versleijen, A.A.M.; Schreuder, F.H.B.M.; Van Nostrand, W.E.; Greenberg, S.M.; Klijn, C.J.M.; Claassen, J.A.H.R.; Verbeek, M.M. Normal Cerebrospinal Fluid Concentrations of PDGFRβ in Patients with Cerebral Amyloid Angiopathy and Alzheimer’s Disease. Alzheimers Dement. 2022, 18, 1788–1796. [Google Scholar] [CrossRef]
  110. Cicognola, C.; Mattsson-Carlgren, N.; van Westen, D.; Zetterberg, H.; Blennow, K.; Palmqvist, S.; Ahmadi, K.; Strandberg, O.; Stomrud, E.; Janelidze, S.; et al. Associations of CSF PDGFRβ With Aging, Blood-Brain Barrier Damage, Neuroinflammation, and Alzheimer Disease Pathologic Changes. Neurology 2023, 101, e30–e39. [Google Scholar] [CrossRef]
Figure 1. The Neurovascular-Glymphatic Dysfunction Cascade in Neurodegeneration. (A) Healthy NVU showing intact BBB with functional pericytes expressing PDGFRβ, endothelial cells with tight junctions, astrocytic endfeet with polarized AQP4, and resting M2 microglia. Normal cerebral blood flow and efficient glymphatic clearance are maintained. (B) 5–10 years before the clinical signs: Early neurovascular dysfunction characterized by pericyte injury with soluble PDGFRβ (sPDGFRβ) release, initial BBB breakdown indicated by weakened tight junctions and fibrinogen extravasation and beginning loss of AQP4 polarization. Early microglial activation is evident. These changes occur years before clinical symptoms. (C) Clinical symptom onset: Progressive pathology showing significant pericyte loss, BBB hyperpermeability with extensive fibrinogen leakage, impaired glymphatic clearance with protein accumulation (Aβ and tau), activated M1 microglia, complement component C1q deposition on synapses, and reactive astrocytes. Created in BioRender. Mavrych, V. (2025) https://BioRender.com/e97uydy.
Figure 1. The Neurovascular-Glymphatic Dysfunction Cascade in Neurodegeneration. (A) Healthy NVU showing intact BBB with functional pericytes expressing PDGFRβ, endothelial cells with tight junctions, astrocytic endfeet with polarized AQP4, and resting M2 microglia. Normal cerebral blood flow and efficient glymphatic clearance are maintained. (B) 5–10 years before the clinical signs: Early neurovascular dysfunction characterized by pericyte injury with soluble PDGFRβ (sPDGFRβ) release, initial BBB breakdown indicated by weakened tight junctions and fibrinogen extravasation and beginning loss of AQP4 polarization. Early microglial activation is evident. These changes occur years before clinical symptoms. (C) Clinical symptom onset: Progressive pathology showing significant pericyte loss, BBB hyperpermeability with extensive fibrinogen leakage, impaired glymphatic clearance with protein accumulation (Aβ and tau), activated M1 microglia, complement component C1q deposition on synapses, and reactive astrocytes. Created in BioRender. Mavrych, V. (2025) https://BioRender.com/e97uydy.
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Table 1. Key Biomarkers of Neurovascular and Glymphatic Dysfunction in Neurodegeneration.
Table 1. Key Biomarkers of Neurovascular and Glymphatic Dysfunction in Neurodegeneration.
BiomarkerSource/LocationPathophysiological RoleClinical SignificanceDetection MethodKey References
sPDGFRβCSF, released from injured pericytesIndicates pericyte injury and BBB breakdown; correlates with neuroinflammationElevated in early-stage neurodegenerative disorders; correlates with cognitive decline and BBB dysfunction (QAlb)ELISA, MSD electrochemiluminescence[12,13,14,15]
CSF/Plasma Albumin Ratio (QAlb)CSF and plasmaReflects BBB permeability; increased ratio indicates BBB breakdownCorrelates with age, pericyte damage, and neuroinflammation; elevated in MCI and ADNephelometry, ELISA[12,13,16]
C1qBrain tissue, synapses (microglia-derived)Tags synapses for complement-mediated elimination; initiates classical complement cascadeIncreased and localized to synapses before plaque deposition in AD; associated with early synapse lossImmunohistochemistry, Western blot[17,18,19]
C3/iC3bBrain tissue, synapses (astrocyte and microglia-derived)Opsonizes synapses for microglial phagocytosis via CR3 receptorElevated in vulnerable brain regions; C3 deficiency protects against age-related synapse lossImmunohistochemistry, flow cytometry[18,19,20]
AQP4 Polarization IndexAstrocytic perivascular endfeetMaintains glymphatic fluid flow; loss of polarization impairs waste clearanceDepolarization correlates with disease progression and impaired Aβ clearanceImmunofluorescence microscopy[21,22,23]
CSF YKL-40CSF (astrocyte activation marker)Indicates astrocytic activation and neuroinflammationElevated in AD and correlates with BBB dysfunction and PDGFRβELISA[24,25]
CSF GFAPCSF (astrocyte marker)Reflects astrocytic reactivity and glial activationIncreased with age and neuroinflammation; associated with BBB dysfunctionELISA, Simoa[26]
miR-124Plasma, CSF, brain tissueAnti-inflammatory microRNA; maintains microglial quiescenceDownregulated in neurodegeneration; loss promotes M1 microglial polarizationqRT-PCR, sequencing[27]
miR-155Plasma, CSF, brain tissuePro-inflammatory microRNA; promotes neuroinflammationUpregulated in MS and AD; correlates with disease severityqRT-PCR, sequencing[28,29]
VEGF-CCSF, brain tissueRegulates meningeal lymphatic vessel function and lymphangiogenesisReduced levels associated with impaired brain clearance; therapeutic targetELISA, Western blot[30,31]
CSF FibrinogenCSF (blood-derived)BBB leakage marker; promotes neuroinflammationElevated in AD; correlates with pericyte loss and reduced oxygenationELISA, immunohistochemistry[12]
Abbreviations: sPDGFRβ, soluble platelet-derived growth factor receptor-β; CSF, cerebrospinal fluid; BBB, blood–brain barrier; QAlb, albumin quotient; MCI, mild cognitive impairment; AD, Alzheimer’s disease; AQP4, aquaporin-4; Aβ, amyloid-β; GFAP, glial fibrillary acidic protein; MS, multiple sclerosis; VEGF-C, vascular endothelial growth factor-C; MSD, Meso Scale Discovery.
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Mansour, G.K.; Bolgova, O.; Hajjar, A.W.; Mavrych, V. Neurovascular Dysfunction and Glymphatic Impairment: An Unexplored Therapeutic Frontier in Neurodegeneration. Int. J. Mol. Sci. 2025, 26, 11843. https://doi.org/10.3390/ijms262411843

AMA Style

Mansour GK, Bolgova O, Hajjar AW, Mavrych V. Neurovascular Dysfunction and Glymphatic Impairment: An Unexplored Therapeutic Frontier in Neurodegeneration. International Journal of Molecular Sciences. 2025; 26(24):11843. https://doi.org/10.3390/ijms262411843

Chicago/Turabian Style

Mansour, Ghaith K., Olena Bolgova, Ahmad W. Hajjar, and Volodymyr Mavrych. 2025. "Neurovascular Dysfunction and Glymphatic Impairment: An Unexplored Therapeutic Frontier in Neurodegeneration" International Journal of Molecular Sciences 26, no. 24: 11843. https://doi.org/10.3390/ijms262411843

APA Style

Mansour, G. K., Bolgova, O., Hajjar, A. W., & Mavrych, V. (2025). Neurovascular Dysfunction and Glymphatic Impairment: An Unexplored Therapeutic Frontier in Neurodegeneration. International Journal of Molecular Sciences, 26(24), 11843. https://doi.org/10.3390/ijms262411843

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