Search Results (91)

Background: Dermal interstitial fluid (ISF) contains both plasma-derived biomarkers and biomarkers unique to ISF, making it a promising biofluid for painless, scalable, and decentralized liquid biopsy and continuous health monitoring. However, efficient ISF collection remains challenging due to the small accessible fluid volume in the dermis, slow physiological turnover, and stratum corneum. Methods: This review reframes dermal ISF sampling as a pressure gradient engineering problem using Darcy’s law. We examine how vacuum-assisted microneedle platforms can effectively drive ISF through the dermal extracellular matrix in a minimally invasive manner. We compare the two architectures: micropore-based and hollow microneedle approaches. Results: In the micropore approach, a vacuum chamber is placed over the transient micropores left by withdrawn microneedles, supporting off-device, multi-omic downstream analyses of the collected ISF. The hollow microneedle approach retains the microneedles in the skin and applies vacuum through internal lumens, allowing integration of the vacuum source, microneedles, and biosensors into a single wearable platform for in situ biomarker detection. Comparative studies across these architectures identify the vacuum seal between the device and the skin as the major engineering bottleneck shared by both architectures. Conclusions: Vacuum-assisted microneedle platforms provide a practical route for generating pressure gradient-driven ISF transport while preserving minimally invasive skin access. Future development should prioritize device–skin vacuum seal robustness, reproducible ISF recovery across users and skin sites, integrated vacuum sources, scalable fabrication, and usability in clinical or at-home settings. Full article

Hepatic malignancies account for a substantial portion of global cancer mortality, with hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (IHC), and metastatic liver disease representing the most common diagnoses. While surgical resection and liver transplantation remain curative options for eligible patients, most patients are diagnosed at stages unsuitable for surgery. This has shifted medical management towards locoregional therapies (LRTs) which are often catheter-directed. Of these interventions, the use of conventional end-hole catheters for therapeutic infusion has been a mainstay of treatment, but this method is constrained by retrograde particle escape and elevated tumoral interstitial fluid pressure. Together, these factors limit drug penetration into the tumor microenvironment. Pressure-enabled drug delivery (PEDD), achieved through balloon-occlusion or microvalve-based catheter platforms, has emerged as a strategy to overcome these limitations. This narrative review synthesizes current evidence regarding PEDD and contextualizes its role within the broader LRT landscape. Preclinical studies and early clinical data illustrate improved drug-delivery characteristics, acceptable safety profiles, and highlight the potential for adaptation to regional immunotherapy regimens. However, while PEDD represents a promising advance in catheter-based hepatic oncologic therapy, prospective randomized comparisons against conventional infusion remain limited, and significant investigation is needed to establish its definitive role in interventional oncology. Full article

The glymphatic system is a recently defined perivascular waste elimination pathway responsible for the efficient clearance of metabolic waste and neurotoxic proteins in the central nervous system. This system facilitates the entry of cerebrospinal fluid (CSF) into the brain parenchyma via arterial perivascular spaces and its interaction with interstitial fluid (ISF) via glial cell-associated aquaporin-4 (AQP4) channels. It functions particularly actively during sleep. Impairment of glymphatic flow contributes to nerve cell damage and neuroinflammation in various pathologies such as Alzheimer’s disease, Parkinson’s disease, traumatic brain injury, subarachnoid hemorrhage, and neurological tumors. In neurosurgical practice, surgical positioning, anesthesia regimen, and intracranial pressure changes play a decisive role in glymphatic function, and perioperative modulation of the system can affect postoperative recovery and cognitive outcomes. Today, non-invasive imaging techniques and molecular biological approaches are deepening our understanding of the functioning of the glymphatic system in humans, and this system is emerging as a potential target in the diagnosis and treatment of neurological diseases. This review comprehensively addresses the basic anatomical and physiological principles of the glymphatic system, its role in pathological processes, and its clinical significance in neurosurgical applications. Full article

Mimicking vascular function in bone may serve to stimulate osteogenesis. We developed a micropump and wireless pressure sensing system to fluctuate and record intramedullary pressure (IMP) in the femoral diaphysis of young (6 months) and old (24 months) male Fischer-344 rats. In vivo IMP was determined (n = 5 per group). Additionally, two bone defects were created in the right femora (EXP) of young (n = 14) and old (n = 11) rats and catheterized to the micropump and wireless pressure sensor. Intramedullary pressure was fluctuated for 10 min. The left femur served as the control (CTL). Seven days post-surgery, femora were scanned by μCT (15 µm) to assess trabecular bone microarchitecture, cortical thickness and new bone volume at the endosteal and periosteal surfaces. Data were analyzed with SPSS software, and significance was p ≤ 0.05. In vivo IMP was lower (p < 0.05) in the old (~16 mmHg) vs. young (~36 mmHg) rats. Trabecular thickness in the proximal metaphysis was higher (p < 0.05) in the old rats, and the cortical shell was thicker (p < 0.05) and new bone volume greater (p < 0.05) in the young rats. Importantly, new bone volume was greater (p < 0.05) in young EXP (14 ± 7 mm³) vs. young CTL (7 ± 7 mm³) femora. A 10-min bout of IMP fluctuation stimulated osteogenesis in young rats. Full article

The tumor microenvironment (TME) acts as a major barrier to effective drug delivery and contributes to drug resistance in solid tumors. Hypoxia, acidosis, and elevated interstitial fluid pressure limit drug penetration, while cancer-associated fibroblasts and immunosuppressive cells promote survival signaling, drug efflux, and metabolic adaptation. Polymeric drug delivery systems offer a promising strategy to address these barriers because their structures can be precisely engineered and designed to respond to TME-specific stimuli. These properties enable controlled drug release at tumor sites and help improve therapeutic efficacy while reducing systemic limitations. This review discusses how physicochemical and cellular components of the TME contribute to drug resistance and how polymeric nanomedicines can be designed to overcome these barriers. In addition, it examines key challenges that limit clinical translation, including tumor heterogeneity, variable enhanced permeability and retention effects, manufacturing scalability, and regulatory requirements. Finally, this review highlights the future direction of polymer nanomedicine and focuses specifically on developing rational material design, enhancing preclinical models, and developing clinically appropriate strategies to combat TME-mediated drug resistance. Full article

Background: Heart failure (HF) has traditionally been interpreted through hemodynamic, neurohormonal, and cardiorenal frameworks. Although these models explain many aspects of clinical decompensation, they do not fully account for persistent tissue congestion, unresolved myocardial edema, chronic sterile inflammation, and progressive fibrosis despite optimized therapy. Objectives: To review the anatomy, physiology, and pathobiological relevance of the cardiac lymphatic system in HF and to evaluate whether cardiac lymphatic dysfunction constitutes a mechanistic bridge linking congestion, inflammation, and adverse remodeling. Methods: This narrative review was based on a structured literature search of PubMed/MEDLINE, supplemented by manual backward reference screening and bibliographic verification through journal webpages. The search covered January 2000 to 15 April 2026, with emphasis on 2018 onward and on seminal mechanistic studies. Search domains included cardiac lymphatics, heart failure, lymphangiogenesis, myocardial edema, congestion, inflammation, myocardial infarction, pressure overload, and HFpEF. Results: Cardiac lymphatics regulate myocardial clearance of interstitial fluid, proteins, cytokines, lipids, and immune cells. Preclinical experimental evidence, mainly derived from myocardial infarction, pressure-overload, and lymphatic-insufficiency models, indicates that impaired lymphatic transport or insufficient lymphangiogenic adaptation promotes myocardial edema, inflammatory persistence, fibroblast activation, collagen deposition, and ventricular dysfunction. Human observational and early translational studies suggest that lymphatic dysregulation may also be relevant in selected HF phenotypes, although direct clinical evidence remains limited. Conversely, lymphangiogenic and lymphatic-restorative strategies, especially through the VEGF-C/VEGFR-3 axis, reduce edema, enhance inflammatory resolution, attenuate fibrosis, and improve ventricular performance in preclinical models. Conclusions: Cardiac lymphatic dysfunction provides a compelling conceptual framework that links congestion and inflammation in HF. Rather than acting as a passive bystander, the cardiac lymphatic circulation appears to be an active determinant of myocardial homeostasis and disease progression. Recognition of lymphatic insufficiency as a pathogenic component of HF may open new diagnostic and therapeutic avenues, including tissue-focused decongestion, lymphatic phenotyping, and targeted lymphatic repair. Full article

Aneurysmal subarachnoid hemorrhage (SAH) remains a devastating cerebrovascular disorder with high morbidity and mortality, despite advances in aneurysm securing and neurocritical care. Clinical outcomes are determined by early brain injury (EBI), delayed cerebral ischemia (DCI), hydrocephalus, and long-term cognitive impairment, extending beyond the traditional focus on large-vessel vasospasm alone. Emerging evidence identifies the dysfunction of the glymphatic system and meningeal lymphatic pathway, the brain’s primary clearance pathways, as a central and unifying mechanism linking acute hemorrhagic injury to delayed and chronic neurological sequelae. Following SAH, acute intracranial pressure elevation, subarachnoid blood clot burden, loss of arterial pulsatility, venous congestion, astrocytic aquaporin-4 perivascular depolarization, and neuroinflammation converge to suppress cerebrospinal fluid–interstitial fluid exchange and outflow in glymphatic system and subsequent meningeal lymphatic drainage. Persistent clearance failure promotes the retention of blood breakdown products, inflammatory mediators, and metabolic waste, amplifying microvascular dysfunction, cortical spreading depolarizations, blood–brain barrier disruption, and secondary ischemic injury. Importantly, accumulating data highlight venous pathology and meningeal lymphatic impairment as critical, yet underappreciated, contributors to delayed injury and post-SAH hydrocephalus. In this review, we synthesize the current knowledge of the physiological organization of glymphatic and meningeal lymphatic systems, delineate the mechanistic and molecular drivers of their dysfunction after SAH, and discuss clinical implications for EBI, DCI, hydrocephalus, and long-term cognitive outcomes. We further outline future directions, including translational imaging, biomarker development, and therapeutic strategies targeting clearance pathways, to advance disease-modifying approaches in SAH. Full article

The discovery of the glymphatic system (GS) transformed understanding of central nervous system homeostasis by revealing a brain-wide network that facilitates cerebrospinal and interstitial fluid exchange along perivascular pathways. This system clears metabolic waste and maintains the precise ionic environment required for neuronal function through the coordinated action of astrocytic aquaporin-4 channels and intact perivascular architecture. Glioblastoma multiforme (GBM), the most aggressive primary brain tumor in adults, alters physiological barriers through pathological angiogenesis, compression of perivascular spaces, depolarization of aquaporin-4 at astrocytic endfeet, and obstruction of venous and lymphatic drainage. This narrative review synthesizes current experimental and clinical literature identified through targeted searches of PubMed and Scopus to examine interactions between glioblastoma, glymphatic system dysfunction, and tumor microenvironmental changes. To minimize selection bias, studies were categorized according to evidence source and experimental design. Evidence from rodent models and advanced imaging demonstrates as tumor growth impairs glymphatic function, the resulting dysfunction promotes tumor progression by enabling accumulation of pro-tumorigenic growth factors, inflammatory mediators, and acidic metabolites, while elevated interstitial fluid pressure limits drug delivery. Impaired antigen drainage further diminishes immune surveillance, contributing to the immunosuppressive microenvironment that limits immunotherapy efficacy. A critical evaluation of these mechanisms highlights how the glymphatic system influences disease progression and suggests novel avenues for diagnostic imaging and therapeutic intervention. Although significant challenges remain in modeling human fluid dynamics, understanding these hidden networks offers a promising frontier for strategies aimed at restoring cerebral clearance and improving clinical outcomes. Full article

Cardiogenic pulmonary edema (CPE) is a life-threatening manifestation of acute heart failure characterized by rapid accumulation of fluid in the interstitial and alveolar spaces, leading to severe dyspnea, hypoxemia, and respiratory failure. The condition arises from elevated left-sided filling pressures that increase pulmonary capillary hydrostatic pressure, disrupt alveolo-capillary barrier integrity, and impair gas exchange. Neurohormonal activation further perpetuates congestion and increases myocardial workload, creating a vicious cycle of hemodynamic overload and respiratory compromise. Respiratory support is a cornerstone of management in CPE, aimed at stabilizing oxygenation, reducing the work of breathing, and facilitating ventricular unloading while definitive therapies, such as diuretics, vasodilators, inotropes, or mechanical circulatory support (MCS), address the underlying cause. Among available modalities, non-invasive ventilation (NIV) with continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) has the strongest evidence base in moderate-to-severe CPE, consistently reducing the need for intubation and providing rapid relief of dyspnea. High-flow nasal cannula (HFNC) represents an emerging alternative in patients with moderate hypoxemia or intolerance to mask ventilation, and should be considered an adjunctive option in selected patients with less severe disease or NIV intolerance, although its efficacy in severe presentations remains uncertain. Invasive mechanical ventilation is reserved for refractory cases, while extracorporeal membrane oxygenation (ECMO) and other advanced circulatory support modalities may be necessary in cardiogenic shock. Integration of respiratory strategies with hemodynamic optimization is essential, as positive pressure ventilation favorably modulates preload and afterload, synergizing with pharmacological unloading. Future directions include personalization of ventilatory strategies using advanced monitoring, novel interfaces to improve tolerability, and earlier integration of MCS. In summary, respiratory support in CPE is both a bridge and a decisive therapeutic intervention, interrupting the cycle of hypoxemia and hemodynamic deterioration. A multidisciplinary, individualized approach remains central to improving outcomes in this high-risk population. Full article

Glioblastoma (GBM) remains one of the most treatment-resistant human malignancies, largely due to the interplay between disrupted fluid dynamics, immune evasion, and the structural complexity of the tumor microenvironment; in addition to these, treatment resistance is also driven by intratumoral heterogeneity, glioma stem cell persistence, hypoxia-induced metabolic and epigenetic plasticity, adaptive oncogenic signaling, and profound immunosuppression within the tumor microenvironment. Emerging evidence shows that dysfunction of the glymphatic system, mislocalization of aquaporin-4, and increased intracranial pressure compromise cerebrospinal fluid–interstitial fluid exchange and impair antigen drainage to meningeal lymphatics, thereby weakening immunosurveillance. GBM simultaneously remodels the blood–brain barrier into a heterogeneous and permeable blood–tumor barrier that restricts uniform drug penetration yet enables tumor progression. These alterations intersect with profound immunosuppression mediated by pericytes, tumor-associated macrophages, and hypoxic niches. Advances in imaging, including DCE-MRI, DTI-ALPS, CSF-tracing PET, and elastography, now allow in vivo characterization of glymphatic function and interstitial flow. Therapeutic strategies targeting the fluid-immune interface are rapidly expanding, including convection-enhanced delivery, intrathecal and intranasal approaches, focused ultrasound, nanoparticle systems, and lymphatic-modulating immunotherapies such as VEGF-C and STING agonists. Integrating barrier modulation with immunotherapy and nanomedicine holds promise for overcoming treatment resistance. Our review synthesizes the mechanistic, microenvironmental, and translational advances that position the glymphatic–immune axis as a new frontier in glioblastoma research. Full article

Basic physiology and molecular mechanisms accounting for the maldistribution of fluid that is characteristic of the “third fluid space” (V_t2) have been known for several decades but have been poorly integrated into the clinical literature. Today, the maldistribution can be quantified and simulated in living humans by using volume kinetic mathematics, which introduces possibilities to validate interventions designed to mitigate the pathophysiology. Fluid accumulation in V_t2 occurs both in fluid overload and inflammation, and both are largely influenced by interstitial fluid pressure. This is normally slightly sub-atmospheric but increases during volume loading to eventually exceed the ambient air pressure, whereby the loss of vacuum allows pools of fluid to appear in the interstitial gel. Opening of V_t2 due to fluid overload can be delayed/minimized by lowering the infusion rate, hemorrhage, and the use of hyper-oncotic fluid. Accumulation of fluid in V_t2 during acute inflammation and tissue injury can be explained by disruption of the cell–matrix interactions that actively regulate the interstitial pressure. Inflammatory mediators, mostly tissue cytokines, cause release of tensile forces that disrupt integrin-dependent adhesion between interstitial fibroblasts and collagen fibers. This disruption causes the interstitial space to expand, which results in a deep negative (suction) pressure. These events can be modulated by α-trinositol and insulin. Full article

Background/Objectives: Idiopathic edema (IE) in women is characterized by swelling of hands and face followed by increasing abdominal and truncal girth, bloating, edema, >1.4 kg weight gain when in upright posture, and nocturia that eliminates the retained fluid. A capillary leak is the primary pathophysiologic abnormality that induces different clinical presentations that were considered untreatable. Methods: We utilized different aspects of Starling forces of edema formation and treated four uncomplicated cases of IE by reducing salt intake with or without diuretics and two cases of life-threatening cases due to seizures and coma induced by acute hyponatremia in one and postural dizziness, fainting, and fractures and dislocations of joints in another. Results: All four uncomplicated cases of IE were treated by reducing salt intake with or without diuretics that eliminated the weight gain and nocturia. The patient with hyponatremia never developed hyponatremia by reducing water intake and signs and symptoms of IE by salt restriction and diuretic therapy and eliminated the postural hypotension, falls, and fainting by use of support hose that increased interstitial hydrostatic pressure to eliminate fluid shifting from intravascular to interstitial spaces. Conclusions: A leaky capillary induces pathophysiologic changes that activate different metabolic pathways. IE is now a treatable condition, following: 1. Salt restriction with or without diuretics for the cyclical weight gain, and 2. Water restriction for hyponatremia, hyponatremic seizures, and coma and 3. support hose for postural hypotension, postural dizziness, and fainting. IE is unrecognized and probably more common than it is perceived. Full article

Repeated mining under insufficiently collapsed gobs is a complex process in underground mining and is associated with safety hazards such as ground collapse and subsidence. The effect of layer spacing on the fracture network evolution and fluid transport mechanisms in rock strata during this process has not been systematically studied. In this work, the discrete element method was employed to analyze the fracture development and seepage evolution of surrounding rocks in the Nanliang coal mine across varying layer spacings (5, 20, 35, 50, and 65 m). A systematic evaluation of the rock mass integrity was conducted through damage coefficient quantification. The key findings revealed that an increase in the layer spacing progressively reduced the damage coefficients in both the overburden strata above the goaf and in the interlayer formations ahead of the working face, accompanied by reduced fracture propagation intensity. Shear failure mechanisms dominated throughout the mining process. Fractal characteristics of the fractures intensified with the advance of the working face, while the hydraulic conductivity and interstitial pressure in the interlayer strata exhibited declining trends with reduced attenuation rates. Our findings provide critical insights for ensuring the safety and improving the efficiency of repeated mining under insufficiently collapsed gobs. Full article

Perfusion offers unique benefits to tissue-engineered systems, enhancing oxygen and nutrient transport, which improves tissue formation and growth. In this study, we present a novel and integrated portable perfusion system. Weighing < 10 lbs, the system can maintain continuous flow in a standard incubation environment (37 °C, 5% CO₂), effectively functioning as a portable perfusion and tissue culturing system. To characterize the perfusion system’s flow parameters, we measured the volumetric flow rate across a range of pressures and found that the system could achieve flow velocities between 1.69 to 4.6 $\mathsf{\mu }$m/s, which is similar to in vivo interstitial flow. Computational fluid dynamics revealed fully developed laminar flow within the sample-containing region of the perfusion system, helping ensure even fluid and nutrient distribution. To study the system’s compatibility with live tissues, bioengineered tissue patches were created and perfused. After 24 h of perfusion, no significant difference in cell viability was observed between the perfused samples and static controls, indicating no adverse effects on cell health. Perfusion also facilitated enhanced spatial organization within tissue patches, reducing the inter-spheroids distance. Furthermore, perfusion strengthened the tissue matrix and reduced the degradation rate of the hydrogel scaffold. Complemented by its ability to provide mobile perfusion and incubation, this novel integrated portable perfusion system holds promise for promoting tissue maturation and advancing tissue bioengineering studies. Full article

Drug delivery to solid tumors is challenged by multiple physiological barriers arising from the tumor microenvironment, including dense extracellular matrix, cellular heterogeneity, hypoxic gradients, and elevated interstitial fluid pressure. These features hinder the uniform distribution and accumulation of therapeutics, reducing treatment efficacy. Despite their widespread use, conventional two-dimensional monolayer cultures fail to reproduce these complexities, contributing to the poor translational predictability of many preclinical candidates. Three-dimensional multicellular tumor spheroids have emerged as more representative in vitro models that capture essential features of tumor architecture, stromal interactions, and microenvironmental resistance mechanisms. Spheroids exhibit spatially organized regions of proliferation, quiescence, and hypoxia, and can incorporate non-tumor cells to mimic tumor–stroma crosstalk. Advances in spheroid analysis now enable detailed evaluation of drug penetration, cellular migration, cytotoxic response, and molecular gradients using techniques such as optical and confocal imaging, large-particle flow cytometry, biochemical viability assays, and microfluidic integration. By combining physiological relevance with analytical accessibility, spheroid models support mechanistic studies of drug transport and efficacy under tumor-like conditions. Their adoption into routine preclinical workflows has the potential to improve translational accuracy while reducing reliance on animal models. Full article