Search Results (319)

Background: Osteoarthritis (OA) is the most common degenerative joint disease globally, with its pathogenesis yet to be fully elucidated. Accumulating evidence has redefined OA as a systemic low-grade inflammatory disorder. While the gut microbiota–joint axis is widely recognized as a key regulatory pathway in OA progression, a definitive causal and mechanistic framework linking microbiota-derived metabolites to OA pathology has not yet been established. Aim of Review: This review aims to comprehensively evaluate the roles of microbiota-derived metabolites in OA pathogenesis by integrating cutting-edge multi-omics data, causal evidence from Mendelian randomization studies, and advanced translational strategies. We propose a conceptual framework linking microbial dysbiosis to joint degeneration and discuss potential therapeutic targets for OA. Key Scientific Concepts of Review: Microbiota-derived signals, including lipopolysaccharides, peptidoglycans, short-chain fatty acids, bile acids, tryptophan metabolites, and hydrogen sulfide, are associated with mucosal barrier impairment, aberrant immune activation, and metabolic–endocrine dysfunction. These systemic host responses, in turn, may collectively contribute to the three core pathological hallmarks of OA: cartilage degeneration, synovial inflammation, and subchondral bone remodeling. We highlight novel regulatory pathways, including bile acid–glucagon-like peptide-1(GLP-1) signaling, aryl hydrocarbon receptor (AhR) modulation, and ferroptosis regulation, as potential critical mediators of OA. Causal evidence from multi-omics and Mendelian randomization analyses is synthesized to move beyond simple descriptive associations. Furthermore, we discuss translational strategies, such as metabolite-targeted interventions (GUDCA, IPA, HDCA) and engineered bacterial extracellular vesicle delivery systems, providing a potential framework for the precision theranostics of OA. Full article

Background and Objectives: The clinical differentiation of peripheral involvement within the spondyloarthritis (SpA) spectrum remains a significant challenge. Identifying patients at the stage of psoriasis without clinical arthritis (PsO), before the onset of overt arthritis, is crucial for early disease management. MicroRNAs (miRNAs) have emerged as potential epigenetic regulators in inflammatory rheumatic diseases. This study aimed to identify circulating miRNA profiles that serve as discriminative biomarkers between PsO and peripheral SpA (p-SpA). Materials and Methods: This exploratory study was conducted in two phases. In the preliminary discovery phase, plasma miRNA expression was analyzed using high-throughput microarrays in patients with p-SpA (modeled by peripheral psoriatic arthritis, n = 6), PsO (psoriasis without clinical arthritis, n = 3), and osteoarthritis (n = 3). In the validation phase, candidate miRNAs were verified using TaqMan-based qPCR in an independent cohort (n = 30) of various SpA phenotypes, categorized into those with peripheral arthritis (SpA-A) and those without (SpA-N). Results: The preliminary discovery phase identified altered levels of hsa-miR-140-5p, hsa-miR-192-5p, and hsa-miR-146a-5p among the groups; however, due to the small sample size, these initial findings required strict downstream verification. Functional enrichment analysis revealed that these candidate miRNAs primarily targeted the NF-κB signaling pathway (hsa04064) and Toll-like receptor (TLR) signaling pathway (hsa04620). The validation cohort confirmed that these three miRNAs could reliably differentiate SpA-A from SpA-N patients. Furthermore, bioinformatic mapping predicted that downstream targets, including TRAF6, IRAK1, and CXCL2, may be associated with these clinical phenotypes, serving as hypothesis-generating observations for future studies. Conclusions: Our findings suggest that specific plasma miRNA profiles are associated with the inflammatory pathways driving peripheral involvement in the SpA spectrum. These miRNAs represent potential biomarkers associated with peripheral arthritis in the SpA spectrum. While they offer new molecular insights into disease pathogenesis, their predictive value for identifying PsO patients at risk of developing overt arthritis requires confirmation in future longitudinal studies. Full article

Osteoarthritis (OA) is a disabling joint disease characterised by cartilage degradation, synovial inflammation, and subchondral bone remodelling. Furthermore, catabolic inflammatory processes as well as dysregulated cellular signalling and oxidative stress are central to OA pathogenesis. Despite its growing global burden, currently available therapies primarily provide symptomatic relief and fail to target underlying molecular mechanisms and halt disease progression. Cold atmospheric plasma (CAP), a partially ionised, non-thermal gas that generates controlled reactive oxygen and nitrogen species (RONS), has emerged as a promising therapeutic modality capable of modulating redox-sensitive signalling pathways. CAP has demonstrated the capacity to suppress pro-inflammatory cytokine expression, enhance antioxidant defence mechanisms, influence macrophage polarisation, and stimulate tissue repair processes in rheumatoid arthritis, diabetic and dermal wound healing models. However, its potential as a disease-modifying therapy for the treatment of OA is not yet fully understood and warrants further experimental investigation. This review explores current pre-clinical evidence from different disease models, which may have implications for the potential application of CAP as a therapeutic intervention for OA, either as a disease-modifying therapy or as an adjuvant therapy for intra-articular drug delivery. Furthermore, key translational challenges including plasma parameter standardisation, interactions with synovial fluid and optimisation of joint-specific delivery strategies are discussed, identifying gaps that require further experimental investigation. Collectively, the findings of this review highlight CAP as a promising multimodal therapy with translational potential for the treatment of OA warranting further experimental validation and may open innovative avenues for future research. Full article

Background: Mitochondrial bioenergetic dysregulation disrupts immune−metabolic homeostasis and promotes pro−inflammatory microenvironments in osteoarthritis (OA) synovitis. However, the mechanistic contributions of mitochondrial energy metabolism to synovitis pathogenesis in OA remain poorly defined. Methods: We analyzed mitochondrial energy metabolism−related genes (MEMRGs) in OA synovitis by integrating transcriptomic data from OA synovial tissues (GSE55235, GSE55457). LASSO regression and maximal clique centrality (MCC) algorithms were applied to identify hub genes, and single−cell RNA sequencing (GSE152805) was used to examine cell−type−specific expression patterns. Functional validation was performed in IRS2−knockdown THP−1 macrophages. Results: We identified 22 mitochondrial energy metabolism−related differentially expressed genes (MEMR−DEGs), which were enriched in the AMPK signaling, glucagon signaling, and insulin signaling pathways. Four hub genes (FOXO3, FASN, PTGS2, IRS2) were identified, and their expression was negatively correlated with synovial macrophage infiltration. Single−cell RNA sequencing revealed that IRS2 was specifically upregulated in a synovial macrophage cluster. Functional studies in IRS2−knockdown THP−1 macrophages demonstrated that IRS2 deficiency impaired IL−4−induced M2 macrophage polarization and reduced mitochondrial membrane potential and ATP synthesis, which was mediated by the suppression of the AKT/FOXO1 signaling. Conclusions: IRS2 potentially influences mitochondrial energy metabolism, as evidenced by the maintenance of mitochondrial membrane potential and ATP synthesis, via the AKT/FOXO1 signaling pathways to maintain synovial macrophage M2 polarization homeostasis. These findings provide novel molecular targets for addressing immune−metabolic pathways in OA therapy. Full article

Background: Osteoarthritis (OA) is a heterogeneous joint disease characterized by cartilage degeneration. The interplay between extracellular matrix (ECM) remodeling, endoplasmic reticulum (ER) stress, and inflammatory signaling in OA pathogenesis remains incompletely understood. This study aimed to identify robust diagnostic biomarkers and explore the mechanistic convergence of key genes in OA cartilage through an integrated transcriptomic framework. Methods: Three independent cartilage transcriptomic datasets (GSE285234, GSE287861, GSE289464) were integrated after ComBat batch correction. Differentially expressed genes (DEGs) were identified using limma, followed by ORA and GSEA for functional enrichment. LASSO logistic regression identified hub genes for a diagnostic model and nomogram, validated by leave-one-out cross-validation (LOOCV). Consensus clustering stratified OA samples into molecular subtypes. Single-cell RNA-sequencing (scRNA-seq) data (GSE169454, GSE220243) were used to validate cell-type-specific expression. Virtual gene knockout (scTenifoldKnk) and pathway analysis inferred downstream functional consequences. Results: Fifty-eight DEGs (predominantly downregulated) were enriched in ECM and ER protein processing pathways. Six hub genes (EIF2S1, GANAB, STT3A, XBP1, MGP, PMP22) showed robust selection stability. The diagnostic model achieved a LOOCV AUC of 0.769, a well-calibrated nomogram, and superior net benefit. Unsupervised clustering revealed two OA subtypes with divergent unfolded protein response (UPR) and TGF-β pathway activities. scRNA-seq confirmed hub gene expression in chondrocytes and other joint microenvironment cells. Notably, virtual knockout of five hub genes convergently perturbed IL-17, NF-κB, and chemokine signaling pathways. Conclusions: This study identified and validated a six-gene signature reflecting ECM-ER-inflammatory crosstalk in OA cartilage. The convergent perturbation of inflammatory pathways by functionally distinct hub genes reveals a mechanistic core that may serve as a diagnostic panel and a platform for targeted therapeutic investigation in OA. Full article

Osteoarthritis (OA) is a highly prevalent joint disorder traditionally considered a consequence of mechanical cartilage wear; however, it is now recognized as a complex, multifactorial disease driven by interconnected molecular and cellular mechanisms. This narrative review synthesizes current knowledge on key pathogenic pathways underlying OA progression, with a focus on inflammatory signaling, subchondral bone remodeling, and dysregulation of mineral metabolism. Chronic low-grade inflammation promotes catabolic responses in chondrocytes and contributes to cartilage degradation. In addition, obesity influences OA pathogenesis through both biomechanical loading and adipokine-mediated inflammatory mechanisms. Alterations in the receptor activator of nuclear factor kappa-B/receptor activator of nuclear factor kappa-B ligand/osteoprotegerin (RANK/RANKL/OPG) axis disrupt bone homeostasis and promote pathological subchondral remodeling, while imbalances in inorganic phosphate metabolism contribute to crystal deposition and further joint damage. These processes interact synergistically, driving disease progression. Current therapeutic strategies remain largely symptomatic and do not adequately target underlying molecular drivers. A deeper understanding of these mechanisms may facilitate the development of disease-modifying therapies. Full article

The homeostasis of bone metabolism relies on the precise synergistic regulation among osteoblasts, osteoclasts, and osteocytes. Disruption of this regulatory network underlies the pathogenesis of osteoporosis, osteonecrosis, osteoarthritis, and other metabolic bone diseases. As an emerging mode of intercellular communication, mitochondrial transport delivers functional mitochondria to impaired cells, thereby reshaping cellular metabolism, alleviating oxidative stress, and restoring cell function. It thus plays an irreplaceable role in maintaining bone metabolic homeostasis. However, studies focusing on mitochondrial transport in bone metabolism are lacking, and the underlying molecular mechanisms have not been elucidated. For metabolic bone diseases, many bottlenecks exist in clinical translation. This review comprehensively summarizes the core molecular mechanism involved in mitochondrial transport, its regulatory functions in bone metabolism homeostasis, its association with metabolic bone diseases, and intervention strategies targeting mitochondrial transport. We aim to provide novel insights into the mechanism and targeted therapy of metabolic bone diseases. Full article

Background: Yes-associated protein 1 (YAP1), a key effector of the Hippo signaling pathway and mechanosensitive transcriptional coactivator, plays a complex role in osteoarthritis (OA) and cartilage regeneration. While YAP1 is essential for tissue homeostasis, its dysregulation has been implicated in both inflammatory and degenerative joint pathologies. However, its precise function remains ambiguous. Methods: We silenced YAP1 with small interfering RNA (siYAP1) in two human-cell-based models relevant to OA pathogenesis and cartilage repair: (1) IL-1β (10 ng/mL)-stimulated articular chondrocytes in monolayer and pellet cultures, and (2) TGF-β1 (10 ng/mL)-induced chondrogenesis in MSC pellet cultures. Outcome measures comprised YAP1 nuclear localization; inflammatory/catabolic markers in chondrocytes (IL6, IL8, ADAMTS5, MMP13); and, in MSC pellets, chondrogenic or hypertrophic markers (COL2A1, ACAN, RUNX2, MMP13, COL10A1) together with glycosaminoglycan (GAG) deposition. Statistical significance was assessed using an ANOVA or Friedman test with post hoc correction (Tukey or Dunn’s test, respectively); p < 0.05 was considered significant. Results: In human chondrocytes, siYAP1 reduced IL-1β-induced nuclear YAP1 localization and suppressed pro-inflammatory mediators IL6 and IL8, indicating an anti-inflammatory effect. YAP1 silencing also downregulated ADAMTS5 expression in 2D monolayers but not in 3D pellet cultures, suggesting reduced regulatory influence in the three-dimensional environment. Notably, MMP13 expression was paradoxically increased following YAP1 knockdown, underscoring the complexity of YAP1’s role in catabolic regulation. In MSC chondrogenesis, siYAP1 enhanced TGF-β1-induced chondrogenesis by increasing COL2A1 and ACAN expression and promoting GAG deposition on day 21. Additionally, it reduced hypertrophic markers RUNX2 and MMP13 on day 7, though COL10A1 remained elevated compared to negative siRNA, indicating only partial suppression of hypertrophic differentiation. Nuclear YAP1 levels were increased by day 21 despite reduced mRNA, suggesting post-transcriptional regulation or enhanced nuclear translocation. Conclusions: These findings demonstrate that YAP1 knockdown exerts context-specific anti-inflammatory and pro-chondrogenic effects while partially mitigating hypertrophy. However, divergent outcomes, namely elevated MMP13 in chondrocytes and upregulated COL10A1 in MSCs, indicate that YAP1 silencing does not uniformly suppress inflammation or hypertrophy. YAP1 represents a potential therapeutic target for OA, but its modulation requires careful consideration of cellular context, siRNA delivery method, and timing to optimize outcomes for cartilage repair and joint preservation. Full article

Background: Reports on subchondral bone mechano-structure in individuals with various stages of knee osteoarthritis (KOA) are limited and often conflicting in contemporary literature. Our study aimed to assess differences in subchondral trabecular bone mechano-structure across late KOA stages in a homogenous group of patients with varus malalignment (confirmed by negative hip-knee-ankle-angle values). Methods: This retrospective cross-sectional study included micro-computed tomography scanning and Vickers micro-hardness testing of 90 bone samples (30 femoral and 60 tibial) collected from 15 adult patients with primary KOA undergoing total knee arthroplasty (TKA). The Kellgren–Lawrence grading system was used to assess the severity of KOA lesions in the included individuals, and bone samples were divided into the following groups: moderate KOA (42 samples from seven patients, age: 70 ± 7 years, females: 3/7) and end-stage KOA (48 samples from eight patients, age: 70 ± 6 years, females: 5/8). Results: Our data revealed site-specific sclerotic alterations in subchondral trabecular bone mechano-structure (thicker trabeculae, coupled with higher bone mineral content and increased bone micro-hardness) in individuals with end-stage KOA compared to moderate KOA, supporting its role in KOA pathogenesis beyond the exclusive cartilage degeneration effect. Our data also revealed that most heterogeneous subchondral trabecular mechano-structure was present in bone samples obtained from the medial part of the tibial and femoral condyle, revealing the substantial effect of mechanical loading during varus knee malalignment. Conclusions: Observed site-specific alterations in subchondral bone mechano-structure in individuals with end-stage KOA supported the role of subchondral sclerosis in primary KOA pathogenesis beyond its exclusive effect on cartilage degeneration. Full article

Most high-tech drugs and tissue engineering products based on human chondrocytes currently available on the market are aimed at restoring traumatic damage to cartilage tissue. However, in the presence of inflammation, their regenerative potential is significantly reduced, which limits their use in patients with osteoarthritis—one of the most common degenerative and inflammatory joint pathologies. The central element of the pathogenesis of osteoarthritis is inflammation—not classical acute inflammation, but rather chronic low-grade inflammation, primarily mediated by mechanisms of the innate immune response. Therefore, a key challenge is to enhance the anti-inflammatory effectiveness of cell-based drugs to broaden their indications to include degenerative diseases such as osteoarthritis and arthrosis. In recent years, cell-based drugs using stem cells, including mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and stromal vascular fraction (SVF) cells, have been actively studied. Despite their confirmed safety in inflammatory processes, meta-analyses of clinical trials show limited effectiveness in improving symptoms and MRI data in the treatment of osteoarthritis. A promising direction appears to be the development of combined cell-based drugs that combine MSCs with M2-polarized macrophages; however, data on their clinical effectiveness are still insufficient. This review explores key cellular effectors of inflammation and its molecular mechanisms, potential strategies for creating tissue engineering products that possess not only regenerative but also pronounced anti-inflammatory effects. The development of such products will expand their application in the treatment of inflammatory-degenerative joint diseases. Full article

Background/Objectives: Osteoarthritis (OA) is an age-related degenerative joint disease whose pathogenic mechanisms remain poorly understood. Experimental evidence implicates dysregulated mechanotransduction mediated by Piezo1 and TRPV4 channels, but how their interaction with inflammation may drive pathogenic state transitions remains unknown. Here, we aimed to study whether a Piezo1–TRPV4 network can intrinsically produce distinct stable physiological and pathological regimes. Methods: Based on literature data, we developed a nonlinear dynamical model describing closed-loop interactions involving Piezo1, TRPV4, and inflammation. The system was translated into a set of ordinary differential equations and studied using stability and bifurcation analysis. Results: Computational analysis revealed bistability, allowing the system to shift from a physiological to a pathogenic regime in response to specific stimuli. Critical bifurcation parameters were linked to Piezo1 and inflammation, suggesting that the bidirectional interaction between these two components represents a key node for interventions aimed at preventing or reversing transitions from non-pathogenic to pathogenic states. Conclusions: Our results suggest that OA pathogenesis may emerge from the intrinsic nonlinear dynamics of Piezo1/TRPV4/inflammation interactions. Bifurcation analysis indicates the sensitivity of TRPV4 to the inhibitory effect of Piezo1 as a key target for preventing or reversing pathogenic state transitions. Further investigations in preclinical and clinical settings are warranted to validate the model. Full article

Hyperuricemia influences several aspects of the immune system. It enhances cytokine production by monocytes and activates neutrophils and natural killer cells. Within the adaptive immune system, hyperuricemia enhances antigen presentation, skews T helper cell differentiation toward the Th17 lineage and may also activate B cells. Beyond its established role in the pathogenesis of gout, hyperuricemia may therefore contribute to other rheumatic diseases. In this review, we summarize current evidence on the role of hyperuricemia in osteoarthritis, psoriatic arthritis, axial spondylarthritis, rheumatoid arthritis, systemic sclerosis, primary Sjögren’s disease and systemic lupus erythematosus. Available data do not support a causal role for hyperuricemia in the disease onset of osteoarthritis or rheumatoid arthritis. In contrast, hyperuricemia is associated with the development of psoriatic arthritis and may be linked to a more severe disease course. Small, predominantly cross-sectional studies further suggest a potentially adverse role of hyperuricemia in systemic sclerosis, Sjögren’s disease, and systemic lupus erythematosus. Across several rheumatic diseases, hyperuricemia is associated with cardiovascular disease, renal dysfunction and interstitial lung disease. However, both mechanistic and causal evidence remain limited, underscoring the need for more studies. Full article

Osteoarthritis (OA) is a complex degenerative joint disease for which early diagnosis and clear molecular characterization remain limited. DNA methylation has been increasingly recognized as an important regulatory factor in OA pathogenesis. In this study, we proposed an integrative computational framework combining statistical analysis, machine learning, deep learning, and functional genomics to identify and validate OA-associated genes and methylation biomarkers for diagnostic and biological interpretation. Candidate CpG sites were obtained using two complementary strategies: differential methylation analysis and selection of loci located near transcription start sites of previously reported OA-related genes. Key features were further refined using support vector machine recursive feature elimination and random forest algorithms. Based on the selected loci, we developed a feature-fusion diagnostic model that combines Transformer and convolutional neural networks with adaptive weighting to capture both global dependency structures and local methylation patterns. A panel of 220 methylation sites demonstrated stable and reproducible diagnostic performance in an independent cohort. Functional annotation and pathway analysis highlighted several established OA-associated genes, including TGFBR2, SMAD3, PPARG, and MAPK3, and suggested INHBB as a potential novel effector gene, with additional support for AMH and INHBE involvement. Overall, this study presents a robust methylation-based framework for identifying key OA-associated genes and provides new insights into the epigenetic mechanisms underlying OA. Full article

Temporomandibular joint osteoarthritis (TMJOA) is a degenerative disease characterized by progressive cartilage destruction, and chondrocyte apoptosis plays a critical role in TMJOA progression. As chondrocytes reside in an avascular microenvironment inside the cartilage matrix, energy production via glycolysis is crucial for their survival. This study investigated the role of the key glycolytic enzyme Hexokinase 2 (HK2) in TMJOA pathogenesis and the therapeutic potential of dental pulp stem cell-derived extracellular vesicles (DPSC-EVs). In a rat experimental TMJOA model induced by monosodium iodoacetate (MIA) intra-articular injection, we observed a significantly decreased expression of HK2 along with cartilage matrix degradation. In the in vitro study, MIA induced chondrocyte apoptosis with caspase-3 activation, accompanied by impaired glycolytic function. Intervention with DPSC-EVs effectively rescued the expression of HK2 within chondrocytes, leading to a notable restoration of cellular glycolysis. Consequently, DPSC-EV treatment markedly attenuated the progression of TMJOA by reducing chondrocyte apoptosis and improved cartilage integrity. Our findings demonstrated that DPSC-EVs represent a promising cell-free therapeutic strategy for TMJOA, exerting their protective effects by targeting HK2, thereby preserving chondrocyte viability and attenuating osteoarthritis development. Full article

Background/Objectives: Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by persistent synovial inflammation and vascular abnormalities. Emerging evidence suggests that dysbiosis of the microbiome contributes to the pathogenesis of this disease, while seasonal and meteorological variations represent significant factors influencing microbial community dynamics. However, the specific pathological mechanisms mediated by microbial populations within knee joint effusions of RA patients remain poorly elucidated. The present study employs 16S rRNA high-throughput sequencing technology to characterize seasonal variation patterns affecting microbial communities in knee joint effusions of RA patients and to investigate the relationship between microbial community structures and climatic lag effects. Methods: Microbial communities in knee joint effusion samples obtained from RA patients were analyzed using 16S rRNA high-throughput sequencing methodologies. A Distributed Lag Non-linear Model (DLNM) was applied to quantify the delayed effects of climatic variables on microbial community composition. The correlation patterns between meteorological parameters and community structure were elucidated through the integration of ridge regression and redundancy analysis (RDA). Preliminary identification of potential biomarkers was conducted using random forest algorithms. Results: According to research findings, the microbial composition of knee joint effusions in RA patients shows seasonal fluctuation patterns that are compatible with those seen in RA patients, even though there is no discernible seasonal change in β-diversity. Compared with samples obtained during other seasons, spring specimens exhibited significantly elevated relative abundances of both beneficial microorganisms and opportunistic pathogenic taxa. Random forest modeling identified Escherichia-Shigella and Curtobacterium as preliminary candidate biomarkers; however, external validation is required to establish their specificity as disease indicators. Further analysis revealed that although short-term meteorological fluctuations exert minimal influence on overall microbial diversity, specific alterations in mean wind speed (MWS) and relative humidity (RH) drive compositional changes in the microbial community, manifested as rapid responses from dominant bacterial taxa and compensatory buffering effects from rare taxa. Conclusions: This study suggests that the synovial cavity microbiota in RA patients may exhibit seasonal variation patterns that are statistically associated with environmental parameters, particularly humidity and temperature. Due to the inherent limitations of the cross-sectional study design, the preliminary candidate biomarkers identified herein require validation through external cohorts. Additional investigations incorporating healthy controls and osteoarthritis (OA) cohorts are necessary to confirm specificity and to elucidate the therapeutic potential of these microbial targets for RA microbiome interventions. Currently, insufficient evidence exists to establish causal relationships among microbial populations, joint pathology, and climatic factors. Longitudinal cohort studies are imperative to validate the temporal dynamics and clinical significance of these associations. Full article