Osteoarthritis: pathogenic signaling pathways and therapeutic targets

Bioinformatic identification of important roles of COL1A1 and TNFRSF12A in cartilage injury and osteoporosis

OBJECTIVE

The aim of this study was to identify the key regulatory mechanisms of cartilage injury and osteoporosis through bioinformatics methods, and to provide a new theoretical basis and molecular targets for the diagnosis and treatment of the disease.

METHODS

Microarray data for cartilage injury (GSE129147) and osteoporosis (GSE230665) were first downloaded from the GEO database. Differential expression analysis was applied to identify genes that were significantly up-or down-regulated in the cartilage injury and osteoporosis samples. These genes were subjected to GO enrichment analysis and KEGG pathway analysis. In addition, we employed SVA and RRA methods to merge the two sets of data, eliminating batch effects and enhancing the statistical power of the analysis. Through WGCNA, we identified gene modules that were closely associated with disease phenotypes and then screened for key genes that intersected with differentially expressed genes. The diagnostic value of these genes as potential biomarkers was evaluated by ROC analysis. Moreover, we performed an immune infiltration analysis to explore the correlation between these core genes and immune cell infiltration.

RESULTS

We performed GO enrichment analysis and KEGG pathway analysis of genes significantly up-or down-regulated in cartilage injury and osteoporosis samples. Important biological processes, cellular components and molecular functions, and key metabolic or signaling pathways associated with osteoporosis and cartilage injury were identified. Through WGCNA, we identified gene modules that were closely associated with the disease phenotype, from which we then screened for key genes that intersected with differentially expressed genes. Ultimately, we focused on two identified core genes, COL1A1 and TNFRSF12A, and assessed the diagnostic value of these genes as potential biomarkers by ROC analysis. Meanwhile, GSVA provided an in-depth view of the role of these genes in disease-specific biological pathways. Immune infiltration analysis further revealed the possible key role of COL1A1 and TNFRSF12A in regulating immune cell infiltration in osteoporosis and cartilage injury.

CONCLUSION

COL1A1 and TNFRSF12A as key regulatory molecules in osteoporosis and cartilage injury.

Selenium nanozyme-crosslinked composite hydrogel for promoting cartilage regeneration in osteoarthritis via an integrated 'outside-in' and 'inside-out' strategy

Osteoarthritis (OA), a degenerative joint disease, is characterized by chondrocyte senescence, extracellular matrix (ECM) degradation, and chronic inflammation, with limited regenerative capacity. Current therapies primarily provide symptom relief, therefore highlighting the need for more effective strategies to address OA's multifactorial pathology. This study introduces an innovative selenium nanozyme-crosslinked injectable composite hydrogel (Se/PRP-OGel), which combines selenium nanoparticles (SeNPs) with platelet-rich plasma (PRP) in a biocompatible oxidized chondroitin sulfate-gelatin scaffold (OGel), to address OA through an integrated "outside-in" and "inside-out" strategy. The "outside-in" strategy utilizes SeNPs to scavenge reactive oxygen species (ROS), alleviate oxidative stress, and restore redox balance, thereby reducing extracellular damage and modulating inflammation in the OA microenvironment. Concurrently, the "inside-out" strategy utilizes PRP's bioactive growth factors (e.g., TGF-β, IGF, FGF) to rejuvenate senescent chondrocytes, stimulate proliferation, and enhance ECM synthesis, creating a regenerative microenvironment. The results showed that Se/PRP-OGel demonstrated excellent biocompatibility, reduced ROS levels, mitigated chondrocyte senescence, and balanced ECM homeostasis. Moreover, it promoted cartilage repair, pain relief, and functional restoration in an OA rat model. This dual approach interrupts OA's degenerative cycle and fosters cartilage regeneration, providing a groundbreaking solution for effective cartilage regeneration and OA treatment.

RNA methylation: A new perspective in osteoarthritis research

Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by cartilage degradation, osteophyte formation, and joint dysfunction, significantly impairing the quality of life in the elderly population. Recently, RNA modifications, as a dynamic and reversible epigenetic modification, have emerged as critical players in the onset and progression of OA. This review systematically summarizes the major types of RNA modifications involved in OA, including N6-methyladenosine (m6A), 5-methylcytosine (m5C), and 7-methylguanosine (m7G), and explores their roles in regulating chondrocyte autophagy, inflammatory responses, and key signaling pathways. with a primary focus on RNA methylation. Special emphasis is placed on the dynamic regulatory functions of key methyltransferases (e.g., METTL3, FTO, WTAP) and their potential contributions to OA pathogenesis. Furthermore, we address current research hotspots and controversies in the field, proposing future research directions, such as leveraging single-cell sequencing to decipher dynamic RNA modification changes during OA progression and uncovering the cooperative networks among various RNA modifications. Advancing our understanding of the biological roles and mechanisms of RNA modifications holds promise for innovative strategies in the early diagnosis, disease stratification, and targeted therapy of OA.

Zn2+-driven metformin conjugated with siRNA attenuates osteoarthritis progression by inhibiting NF-κB signaling and activating autophagy

Osteoarthritis (OA) is a type of joint disease that influences millions of individuals. Regrettably, effective treatment for OA is currently unavailable. The challenge lies in the deep location of chondrocytes within the dense cartilage matrix that hinders the delivery and efficiency of clinical OA drugs. To overcome this obstacle, the present study proposed a hybrid nanodrug by Zinc(II) metal-drug coordination-driven self-assembly as highly efficient delivery system. This nano-assembly formulations possessed the ability to deliver two types of drugs, namely metformin (Met) and therapeutic genes (p65 siRNA). Results showed that this nano-assembly not only exhibited positive charge-driven anchoring to the cartilage matrix and effective drug delivery capacity, but also synergistically inhibited NF-κB activity and activates autophagy of OA chondrocytes, thus safeguarding the cartilage. The successful achievement of this project not only contribute to the advancement of research on bio-nanomaterials for treating OA, but also establish a robust theoretical foundation for realizing promising and functional integration of nanomedicine targeting OA.

Physical exercise ameliorates pain, mood alterations and neuroinflammation in a murine model of osteoarthritis

Osteoarthritis (OA) is largely associated with chronic pain, and it is a social and economic problem worldwide. OA pain can lead to psychiatric symptom onset, such as anxiety and depression. Emerging evidence suggest neuroinflammation as a common denominator between OA pain and mood disorders. OA pain pharmacological strategies are often ineffective or cause side effects, therefore, identifying novel non-pharmacological therapeutic approaches, like diet and exercise, could be important. Here, using 8-month-old male C57BL/6 J mice, we evaluated the effect of regular physical exercise on OA pain and related comorbidities. OA was induced by monoiodoacetate-(MIA) administration in knee joint in mice that had undergone physical exercise-(PE) or a sedentary lifestyle-(SL) for two months. After OA induction, mice continued the exercise/not-exercise protocol for another month and subsequently all animals were sacrificed. An in-depth biochemical evaluation (RT-qPCR) was performed at the level of the knee joint, sciatic nerve, dorsal root ganglia, spinal cord and brain areas (brainstem, hypothalamus and hippocampus) and myenteric plexus to evaluate the effect of both OA and exercise on (neuro)inflammation in regions involved in pain and mood regulation. Throughout the experimental protocol, pain-like behavior and motor performance were evaluated, and before sacrifice, mood alterations and metabolic changes were also assessed. Our results showed that OA_SL mice exhibit painful symptoms and mood disturbances. These alterations were also associated with (neuro)inflammation. PE mitigates pain-like behavior and mood alterations and reduces (neuro)inflammation, suggesting that a healthy and active lifestyle may have a positive impact in preventing and/or counteracting OA onset and related comorbidities.

Chitosan nanovectors for siRNA delivery: New horizons for nonviral gene therapy

The growing interest in RNA-based therapeutics has positioned small interfering RNA (siRNA) as a promising tool for gene silencing with high specificity and efficacy. However, the successful clinical application of siRNA therapies requires efficient delivery systems to overcome extracellular and intracellular barriers. Chitosan, a naturally derived polysaccharide, has gained significant attention as a non-viral vector due to its biodegradability, biocompatibility, mucoadhesive properties, and capacity to enhance cellular uptake. These attributes make chitosan an attractive alternative to lipid-based nanoparticles, which currently dominate siRNA delivery platforms. Recent advancements in chitosan-based nanoformulations, including chemical modifications and functionalization strategies, have improved siRNA stability, targeting efficiency, and transfection potential, addressing key limitations such as low bioavailability and immunogenicity. Despite these advances, challenges remain in achieving optimal release kinetics, scalability, and consistent therapeutic efficacy. Future research efforts will focus on engineering chitosan derivatives with enhanced physicochemical properties, integrating multifunctional nanocarriers, and refining formulation strategies to bridge the gap between preclinical research and clinical translation. The continued development of chitosan-based siRNA therapeutics holds significant potential for advancing precision medicine and expanding treatment options for a variety of diseases, including cancer, metabolic disorders, and inflammatory conditions.

CRISPR/CasRx-mediated RNA knockdown targeting β-catenin and Ihh signaling alleviates osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease. Currently, OA is incurable. Abnormal activation of canonical Wnt/β-catenin or Indian hedgehog (Ihh) signaling could lead to OA development and progression. This study aimed to determine if targeting β-catenin and Ihh signaling could yield an effective therapeutic intervention for OA disease. CRISPR/CasRx is a new RNA interference tool that can precisely and efficiently cleave single-strand RNAs. In this study, we screened CRISPR-derived RNA (crRNA) targeting Ctnnb1 and Smo in vitro and selected two optimal crRNAs for each gene. CasRx-mediated Ctnnb1 and Smo knockdown showed high efficiency and specificity with no obvious off-target effects in vitro. We then performed intra-articular injection of selected crRNAs driven by the adeno-associated virus into an OA mouse model. Micro-CT, histological, and histomorphometric analyses were conducted to evaluate the efficacy of CasRx approach on OA treatment. We found that the knockdown of Ctnnb1 and Smo decelerated pathological damage in the keen joint of the experimental OA mouse model. Our findings suggest that CasRx-mediated Ctnnb1 and Smo knockdown could be a potential strategy for OA treatment.

Blocking the LRH-1/LCN2 axis by ML-180, an LRH-1 inverse agonist, ameliorates osteoarthritis via inhibiting the MAPK pathway

Osteoarthritis (OA) is a chronic and degenerative disease marked by inflammation and extracellular matrix (ECM) degeneration, contributing to synovial inflammation and cartilage destruction. Accumulating evidence has demonstrated that Liver receptor homolog-1 (LRH-1), an orphan nuclear receptor, mediates inflammatory response. However, there is a lack of evidence regarding the regulatory role of LRH-1 in OA pathogenesis. In this study, we confirmed that chondrocytes expressed LRH-1, and observed its upregulation in both IL-1β-treated chondrocytes and cartilage of destabilization of the medial meniscus (DMM)-operated mice. Overexpression of LRH-1 promoted inflammation and dysregulation of ECM metabolism in IL-1β-induced chondrocytes, reversed by inhibition of LRH-1 with ML-180 or gene silencing to protect chondrocytes. Moreover, ML-180 treatment in vivo improved the deteriorated OA phenotypes in mouse models, alleviating OA development. Mechanistically, RNA sequencing revealed that Lipocalin-2 (LCN2), a member of the lipocalin family associated with inflammation, is located downstream of LRH-1 and is positively regulated by it. Furthermore, the LRH-1/LCN2 axis mainly relied on activating the mitogen-activated protein kinase (MAPK) signaling pathway to promote inflammation and dysregulation of ECM metabolism, ultimately damaging chondrocytes. Our findings demonstrate that LRH-1 positively modulates LCN2,activating the MAPK pathway, indicating that targeting the LRH-1/LCN2/MAPK axis may represent a potential therapeutic strategy for OA.

Modulating systemic anti-inflammatory response mitigates osteoarthritis progression and associated pain after low-dose radiotherapy

Osteoarthritis (OA) is a degenerative joint disease, often accompanied by inflammation. It has reported that low-dose radiotherapy (LDRT) has anti-inflammatory effect for benign pathologies and has been used for clinical treatment of OA in some European regions. However, the underlying molecular mechanisms of LDRT alleviating OA are only poorly understood. Herein, it is verified that LDRT improved the locomotor ability of OA rats, increased the locomotor distance and speed in the in vivo experiments. Moreover, LDRT decreased the degree of cartilage damage, attenuated the synovial inflammation, and promoted macrophage polarization towards M2 type. For the in vitro experiments, LDRT promoted macrophage polarization towards M2-type, which enhanced cell growth and adjusted the inflammatory factors in chondrocyte. Additionally, it is found LDRT could ameliorate OA pain through inhibiting spinal cord inflammation. Take together, our study suggests that LDRT could ameliorate OA symptoms and relieve OA-related pain by exerting its anti-inflammatory effect.

Asarum heterotropoides F. schmidt attenuates osteoarthritis via multi-target anti-inflammatory actions: A network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Asarum heterotropoides F. Schmidt (ARR) has a well-documented history of traditional use in East Asia for musculoskeletal pain disorders, including osteoarthritis (OA), attributed to its significant anti-inflammatory properties. While preliminary studies suggest potential anti-inflammatory effects, conclusive evidence regarding the ability of ARRs to modulate the multiple inflammatory pathologies involved in OA pathogenesis is currently lacking.

AIM OF THE STUDY

This study aimed to experimentally evaluate the effects of ARR extract on pain, cartilage integrity, and inflammatory responses using in vitro and in vivo models relevant to OA, guided by initial computational predictions.

MATERIALS AND METHODS

Active ingredients of ARRs were retrieved from four databases and screened using SwissADME for ADME predictions. Disease targets were combined with OA-related genes from GEO microarray database. The intersecting genes underwent protein-protein interaction construction, GO, and KEGG enrichment analysis. A compound-target-pathway network was constructed using Cytoscape and was validated via molecular docking. Pain-relieving, functional, and chondroprotective effects were assessed in vivo using acetic acid-induced peripheral pain mice and monosodium iodoacetate (MIA)-induced osteoarthritis rat models. Furthermore, anti-inflammatory properties were explored by evaluating serum cartilage tissue and lipopolysaccharide-stimulated RAW 264.7 cells.

RESULTS

Network pharmacology analysis elucidated five principal active constituents of ARR (cryptopine, 5-[2-(2-hydroxyphenyl)ethyl]-2,3-dimethoxy-phenol, 5-[2-(3-hydroxyphenyl)ethyl]-2-methoxybenzene-1,3-diol, naringenin, resorstatin) alongside 22 putative herbal targets. Molecular docking analyses revealed strong binding affinities (-8 to -9.4 kcal/mol) of these constituents towards principal target proteins. Functional GO and KEGG enrichment analyses indicated that ARR exerts its effects potentially involving pathways associated with cancer, fluid shear stress, and atherosclerosis. In vivo assessments demonstrated significant mitigation of pain, functional deficits, and cartilage degradation by ARR within an MIA-induced osteoarthritis model. Molecular dynamics simulations validated stable interactions between the primary compounds and their designated target proteins. The therapeutic efficacy of ARR was characterized by dose-dependent suppression of diverse inflammatory mediators (IL-1β, IL-6, TNF-α), matrix metalloproteinases (MMP-1, -3, -8, -13), and signaling pathways including CCND1, CDK2, IKBKB, HIF1A, BDKRB1, SIRT1, MAPK8, and NLRP3 within both RAW264.7 cells and articular cartilage tissue.

CONCLUSIONS

This investigation demonstrates that ARR exerts pain alleviation, functional enhancement, and chondroprotective effects in osteoarthritis via multi-target anti-inflammatory actions. Integrating network pharmacology, molecular docking, animal models, and cellular experiments, this study comprehensively elucidated the multifaceted anti-inflammatory mechanisms attributed to ARR. These findings collectively provide a crucial foundation for understanding the potential therapeutic efficacy and operative mechanisms of ARR for osteoarthritis management.

Echinatin inhibits osteoarthritis through the NF-κB signaling pathway

Osteoarthritis (OA) is currently the most common degenerative joint disease in China and even worldwide and is the leading cause of disability in the elderly population. So far, due to an insufficient understanding of the pathogenesis and etiology of the disease, there is still no effective targeted treatment for early OA. Pro-inflammatory cytokine interleukin-1 is an important inflammatory mediator secreted in early OA, and IL-1β plays a crucial role in the pathogenesis of OA, affecting chondrocytes and the extracellular matrix of CARTILAGE. Echinatin has been used for years as a health supplement, retaining its antioxidant, anti-inflammatory, and autophagy-promoting effects. However, whether echinatin has inhibitory effects on OA is still unknown. In this study, we used an in vitro OA model of chondrocytes induced by IL-1β and an in vivo OA model of rats induced by anterior cruciate ligament transection (ACLT), and through experiments such as western blotting and IHC, we demonstrated that echinatin can be used as a novel drug for treating OA. Mechanistically, we found that echinatin inhibits the activity of chondrocytes induced by IL-1β through the NF-kB signaling pathway. This study can provide more effective treatment options for OA patients and further diagnostic and therapeutic methods for clinical treatment.

MXene-Based Photothermal-Responsive Injectable Hydrogel Microsphere Modulates Physicochemical Microenvironment to Alleviate Osteoarthritis

Osteoarthritis (OA) is a physical lubrication microenvironment-inadequate disease accompanied by a sustained chronic chemical inflammation microenvironment and the progression of articular cartilage destruction. Despite the promising OA treatment outcomes observed in the enhancement of lubrication inspired by ball bearings to reduce friction and support loads, the therapeutic effect of near-infrared (NIR) irradiation-based photothermal-responsive controlled release "smart hydrogel microspheres" on OA remains unclear. Here, we prepared MXene/NIPIAM-based photothermal-responsive injectable hydrogel microspheres encapsulating diclofenac sodium using a microfluidic system. Consequently, NIR irradiation-based photothermal-responsive controlled release "smart hydrogel microspheres" demonstrate beneficial therapeutic effects in the treatment of OA by modulating the physical lubrication and chemical chronic inflammation microenvironment, laying the foundation for the application of smart hydrogel microsphere delivery systems loaded with bioactive factors (including agents, cells, and factors) to regulate multiple pathological microenvironments in regenerative medicine.

Advance in candidate genes in mandibular retrognathism: A systematic review

OBJECTIVE

This research aims to dissect the polygenic nature of non-syndromic mandibular retrognathism (MR) and to better understand the genetic underpinnings of MR, with a particular focus on the role of ethnic diversity in influencing genetic predispositions.

METHODS

A comprehensive systematic review was conducted on MR. Electronic databases such as PubMed and Google Scholar were employed, utilizing terms like 'mandibular', 'retrognathism', 'gene', and 'genetic'. This study strictly adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework.

RESULTS

Ten genetic studies were identified that satisfied the eligibility criteria, involving 1010 participants. Variations in candidate genes were reported across different populations, including myosin 1 H (MYO1H), matrilin 1 (MATN1), a disintegrin and metalloproteinase with thrombospondin motifs 9 (ADAMTS9), bone morphogenetic protein 2 (BMP2), parathyroid hormone (PTH), the vitamin-D related genes: vitamin D receptor (VDR), cytochrome P450 family 24 subfamily A member 1 (CYP24A1), and cytochrome P450 family 27 subfamily B member 1 (CYP27B1), collagen type II alpha 1 chain (COL2A1), transforming growth factor-β (TGF-β), TGF-β receptor 2 (TGFBR2), epidermal growth factor (EGF), and EGF receptor gene (EGFR).

CONCLUSION

These findings shed light on the role of genetic factors in MR. Future studies should adopt a multicentric approach to expand sample sizes and enhance the analysis of genetic variants associated with MR.

Sex-stratified osteochondral organ-on-chip model reveals sex-specific responses to inflammatory stimulation

Osteoarthritis (OA) is a musculoskeletal degenerative disease characterized by alterations in cartilage and subchondral bone leading to impaired joint function. OA disproportionally affects females more than males, yet the molecular mechanisms underlying these biological sex differences remain elusive. Current therapeutic strategies to halt the progression of OA are still lacking, in part due to the limited predictive potential of standard models which often do not account for sex disparities. Herein, an organ-on-chip microfluidic platform was developed to model the osteochondral unit, composed of adjacent bone and cartilage culture chambers, and capture sex-specific hallmarks of OA. Sex-stratified human primary chondrocytes and osteoblasts were compartmentalized within biomimetic hydrogels emulating the bone-cartilage interface, which were subjected to inflammatory triggers to mimic the onset of OA. We confirmed that interleukin-1β and Tumor Necrosis Factor-α stimulation triggered upregulation of pro-inflammatory cytokines and matrix metalloproteinases related genes in all donors, with marginal trends for increased expression in female cells. In addition, metabolic labeling coupled with confocal imaging revealed that inflammatory stimulation modulated extracellular matrix deposition by human chondrocytes in a sex-specific fashion. Not only matrix deposition but also matrix remodeling was altered upon inflammation, leading to a significant reduction in matrix stiffness in both cartilage and bone compartments. Overall, sex-stratified osteochondral unit on-chips offer novel insights into sex-specific cellular responses to inflammatory insults, demonstrating the importance of incorporating sex stratification in emergent organ-on-chip models. Thus, this platform provides a physiologically relevant 3D microenvironment to further investigate sex-specific drivers of OA, paving the way for targeted therapies.

Novel pH-responsive lipid nanoparticles deliver UA-mediated mitophagy and ferroptosis for osteoarthritis treatment

Synovial inflammation plays a crucial role in osteoarthritis (OA) development, leading to chronic inflammation and cartilage destruction. Although targeting synovitis can alleviate OA, clinical outcomes have been disappointing due to poor drug targeting and joint cavity heterogeneity. This study presents pH-responsive lipid nanoparticles (LNPs@UA), loaded with Urolithin A (UA), as a potential OA treatment. LNPs@UA showed uniform particle size, low zeta potential, and effective mitochondria-targeting and pH-responsive capabilities. In vitro, LNPs@UA reduced reactive oxygen species (ROS), pro-inflammatory factors (IL-1β, IL-6, TNF-α), and promoted M2 macrophage polarization. It improved mitochondrial structure, enhanced autophagy, and inhibited ferroptosis. In vivo, LNPs@UA alleviated OA progression in an ACLT-induced OA mouse model. Transcriptomic analysis revealed inhibition of NF-κB signaling and activation of repair pathways. These results suggest LNPs@UA could offer a promising therapeutic approach for OA.

The influence of zinc levels on osteoarthritis: A comprehensive review

Osteoarthritis (OA), a disease with a multifactorial aetiology and an enigmatic root cause, affects the quality of life of many elderly patients. Even though there are certain medications utilised to reduce the symptomatic effects, a reliable treatment method to reverse the disease is yet to be discovered. Zinc is a cofactor of over 3000 proteins and is the only metal found in all six classes of enzymes. We explored zinc’s effect on the immune system and the bones as OA affects both. We also discussed zinc-dependent enzymes, highlighting their significant role in the disease’s pathogenesis. It is important to note that both excessive and deficient zinc levels can negatively affect bone health and immune function, thereby exacerbating OA. The purpose of this review is to offer a better understanding of zinc’s impact on OA pathogenesis and to provide clarity regarding its beneficial and detrimental outcomes. We searched thoroughly systematic reviews, meta-analysis, review articles, research articles and randomised controlled trials to ensure a comprehensive review. In brief, using zinc supplementation in the treatment of OA may act as a doubled-edged sword, offering potential benefits but also posing risks.

Membrane biomimetic nanoenzyme-incorporated hybrid glycyrrhizic acid hydrogel for precise mitochondrial ROS scavenging for osteoarthritis treatment

Osteoarthritis (OA) is a progressive degenerative disorder which severely threatens the quality of life of older individuals. OA progression is closely related to heightened levels of mitochondrial reactive oxygen species (mtROS). Although nanozymes have a good ROS-scavenging effect, they cannot precisely scavenge mtROS because of the immune rejection of cell membranes, lysosomal escape, and the inability of conventional nanozymes to directly target mitochondria. Dual-target nanozymes were engineered to precisely scavenge mtROS in chondrocytes. We used chondrocyte membrane-camouflaged TPP-modified hollow Prussian blue nanozymes and subsequently encapsulated these nanozymes in a hybrid glycyrrhizic acid hydrogel. The therapeutic efficacy and underlying mechanisms were assessed in vitro and in vivo. The novel nanozymes enhanced cell selectivity, immune evasion capabilities, and mitochondrial targeting. The dual-targeted nanozymes exerted a pronounced therapeutic impact on inflammatory chondrocytes, mitigated mtDNA leakage by precisely scavenging mtROS, dampened cGAS-STING-NF-κB signaling, and enhanced chondrocyte function. The hybrid hydrogels also exhibited improved therapeutic outcomes. We confirmed the beneficial effects of the nanozyme-hydrogel combination on OA progression in mice. The nanozyme-hydrogel combination can reduce precisely scavenge mtROS in chondrocytes, avoiding the leakage of mtDNA and suppressing the cGAS-STING-NF-κB signaling pathway, thereby decreasing inflammatory responses and alleviate OA progression.

HAMA-SBMA hydrogel with anti-inflammatory properties delivers cartilage organoids, boosting cartilage regeneration

Cartilage tissue lacks blood supply, which limits its ability to self-repair. Cartilage organoid (CO) technology, which replicates the structure and function of cartilage, holds significant promise. However, it is essential to maintain cellular function and ensure secure fixation at the site of injury. Therefore, we loaded allogeneic bone marrow mesenchymal stem cells (BMSCs) onto decellularized extracellular matrix microparticles of porcine articular cartilage (CEP) to construct CO-CCO, which demonstrated characteristics of articular cartilage. Additionally, betaine sulfonate methacrylate (SBMA) was incorporated into hyaluronic acid methacrylate (HAMA) to synthesize a novel hydrogel, HAMA-SBMA (HS), characterized by its adhesive properties, promotion of chondrogenesis, and inhibition of inflammation. In Vivo studies revealed that the combination of HS and CCO (HS + CCO) exhibited excellent repair efficacy in both rat and sheep models of cartilage defects. Mechanistically, we found that HS + CCO promoted cartilage repair by activating the Frizzled-related protein (Frzb), which inhibited inflammatory factors and enhanced the expression of the adhesion factor integrin ɑ5β1. This strategy, which combines hydrogels and organoids, enhances cartilage repair, offering substantial potential for clinical applications in cartilage regeneration.

Association between systemic Immune-inflammation index, systemic inflammation response index and adult osteoarthritis: national health and nutrition examination survey

BACKGROUND

Osteoarthritis (OA) is a degenerative and inflammatory joint disease caused by multiple factors, the underlying mechanisms of which are not fully understood. The systemic immune-inflammation index (SII) and systemic inflammation response index (SIRI) are both novel biomarkers and predictors of inflammation. Thus, this study aimed to evaluate the relationship between SII, SIRI and OA in adult.

OBJECTIVE

The ultimate goal is to gain a deeper understanding of how SII, SIRI influences OA and the implications of this relationship.

MATERIALS AND METHODS

We analyzed data from 7204 participants aged 20 and older from the NHANES surveys conducted in 1999-2020, all of whom provided comprehensive data for this study. Standardized surveys assessed the presence of osteoarthritis and SII, SIRI. To thoroughly understand their relationship, we employed statistical techniques including multivariable logistic regression, stratified analysis with interaction, restricted cubic splines (RCS), and threshold effect analysis.

RESULTS

A total of 7204 adult participants were enrolled, composing of 2830 (39.3%) male and 4374 (60.7%) female with a median age of 62.2 ± 13.9 years, 2955 (41.0%) were diagnosed with OA. Accordingly, A linear relationship between SII and OA was discovered after adjusting for underlying confounders, (p > 0.05) in RCS, and the association between the SIRI and OA exhibited a nonlinear relationship (p = 0. 042) in RCS. In the threshold analysis, the OR of developing OA was 1.648 (95% CI: 1.144 ~ 2.374, p < 0.05) in participants with SIRI of < 0.99 103 cells/ml. There was no significantly association between the SIRI and OA when the SIRI was ≥ 0.99 103 cells/ml. Further sensitivity analyses provided confidence that the results are robust and not likely to be substantially influenced by unmeasured confounding factors.

CONCLUSIONS

This cross-sectional study demonstrated that a linear relationship between SII and OA, and the association between the SIRI and OA was found to be nonlinear.

CLINICAL TRIAL NUMBER

Not applicable.

Integrated network pharmacology reveals the mechanism of action of Xianlinggubao prescription for inflammation in osteoarthritis

BACKGROUND

Osteoarthritis (OA), a leading cause of disability worldwide, is characterized by complex interactions between cartilage degradation and synovial inflammation. While NSAIDs are the primary treatment, their prolonged use exacerbates gastrointestinal risks and does not alter disease progression. Xianlinggubao (XLGB), an approved Chinese herbal remedy for osteoporosis, has demonstrated promising anti-osteoarthritic effects in preliminary studies. However, its multi-component mechanisms targeting OA-related inflammation require further clarification. This study integrates network pharmacology with experimental validation to investigate XLGB's anti-inflammatory mechanisms in OA.

METHODS

Bioactive compounds of XLGB and their respective targets were sourced from the TCMSP, ETCM, SymMap, and ChEMBL databases. Targets linked to OA-related inflammation were identified through differential expression analysis and by querying OMIM, GeneCards, and PubMed Gene databases. Network pharmacology and bioinformatics approaches were employed to construct compound-target and protein-protein interaction (PPI) networks, enabling the identification of pivotal therapeutic targets. Functional enrichment of these targets was performed using the ClusterProfiler package in R. The binding affinity of compounds to anti-inflammatory OA targets was assessed through molecular docking, dynamics simulations, RT-PCR, and immunofluorescence assays.

RESULTS

Fifty-five bioactive compounds corresponding to 475 XLGB targets and 125 genes involved in OA-related inflammation were identified. PPI network analysis revealed that XLGB may alleviate OA inflammation by modulating key genes, including COX-2, IL-1β, TNF, IL-6, and MMP-9. Molecular simulations indicated strong binding affinities between bioactive compounds in XLGB and these critical targets. Functional enrichment analysis suggested that XLGB's anti-inflammatory action in OA may involve regulation of pathways such as IL-17, TNF, and NF-κB. In vitro experiments further confirmed that XLGB mitigates OA inflammation by modulating these genes, proteins, and signaling pathways.

CONCLUSIONS

Through network pharmacology, this study elucidated the mechanisms of XLGB in OA inflammation, highlighting its modulation of IL-6, IL-1β, TNF-α, PTGS2, MMP-9, and the NF-κB pathway. These findings provide strong support for the clinical application of XLGB in managing OA-related inflammation.

Chondrocyte fatty acid oxidation drives osteoarthritis via SOX9 degradation and epigenetic regulation

Osteoarthritis is the most prevalent age-related degenerative joint disease and is closely linked to obesity. However, the underlying mechanisms remain unclear. Here we show that altered lipid metabolism in chondrocytes, particularly enhanced fatty acid oxidation (FAO), contributes to osteoarthritis progression. Excessive FAO causes acetyl-CoA accumulation, thereby altering protein-acetylation profiles, where the core FAO enzyme HADHA is hyperacetylated and activated, reciprocally boosting FAO activity and exacerbating OA progression. Mechanistically, elevated FAO reduces AMPK activity, impairs SOX9 phosphorylation, and ultimately promotes its ubiquitination-mediated degradation. Additionally, acetyl-CoA orchestrates epigenetic modulation, affecting multiple cellular processes critical for osteoarthritis pathogenesis, including the transcriptional activation of MMP13 and ADAMTS7. Cartilage-targeted delivery of trimetazidine, an FAO inhibitor and AMPK activator, demonstrates superior efficacy in a mouse model of metabolism-associated post-traumatic osteoarthritis. These findings suggest that targeting chondrocyte-lipid metabolism may offer new therapeutic strategies for osteoarthritis.

Therapeutic potential of CHI3L1 in osteoarthritis: Inhibition of cartilage matrix degradation and inflammation through TLR4-MAPK-STAT1 pathway

AIMS

CHI3L1 has been identified as a protein expressed in various tissues and tumor tissues, playing critical roles in diverse physiological and pathological processes such as inflammation, oxidative stress, cell death, and immune regulation. Previous studies have indicated that the elevated CHI3L1 levels in synovial fluid and serum of osteoarthritis patients may serve as a biomarker for osteoarthritis. However, the mechanisms by which CHI3L1 affects chondrocytes and the significance of its upregulated expression remain to be fully elucidated. This study aims to investigate the effects of CHI3L1 on chondrocytes and elucidate its molecular mechanisms.

METHODS

Interleukin-1 beta (IL-1β) was utilized in vitro to induce an inflammatory injury model in chondrocytes. The destabilization of the medial meniscus (DMM) surgery was employed to establish a mouse model of osteoarthritis in vivo. Experimental techniques, including Western blot, RT-qPCR, immunofluorescence, transcriptome sequencing, and co-immunoprecipitation, were applied to investigate the effects and mechanisms of CHI3L1 on chondrocytes. Microcomputed tomography (micro-CT), X-ray imaging, and IHC were used to evaluate the impact of CHI3L1 on knee joint osteoarthritis in mice.

RESULTS

In vitro experiments demonstrated that CHI3L1 enhanced matrix synthesis markers, suppressed matrix degradation indicators, and reduced inflammatory factors levels in chondrocytes. In vivo studies showed that intra-articular overexpression of CHI3L1 via rAAV-Chi3l1 alleviated cartilage degeneration and synovial inflammation in a murine osteoarthritis model. Mechanistically, integrated transcriptomic profiling and functional assays revealed that CHI3L1 interacts with TLR4 to attenuate MAPK phosphorylation, thereby inhibiting STAT1 phosphorylation and nuclear translocation.

CONCLUSION

The expression of CHI3L1 is upregulated in osteoarthritis. CHI3L1 alleviates osteoarthritis inflammation and cartilage matrix degradation through the TLR4-MAPK-STAT1 pathway, thereby inhibiting the progression of osteoarthritis. These findings indicate that CHI3L1 is a cytokine with protective effects in osteoarthritis and may represent a promising therapeutic target for alleviating osteoarthritis.

ARTICLE FOCUS

The objective of this study is to investigate the effects of CHI3L1 on chondrocytes and to further elucidate the underlying mechanisms by which CHI3L1 exerts its influence on chondrocytes.

KEY MESSAGES

In this study, it is proposed that CHI3L1 maintains the homeostasis of the cartilage matrix and alleviates inflammation by inhibiting the activation of the TLR4-MAPK-STAT1 signaling pathway.

STRENGTHS AND LIMITATIONS

We have established the protective role of CHI3L1 in maintaining cartilage matrix homeostasis, identified potential receptors and pathways associated with CHI3L1, and elucidated its mechanisms of action. The role of CHI3L1 in osteoarthritic synovial tissue has not yet been investigated. Further research is needed to elucidate the effects of CHI3L1 secreted by synovial tissue on chondrocytes.

Integrating bioinformatics and machine learning to identify biomarkers of branched chain amino acid related genes in osteoarthritis

BACKGROUND

Branched-chain amino acids (BCAA) metabolism is significantly associated with osteoarthritis (OA), but the specific mechanism of BCAA related genes (BCAA-RGs) in OA is still unclear. Therefore, this research intended to identify potential biomarkers and mechanisms of action of BCAA-RGs in OA tissues.

METHODS

Differential genes were obtained from the Gene Expression Omnibus (GEO) database and intersections were taken with BCAA-RGs to identify candidate genes. The underlying mechanisms were revealed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Subsequently, by combining three machine learning algorithms to identify genes with highly correlated OA features. In addition, created diagnostic maps and subject Receiver operating characteristic curves (ROCs) to assess the ability of the signature genes to diagnose OA and to predict their possible roles in molecular regulatory network axes and molecular signaling pathways.

RESULTS

Eight candidate genes were acquired by intersecting 4,178 DEGs and 14 BCAA-RGs. Subsequently, five candidate biomarkers were obtained, namely SLC3A2, SLC7A5, SLC43A2, SLC43A1, and SLC7A7. Importantly, SLC3A2 and SLC7A5 were validated by validation set and qRT-PCR. Furthermore, the nomogram constructed by SLC3A2 and SLC7A5 exhibited excellent accuracy in predicting the incidence of OA. The enrichment results demonstrated that SLC3A2 and SLC7A5 were significantly enriched in ribosome, insulin signaling pathway, olfactory transduction, etc. Meanwhile, we also found XIST regulated SLC7A5 through hsa-miR-30e-5p, and regulated SLC3A2 through hsa-miR-7-5p.OIP5-AS1 regulated SLC7A5 and SLC3A2 through hsa-miR-7-5p. By the way, 150 drugs were identified, including Acetaminophen and Acrylamide, which exhibited simultaneous targeting of these two biomarkers.

CONCLUSION

Based on bioinformatics, SLC3A2 and SLC7A5 were identified as biomarkers related to BCAA in OA, which may provide a new reference for the treatment and diagnosis of OA patients.

Association between insulin resistance indices and prevalence of knee osteoarthritis using the Korean National health and examination survey

Knee osteoarthritis (OA) is associated with high insulin resistance, particularly in individuals with metabolic syndrome and type 2 diabetes. In this cross-sectional study, we aimed to explore the relationship between insulin resistance indices and the prevalence of knee OA using data from 4,209 participants of the 2009-2010 Korea National Health and Nutrition Examination Survey. We used several insulin resistance indices in our analysis: Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), triglyceride-glucose (TyG) index, TyG-body mass index (TyG_BMI), TyG-waist circumference (TyG_WC), and visceral adiposity index (VAI). Without adjusting for confounding variables, the TyG_index increased the risk of knee OA by 1.056. After adjusting for confounders, the risk increased significantly by 1.082. Similarly, the TyG_BMI, TyG_WC, and VAI showed significant associations with knee OA. However, the association between HOMA-IR and knee OA was not significant. BMI (with and without confounding variable adjustments) was significantly associated with knee OA, whereas no significant associations were found for hypertension, dyslipidemia, diabetes, or WC. These results suggest that insulin resistance indices, particularly TyG-related indices, are significantly associated with knee OA. This highlights the potential benefits of managing knee OA in the context of metabolic syndrome, which is often associated with increased insulin resistance.

Cross-species transcriptome-wide meta-analysis of anterior cruciate ligament rupture

BACKGROUND

The Anterior Cruciate Ligament (ACL) plays a critical role in maintaining the musculoskeletal stability of the knee. Its injury has been linked to an increased risk of developing osteoarthritis. This study aims to identify cross-species responses to ACL rupture providing insights on its molecular basis. We analyzed five publicly available transcriptomic datasets from Homo sapiens, Mus musculus, Canis lupus familiaris, and Oryctolagus cuniculus. Differential gene expression analysis was performed for each dataset, producing a genome-wide transcriptional signature of fold-change significance for individual genes. Stouffer's method was used to integrate the results, identifying genes significantly deregulated across all species. Additionally, gene-set enrichment analysis revealed pathways that were consistently upregulated or downregulated.

RESULTS

A positive correlation in expression was observed between human and the other three species (r2 = 0.177-0.305, p-value ≤ 2.7 × 10- 113), identifying 210 genes as the most consistently up- and down-regulated in response to ACL rupture (p-adjusted ≤ 1.27 × 10- 23). These genes are primarily involved in cellular mitosis, collagen pathways, and cartilage development. Furthermore, 60 pathways were found to be significantly up- or down-regulated across all species (p-adjusted ≤ 4.57 × 10- 4). Among these, the upregulation of inhibition of bone mineralization (p-adjusted ≤ 2.99 × 10- 6) aligns with previous findings on the reduction of subchondral bone mineral density following ACL rupture.

CONCLUSIONS

This study highlights that distinct species exhibit common molecular responses to ACL rupture, underscoring the value of mice, dogs, and rabbits as potential translational model organisms for ACL rupture research. Furthermore, the identified genes and pathways highlight the molecular mechanisms underlying ACL rupture.

Intra-articular metformin-curcumin cationic PLGA nanoparticles rejuvenate articular structure in MIA induced osteoarthritis model via modulating the crosstalk between miR93, TNFAIP3/TLR/NF-κB and AMPK/SIRT1 trajectories

Osteoarthritis (OA), a degenerative bone disease, restrains patient's productivity and quality of life. Herein, the potential of uncoated and hyaluronic acid (HA)-coated cationic - PLGA (cPL) nanoparticles loaded with metformin (MT) and curcumin (Cu) was investigated for IA administration for the first time. Optimized MT-Cu-cPL2 showed particle size 266.2 ± 2.35 nm, zeta potential +13.6 ± 0.6 mV; entrapment efficiency of 42.56 % ± 0.04 and 93.65 % ± 0.017 for MT and Cu, respectively. Optimized HA-MT-Cu-cPL4 displayed particle size 254.1 ± 3.96 nm, zeta potential -21.6 ± 0.4 mV; and entrapment efficiency of 71.4 % ± 1.06 and 93.2 % ± 0.93 for MT and Cu, respectively. HA-MT-Cu-cPL4 demonstrated a sustained release of MT and Cu over 24 h and stability over 3-months at 4 °C. The IA administration of MT-Cu-cPL2 and HA-MT-Cu-cPL4 to MIA-induced OA rats revealed their significant antiarthritic potential. Treatment with HA-MT-Cu-cPL4 showed the most significant repression of OA advancement due to enhancement of miR-93 and TNFAIP3 knee tissue expression levels that have been correlated to upregulation of AMPK/SIRT1 activity and downstream inhibition of TLR4/NF-κB signaling pathway. The optimized nano-formulations also exhibited anti-edematous, anti-nociceptive, and locomotor-enhancing activity, highlighting the IA MT-Cu combinational therapy as a prosperous approach for management of OA.

RNA Modifications in Osteoarthritis: Epitranscriptomic Insights into Pathogenesis and Therapeutic Targets

Osteoarthritis (OA) is a chronic joint disorder characterized by progressive degeneration of articular cartilage, pain, synovial inflammation, and bone remodeling. Post-transcriptional RNA modifications, known as epitranscriptome, are a group of biochemical alterations in the primary RNA transcript that might influence RNA structure, stability, and function. Different kinds of RNA modifications have been recognized, such as methylation, acetylation, pseudouridylation, and phosphorylation. N6-methyladenosine (m6A), 5-methylcytosine (m5C), N7-methylguanosine (m7G), 2'-O-ribose methylation (2'-O-Me), and pseudouridylation (Ψ) are the most prevalent RNA modifications. Recent studies have shown that disruption in these modifications can interfere with gene expression and protein function. Here, we will review all types of RNA modifications and how they contribute to the onset and progression of OA. To the best of our knowledge, this is the first review comprehensively addressing all epitranscriptomic modifications in OA.

Theranostics of osteoarthritis: Applications and prospects of precision targeting nanotechnology

Osteoarthritis (OA), a complex degenerative joint disease driven by cartilage degeneration, synovial inflammation, and subchondral bone remodeling, lacks effective disease-modifying therapies. Precision-targeted nanotechnology has emerged as a breakthrough strategy, offering enhanced drug delivery, reduced toxicity, and synergistic diagnostic-therapeutic capabilities. This review summarizes OA pathogenesis, focusing on dysregulated immune networks and self-perpetuating synovial microenvironmental interactions. We discuss advanced nanomedicine approaches, which leverage OA-specific pathological cues for localized treatment. Innovations in cytokine modulation, photothermal therapy, and integrated theranostics (photoacoustic/fluorescence imaging) are highlighted as transformative tools for real-time diagnosis and personalized intervention. Despite progress, challenges such as biocompatibility optimization, clinical translation barriers, OA heterogeneity necessitate further development of multifunctional nanocarriers and rationaldesigns. This work underscores the potential of nanotechnology to advance OA therapeutics, bridging preclinical innovation with clinical applicability in pharmaceutical sciences.

Chondrocyte lysates activate NLRP3 inflammasome-induced pyroptosis in synovial fibroblasts to exacerbate knee synovitis by downregulating caveolin-1

BACKGROUND

Synovitis, among the most common signs of early-stage osteoarthritis (OA), is mainly mediated by fibroblast-like synoviocytes (FLSs). Cartilage destruction creates chondrocyte lysates (CLs) that activate synovial inflammation. A comprehensive understanding of chondrocyte-FLS communication might offer novel, specific therapeutic targets for treating synovitis and OA. Hence, we sought to uncover the specific role of CLs in OA-FLSs and synovitis.

METHODS

Isolated CLs were cocultured with FLSs to test whether they could stimulate synovial inflammation. A model of medial meniscus destabilization was prepared in C57BL/6 mice and NLRP3 knockout mice, and adeno-associated virus overexpressing Caveolin-1 (CAV1) was intra-articularly injected for 8 weeks once a week after dissection of the medial meniscus (DMM). Proteins expressed in FLSs with and without CL coculture were screened using liquid chromatography-tandem mass spectrometry to identify CL-specific regulators of NLRP3 inflammasome-mediated pyroptosis.

RESULTS

CLs were engulfed by FLSs, which aggravated inflammatory cytokine release and NLRP3 inflammasome-mediated FLS pyroptosis. NLRP3 expression was significantly upregulated in human OA-FLSs and FLSs cocultured with CLs, while CAV1 was downregulated. CAV1 overexpression reversed the inflammatory phenotype in FLSs and simultaneously rescued pyroptosis in CL-pre-treated FLSs. Both synovial hyperplasia and inflammatory infiltration in C57BL/6 mice with DMM surgery were alleviated after intra-articular AAV-CAV1 injection. Moreover, the CL-specific protein LIM-containing lipoma preferred partner (LPP) markedly exacerbated FLS pyroptosis and inflammation.

CONCLUSIONS

CLs were endocytosed by FLSs through CAV1, and the CL-specific protein LPP stimulated NLRP3 inflammasome-mediated pyroptosis and synovitis by inhibiting CAV1 expression. Our findings offer a novel therapeutic target for treating synovitis.

Patients with Higher Pulse Wave Velocity Are More Likely to Develop a More Severe Form of Knee Osteoarthritis: Implications for Cardiovascular Risk

Background/Objectives: Knee osteoarthritis (KOA) is a progressive degenerative joint disease characterised by low-grade inflammation and is associated with increased cardiovascular (CV) risk and arterial stiffness. Pulse wave velocity (PWV) is a quantitative measure of arterial stiffness and an important tool for detecting subclinical arterial calcification and CV risk. This study aimed to determine whether PWV can distinguish radiographically mild KOA (Kellgren-Lawrence grades 1-2) from severe KAO (Kellgren-Lawrence grades 3-4) in terms of CV risk factors. Methods: A total of 223 postmenopausal women with KOA participated in this cross-sectional study. Assessments included anthropometry, laboratory analyses, blood pressure and PWV measurements, a 6 min walk test, pain evaluation using a visual analogue scale (VAS), and completion of the International Physical Activity Questionnaire (IPAQ). Results: PWV was significantly higher in the severe KOA group (10.53 m/s vs. 8.78 m/s, p < 0.001). A cut-off value of 8.4 m/s effectively distinguished between severe and mild forms of KOA (AUC = 0.798, p = 0.001). OA grade, pain, age, waist circumference, WHR, SCORE 2/SCORE 2OP, systolic blood pressure, serum glucose, HbA1c, uric acid, creatinine, and erythrocyte sedimentation rate were increased in the group with PWV > 8.4 m/s, compared to the group with PWV ≤ 8.4 m/s. Conversely, eGFR, the 6 min walk test and physical activity of patients were reduced in the group with PWV > 8.4 m/s. A patient with a PWV > 8.4 m/s has a 1.77 times higher chance of developing a more severe form of the disease than a patient with a lower PWV. Conclusions: Patients with a higher PWV are more likely to develop a more severe form of KOA, which is associated with increased cardiovascular risk.

Calcified Cartilage Zone Remodeling Induced by IL-1β Derived from Necrotic Subchondral Bone Initiates Cartilage Degeneration in Patients with Glucocorticoids-induced Osteonecrosis of the Femoral Head

Glucocorticoids-induced osteonecrosis of the femoral head (GONFH) is characterized by progressive cartilage degeneration, yet the role of calcified cartilage zone (CCZ) remodeling in this process remains poorly understood. This study investigated how the inflammatory microenvironment within necrotic subchondral bone drove CCZ remodeling and subsequent cartilage degeneration. Using osteochondral tissues from GONFH patients and interleukin-1β (IL-1β)-treated hypertrophic chondrocytes induced by ATDC5 cells, we combined histology, immunohistochemistry, scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, nanoindentation testing, enzyme linked immunosorbent assay and fluorescent tracking to evaluate morphological, biomechanical, and molecular changes. Our findings revealed that CCZ of GONFH exhibited significant thinning, matrix decomposition, demineralization, diminished mechanical strength, and increased porosity. Spatial analysis demonstrated a strong correlation between CCZ remodeling and site-specific cartilage degeneration. Notably, IL-1β was overexpressed in necrotic subchondral bone and the site deep zones of cartilage. It potently enhanced catabolic activity in hypertrophic chondrocytes, promoting matrix metalloproteinase expression while impairing mineralization capacity. This study uncovers a novel pathological cascade in GONFH: necrotic subchondral bone-derived IL-1β drives CCZ remodeling via biomechanical and biological pathways, leading to cartilage degeneration independent of femoral head collapse. Our findings highlight IL-1β as a critical therapeutic target, providing a rationale for subchondral bone-targeted anti-inflammatory strategies to mitigate GONFH progression.

Cartilage degradation is followed by PAC1 receptor reduction in articular cartilage of human knee joints

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide expressed in the nervous system and also in various peripheral tissues, including the musculoskeletal system. PACAP has an important function in the regulation of chondrogenesis and plays a protective role in cartilage oxidative and mechanical stress. PACAP knockout (KO) mice show early signs of aging and osteoarthritis in knee joint articular cartilage. Its specific, most potent receptor is the PAC1 receptor, the activation of which leads to enhanced Sox9 expression and subsequently, it increases the expression of collagen type II, glucosaminoglycans and aggrecan. In the present study, we investigated articular cartilage of human knee joints taken from cadavers of varying ages. Thickness and extracellular matrix content of articular cartilage of knee joints decreases with aging. The cartilage degeneration process most likely begins between the ages of 40 to 50. Expression of PAC1 receptor decreases in parallel with the reduction of cartilage thickness, leading to subsequent reduced Sox9 expression with cartilage specific matrix production. In summary, we found correlation in the reduction of cartilage thickness and quality together with PAC1 receptor expression and activity.

Enhancing Cartilage Repair in Osteoarthritis Using Platelet Lysates and Arthroscopic Microfracture

Background

Osteoarthritis (OA) is the most prevalent joint degenerative disease. MF is considered as a first-line treatment for OA. In the long term, the cartilage tissue regenerated after MF is fibrocartilage. In this study, we examine whether combined treatment of MF and Platelet lysate (PL) can inhibit promotion of cartilage repair and antifibrosis.

Methods

OA rat model established by the modified Hulth method. Rat PL injected into treated knee joints after MF surgery. The expression levels of metabolic and fibrosis molecules (Col2, Mmp13, Col1, Col3, α-SMA, and Ctgf) of chondrocytes were examined by immunohistochemistry. Cell immunofluorescence was used to assess bone marrow MSCs (BMSCs) proliferation. Transwell assays evaluated BMSCs migration, and qPCR and Western blot analyzed the mechanisms of PL. Moreover, a retrospective analysis was conducted to determine the clinical efficacy and safety of the combined treatment of MF and PL on OA patients.

Results

In vivo data showed that the combined treatment of MF and PL significantly alleviated joint pain, protected chondrocytes and inhibited synovial fibrosis on OA rats, as was confirmed by upregulation of Collagen II and downregulation of Mmp13, Col1, Col3, α-SMA, and Ctgf. Such anti-OA and antifibrosis effects of the combined treatment of MF and PL were superior to MF alone. In vitro data showed that PL induced cellular chondrogenic differentiation and migration of BMSCs, suggesting that PL facilitated stem cell homing to the cartilage injury sites and promoted cartilage repair and regeneration. Furthermore, the clinical data showed significant improvements of pain reduction and cartilage repair in OA patients.

Conclusion

This study demonstrated the anti-OA and antifibrosis effects of the combination of MF and PL, providing a promising synergistic therapeutic option for the treatment of OA.

Micelle-to-Gel: Thermosensitive intra-articular hydrogels for osteoarthritis management

Osteoarthritis (OA) is a chronic and degenerative joint disease with a rising incidence worldwide. Current therapeutic approaches primarily focus on symptom relief through systemic administration, which raises safety concerns related to side effects and long-term use. In this context, the local administration of natural compounds with anti-inflammatory and anti-arthritic properties, such as β-Lapachone constitutes an interesting alternative. In this work, we prepared and characterized injectable thermosensitive hybrid hydrogels loaded with β-Lapachone. A comprehensive characterization of the hydrogel systems was performed, including micellar diameter, mechanical properties at different temperatures, the ability to control drug release and microstructure. The anti-inflammatory activity of the free drug, as well as that of the blank or loaded hydrogels was then evaluated ex vivo, using OA cartilage explants. Additionally, in vivo studies were carried out in a rabbit model of OA to assess their clinical potential. The results suggest that the hydrogel systems possess a composite microstructure integrating micelles, together with a temperature-responsive stiffness and the ability to modulate drug release. In addition, β-Lapachone-loaded hydrogels display an interesting immunomodulatory potential ex vivo, as they were able to efficiently reduce the secretion of several proinflammatory mediators, such as IL-6, MMP9, MMP13 and CXCL8. Furthermore, the drug-loaded hydrogels were found to improve in vivo cartilage and bone histomorphometric markers, such as subchondral bone thickness, as well as early signs of cartilage damage, such as the fibrillation index. Therefore, the developed β-Lapachone-loaded thermosensitive hydrogels constitute a promising alternative for OA management.

Association Between Mouth Breathing and the Temporomandibular System: A Narrative Review

OBJECTIVE

Children with chronic pathological mouth breathing (MB) may alter the development of the skeletal and myofunctional systems, including the temporomandibular system, and often exhibit symptoms of temporomandibular disorder (TMD), including pain or palpation pain in the temporomandibular joint (TMJ) region, limited or deviated mouth opening and TMJ noise. This review aims to summarise the correlation between mouth breathing and TMD in children and elucidate the potential impact and possible mechanisms of MB on the development of the temporomandibular system.

METHODS

Searches related to mouth breathing, temporomandibular joint, temporomandibular system and temporomandibular disorder were performed using PubMed and Web of Science through September 2024. A narrative review of current literature was conducted to summarise and elaborate. Literature reviews, systematic reviews, meta-analyses, clinical trials and pre-clinical studies focusing on the current topic were included.

RESULTS

We accumulated knowledge of the clinical status of MB, correlation between MB and TMD, specifically the pathogenic factors and signalling pathways involved in MB-related TMD pathology. Modifications in these signalling pathways result in pathological alterations within the TMJ tissues, impacting the degradation of the cartilage matrix, chondrocyte apoptosis and pain.

CONCLUSION

Multiple signalling pathways were involved in the pathological process of MB-related TMD. Novel or improved animal models, new techniques and new therapeutic strategies targeting these pathways may be applied in MB-related TMD studies.

Subchondral injection of human umbilical cord mesenchymal stem cells ameliorates knee osteoarthritis by inhibiting osteoblast apoptosis and TGF-beta activity

BACKGROUND

Osteoarthritis (OA) is a common degenerative disease caused by multiple pathological mechanisms wherein subchondral bone malfunction plays a substantial role. Recently, subchondral (SC) injection of orthobiologics has been attracting growing interest albeit the mainstream delivery method of mesenchymal stem cells (MSCs) is through intra-articular (IA). This study investigates the effect of SC injection of human umbilical cord mesenchymal stem cells (UCMSCs) on OA and its possible therapeutic mechanism compared to IA injection.

METHODS

Male Sprague-Dawley rats with anterior cruciate ligament transection (ACLT) received saline or UCMSC injections via SC or IA. Consecutive injections once a week for three weeks and withdrawal for another four weeks, followed by Radiographical scanning, histopathological, immunohistochemical, and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) staining. Cell counting Kit-8 (CCK-8) assay, alkaline phosphatase (ALP), alizarin red staining (ARS), TUNEL, flow cytometry, quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were employed in TNFα-induced MC3T3-E1 cells to illustrate the exact pathogenesis mechanism.

RESULTS

IA and SC UCMSC injections preserved cartilage, synovium, and subchondral bone parameters like trabecular bone volume fraction (BV/TV). SC injection uniquely improved Trabecular separation (Tb.Sp) and Trabecular number (Tb.N). SC and IA injections of UCMSCs demonstrated equivalent efficacy in promoting osteoblastic bone formation and attenuating aberrant angiogenesis of subchondral bone. In addition, we demonstrated that osteoblast apoptosis and Smad2-dependent TGF-beta (TGF-β) are crucial and interactive subchondral bone pathological features in OA. In vivo and vitro studies further revealed that UCMSCs inhibited excessive TGF-β/pSmad2 signaling to regulate aberrant vascularization, osteoblast apoptosis and differentiation imbalance, ultimately maintaining osteochondral homeostasis.

CONCLUSIONS

The efficacy of UCMSCs for treating OA rats via SC injection was equivalent to that of IA; and even superior to IA in terms of subchondral bone phenotype via regulating apoptosis and TGF-β/pSmad2 signaling in osteoblasts, suggesting SC injection of UCMSCs as a potential and promising cell therapy for OA treatment.

Matrix stiffness in osteoarthritis: from mechanism introduction to biomaterial-based therapies

Osteoarthritis (OA), the most prevalent joint disorder associated with aging, is characterized by impaired extracellular matrix (ECM) synthesis and the degradation of articular cartilage. It is influenced by various factors, including aging and mechanical stress (such as traumatic injury). Increasing evidence suggests that alterations in cartilage stiffness occur during OA progression, particularly at its onset. This review comprehensively examines how aging and mechanical stress contribute to ECM stiffening, a precursor to irreversible cartilage degradation. We also discuss how increased matrix stiffness disrupts the homeostatic balance between chondrocyte catabolism and anabolism and the mechanotransduction pathways involved in cartilage stiffening. Furthermore, the potential of cartilage engineering to target the stiffness of synthetic materials is explored as a promising approach to advancing cartilage repair and regeneration in OA. A deeper understanding of this research area may not only lead to more innovative strategies for early OA detection and diagnosis but also offer novel insights into OA treatment and prognosis.

Trends in Shoulder Arthroplasty: A Narrative Review of Predominant Indications and the Most Commonly Employed Implant Designs

Background: Over the past few decades, shoulder arthroplasty has evolved rapidly, driven by a growing demand for surgical solutions to degenerative, traumatic, and irreparable rotator cuff-related pathologies, particularly in an aging but increasingly active population. Objective: This narrative review aims to examine the main clinical indications and the most commonly used implant designs, highlighting differences in functional outcomes, complication rates, and revision rates between anatomic total shoulder arthroplasty (ATSA) and reverse total shoulder arthroplasty (RTSA). Methods: Articles published between 2011 and 2025 were selected through PubMed and the Australian Joint Replacement Registry reports from 2023 and 2024. The included studies comprised randomized controlled trials, systematic reviews, and meta-analyses involving adult patients treated for primary osteoarthritis, proximal humerus fractures, and massive irreparable rotator cuff tears. Results: ATSA remains the preferred option in younger patients with an intact rotator cuff, due to superior outcomes in mobility and prosthesis longevity. However, glenoid component loosening remains a significant limitation. Initially reserved for irreparable cuff tears and complex fractures, RTSA has seen a progressive expansion of its indications, offering lower revision rates and satisfactory functional results, particularly in elderly patients. Recent prosthetic innovations include stemless implants, augmented glenoid components, and convertible platforms. Conclusions: The choice between ATSA and RTSA should be individualized, based on patient-specific factors such as age, rotator cuff integrity, functional demands, and bone quality. Advances in implant materials and design, together with improved patient selection, have significantly enhanced clinical outcomes.

Obacunone acts as a histone deacetylase 1 inhibitor to limit p38MAPK signaling and alleviate osteoarthritis progression

BACKGROUND

Osteoarthritis (OA) is an age-related progressive degenerative disorder characterized by cartilage extracellular matrix degradation and inflammation. In this study, we explored the function and mechanism of action of obacunone (OB) in inhibiting OA progression.

METHODS

The degradation of articular cartilage and its severity were examined using Safranin O-fast green and hematoxylin and eosin (HE) staining. Chondrocyte survival was evaluated using a cell counting kit-8 assay. In addition, qRT-PCR, western blot analysis, immunohistochemical staining, and enzyme-linked immunosorbent assay were performed to evaluate the effects of OB on cartilage injury.

RESULTS

OB mitigated cartilage lesions in rats with anterior cruciate ligament transaction-induced OA. The protein expression of collagen II was increased and the protein expression of ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS-5), matrix metalloproteinase (MMP)-13, and RUNX family transcription factor 2 (RUNX2) was reduced in the articular cartilage of OB-treated rats. Moreover, OB exhibited anti-inflammatory activities by reducing the serum levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-1β, and IL-18. In IL-1β-stimulated primary chondrocytes, OB dose-dependently elevated the expression of collagen II, and decreased the expression of ADAMTS-5, MMP-13, RUNX2 and inflammatory cytokines. Histone deacetylase 1 (HDAC1) was identified as a predicted OB target. OB inhibited HDAC1 expression to limit the activation of p38MAPK signaling. The transfection of chondrocytes with HDAC1 or p38MAPK overexpression plasmids reversed the chondroprotective effects of OB.

CONCLUSION

OB mitigated OA progression by binding to HDAC1 and inhibiting p38MAPK signaling, indicating that OB may be a promising drug for the treatment of OA.

The preparation of silk fibroin-based hydrogels and their applications in cartilage repair

With the social development, the number of patients with osteoarthritis (OA) is increasing year by year, making it crucial to explore novel therapies and treatments to facilitate cartilage repair. Among these, hydrogels have become a center of conversation as potential cartilage substitutes in view of their swelling capacity, mechanical properties, lubricating performance, and other characteristics similar with that of extracellular matrix of articular cartilage. Therefore, it is of important values to generate multi-functional hydrogels with various bioactive materials for cartilage repair. As a natural fibrous protein known for its wonderful biocompatibility, degradability, as well as mechanical strength, silk fibroin (SF) with collagen-like structure has been widely applied in cartilage repair. Therefore, utilizing SF to construct hydrogels through various crosslinking methods shows greater application potential in cartilage repair and the treatment of OA. Besides having the benefits of both SF and hydrogels, the resulting SF-based hydrogels can further load various drugs, growth factors, stem cells, etc., so as to effectively promote cartilage repair. This review summarized the construction methods of SF-based hydrogels and the research progress in cartilage repair. The future development for SF-based hydrogels in cartilage repair was also discussed, which lay the foundation for further treatment of OA.

Carboxybetaine modified chitosan as viscosupplementation for osteoarthritis therapy

Viscosupplementation treatment of osteoarthritis with sodium hyaluronate (HA) is prevalent in clinical practice but always associated with rapid degradation. Another natural polysaccharide chitosan (CS) has the potential to be used in viscosupplementation but is limited by the poor aqueous solubility. Herein, we formulated a viscosupplementation agent with a zwitterionic polymer modified chitosan (CS-CBAA), which featured with bottle-brush structure and poly(carboxybetaine acrylate) side chains. It was found that the incorporation of zwitterionic sidechains greatly enhanced chitosan's solubility up to approximately 130 mg/ml in solutions of pH 7.4. A gel-like behavior was also found in CS-CBAA solution due to intermolecular interactions between zwitterionic sidechains. Compared to HA, the viscosity of CS-CBAA solutions was obviously retained when subjected to hyaluronidase degradation tests. CS-CBAA was also approved comparable protection effect to cartilage and prior effect to ceramic materials. In a papain induced osteoarthritis mice model, CS-CBAA solutions of 120 mg/ml offered comparable cartilage protection to HA. This work presented a systematic study on a new viscosity supplement CS-CBAA, which exhibits exceptional lubricating properties and holds promise as a potential replacement for the current HA-based viscosity supplement in the treatment of early-stage OA.

Fibrocartilage hyalinization: A potential therapeutic strategy for articular fibrocartilage

Articular fibrocartilage is commonly observed on the joint surface in osteoarthritis (OA) or cartilage injury, often seen as a result of cartilage degeneration. Compared to hyaline cartilage, fibrocartilage exhibits inferior mechanical properties and biological functions, which contribute to further cartilage degeneration and the progression of OA. Despite this, research on cartilage regeneration has not sufficiently addressed the specific challenges and strategies related to fibrocartilage. Although fibrocartilage formation is an unavoidable outcome during cartilage repair, it offers several benefits in the regeneration process, such as providing a natural cell source and establishing a strong integration with surrounding tissues. Recently, a therapeutic approach focused on the in-situ modification of fibrocartilage to promote hyaline cartilage regeneration, referred to as "fibrocartilage hyalinization", has been proposed. Our recent work has demonstrated the feasibility of converting existing fibrocartilage into hyaline cartilage in vivo within the injured area. Key elements of this strategy include modifying the extracellular matrix (ECM), targeting fibrotic chondrocytes, and altering the local microenvironment. This review summarizes the current understanding of articular fibrocartilage's characteristics and mechanisms, while also discussing potential approaches and the feasibility of fibrocartilage hyalinization for cartilage regeneration.

Sp2 Transcription Factor Alleviates Chondrocyte Loss in Osteoarthritis by Repressing the DVL1-Dependent Wnt/β-Catenin Signaling Pathway

BACKGROUND

Osteoarthritis (OA) ranks as the most prevalent condition affecting the musculoskeletal system, where chondrocyte loss or dysfunction plays a crucial pathogenic role. This study is aimed at investigating key molecular cascades implicated in chondrocyte loss and cartilage injury in OA.

METHODS

A mouse model of OA was generated by destabilization of the medial meniscus. Histological staining was performed to evaluate the pathological changes in the knee joint tissue, the cartilage morphology, and the osteoblast population. A high-throughput sequencing analysis was performed to analyze aberrantly expressed genes in OA cartilage. Gain- or loss-of-function assays of dishevelled segment polarity protein 1 (DVL1) and Sp2 transcription factor (SP2) were carried out to analyze their effects on cartilage injury in mice and chondrocyte apoptosis in vitro. The interaction between SP2 and DVL1 was verified by chromatin immunoprecipitation and luciferase assays.

RESULTS

DVL1 was expressed at aberrantly high levels in the cartilage of OA mice. Its knockdown suppressed protein levels and transcriptional activity of β-catenin, thereby reducing cartilage damage and loss in mice. In vitro, chondrocyte apoptosis was inhibited upon DVL1 silencing. SP2, poorly expressed in OA cartilage, was found to repress DVL1 transcription by binding to its promoter. Overexpression of SP2 similarly alleviated cartilage injury and chondrocyte loss; however, these effects were negated by the additional DVL1 overexpression.

CONCLUSION

This study demonstrates that SP2 represses DVL1 transcription and inactivates the Wnt/β-catenin signaling, thus alleviating chondrocyte loss and cartilage injury in OA mice.

Osteo-F, a Newly Developed Herbal Formula, Ameliorates Osteoarthritis Through the NF-κB/IκB/JNK Pathway Based on Network Pharmacology

Osteoarthritis (OA) is a painful joint condition primarily caused by cartilage degradation, leading to pain and reduced mobility. Given the side effects of current treatments, this study investigates Osteo-F, a novel herbal-based functional ingredient formulated with Schizandra chinensis, Lycium chinense, and Eucommia ulmoides, traditionally valued for their bioactive and health-promoting properties. Network pharmacology analysis identified significant interactions involving Osteo-F within the TNF signaling pathway, highlighting its role in modulating key inflammatory processes in OA. In vivo experiments using a monosodium iodoacetate-induced OA rat model demonstrated significant improvements in arthritis scores, bone mineral content, and bone mineral density, alongside preservation of cartilage integrity, as confirmed by histological analyses. In vitro studies further revealed that this formulation reduced the activation of JNK and NF-κB pathways, decreasing inflammatory cytokines and matrix metalloproteinases critical in cartilage breakdown. These findings underscore the potential of Osteo-F as a functional food candidate to reduce inflammation and support cartilage preservation in OA. Future clinical trials are required to validate these findings and explore its dietary integration in OA management.

Combined Intra-Articular PN HPT™ and Hyaluronic Acid: Regeneration Medicine in Knee Osteoarthritis

Background/Objectives: Natural-origin PN HPT™ (Polynucleotides High Purification Technology) protect and revitalize chondrocytes, synoviocytes, and cartilage with a regenerative medicine perspective following intra-articular injection. This six-month, open-label data collection aimed to validate the benefits documented in previous studies of a single intra-articular injection of a proprietary PN HPT™/HA-based medical device in improving both subjective and objective manifestations of knee osteoarthritis in real-life ambulatory patients of both genders with unilateral or bilateral knee osteoarthritis. Methods: Efficacy and safety assessments, conducted at baseline before a single PN HPT™/HA injection and after three and six months of follow-up, included the Lequesne index and the patient-assessed Numeric Pain Rating Scale (NPRS), which focuses on pain intensity, as primary endpoints. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was a secondary endpoint. Results: After three and six months, the mean baseline Lequesne index score improved by 43.8% and 51.4%, respectively. Concurrently, the mean NPRS score improvements were 42.2% and 54.7%. Furthermore, 32% of investigators and 15.5% of treated patients deemed optimal the clinical outcomes with no clinical worsening. Conclusions: With some limitations due to the uncontrolled design and relying on subjective rating scales only, the study confirms all previous findings about the benefits of combining PN HPT™ and HA in the same medical device for intra-articular injection in knee osteoarthritis.

RNA-binding protein HuR interacts with UFM1 mRNA to ameliorate chondrocyte inflammation, apoptosis and extracellular matrix degradation

OBJECTIVE

To investigate the mechanisms by which the RNA-binding protein HuR /ELAVL1 interacts with UFM1 mRNA to ameliorate chondrocyte inflammation, apoptosis, and extracellular matrix (ECM) degradation in osteoarthritis (OA).

METHODS

OA cartilage tissues were collected. A lipopolysaccharide-induced chondrocyte inflammation model was constructed and transfected with relevant sequences or plasmids, chondrocyte viability was detected by MTT, and chondrocyte apoptosis was detected by flow cytometry. OA was induced in rats via anterior cruciate ligament transection (ACLT), and lentiviral vectors mediating overexpression or silencing of HuR/UFM1 were administered via intra-articular injection following surgery. The pathology of cartilage tissue in rats was observed by hematoxylin and eosin staining and safranin O/fast green staining, apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining, and Collagen II, Aggrecan, MMP3, and MMP13 were measured by immunohistochemistry. Western blot was conducted to measure PCNA, Cleaved-caspase 3, Collagen II, Aggrecan, MMP3 and MMP13. Inflammatory factors in chondrocyte supernatant and rat serum were detected using an enzyme-linked immunosorbent assay. HuR and UFM1 detection was performed using real-time fluorescence quantitative PCR and Western blot. Bioinformatics software, RIP, RNA pull down and mRNA stability analysis were combined to study the binding relationship between HuR and UFM1.

RESULTS

HuR expression was down-regulated in OA. HuR overexpression ameliorated OA chondrocyte inflammation, apoptosis, and ECM degradation, and HuR downregulation aggravated these pathologies. HuR regulated UFM1 stability by binding to UFM1 3'UTR. UFM1 expression was downregulated in OA and positively correlated with HuR expression. UFM1 silencing counteracted the ameliorative effect of HuR on OA chondrocyte inflammation, apoptosis, and ECM degradation.

CONCLUSION

HuR ameliorates OA chondrocyte inflammation, apoptosis, and ECM degradation through post-transcriptional regulation of UFM1.

Primary cilia and inflammatory response: unveiling new mechanisms in osteoarthritis progression

Osteoarthritis (OA) is a common degenerative joint disease that can lead to chronic pain and disability. The pathogenesis of OA involves chronic low-grade inflammation, characterized by the degradation of chondrocytes, inflammation of the synovium, and systemic low-grade inflammation. This inflammatory response accelerates the progression of OA and contributes to pain and functional impairment. Primary cilia play a crucial role in cellular signal transduction and the maintenance of cartilage matrix homeostasis, and their dysfunction is closely linked to inflammatory responses. Given these roles, primary cilia may significantly contribute to the pathogenesis of OA. This review explores inflammation-associated signaling pathways in OA, including NF-κB, MAPK, JAK/STAT, and PI3K/AKT/mTOR signaling. In addition, we place particular emphasis on cilia-mediated inflammatory modulation in OA. Primary cilia mediate chondrocyte responses to mechanical loading and inflammatory cytokines via pathways including NF-κB, MAPK, TRPV4, and Hedgehog signaling. Notably, alterations in the length and incidence of primary cilia in chondrocytes during OA further underscore their potential role in disease pathogenesis. The identification of biomarkers and therapeutic targets related to primary cilia and inflammatory pathways offers new potential for the treatment and management of OA.

Shed Syndecan-4 and Its Possible Roles in Osteoarthritis

The specific pathogenesis of osteoarthritis (OA) remains not fully understood. As a transmembrane heparan sulfate proteoglycan, syndecan-4 (SDC4) has been proven to play an important role in the development of OA. Notably, the extracellular domain of SDC4 can be cleaved by proteolytic enzymes, leading to the release of shed SDC4 (sSDC4), which subsequently regulates various biological processes in an autocrine or paracrine manner. This review analyzed 97 publications (1987-2025) from Pubmed and the Web of Science Core Collection using specific key words (syndecan-4, shed syndecan-4, and osteoarthritis), providing a comprehensive overview of the current research on sSDC4, including its shedding enzymes and specific cleavage sites, as well as the factors and mechanisms that influence SDC4 shedding. Furthermore, it summarizes the functions of both sSDC4 and its remaining membrane-bound domain. Finally, the roles of sSDC4 in OA are discussed to identify potential therapeutic targets and explore new strategies for the treatment of OA.

Glycine N-Acyltransferase deficiency in sensory neurons suppresses osteoarthritis pain

Osteoarthritis (OA) is a degenerative joint disease characterized by chronic pain, which profoundly impacts patients' quality of life. The analgesic treatment for OA is an urgent clinical problem to be addressed. Glycine N-acyltransferase (GLYAT) is an enzyme that plays a vital role in facilitating biochemical reactions through the catalysis of glycine conjugation. Here, this study constructed an OA pain model using sodium monoiodoacetate (MIA) and discovered a significant upregulation of GLYAT in the dorsal root ganglia (DRG) of OA mice through transcriptomic sequencing. This study demonstrates GLYAT is predominantly expressed in DRG neurons and co-localizes with CGRP, IB4, or NF200-positive neurons. Overexpression of GLYAT leads to the development of prominent mechanical and thermal hyperalgesia. Loss of GLYAT effectively alleviates pain-like behaviors in OA mice without impairing baseline nociception and tactile sensations. Subsequent investigations show that GLYAT overexpression disrupts the redox balance and increases reactive oxygen species (ROS) levels within DRG neurons, leading to the upregulation of transient receptor potential vanilloid 1 (TRPV1) channel. Furthermore, ROS clearance or TRPV1 blockade in GLYAT-overexpressing mice significantly increased mechanical withdrawal threshold and thermal withdrawal latency. Collectively, these results demonstrate that GLYAT regulates OA pain by increasing ROS production and TRPV1 channel expression. This work also suggests the potential of GLYAT as a novel target for analgesic therapies. PERSPECTIVE: This article highlights the innovative finding of increased GLYAT levels in DRG neurons of the mice with OA pain. The role of GLYAT in regulating ROS and TRPV1 levels suggests its potential as a target for managing OA pain.

Engineered Stem Cell Clusters for Extracellular Vesicles-Mediated Gene Delivery to Rejuvenate Chondrocytes and Facilitate Chondrogenesis in Osteoarthritis Therapy

Gene therapy offers an ideal potential treatment strategy for osteoarthritis (OA). However, the safe and efficient delivery of therapeutic genes remains highly challenging because of the inactivation in direct delivery of miRNA, low transfection efficiency, and a short half-life. This study introduced a gene therapy strategy using mesenchymal stem cells (MSCs) as a gene delivery platform and achieved the sustained delivery of therapeutic genes via engineered MSCs-derived extracellular vesicles (EVs). The miRNA-874-3p is combined with an exosome-targeting motif and transfected into bone marrow mesenchymal stem cells (BMSCs). The BMSCsmotif+miR874 are then seeded onto hydrogel microspheres, creating the BMSCmotif+miR874/MS system for OA treatment. In vitro experiments demonstrated that miRNA-874-3p not only alleviated inflammation and oxidative stress-induced damage to chondrocytes by downregulating the NF-κB signaling pathway, thereby rejuvenating chondrocytes, but also promoted chondrogenesis in the inflammatory microenvironment. Furthermore, the engineered BMSCs in the system demonstrated prolonged retention in vivo, thereby enabling the sustained delivery of the therapeutic gene, miRNA-874-3p, over an extended duration. In the rat OA model, BMSCmotif+miR874/MS successfully delivered miRNA-874-3p to the articular cartilage and effectively alleviated cartilage degeneration. In conclusion, this EVs-mediated therapeutic gene delivery approach enables miRNA-based gene therapy a viable alternative to surgery for OA treatment and provides a novel option for gene therapy.