Ageing and the pathogenesis of osteoarthritis

Latest developments of microphysiological systems (MPS) in aging-related and geriatric diseases research: A review

Aging is a gradual and irreversible process accompanied by the decline in tissue function and a significantly increased risk of various aging-related and geriatric diseases. Especially in the paradoxical context of accelerated global aging and the widespread emergence of pandemics, aging-related and geriatric diseases have become leading causes of individual mortality and disability, drawing increasing attention from researchers and investors alike. Despite the utility of current in vitro systems and in vivo animal models for studying aging, these approaches are limited by insurmountable inherent constraints. In response, microphysiological systems (MPS), leveraging advances in tissue engineering and microfluidics, have emerged as highly promising platforms. MPS are capable of replicating key features of the tissue microenvironment within microfabricated devices, offering biomimetic tissue culture conditions that enhance the in vitro simulation of intact or precise human body structure and function. This capability improves the predictability of clinical trial outcomes while reducing time and cost. In this review, we focus on recent advancements in MPS used to study age-related and geriatric diseases, with particular emphasis on the application of organoids and organ-on-a-chip technologies in understanding cardiovascular diseases, cerebrovascular diseases, neurodegenerative diseases, fibrotic diseases, locomotor and sensory degenerative disorders, and rare diseases. And we aim to provide readers with critical guidelines and an overview of examples for modeling age-related and geriatric diseases using MPS, exploring mechanisms, treatments, drug screening, and other subsequent applications, from a physiopathological perspective, emphasizing the characteristic of age-related and geriatric diseases and their established correlations with the aging process. We also discuss the limitations of current models and propose future directions for MPS in aging research, highlighting the potential of interdisciplinary approaches to address unresolved challenges in the field.

Unraveling the crucial role of SDF-1 in osteoarthritis progression: IL6/HIF-1α positive feedback and chondrocyte ferroptosis

BACKGROUND

Osteoarthritis (OA) is a common joint disease with an incompletely understood pathogenesis. SDF-1, a key factor in cartilage matrix degradation, is involved in OA cartilage degeneration, yet its mechanism, especially regarding ferroptosis, remains unclear. This study focuses on elucidating the role of SDF-1-induced chondrocyte ferroptosis and the IL6/HIF-1α signalling axis in OA.

METHODS

A rabbit OA model was created via SDF-1 induction. Knee cartilage tissues were sequenced and analyzed bioinformatically to identify key genes, and explore critical pathways. Clinical tissue samples were utilized to validate their clinical relevance. Furthermore, cell and rabbit models were constructed through gene interference and pathway blocking. The expression of related genes and proteins was detected by QPCR, ELISA, Western blot, and immunofluorescence. Additionally, OA and ferroptosis indicators such as cell viability, immunohistochemistry, ROS, lipid ROS, Fe2+, MDA, and mitochondrial morphology were evaluated to uncover the molecular mechanism by which SDF-1 regulates the IL6/HIF-1α signalling axis to mediate chondrocyte ferroptosis.

RESULTS

Bioinformatics revealed that ferroptosis was significantly activated in SDF-1-induced OA, with IL6 and HIF-1 pathways implicated. In vitro and in vivo, SDF-1 increased the expression and secretion of MMP13 but decreased COL2A1 and ACAN in chondrocytes, leading to OA-like changes. It also suppressed the expression levels of SLC7A11 and GPX4, upregulated the gene and protein levels of ACSL4, promoted the accumulation of MDA, Fe2+, and ROS, and caused mitochondrial morphological changes. These ferroptosis manifestations could be alleviated by the ferroptosis inhibitor Fer-1. IL6 was an important mediator of SDF-1-induced ferroptosis, and knocking down IL6 also inhibited chondrocyte ferroptosis changes. Overexpressing IL6 (oeIL6) and using PX478 to inhibit the HIF-1 signalling pathway showed that PX478 could significantly relieve the cytotoxicity produced by the culture of oeIL6 and SDF-1, enhance chondrocyte viability, reverse the decreased expression of SLC7A11 and GPX4 caused by oeIL6, increase the expression of ACSL4, reverse the accumulation of MDA, Fe2+, and ROS. Moreover, PX478 could also significantly reduce the expression and secretion of IL6.

CONCLUSION

SDF-1 mediates chondrocyte ferroptosis via the IL6/HIF-1α positive feedback, promoting OA.

SPI1 activates mitochondrial unfolded response signaling to inhibit chondrocyte senescence and relieves osteoarthritis

Chondrocyte senescence is a critical pathological hallmark of osteoarthritis (OA). Aberrant mechanical stress is considered a pivotal determinant in chondrocyte aging; however, the precise underlying mechanism remains elusive. Our findings demonstrate that SPI1 plays a significant role in counteracting chondrocyte senescence and inhibiting OA progression. SPI1 binds to the PERK promoter, thereby promoting its transcriptional activity. Importantly, PERK, rather than GCN2, facilitates eIF2α phosphorylation, activating the mitochondrial unfolded protein response (UPRmt) and impeding chondrocyte senescence. Deficiency of SPI1 in mechanical overload-induced mice leads to diminished UPRmt activation and accelerated OA progression. Intra-articular injection of adenovirus vectors overexpressing SPI1 and PERK effectively mitigates cartilage degeneration. In summary, our study elucidates the crucial regulatory role of SPI1 in the pathogenesis of chondrocyte senescence by activating UPRmt signaling through PERK, which may present a novel therapeutic target for treating OA. SPI1 alleviates the progression of OA by inhibiting mechanical stress-induced chondrocyte senescence through mitochondrial UPR signaling.

Supersulfides contribute to joint homeostasis and bone regeneration

The physiological functions of supersulfides, inorganic and organic sulfides with sulfur catenation, have been extensively studied. Their synthesis is mainly mediated by mitochondrial cysteinyl-tRNA synthetase (CARS2) that functions as a principal cysteine persulfide synthase. This study aimed to investigate the role of supersulfides in joint homeostasis and bone regeneration. Using Cars2AINK/+ mutant mice, in which the KIIK motif of CARS2 essential for supersulfide production was replaced with AINK, we evaluated the role of supersulfides in fracture healing and cartilage homeostasis during osteoarthritis (OA). Tibial fracture surgery was performed on the wild-type (Cars2+/+) and Cars2AINK/+ mice littermates. Bulk RNA-seq analysis for the osteochondral regeneration in the fracture model showed increased inflammatory markers and reduced osteogenic factors, indicative of impaired bone regeneration, in Cars2AINK/+ mice. Destabilization of the medial meniscus (DMM) surgery was performed to produce the mouse OA model. Histological analyses with Osteoarthritis Research Society International and synovitis scores revealed accelerated OA progression in Cars2AINK/+ mice compared with that in Cars2+/+ mice. To assess the effects of supersulfides on OA progression, glutathione trisulfide (GSSSG) or saline was periodically injected into the mouse knee joints after the DMM surgery. Thus, supersulfides derived from CARS2 and GSSSG exogenously administered significantly inhibited inflammation and lipid peroxidation of the joint cartilage, possibly through suppression of ferroptosis, during OA development. This study represents a significant advancement in understanding anti-inflammatory and anti-oxidant functions of supersulfides in skeletal tissues and may have a clinical relevance for the bone healing and OA therapeutics.

Comparative Analysis of the Therapeutic Potential of Extracellular Vesicles Secreted by Aged and Young Bone Marrow-Derived Mesenchymal Stem Cells in Osteoarthritis Pathogenesis

Osteoarthritis (OA), a joint disease, burdens global healthcare due to aging and obesity. Recent studies show that extracellular vesicles (EVs) from bone marrow-derived mesenchymal stem cells (BMSCs) contribute to joint homeostasis and OA management. However, the impact of donor age on BMSC-derived EV efficacy remains underexplored. In this study, we investigated EV efficacy from young BMSCs (2-month-old) in mitigating OA, contrasting them with EVs from aged BMSCs (27-month-old). The study used destabilisation of the medial meniscus (DMM) surgery on mouse knee joints to induce accelerated OA. Cartilage degeneration markers and senescence markers' expression levels were investigated in response to EV treatment. The therapeutic impact of EVs on chondrocytes under inflammatory responses was also evaluated. Despite having similar morphologies, EVs from young BMSCs markedly decreased senescence and improved chondroprotection by activating the PTEN pathway while simultaneously suppressing the upregulation of the PI3K/AKT pathways, proving to be more effective than those from older BMSCs in vitro. Furthermore, intraperitoneal injections of EVs from young donors significantly mitigated OA progression by preserving cartilage and reducing synovitis in a surgical OA model using DMM in mice. These findings highlight that donor age as a critical determinant in the therapeutic potential of BMSC-derived EVs for clinical use in OA treatment.

Adenosine metabolism and receptors in aging of the skin, musculoskeletal, immune and cardiovascular systems

Aging populations worldwide face an increasing burden of age-related chronic conditions, necessitating a deeper understanding of the underlying mechanisms. Purine metabolism has emerged as a crucial player in the pathophysiology of aging, affecting various tissues and organs. Dysregulation of purine metabolism, particularly alterations in extracellular adenosine levels and adenosine receptor signaling, contributes to age-related musculoskeletal problems, cardiovascular diseases, inflammation, and impaired immune responses. Changes in purine metabolism are associated with diminished tissue repair and regeneration, altered bone density, and impaired muscle regeneration. Mechanistically, age-related alterations in purine metabolism involve reductions in extracellular adenosine production, impaired autocrine signaling, and dysregulated expression of CD73 and CD39. Targeting adenosine receptors, such as A2A and A2B receptors, emerges as a promising therapeutic approach to mitigate age-related conditions, including sarcopenia, obesity, osteoarthritis, and impaired wound healing. Since we cannot reverse time, understanding the intricate molecular interplay between purine metabolism and aging-related pathologies holds significant potential for developing novel therapeutic strategies to improve the health and quality of life of aging populations. In this review, we compile the findings related to purine metabolism during aging in several tissues and organs and provide insights into how these signals can be manipulated to circumvent the deleterious effects of the passage of time on our body.

Differences in the clinical presentation of chronic whiplash-associated disorders and nontraumatic neck pain: a systematic review and meta-analysis

ABSTRACT

Health outcomes may be worse for individuals with whiplash-associated disorders (WAD) compared to nontraumatic neck pain (NTNP), and clinical characteristics may differ. This systematic review examined evidence comparing WAD and NTNP in terms of pain, disability, psychological status, quality of life, measures of nociceptive processing, movement, sensorimotor, and muscle function. Studies were identified through electronic database searches and included after screening against predefined eligibility criteria. Standardized mean differences (SMD) or mean differences (MD) and 95% confidence intervals (CI) were calculated. Associations between MDs with demographics and study characteristics were explored using meta-regression. Certainty of evidence was assessed using Grades of Recommendation, Assessment, Development, and Evaluation. Sixty-one studies were eligible with 45 included in meta-analysis. Individuals with WAD reported clinically relevant higher disability (100-point Neck Disability Index MD [95% CI] 11.15 [8.63, 13.68]), greater remote cold sensitivity (SMD 0.89 [0.57, 1.21]), lower quality of life (SMD -0.96 [-1.77, -0.16]), greater depression (SMD 0.60 [0.27, 0.93]), greater local (SMD -0.56 [-1.00, -0.13]) and remote (SMD -0.50 [-0.81, -0.19]) pressure sensitivity, less cervical flexion (MD -5.30° [-7.44, -3.16]) and extension (MD -5.43° [-9.31, -1.55]), higher pain intensity (100-point numerical rating scale: MD 8.15 [5.80, 10.50]), and greater kinesiophobia (SMD 0.35 [0.11, 0.59]). No between-group differences were found for dizziness symptoms, stress, anxiety, balance, and local cold sensitivity. Meta-regression indicated that disability differences were negatively associated with age (R2 = 29.6%, P = 0.006). Certainty of evidence was mostly moderate. Individuals with chronic WAD have a worse clinical presentation compared to those with chronic NTNP, which has implications for patient assessment and management.

Metabolic Reprogramming in Stromal and Immune Cells in Rheumatoid Arthritis and Osteoarthritis: Therapeutic Possibilities

Metabolic reprogramming of stromal cells, including fibroblast-like synoviocytes (FLS) and chondrocytes, as well as osteoclasts (OCs), are involved in the inflammatory and degenerative processes underlying rheumatoid arthritis (RA) and osteoarthritis (OA). In RA, FLS exhibit mTOR activation, enhanced glycolysis and reduced oxidative phosphorylation, fuelling inflammation, angiogenesis, and cartilage degradation. In OA, chondrocytes undergo metabolic rewiring, characterised by mTOR and NF-κB activation, mitochondrial dysfunction, and increased glycolysis, which promotes matrix metalloproteinase production, extracellular matrix (ECM) degradation, and angiogenesis. Macrophage-derived immunometabolites, including succinate and itaconate further modulate stromal cell function, acting as signalling molecules that modulate inflammatory and catabolic processes. Succinate promotes inflammation whilst itaconate is anti-inflammatory, suppressing inflammatory joint disease in models. Itaconate deficiency also correlates inversely with disease severity in RA in humans. Emerging evidence highlights the potential of targeting metabolic processes as promising therapeutic strategies for connective tissue disorders.

The miR-6779/XIAP axis alleviates IL-1β-induced chondrocyte senescence and extracellular matrix loss in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a long-term degenerative joint disease worsening over time. Aging and chondrocyte senescence contribute to OA progression. MicroRNAs have been confirmed to regulate different cellular processes. They contribute to OA pathology and may help to identify novel biomarkers and therapies for OA.

METHODS

This study used bioinformatics and experimental investigations to analyze and validate differentially expressed miRNAs in OA that might affect chondrocyte apoptosis and senescence.

RESULTS

miR-6779 was found to be significantly down-regulated in OA. Seventy-six of the predicted and miR-6779 targeted genes and the OA-associated disease genes overlapped, and these were enriched in cell proliferation, cell apoptosis, and cell cycle. miR-6779 overexpression remarkably attenuated IL-1β effects on chondrocytes by reducing MMP3 and MMP13 levels, promoting cell apoptosis, suppressing cell senescence, and increasing caspase-3, caspase-9 and reducing P16 and P21 levels. miR-6779 targeted inhibition of X-linked inhibitor of apoptosis protein (XIAP) expression. XIAP knockdown partially improved IL-1β-induced chondrocyte senescence and dysfunction. Lastly, when co-transfected with a miR-6779 agomir, the XIAP overexpression vector partially attenuated the effects of miR-6779 overexpression on chondrocytes; miR-6779 improved IL-1β-induced senescence and dysfunction in chondrocytes through targeting XIAP.

CONCLUSION

miR-6779 is down-regulated, and XIAP is up-regulated in OA cartilage and IL-1β-treated chondrocytes. miR-6779 inhibits XIAP expression, thereby promoting senescent chondrocyte cell apoptosis and reducing chondrocyte senescence and ECM loss through XIAP.

Metformin treatment for patients with hand osteoarthritis: protocol for the multicentre, randomised, placebo-controlled METRO trial

INTRODUCTION

Hand osteoarthritis (OA) is a prevalent joint disorder with limited treatment options. Accumulating evidence suggests that the antidiabetic drug metformin has beneficial effects on knee OA and may likewise be beneficial for hand OA. The objective of this randomised, double-blinded, placebo-controlled trial is to investigate the effect of metformin 1000 mg two times a day, or maximum tolerated dose, compared with placebo on reducing finger joint pain after 16 weeks of treatment.

METHODS AND ANALYSIS

The participants will be enrolled from the OA clinic at the Parker Institute at Copenhagen University Hospital - Bispebjerg and Frederiksberg, Copenhagen, Denmark and from the Department of Rheumatology, Hospitalsenhed Midt, Silkeborg, Denmark. 150 participants with painful hand OA according to the American College of Rheumatology criteria will be randomly allocated in a 1:1 ratio to receive either metformin or a matching placebo for 16 weeks. The initial dose of 500 mg of metformin or placebo once daily is increased by 500 mg every week until the target dose of 1000 mg two times a day, or the maximum tolerated dose, is reached. The participants will have clinical visits every 4 weeks, except the week 12 visit, which is by telephone. The primary endpoint is the between-group difference in least squares means for the change in the Visual Analogue Scale (VAS) finger joint pain scores between the metformin and placebo groups at 16 weeks. The main analysis will be conducted on the intention-to-treat population, comprising all participants assessed and randomly assigned at baseline. Least squares means and the differences between them, along with their respective 95% CIs, will be derived from a mixed-effects model for repeated measurements (outcomes collected at baseline and at weeks 4, 8, 12 and 16). Adverse events will be registered systematically.

ETHICS AND DISSEMINATION

Approval has been obtained from the European Medicines Agency (EudraCT: 2023-509181-38-00), which also includes approval from the local health research ethics committee. Written informed consent will be obtained from all participants. Study findings will be published in international peer-reviewed journals and will be presented in relevant media and at international scientific conferences.

TRIAL REGISTRATION NUMBER

EudraCT, 2023-509181-38-00; ClinicalTrials.gov, NCT06367283.

TRIM15 drives chondrocyte senescence and osteoarthritis progression

Osteoarthritis (OA) is a prevalent joint disease characterized by pain, disability, and loss of physical function, posing a challenge to public health. However, molecular mechanisms of OA pathogenesis have not been fully described. We report that tripartite motif containing 15 (TRIM15) is a regulator in chondrocyte senescence and OA. Our study revealed heightened expression of TRIM15 in chondrocytes of senescent cartilage from patients with OA and in aged wild-type mice. Using gain- and loss-of-function studies, we found that TRIM15 facilitated human chondrocyte senescence. Conditional deletion of Trim15 in mouse chondrocytes severely impaired skeletal growth, partially because of impaired embryonic chondrocyte senescence. Compared with conditionally knocked out Col2a1-CreERT2/Trim15flox/flox mice, Trim15flox/flox control mice exhibited accelerated OA phenotypes, increased senescence markers, and senescence-associated secretory phenotype during aging. Mechanistically, TRIM15 bound with yes-associated protein (YAP) and mediated K48-linked YAP ubiquitination at K254, which interrupted the interaction between YAP and angiomotin, leading to enhanced YAP nuclear translocation. Dysregulation of TRIM15-YAP and transcriptional coactivator with PDZ-binding motif (TAZ) signaling promoted OA progression in both the surgery-induced and natural aging-induced mouse OA model. Intra-articular injection of adeno-associated virus 5 (AAV5)-Trim15 shRNA decelerated OA progression in mice. In particular, YAP and TAZ protein amounts were increased in chondrocytes of patients with OA. Our preclinical results demonstrated that the AAV5-TRIM15 shRNA treatment protected human OA explants against degeneration through inhibiting chondrocyte senescence. Together, our findings underscore the potential of targeting TRIM15 in reshaping the aging cartilage microenvironment and suggest a promising therapeutic avenue for OA.

Targeting Txnip-mediated metabolic reprogramming has therapeutic potential for osteoarthritis

Osteoarthritis (OA) inflammatory microenvironment triggered glucose metabolism and mitochondrial dysfunction in chondrocytes, leading to a shift of metabolic tendency between oxidative phosphorylation and anaerobic glycolysis. Thioredoxin-interacting protein (Txnip) increased production of reactive oxygen species (ROS), which exacerbates oxidative stress, inflammation and further accelerates cartilage degeneration and extracellular matrix (ECM) degradation. Txnip expression is also positively correlated with several critical pathological glucose and lipid metabolism processes beyond inflammation and endoplasmic reticulum stress (ERS). While the role of Txnip-mediated chondrocyte metabolic reprogramming in OA has not been explored. This study focuses on the unexplored role of Txnip-mediated chondrocyte metabolic reprogramming in chondrogenesis and ECM deposition. The study reveals that upregulated glycolysis after Txnip knockdown significantly contributes to mouse chondrogenesis and ECM deposition. Moreover, verapamil, a clinically used drug that targets Txnip, shows potential for treating mouse OA. These findings suggest that targeting Txnip-mediated metabolic reprogramming could offer a novel therapeutic strategy for OA treatment.

Aging-associated Increase of GATA4 levels in Articular Cartilage is Linked to Impaired Regenerative Capacity of Chondrocytes and Osteoarthritis

Although the causal association between aging and osteoarthritis (OA) has been documented, our understanding of the underlying mechanism remains incomplete. To define the regulatory molecules governing chondrocyte aging, we performed transcriptomic analysis of young and old human chondrocytes from healthy donors. The data predicted that GATA binding protein 4 (GATA4) may play a key role in mediating the difference between young and old chondrocytes. Results from immunostaining and western blot showed significantly higher GATA4 levels in old human or mouse chondrocytes when compared to young cells. Moreover, overexpressing GATA4 in young chondrocytes remarkably reduced their cartilage-forming capacity in vitro and induced the upregulation of proinflammatory cytokines. Conversely, suppressing GATA4 expression in old chondrocytes, through either siRNA or a small-molecule inhibitor NSC140905, increased the production of aggrecan and collagen type II, and also decreased levels of matrix-degrading enzymes. In OA mice induced by surgical destabilization of the medial meniscus, intraarticular injection of lentiviral vectors carrying mouse Gata4 resulted in a higher OA severity, synovial inflammation, and pain level when compared to control vectors. Mechanistically, we found that overexpressing GATA4 significantly increased the phosphorylation of SMAD1/5. Our work demonstrates that the aging-associated increase of GATA4 in chondrocytes plays a vital role in OA progression, which may also serve as a target to reduce osteoarthritis in the older population.

Organelle-tuning condition robustly fabricates energetic mitochondria for cartilage regeneration

Mitochondria are vital organelles whose impairment leads to numerous metabolic disorders. Mitochondrial transplantation serves as a promising clinical therapy. However, its widespread application is hindered by the limited availability of healthy mitochondria, with the dose required reaching up to 109 mitochondria per injection/patient. This necessitates sustainable and tractable approaches for producing high-quality human mitochondria. In this study, we demonstrated a highly efficient mitochondria-producing strategy by manipulating mitobiogenesis and tuning organelle balance in human mesenchymal stem cells (MSCs). Utilizing an optimized culture medium (mito-condition) developed from our established formula, we achieved an 854-fold increase in mitochondria production compared to normal MSC culture within 15 days. These mitochondria were not only significantly expanded but also exhibited superior function both before and after isolation, with ATP production levels reaching 5.71 times that of normal mitochondria. Mechanistically, we revealed activation of the AMPK pathway and the establishment of a novel cellular state ideal for mitochondrial fabrication, characterized by enhanced proliferation and mitobiogenesis while suppressing other energy-consuming activities. Furthermore, the in vivo function of these mitochondria was validated in the mitotherapy in a mouse osteoarthritis model, resulting in significant cartilage regeneration over a 12-week period. Overall, this study presented a new strategy for the off-the-shelf fabrication of human mitochondria and provided insights into the molecular mechanisms governing organelle synthesis.

The Interaction Between Microbiota and Stem Cells on Progression of Osteoarthritis and Engineered Stem Cell for Enhancing Osteoarthritis Treatment

Osteoarthritis (OA) is characterized by the degeneration of articular cartilage caused by several factors of which novel most trends include microbiota. Specific microbiota and the role in the development of OA is less clear. The microbiota is presumed to influence OA occurrence and progression mainly via immune modulation. In recent years, bone marrow mesenchymal stem cells (MSCs) have shown great potential for the treatment of OA, however, the therapeutic efficiency has been seriously affected by the harsh microenvironment in the joint cavity. At present, many strategies have been used to enhance the function of MSCs, among them, engineering are a promising method. Therefore, this review mainly focuses on the latest research on how the microbiota affects the development of OA, stem cell repair, and the use of engineered MSCs in the treatment of OA. In addition, engineered MSCs can enhance the therapeutic potential of exosomes as a novel strategy for treating OA. Our review provides a comprehensive perspective on the role of microbiota in OA and the influence of MSCs therapy and engineered MSCs on the treatment of OA.

Microalgae-Derived Extracellular Vesicles Synergize with Herbal Hydrogel for Energy Homeostasis in Osteoarthritis Treatment

Treatment of osteoarthritis (OA) remains challenging owing to its complex pathological microenvironment, which involves reactive oxygen species, chronic inflammation, mitochondrial dysfunction, energy deficiency, and cartilage degeneration. Herein, we report for extracellular vesicles (SP-EVs) derived from the photosynthetic microorganism Spirulina platensis contain antioxidative and ATP-dependent active and metabolic-related compounds for OA treatment. SP-EVs were effectively delivered to chondrocytes, demonstrating the potential for modulating cellular communication and energy homeostasis. To facilitate sustained delivery of SP-EVs, the rhein hydrogel system was used for intra-articular injection (Rh Gel@SP-EVs), which demonstrated pH responsiveness under mildly acidic conditions and synergistic anti-inflammatory effects. Rh Gel@SP-EVs significantly rescued mitochondrial dysfunction by ameliorating inflammation-mediated oxidative stress and restoring the mitochondrial membrane potential in chondrocytes. Improved mitochondrial function facilitates the replenishment of ATP levels, further contributing to the balance of anabolic and catabolic processes within the cartilage matrix, eventually decelerating OA progression. Rh Gel@SP-EVs also modulated the Janus kinase-signal transducer and activator of transcription 3 signaling pathway, implicated in suppressing inflammatory responses. This therapeutic strategy utilized a microalgae-based herbal hydrogel system to modulate the sustained release of SP-EVs, offering an effective approach for treating OA by regulating energy metabolism and anti-inflammatory mechanisms.

Metabolic Profiles of Encapsulated Chondrocytes Exposed to Short-Term Simulated Microgravity

The mechanism by which chondrocytes respond to reduced mechanical loading environments and the subsequent risk of developing osteoarthritis remains unclear. This is of particular concern for astronauts. In space the reduced joint loading forces during prolonged microgravity (10-6 g) exposure could lead to osteoarthritis (OA), compromising quality of life post-spaceflight. In this study, we encapsulated human chondrocytes in an agarose gel of similar stiffness to the pericellular matrix to mimic the cartilage microenvironment. We then exposed agarose-chondrocyte constructs to simulated microgravity (SM) for four days using a rotating wall vessel (RWV) bioreactor to better assess the cartilage health risks associated with spaceflight. Metabolites extracted from media and agarose gel constructs were analyzed on liquid chromatography-mass spectrometry. Global metabolomic profiling detected a total of 1205 metabolite features, with 497 significant metabolite features identified by ANOVA (FDR-corrected p-value < 0.05). Specific metabolic shifts detected in response to SM exposure resulted in clusters of co-regulated metabolites, with glutathione, nitrogen, histidine, vitamin B3, and aminosugars metabolism identified by variable importance in projection scores. Microgravity-induced metabolic shifts in gel constructs and media were indicative of protein synthesis, energy and nucleotide metabolism, and oxidative catabolism. Microgravity associated-metabolic shifts were consistent with our previously published early osteoarthritic metabolomic profiles in human synovial fluid, suggesting that even short-term exposure to microgravity (or other reduced mechanical loading environments) may lead to the development of OA. This work further suggests the potential to detect these metabolic perturbations in synovial fluid in vivo to ascertain osteoarthritis risk in astronauts.

Association between the immune-inflammation indicators and osteoarthritis - NHANES 1999-2018

Background

Investigate the link between systemic immune-inflammatory index (SII) and Systemic Immune Response Index (SIRI) with osteoarthritis (OA) using National Health and Nutrition Examination Survey (NHANES) data (1999-2018).

Methods

Extracted NHANES data (1999-2018) and selected a study population based on demographic, examination, and laboratory data. Calculated SII (platelet count ​× ​neutrophil count/lymphocyte count) and SIRI (neutrophil count ​× ​monocyte count/lymphocyte count). Employed multivariate logistic regression and restricted cubic spline (RCS) regression for Ln-SII, SIRI, and OA relationship investigation. Conducted subgroup analyses.

Results

Study involved 32,144 participants (16,515 males, 15,629 females), with 12.16% having OA. Positive correlation between highest SII quartile and OA in unadjusted and adjusted model 1 (Unadjusted Model, P ​< ​0.001; Model 1, P ​= ​0.01). In Model 2, adjusting for all factors, positive correlation observed, not statistically significant (Model 2, P ​= ​0.07). Similar SIRI-OA correlation trends from Unadjusted Model to Model 2 (Unadjusted Model, P ​< ​0.0001; Model 1, P ​< ​0.0001; Model 2, P ​< ​0.001). Subgroup analysis found no significant factors. Identified critical point at ln-SII ≈6.39 (SII ​= ​595.86), beyond which OA prevalence significantly increased. No potential nonlinear SIRI-OA association (NL-P value ​> ​0.05).

Conclusion

When SII exceeds 595.86, OA prevalence may rise. Besides, there was a significant positive correlation between SIRI and OA prevalence. SII and SIRI may be useful markers for OA research, warranting further exploration in this area.

Targeting p21-Positive Senescent Chondrocytes via IL-6R/JAK2 Inhibition to Alleviate Osteoarthritis

Osteoarthritis (OA) is an age-related degenerative joint disease, prominently influenced by the pro-inflammatory cytokine interleukin-6 (IL-6). Although elevated IL-6 levels in joint fluid are well-documented, the uneven cartilage degeneration observed in knee OA patients suggests additional underlying mechanisms. This study investigates the role of interleukin-6 receptor (IL-6R) in mediating IL-6 signaling and its contribution to OA progression. Here, significantly elevated IL-6R expression is identified in degenerated cartilage of OA patients. Further, in vivo experiments reveal that intra-articular injection of recombinant IL-6R protein or activation of gp130 (Y757F mutation) accelerates OA progression. Conversely, knockout of IL-6R or JAK2, as well as treatment with a JAK inhibitor, alleviates OA symptoms. Mechanistically, chondrocytes derived from degenerative cartilage exhibit impaired nuclear localization of SOX9, a key regulator of cartilage homeostasis. JAK inhibition stabilizes SIRT1, reduces SOX9 acetylation, and thereby facilitates SOX9 nuclear localization, promoting cartilage repair. Additionally, the JAK inhibitor-induced apoptosis in p21-positive senescent cells, and their targeted clearance successfully alleviates OA in p21-3MR mice. In conclusion, these findings reveal a novel mechanism by which inhibiting the IL-6R/JAK2 pathway can alleviate OA. Furthermore, this study proposes targeting p21-positive senescent cells as a new therapeutic strategy for OA.

Exosomes of stem cells: a potential frontier in the treatment of osteoarthritis

The aging population has led to a global issue of osteoarthritis (OA), which not only impacts the quality of life for patients but also poses a significant economic burden on society. While biotherapy offers hope for OA treatment, currently available treatments are unable to delay or prevent the onset or progression of OA. Recent studies have shown that as nanoscale bioactive substances that mediate cell communication, exosomes from stem cell sources have led to some breakthroughs in the treatment of OA and have important clinical significance. This paper summarizes the mechanism and function of stem cell exosomes in delaying OA and looks forward to the development prospects and challenges of exosomes.

Platelet-rich plasma combined with isometric quadriceps contraction regulates autophagy in chondrocytes via the PI3K/AKT/mTOR pathway to promote cartilage repair in knee osteoarthritis

Background

This study investigated the molecular mechanism by which the combination of platelet-rich plasma (PRP) and isometric contraction of the quadriceps (ICQ) intervention regulates autophagy in chondrocytes to prevent and treat knee osteoarthritis (KOA).

Methods

Thirty Sprague-Dawley rats were divided into a control group (CG, n = 6) and a model group (n = 24). After one week, the model group was randomly divided into a joint intervention group (JIG), a rapamycin group (RAG), an MHY1485 group (MYG), and a model blank group (MBG), with JIG, RAG, and MYG receiving the same combined intervention.

Results

The trend of cartilage lesions in each group was CG < RAG < JIG < MYG < MBG. Compared with MBG and MYG, JIG and RAG showed downregulation of IL-1β, IL-6, IL-18, MMP-13, and TNF-α mRNA in the cartilage (p < 0.01); mTOR protein expression: compared with JIG, RAG showed downregulation, and MYG showed upregulation. Compared with RAG, MYG showed upregulation (p < 0.01); ATG5 protein expression: compared with RAG, MYG showed downregulation (p < 0.01); Beclin1, LC3-I, and ULK1 protein expression: compared with JIG, RAG showed upregulation, and MYG showed downregulation (p < 0.01). Compared with RAG, MYG showed downregulation (p < 0.01); P62 protein expression: compared with RAG, both MBG and RAG showed upregulation, and MYG showed downregulation (p < 0.05); LC3-II/LC3-I ratio: compared with JIG and RAG, the ratio in MYG was decreased (p < 0.01).

Conclusion

The combined intervention promotes autophagy in chondrocytes by inhibiting the PI3K/AKT/mTOR pathway, downregulating inflammatory factors and MMP-13 in the cartilage, upregulating autophagy markers, inhibiting matrix degradation, and promoting cartilage repair.

M6A Demethyltransferase FTO Attenuates Meniscus Degeneration and Osteoarthritis via Orchestrating Autophagy and Energetic Metabolism

Impaired autophagy is reported to promote osteoarthritis (OA). However, the mechanism by which autophagy in regulating meniscus degeneration and OA remains unclear. Here, unconvered aberrant energetic metabolism pattern in meniscus cells with OA is uncovered first, which results in lower adenosine triphosphate (ATP) production. And these phenomena are induced by impaired autophagy in meniscus cells with OA. It is further revealed that the suppression of m6A demethylase fat mass and obesity-associated protein (FTO) inhibits autophagy and causing lower ATP production by reducing oxidative phosphorylation. Specific deletion of FTO in meniscus cells by generating FTOflox/flox; COL1A1-CreERT2 (FTOcko) mice impair autophagy and promote meniscus degeneration and OA, while intra-articular injection of adeno-associated virus of FTO (AAV-FTO) restores autophagy and alleviates meniscus degeneration and OA. Mechanistically, FTO regulates the mRNA stability of ATG16L1 by targeting the m6A methylation sites on ATG16L1 in a YTHDF2-dependent manner, thereby inhibiting the formation of autophagosomes and causing an imbalance in energetic metabolism. Intra-articular injection of AAV-FTO reverses the catabolic phenotype of meniscus degeneration and OA in FTOcko mice. In summary, these findings reveal FTO orchestrates autophagy and energetic metabolism by regulating ATG16L1 in a m6A-dependent manner. Therefore, targeting FTO might be a potential therapeutic strategy for meniscus degeneration and early-stage OA.

Kat7 accelerates osteoarthritis disease progression through the TLR4/NF-κB signaling pathway

Osteoarthritis (OA) is a common degenerative bone and joint disease with an unclear pathogenesis. Our study identified that the histone acetyltransferase encoded by Kat7 is upregulated in the affected articular cartilage of OA patients and in a mice model of medial meniscal instability-induced OA. Chondrocyte-specific knockdown of Kat7 expression exhibited a protective effect on articular cartilage integrity. In vitro experiments demonstrated that KAT7 promotes cartilage catabolism, inhibits cartilage anabolism, and induces chondrocyte senescence and apoptosis. Conversely, knocking down Kat7 was shown to protect chondrocyte function. Corresponding in vivo results indicated that silencing Kat7 effectively enhances cartilage anabolism, prevents articular cartilage damage, and significantly slows OA progression. Mechanistically, KAT7 activates the TLR4/NF-κB signaling pathway, and inhibition of this pathway reverses the catabolic effects and restores anabolic activity in the presence of Kat7 overexpression. Collectively, these findings confirm the critical role of KAT7 in the pathogenesis of OA and suggest that Kat7 represents a potential therapeutic target for OA treatment. KEY MESSAGES: There is a lack of clinically effective drugs for the treatment of osteoarthritis (OA). Kat7 plays a key role in the development of OA. Knocking down Kat7 expression can alleviate the progression of OA. Kat7 accelerates the progression of OA by activating the TLR4/NF-KB signaling pathway.

Advances in biomarkers and diagnostic significance of organ aging

A complete understanding of aging is a critical first step in treating age-related diseases and postponing aging dysfunction in the context of an aging global population. Aging in organisms is driven by related molecular alterations that gradually occur in many organs. There has previously been a wealth of knowledge of how cells behave as they age, but when aging is investigated as a disease, the discovery and selection of aging biomarkers and how to diagnose the aging of the organism are crucial. Here, we provide a summary of the state of the field and suggest future potential routes for research on organ senescence markers. We reviewed research on biomarkers of risk of aging from the perspective of organ aging and summarized the biomarkers currently used on three scales. We emphasize that the combination of traditional markers with emerging multifaceted biomarkers may be a better way to diagnose age-related diseases.

Sympathetic innervation induces exosomal miR-125 transfer from osteoarthritic chondrocytes, disrupting subchondral bone homeostasis and aggravating cartilage damage in aging mice

INTRODUCTION

Osteoarthritis (OA) is a progressive disease that poses a significant threat to human health, particularly in aging individuals: Although sympathetic activation has been implicated in bone metabolism, its role in the development of OA related to aging remains poorly understood. Therefore, this study aimed to investigate how sympathetic regulation impacts aging-related OA through experiments conducted both in vivo and in vitro.

METHODS

To analyze the effect of sympathetic regulation on aging-related OA, we conducted experiments using various mouse models. These models included a natural aging model, a medial meniscus instability model, and a load-induced model, which were used to examine the involvement of sympathetic nerves. In order to evaluate the expression levels of β1-adrenergic receptor (Adrβ1) and sirtuin-6 (Sirt6) in chondrocytes of naturally aging OA mouse models, we performed assessments. Additionally, we investigated the influence of β1-adrenergic receptor knockout or treatment with a β1-adrenergic receptor blocker on the progression of OA in aging mice and detected exosome release and detected downstream signaling expression by inhibiting exosome release. Furthermore, we explored the impact of sympathetic depletion through tyrosine hydroxylase (TH) on OA progression in aging mice. Moreover, we studied the effects of norepinephrine(NE)-induced activation of the β1-adrenergic receptor signaling pathway on the release of exosomes and miR-125 from chondrocytes, subsequently affecting osteoblast differentiation in subchondral bone.

RESULTS

Our findings demonstrated a significant increase in sympathetic activity, such as NE levels, in various mouse models of OA including natural aging, medial meniscus instability, and load-induced models. Notably, we observed alterations in the expression levels of β1-adrenergic receptor and Sirt6 in chondrocytes in OA mouse models associated with natural aging, leading to an improvement in the progression of OA. Critically, we found that the knockout of β1-adrenergic receptor or treatment with a β1-adrenergic receptor blocker attenuated OA progression in aging mice and the degraded cartilage explants produced more exosome than the nondegraded ones, Moreover, sympathetic depletion through TH was shown to ameliorate OA progression in aging mice. Additionally, we discovered that NE-induced activation of the β1-adrenergic receptor signaling pathway facilitated the release of exosomes and miR-125 from chondrocytes, promoting osteoblast differentiation in subchondral bone.

CONCLUSION

In conclusion, our study highlights the role of sympathetic innervation in facilitating the transfer of exosomal miR-125 from osteoarthritic chondrocytes, ultimately disrupting subchondral bone homeostasis and exacerbating cartilage damage in aging mice. These findings provide valuable insights into the potential contribution of sympathetic regulation to the pathogenesis of aging-related OA.

Hydroxycitric acid reconstructs damaged articular cartilages by modifying the metabolic cascade in chondrogenic cells

Objective

Osteoarthritis, a degenerative joint disease, requires innovative therapies due to the limited ability of cartilage to regenerate. Since mesenchymal stem cells (MSCs) provide a cell source for chondrogenic cells, we hypothesize that chemicals capable of enhancing the chondrogenic potential of MSCs with transforming growth factor-beta (TGFβ) in vitro may similarly promote chondrogenesis in articular cartilage in vivo.

Design

Chemical compounds that enhance the TGFβ signaling for chondrogenesis were investigated utilizing mesenchymal stem cells derived from human induced pluripotent stem cells. The mechanisms of action underlying the identified compound were explored in vitro, and its therapeutic effects were validated in vivo using a mouse model of exercise-induced osteoarthritis.

Results

Hydroxycitric acid (HCA) emerged as the lead compound. In vitro, HCA effectively enhanced chondrogenesis by inhibiting ATP citrate lyase, inducing citrate and alpha-ketoglutarate (α-KG), while reducing cytosolic acetyl coenzyme A (Ac-CoA). This induction of α-KG promoted collagen prolyl-4-hydroxylase activity, boosting hydroxyproline production and matrix formation. The reduction of Ac-CoA attenuated the inhibitory effect of β-catenin on mitochondrial activity by diminishing its acetylation. In vivo, orally administered HCA accumulated in joint tissues of mice and histological examination demonstrated newly synthesized cartilage tissues in damaged area. Analysis of joint tissue extracts revealed a downregulation of Ac-CoA and an upregulation of citrate and α-KG, accompanied by a systemic increase in an anabolic biomarker.

Conclusions

HCA demonstrates promise as an osteoarthritis therapy by enhancing chondrogenic differentiation. Its ability to modulate crucial metabolic pathways and facilitate cartilage repair suggests potential for clinical translation, addressing a critical need in the treatment of osteoarthritis.

Isoquercetin alleviates osteoarthritis via regulating the NOX4/Nrf2 redox imbalance in senescent chondrocytes

The redox imbalance induced by excessive reactive oxygen species (ROS) contributes to senescent phenotypes of chondrocytes in osteoarthritis (OA). However, there is limited evidence regarding the involvement of NADPH oxidase-4 (NOX4)/NFE2-related factor 2 (Nrf2) redox imbalance in OA. Isoquercetin (IQ), a quercetin derivative, exhibits promising antioxidative and anti-aging properties. Here, we found that IQ promoted redox homeostasis by inhibiting NOX4 and activating Nrf2-mediated antioxidant responses, thereby ameliorating OA. Specifically, IQ significantly suppressed the expression of senescence-associated secretory phenotypes (SASPs) in senescent chondrocytes. RNA sequencing analysis revealed that cellular senescence and oxidative stress were involved in the mechanism of IQ's effect on senescent chondrocytes. IQ effectively reversed redox imbalance, as evidenced by reduced levels of ROS and endogenous oxidants, and increased mitochondrial membrane potential and, elevated levels of endogenous antioxidants. Mechanistically, the elevated expression of NOX4 observed in patients with severe OA confirms its role in OA pathogenesis. Molecular docking and NOX4 knockdown experiments suggested that IQ may interact with NOX4 and inhibit its expression. This study identifies a potential therapeutic target and provides a promising candidate for OA treatment.

The intersection of aging and estrogen in osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage degradation, inflammation, and pain. While multiple factors contribute to OA development, age and sex are primary risk factors, particularly affecting postmenopausal women. The dramatic increase in OA risk after menopause suggests estrogen deficiency accelerates disease progression. This review explores the molecular mechanisms connecting aging and estrogen deficiency in OA development, focusing on key genes and pathways identified through RNA sequencing.

Monocyte eukaryotic initiation factor 2 signaling differentiates 17-hydroxy-docosahexaenoic acid levels and pain

Our goal was to probe the potential transcriptomic basis for the relationship between plasma levels of the specialized pro-resolving precursor, 17-hydroxy-docosahexaenoic acid (17-HDHA) and chronic pain. Participants with osteoarthritis (average age of 62.3, 60% were female, n = 30) were stratified by levels of 17-HDHA and self-reported pain scores. RNAs from CD14++/CD16-/CD66b-/HLA-DR+ (classical) monocytes were sequenced and differentially expressed mRNAs were identified with DESeq2. QIAGEN ingenuity pathway analysis identified the top ranked canonical biological pathway to be eukaryotic initiation factor 2 (EIF2) signaling (lower activation level in the low 17-HDHA-high pain group compared to the high 17-HDHA-low pain group (Z score -3)), followed by EIF4 and P70S6K signaling pathways and mTOR signaling. Our approach provides insight into the biological pathways contributing to the association between 17-HDHA and chronic osteoarthritis (OA) pain, identifying EIF2 signaling, with known roles in osteoclast differentiation, OA pathology, and pain, as a potential downstream target.

Foundations of a knee joint digital twin from qMRI biomarkers for osteoarthritis and knee replacement

This study forms the basis of a digital twin system of the knee joint, using advanced quantitative MRI (qMRI) and machine learning to advance precision health in osteoarthritis (OA) management and knee replacement (KR) prediction. We combined deep learning-based segmentation of knee joint structures with dimensionality reduction to create an embedded feature space of imaging biomarkers. Through cross-sectional cohort analysis and statistical modeling, we identified specific biomarkers, including variations in cartilage thickness and medial meniscus shape, that are significantly associated with OA incidence and KR outcomes. Integrating these findings into a comprehensive framework represents a considerable step toward personalized knee-joint digital twins, which could enhance therapeutic strategies and inform clinical decision-making in rheumatological care. This versatile and reliable infrastructure has the potential to be extended to broader clinical applications in precision health.

Extracecellulr vesicles (EVs) microRNAs (miRNAs) derived from mesenchymal stem cells (MSCs) in osteoarthritis (OA); detailed role in pathogenesis and possible therapeutics

The primary cause of pain and disability in the world is osteoarthritis (OA), a common joint disease characterized by the primary pathological alteration in articular cartilage deterioration. The general outcome of treatment is not acceptable despite current interventions. Therefore, joint replacement surgery is frequently needed by patients with severe OA. Mesenchymal stem cells (MSCs) have become a practical treatment choice for preclinical and clinical OA palliation in recent years, mainly due to their unique immunomodulatory attributes. Further, attractive candidates for cell-free therapy for OA are MSC-derived extracecellulr vesicles (EVs) that convey bioactive molecules of the original cells, such as microRNAs. These EVs have been shown to significantly influence the regulation of various physiological activities of cells in the joint cavity. Dysregulated miRNAs upregulate the synthesis of enzymes that degrade cartilage, downregulate the expression of components in the cartilage matrix, promote the production of proinflammatory cytokines, induce programmed cell death in chondrocytes, inhibit the process of autophagy in chondrocytes, and participate in pathways related to pain. MiRNAs are also found in extracellular membranous vesicles (EVs), such as exosomes, and play a role in intercellular communication in osteoarthritic joints. Thus, the biosynthesis, chemical makeup, and mechanism of action of miRNAs-enriched EVs in OA are all thoroughly covered in this review. We additionally discussed how miRNA-enriched MSC-EVs might be used therapeutically to change intercellular interaction in OA.

Recent development of mitochondrial metabolism and dysfunction in osteoarthritis

Osteoarthritis is a degenerative joint disorder characterized by cartilage degradation, synovial inflammation, and altered subchondral bone structure. Recent insights have identified mitochondrial dysfunction as a pivotal factor in OA pathogenesis, contributing to chondrocyte apoptosis, oxidative stress, and extracellular matrix degradation. Disruptions in mitochondrial dynamics, including impaired biogenesis, mitophagy, and metabolic shifts from oxidative phosphorylation to glycolysis, exacerbate cartilage damage by promoting the production of reactive oxygen species and matrix-degrading enzymes such as ADAMTS and MMPs. This review explores the molecular mechanisms underlying mitochondrial dysfunction in OA, emphasizing its role in cartilage homeostasis and inflammation. Furthermore, it highlights emerging therapeutic strategies targeting mitochondrial pathways, including antioxidants, mitophagy enhancers, and metabolic modulators, as potential interventions to mitigate disease progression, which offer promising avenues for advancing personalized and disease-modifying treatments in OA.

Relationship between serum carotenoids and osteoarthritis or degenerative arthritis: A cross-sectional study using the National Health and Nutrition Examination Survey

BACKGROUND

Carotenoids possess essential antioxidant and anti-inflammatory properties; however, the relationships between carotenoids and osteoarthritis or degenerative arthritis (OA) remain inadequately understood. This study aimed to investigate the correlation between diverse serum carotenoid concentrations and OA in a large American cohort and to examine the influence of various factors on the association between carotenoids and OA.

METHODS

Data from the 2001-2006 and 2017-2018 National Health and Nutrition Examination Surveys were utilized. In our analysis, we utilized a directed acyclic graph to identify potential confounding variables. The associations between serum carotenoids (including total carotenoid, trans-lycopene, β-cryptoxanthin, lutein/zeaxanthin, α-carotene, and β-carotene) and OA were comprehensively evaluated via a weighted generalized linear model (GLM) and restricted cubic spline models. Threshold effect analyses were used to identify potential cutoff points, subgroup analyses were used to explore heterogeneity, interaction analyses were used to examine potential modifiers, and sensitivity analyses were used to validate the robustness of the findings.

RESULTS

The weighted GLM results revealed that, overall, the concentrations of various serum carotenoids did not exhibit a significant linear correlation with the probability of OA. Dose‒response curves and threshold effect analysis revealed a significant nonlinear relationship (P for overall = 0.027; P for nonlinearity = 0.019; P for likelihood ratio = 0.0128) between trans-lycopene (threshold effect) and OA, with an inflection point at 19.49 µg/dl. Further subgroup weighted linear regression analysis indicated that when the serum trans-lycopene concentration exceeded 19.49 µg/dl, there was a significant association [odds ratio (OR) = 0.89 (0.80-0.99); P = 0.027] between the per standard deviation trans-lycopene increase and a lower probability of OA after adjusting for other variables. Moreover, individuals with elevated trans-lycopene [0.70 (0.52-0.94); P = 0.018] in the fifth quintile had notably reduced odds of OA compared with those in the first quintile. When the trans-lycopene level is less than 19.49 µg/dl, no correlation exists between the two variables. Linear subgroup and interaction analyses revealed that when the concentration of carotenoids exceeded 19.49 µg/dl, various categorical factors did not significantly influence the relationship between trans-lycopene and OA overall. However, pairwise comparisons revealed that lower serum trans-lycopene concentrations are more closely associated with a greater probability of OA in elderly individuals [OR (95% CI) = 0.270 (0.112-0.654); P = 0.005; P for trend = 0.003] than in younger individuals [0.973 (0.385-2.463); P = 0.954; P for trend = 0.61] (P for interaction = 0.007).

CONCLUSIONS

In the American population, trans-lycopene rather than other types of carotenoids may exhibit a significantly negative correlation with OA, displaying a nonlinear pattern with a threshold point of approximately 19.49 µg/dl. This relationship may become more pronounced with increasing age.

Senile Osteoarthritis Regulated by the Gut Microbiota: From Mechanisms to Treatments

Osteoarthritis (OA) is a chronic, progressive degenerative joint disease that affects the entire synovial joint, leading to the progressive degeneration of articular cartilage. It seriously affects the quality of life and global disability of patients. OA is affected by a variety of factors; the most significant risk factor for OA is age. As individuals age, the risk and severity of OA increase due to the exacerbation of cartilage degeneration and wear and tear. In recent years, research has indicated that the gut microbiota may play a significant role in the aging and OA processes. It is anticipated that regulating the gut microbiota may offer novel approaches to the treatment of OA. The objective of this paper is to examine the relationship between the gut microbiota and senile OA, to investigate the potential mechanisms involved. This review also summarizes the therapeutic strategies related to gut flora in OA management, such as prebiotics and probiotics, diet, exercise, traditional Chinese medicine (TCM) modification, and fecal microbiota transplantation (FMT), highlighting the potential clinical value of gut flora and elucidating the current challenges. The foundation for future research directions is established through the summarization of current research progress.

B Cell Activation, Differentiation, and Their Potential Molecular Mechanisms in Osteoarthritic Synovial Tissue

Objective

The objective of this study was to characterize the activation and differentiation of B cells in the synovium of osteoarthritis (OA) and to explore the underlying molecular mechanisms.

Methods

Peripheral blood and synovial samples from OA patients at different stages were collected, and flow cytometry was employed to analyze the activation and differentiation of B cells. Immunofluorescence staining of joint synovium from OA mice at different stages was conducted to assess mice joint synovium B cell activation and differentiation. Co-culture experiments of synovial fibroblasts with B cells were performed to investigate the influence of synovial cells on B cell activation and differentiation. Finally, transcriptome analysis was utilized to identify potential key molecules and pathways.

Results

In OA patients, the infiltration, activation, and differentiation of B cells in synovium and peripheral blood exhibited distinct characteristics. Specifically, the proportion of activated CD86+ B cells and the differentiation marker HLA-DR+ increased with disease severity, whereas the proportion of the differentiation marker IgM decreased. The proportion of CD38+ B cells also decreased with increasing severity, although this change lacked statistical significance. Immunofluorescence staining of CD19+ and CD86+ cells in mice indicated increased expression with greater OA severity. Co-culture experiments demonstrated that OA synovial fibroblasts promoted B cell activation and differentiation, as evidenced by higher expression levels of CD86+ and HLA-DR+ in the OA group compared to controls. Additionally, the proportion of naive B cells decreased as disease severity progressed.

Conclusion

Synovial fibroblasts in OA have been shown to promote the differentiation and activation of B cells, indicating that B cells play a significant role in the pathogenesis of synovium inflammation in OA.

Asthma, social isolation and loneliness, and risk of incident osteoarthritis

BACKGROUND

Incidence of osteoarthritis (OA) was increased in patients with asthma, while no prospective cohort study has tested the association of asthma with OA, and the modified effect of social isolation and loneliness remains unclear.

METHODS

This prospective cohort study included 448,920 participants without OA at baseline from UK Biobank cohort. The evaluation of asthma was based on diagnosis and self-reported history. The outcome was OA including knee OA, hip OA and hand OA by referring to hospital admission records. Two Cox regression models were constructed to assess the relationship of asthma and risk of OA.

RESULTS

With a median of 12.5 years of follow up, a total of 57,573 incident OA were recorded. Compared with participants without asthma, the hazard ratios (HRs) were 1.32 (95% CI: 1.29-1.35) for all OA, 1.21 (95% CI: 1.16-1.25) for knee OA, 1.12 (95% CI: 1.07-1.18) for hip OA and 1.62 (95% CI:1.42-1.85) for hand OA in participants with asthma. In addition, we found that social isolation and loneliness significantly modified the associations of asthma with OA (P-interaction < 0.001). Asthma was a stronger predictor of OA than lifestyle risk factors including smoking, alcohol and healthy diet.

CONCLUSIONS

In this cohort study of UK Biobank participants, asthma was related to increased risk of OA; such association was more pronounced among those with higher social isolation or loneliness score.

Remodeling the Proinflammatory Microenvironment in Osteoarthritis through Interleukin-1 Beta Tailored Exosome Cargo for Inflammatory Regulation and Cartilage Regeneration

Osteoarthritis (OA) presents a significant therapeutic challenge, with few options for preserving joint cartilage and repairing associated tissue damage. Inflammation is a pivotal factor in OA-induced cartilage deterioration and synovial inflammation. Recently, exosomes derived from human umbilical cord mesenchymal stem cells (HucMSCs) have gained recognition as a promising noncellular therapeutic modality, but their use is hindered by the challenge of harvesting a sufficient number of exosomes with effective therapeutic efficacy. Given that HucMSCs are highly sensitive to microenvironmental signals, we hypothesized that priming HucMSCs within a proinflammatory environment would increase the number of exosomes secreted with enhanced anti-inflammatory properties. Subsequent miRNA profiling and pathway analysis confirmed that interleukin-1 beta (IL-1β)-induced exosomes (C-Exos) exert positive effects through miRNA regulation and signaling pathway modulation. In vitro experiments revealed that C-Exos enhance chondrocyte functionality and cartilage matrix production, as well as macrophage polarization, thereby enhancing cartilage repair. C-Exos were encapsulated in hyaluronic acid hydrogel microspheres (HMs) to ensure sustained release, leading to substantial improvements in the inflammatory microenvironment and cartilage regeneration in a rat OA model. This study outlines a strategy to tailor exosome cargo for anti-inflammatory and cartilage regenerative purposes, with the functionalized HMs demonstrating potential for OA treatment.

BCLAF1 Regulates Osteoarthritic Cartilage Degradation Through Interaction with LAMTOR2

Osteoarthritis (OA) is a progressive degenerative joint disorder with cartilage degradation as the primary cause of joint pain and loss of joint function. B-cell lymphoma-2-associated transcription factor 1 (BCLAF1) is a key regulator of apoptosis and serves as a signal transducer of the NFκB and Hif-1α pathways, both of which are involved in osteoarthritic cartilage degradation. However, whether BCLAF1 contributes to the pathogenesis of OA remains unclear. The present study aims to elucidate the role of BCLAF1 in osteoarthritic cartilage degradation and the underlying mechanisms. We found that BCLAF1 levels were increased in cartilage tissue from OA patients, elder and surgery-induced OA mice, and primary chondrocytes treated with inflammatory cytokines. Knockdown of Bclaf1 in chondrocytes inhibited the expression of catabolic factors and apoptosis rate, while promoting the expression of anabolic factors and enhancing chondrocyte functions such as viability and migration. Conversely, overexpression of Bclaf1 produced the opposite effects. Furthermore, intra-articular injection of adenovirus containing shRNA targeting Bclaf1 attenuated cartilage degradation and osteophytosis in a mouse OA model, while overexpression of BCLAF1 further aggravated cartilage degradation and osteophytosis in vivo. Through immunoprecipitation and protein mass spectrometry, we identified LAMTOR2 as a key mediator of BCLAF1 by regulating the translocation of BCLAF1 into the nucleus. Our findings reveal the critical role and key mechanisms of BCLAF1 in regulating cartilage degradation, representing a novel molecular target for the therapeutic development of OA.

Increased oxidative phosphorylation through pyruvate dehydrogenase kinase 2 deficiency ameliorates cartilage degradation in mice with surgically induced osteoarthritis

Chondrocytes can shift their metabolism to oxidative phosphorylation (OxPhos) in the early stages of osteoarthritis (OA), but as the disease progresses, this metabolic adaptation becomes limited and eventually fails, leading to mitochondrial dysfunction and oxidative stress. Here we investigated whether enhancing OxPhos through the inhibition of pyruvate dehydrogenase kinase (PDK) 2 affects the metabolic flexibility of chondrocytes and cartilage degeneration in a surgical model of OA. Among the PDK isoforms, PDK2 expression was increased by IL-1β in vitro and in the articular cartilage of the DMM model in vivo, accompanied by an increase in phosphorylated PDH. Mice lacking PDK2 showed significant resistance to cartilage damage and reduced pain behaviors in the DMM model. PDK2 deficiency partially restored OxPhos in IL-1β-treated chondrocytes, leading to increases in APT and the NAD+/NADH ratio. These metabolic changes were accompanied by a decrease in reactive oxygen species and senescence in chondrocytes, as well as an increase in the expression of antioxidant proteins such as NRF2 and HO-1 after IL-1β treatment. At the signaling level, PDK2 deficiency reduced p38 signaling and maintained AMPK activation without affecting the JNK, mTOR, AKT and NF-κB pathways. p38 MAPK signaling was critically involved in reactive oxygen species production under glycolysis-dominant conditions in chondrocytes. Our study provides a proof of concept for PDK2-mediated metabolic reprogramming toward OxPhos as a new therapeutic strategy for OA.

GAS5 long non-coding RNA interacts with microRNA-205 to relieve fibroblast-like synoviocyte inflammation and ferroptosis in osteoarthritis

This study aimed to explore the role of the growth arrest-specific five gene (GAS5) long non-coding RNA (lncRNA) in fibroblast-like synoviocytes (FLSs) during the development of osteoarthritis (OA). A total of 25 OA synovial tissues and nine healthy control tissues were collected, and their GAS5 expression was compared. To confirm GAS5 expression in vitro, interleukin (IL)-1β was used to mimic a cellular OA model based on isolated FLSs. Quantitative polymerase chain reaction revealed higher expression levels of GAS5 in OA samples than in non-OA samples. In vitro, the stimulation of FLSs by IL-1β induced high GAS5 expression. The IL-1β-exposed cells exhibited impaired growth, viability, and antioxidant capacity, as well as increased cell death, production of cellular and lipid ROS, and inflammatory cytokine levels. The expression levels of ferroptosis-related proteins in FLSs were also altered in IL-1β-exposed cells. GAS5 was observed to directly target and inhibit micro-RNA 205, partially reversing the effect of GAS5 silencing on cell proliferation, cell death, oxidative stress, inflammation, and FLS ferroptosis. FLS ferroptosis is recognized to be involved in OA development, and the downregulation of the GAS5 lncRNA exhibits protective effects by suppressing ferroptosis and sponging miR-205 in FLSs in OA, thereby providing a novel strategy for the treatment of OA. The GAS5-miR-205 axis can regulate inflammation and oxidative stress in the FLSs of patients with OA.

The cross-talk between the cGAS-STING signaling pathway and chronic inflammation in the development of musculoskeletal disorders

Musculoskeletal disorders (MSDs) comprise diverse conditions affecting bones, joints, and muscles, leading to pain and loss of function, and are one of the most prevalent and major global health concerns. One of the hallmarks of MSDs is DNA damage. Once accumulated in the cytoplasm, the damaged DNA is sensed by the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway, which triggers the induction of type I interferons and inflammatory cytokines. Thus, this pathway connects the musculoskeletal and immune systems. Inhibitors of cGAS or STING have shown promising therapeutic effects in the pre-clinical models of several MSDs. Systemic, chronic, low-grade inflammation (SCLGI) underlies the development and maintenance of many MSDs. Failure to resolve SCLGI has been hypothesized to play a critical role in the development of chronic diseases, suggesting that the successful resolution of SCLGI will result in the alleviation of their related symptomatology. The process of inflammation resolution is feasible by specialized pro-resolving mediators (SPMs), which are enzymatically generated from dietary essential polyunsaturated fatty acids (PUFAs). The supplementation of SPMs or their stable, small-molecule mimetics and receptor agonists has revealed beneficial effects in inflammation-related animal models, including arthropathies, osteoporosis, and muscle dystrophy, suggesting a translational potential in MSDs. In this review, we substantiate the hypothesis that the use of cGAS-STING signaling pathway inhibitors together with SCLG-resolving compounds may serve as a promising new therapeutic approach for MSDs.

Dipeptidyl Peptidase 4 (DPP4) Exacerbates Osteoarthritis Progression in an Enzyme-Independent Manner

Chondrocyte senescence is a key driver of osteoarthritis (OA). Mitochondrial dysfunction and oxidative stress can induce chondrocyte senescence. However, the specific mechanisms by which senescence contributes to OA progression are not fully understood. Here, it is attested that Dipeptidyl peptidase 4 (DPP4) is significantly upregulated in osteoarthritic chondrocytes in both humans and mice. DPP4 promotes oxidative stress and cellular senescence in chondrocytes through excessive mitochondrial fission in an enzyme-independent manner. Intra-articular injection of adeno-associated virus 2 to upregulate DPP4 in chondrocytes promotes post-traumatic and aging-induced OA in mice in an enzyme-independent manner. Mechanistically, DPP4 competitively binds to Myosin heavy chain 9 (MYH9), interfering with its E3 ubiquitin ligase Carboxyl terminus of Hsc70-interacting protein (CHIP), and thereby upregulates MYH9 expression. Finally, a small molecule, 4,5-Dicaffeoylquinic acid is identified, which disrupts the interaction between DPP4 and MYH9, thereby ameliorating post-traumatic and aging-induced OA in mice caused by DPP4 upregulation. The study indicates that the non-enzymatic activity of DPP4 is a promising target for OA treatment.

Cartilage Tissue Engineering in Multilayer Tissue Regeneration

The functional and structural integrity of the tissue/organ can be compromised in multilayer reconstructive applications involving cartilage tissue. Therefore, multilayer structures are needed for cartilage applications. In this review, we have examined multilayer scaffolds for use in the treatment of damage to organs such as the trachea, joint, nose, and ear, including the multilayer cartilage structure, but we have generally seen that they have potential applications in trachea and joint regeneration. In conclusion, when the existing studies are examined, the results are promising for the trachea and joint connections, but are still limited for the nasal and ear. It may have promising implications in the future in terms of reducing the invasiveness of existing grafting techniques used in the reconstruction of tissues with multilayered layers.

Mechanistic study of the regulation of mitochondrial function by the GPNMB/Nrf2/NF-κB signaling pathway mediated by Quzhi Tang to alleviate chondrocyte senescence

ETHNOPHARMACOLOGICAL RELEVANCE

Quzhi Tang (QZT) is a compound formula consisting of six traditional Chinese medicinal herbs. It has achieved good clinical results in the treatment of knee osteoarthritis (KOA), and the potential drug mechanisms involved are worth exploring in depth.

MATERIALS AND METHODS

Using single-cell transcriptome analysis, this study identified the key target of senescence, GPNMB. Then, it investigated the mechanism by which QZT regulates the GPNMB/Nrf2/NF-κB signaling pathway to repair mitochondrial damage and ameliorate the process of chondrocyte senescence.

RESULTS

We collected cartilage tissues from mice and identified GPNMB as a key target of chondrocyte senescence by combining transcriptomics, histopathology, molecular biology, and immunology methods. The effects of QZT on the level of chondrocyte senescence in mice and its ameliorative effect on KOA were studied. In in vivo experiments, we explored the mechanism of GPNMB in the development of senescence in detail and revealed that, after siRNA-GPNMB interference, chondrocytes exhibited reduced impairment of mitochondrial function and senescence under equal amounts of stimuli, increasing Nrf2 expression and reducing NF-κB expression. In addition, the level of oxidative stress increased in chondrocytes overexpressing GPNMB after lentiviral infiltration, aggravating the impairment of mitochondrial function. After treatment with QZT, chondrocytes overexpressing GPNMB were able to increase Nrf2 expression, decrease NF-κB expression, repair mitochondrial damage, and improve the degree of chondrocyte aging.

CONCLUSION

We concluded that the GPNMB/Nrf2/NF-κB signaling pathway plays an important role in chondrocyte senescence and that QZT was able to reduce intracellular oxidative stress and restore impaired mitochondrial function by regulating the expression level of the GPNMB/Nrf2/NF-κB signaling pathway, reducing the level of chondrocyte senescence in the KOA process.

Advances in the pathology and treatment of osteoarthritis

BACKGROUND

Osteoarthritis (OA), a widespread degenerative joint disease, predominantly affects individuals from middle age onwards, exhibiting non-inflammatory characteristics. OA leads to the gradual deterioration of articular cartilage and subchondral bone, causing pain and reduced mobility. The risk of OA increases with age, making it a critical health concern for seniors. Despite significant research efforts and various therapeutic approaches, the precise causes of OA remain unclear.

AIM OF REVIEW

This paper provides a thorough examination of OA characteristics, pathogenic mechanisms at various levels, and personalized treatment strategies for different OA stages. The review aims to enhance understanding of disease mechanisms and establish a theoretical framework for developing more effective therapeutic interventions.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review systematically examines OA through multiple perspectives, integrating current knowledge of clinical presentation, pathological mechanisms, and associated signaling pathways. It assesses diagnostic methods and reviews both pharmacological and surgical treatments for OA, as well as emerging tissue engineering approaches to manage the disease. While therapeutic strategies such as exercise, anti-inflammatory drugs, and surgical interventions are employed to manage symptoms and modify joint structure, none have been able to effectively halt OA's advancement or achieve long-lasting symptom relief. Tissue engineering strategies, such as cell-seeded scaffolds, supportive matrices, and growth factor delivery, have emerged as promising approaches for cartilage repair and OA treatment. To combat the debilitating effects of OA, it is crucial to investigate the molecular basis of its pathogenesis and seek out innovative therapeutic targets for more potent preventive and treatment strategies.

Metabolism-Related Adipokines and Metabolic Diseases: Their Role in Osteoarthritis

Osteoarthritis (OA) affects several joints but tends to be more prevalent in those that are weight-bearing, such as the knees, which are the most heavily loaded joints in the body. The incidence and disability rates of OA have continued to increase and seriously jeopardise the quality of life of middle-aged and older adults. However, OA is more than just a wear and tear disease; its aetiology is complex, and its pathogenesis is poorly understood. Metabolic syndrome (MetS) has emerged as a critical driver of OA development. This condition contributes to the formation of a distinct phenotype, termed metabolic syndrome-associated osteoarthritis (MetS-OA),which differs from other metabolically related diseases by its unique pathophysiological mechanisms and clinical presentation. As key mediators of MetS, metabolic adipokines such as leptin, lipocalin, and resistin regulate inflammation and bone metabolism through distinct or synergistic signaling pathways. Their modulation of inflammatory responses and bone remodeling processes plays a critical role in the pathogenesis and progression of OA. Due to their central role in regulating inflammation and bone remodeling, metabolic adipokines not only deepen our understanding of MetS-OA pathogenesis but also represent promising targets for novel therapeutic strategies that could slow disease progression and improve clinical outcomes in affected patients.

Delivery of FGF18 using mRNA-LNP protects the cartilage against degeneration via alleviating chondrocyte senescence

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease with an immense unmet medical need. FGF18 protein is a potential regenerative factor for cartilage repair. However, traditional protein delivery methods have limited efficacy due to the short lifetime and shallow infiltration.

RESULTS

In this work, we discovered that lipid nanoparticle (LNP) can infiltrate and deliver FGF18 mRNA deeper in the cartilage than proteins. After mRNA UTR optimization and chemical modification, the expression of FGF18 can last up to 6 days in the cartilage. Furthermore, delivering FGF18 mRNA activates FOXO3a-autophagy pathway, which protects against chondrocyte degeneration and senescence. Local intra-articular injection of FGF18 mRNA-LNP significantly alleviates OA symptoms in DMM and senile OA models. Sustained expression and accessibility of FGF18-mRNA to deeper chondrocytes makes LNP-mRNA more effective than FGF18 recombinant protein.

CONCLUSIONS

In summary, this study presents a novel approach superior to recombinant protein alone and holds promise as a new therapeutic strategy for OA.

Recent advances in the management of knee osteoarthritis: a narrative review

Knee osteoarthritis (OA) is a common condition that causes pain and reduces the quality of life for many people. It also leads to high health and financial costs. Managing knee OA pain requires using different methods together for the best results. This review overviews current therapeutic options for knee OA pain, focusing on their efficacy, safety, and potential roles in clinical practice. Topical treatments, such as NSAIDs and capsaicin, offer significant pain relief with minimal systemic side effects and are suitable for initial therapy, together with nonpharmacologic interventions like exercise and, when relevant, weight loss. Oral analgesics, including acetaminophen and opioids, have limited efficacy and serious side effects, making them appropriate only for short-term or rescue therapy. Intra-articular injections, such as corticosteroids, hyaluronic acid, and platelet rich plasma, demonstrate varying levels of efficacy and safety. Nutritional supplements, including curcumin, Boswellia serrata, and glucosaminechondroitin combinations, offer modest benefits and are best used as adjuncts to standart treatment. Nonpharmacological treatments, such as transcutaneous electrical nerve stimulation (TENS), acupuncture, and local heat therapy, provide variable pain relief and should be customized based on individual patient responses. Targeted biologic agents, such as antibodies to TNF-α, IL-1, and NGF, hold promise for more precise pain relief; however, further research is required to establish their routine use. Treating knee OA pain should be personalized, combining several methods. Research must continue to improve treatments and make them safer.

Evaluating the efficacy of intra-articular polydioxanone (PDO) injections as a novel viscosupplement in osteoarthritis treatment

AIMS

Osteoarthritis (OA) is a chronic joint disorder marked by cartilage breakdown, bone alterations, and inflammation, leading to significant pain and disability. Current therapeutic strategies, ranging from lifestyle interventions to pharmacological and surgical treatments, offer limited efficacy and are often accompanied by side effects. This study investigates the potential of Polydioxanone (PDO), a biocompatible synthetic polymer, as a novel intra-articular (IA) viscosupplement in OA.

MATERIALS AND METHODS

A validated rabbit model of OA was employed to compare the therapeutic effects of IA injections of PDO against established viscosupplements like hyaluronic acid (HA) and Conjuran (CJR). Sixty rabbits with collagenase-induced OA were randomized into four groups, receiving respective treatments over 12 weeks. The effect of PDO was analyzed by histopathological examination, immunofluorescence staining (IF), immunoblotting, quantitative real-time polymerase chain reaction (qRT-PCR), and enzyme-linked immunosorbent assay (ELISA).

KEY FINDINGS

The histopathological examination revealed substantial improvements in the PDO group's cartilage structure and matrix composition. qRT-PCR, IF staining, and Western Blot showed significant downregulation of matrix metalloproteinases (MMPs) and upregulation of type II collagen (COL II) and aggrecan (ACAN). ELISA results corroborated decreased inflammatory mediators- interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) in the PDO-treatment group.

SIGNIFICANCE

Preliminary results indicate that PDO may enhance cartilage regeneration and reduce inflammation, suggesting it is a viable and superior treatment option for OA. These findings merit further investigation to translate into clinical applications.

VEGFA, MYC, and JUN are abnormally elevated in the synovial tissue of patients with advanced osteoarthritis

Osteoarthritis (OA), affecting > 500 million people worldwide, profoundly affects the quality of life and ability to work. The mitogen-activated protein kinase (MAPK) signaling pathway plays an essential role in OA. To address the lack of studies focused on synovial cells in OA, we evaluated the expression patterns and roles of the MAPK signaling pathway components in OA synovial tissues using bioinformatics. The JUN, MYC, and VEGFA expression levels were significantly higher in the synovial tissues of patients with OA than in control tissues. These loci were closely related to abnormal proliferation, inflammation, and angiogenesis in the synovial tissues of patients with OA. We speculate that Myc and VEGFA activate the p38-MAPK signaling pathway to further activate Jun, thereby promoting abnormal inflammation, proliferation, and angiogenesis in OA synovial tissue. The high MYC, JUN, and VEGFA expression was positively correlated with the patients' K-L score, pain time, and synovial score. Furthermore, the high p38-MAPK and P-p38-MAPK expression confirmed that the abnormal expression and activation of the MAPK signaling pathway occurred in the synovial tissue of patients with OA. Our findings may provide a new direction for the clinical diagnosis and treatment of OA and insights into its pathogenesis.