Mechanical stress abnormalities promote chondrocyte senescence - The pathogenesis of knee osteoarthritis

Klotho senses mechanical stimuli and modulates tension-induced osteogenesis

Delicate external mechanosensing, efficient intracellular mechanotransduction and effective alveolar bone remodeling lay the foundation of orthodontic tooth movement (OTM). Periodontal ligament stem cells (PDLSCs) are thought to be the primary cells that withstand mechanical stimuli and respond to biomechanical signals during orthodontic treatment. Nevertheless, the cellular and molecular mechanisms of orthodontic force-induced mechanosignaling and osteogenesis in PDLSCs still remain unclear. In the present study, we hypothesize that the ageing suppressor, Klotho, is correlated with orthodontic force-triggered mechanical signaling cascades, further contributing to alveolar bone remodeling. This study reveals that Klotho expression is notably upregulated via cytoskeletal-nuclei-mediated epigenetic modifications, consistent with osteogenic differentiation on the tension side during OTM. Additionally, Klotho deficiency undermines tensile force-induced new bone formation in NFκB- and PI3K/Akt-dependent manners. Notably, RNA sequencing (RNA-seq) results and targeted force application experiments unveil that Klotho not only functions as a downstream effector of external stress but also acts as an upstream regulator in mechanical signaling for the first time. In summary, we identify the indispensable role of Klotho in mechanotransduction and alveolar bone formation, which provide a latent target of linking cell senescence to mechanical force in future studies and offer novel insights into orthodontic force-induced tooth movement and bone remodeling.

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.

Hyperosmotic stress-induced NLRP3 inflammasome activation via the mechanosensitive PIEZO1 channel in dry eye corneal epithelium

The activation of the NLRP3 inflammasome by hyperosmotic stress is a critical pathophysiological response in dry eye disease (DED), driving the chronic cycle of inflammation on the ocular surface. The specific mechanism underlying hyperosmotic mechanical stimulation activates the NLRP3 inflammasome remains unclear. This study provides evidence that PIEZO1, a mechanosensitive ion channel, functions as the primary receptor for corneal epithelial cells in sensing mechanical stimulation induced by tear hyperosmolarity. Inhibition of PIEZO1 significantly reduces NLRP3 inflammasome-associated pyroptosis in corneal epithelial cells. These findings suggest a therapeutic strategy targeting mechanosensitive ion channels to manage chronic ocular surface inflammation in DED patients. Structured Abstract.

PURPOSE

PIEZO1 modulates the inflammatory response by translating mechanical signals from osmotic pressure into biological processes. This study investigates the functional role of PIEZO1 in activating the NLRP3 inflammasome in corneal epithelial cells under hyperosmotic stress and evaluates its contribution to the pathogenesis of dry eye disease (DED).

METHODS

In the in vitro experiments, immortalized human corneal epithelial cells (HCECs) were cultured under hyperosmotic conditions (450mOsm). For in vivo studies, a dry eye disease mouse model was established by subcutaneous injection of scopolamine (SCOP) in C57BL/6 mice. After successfully inducing the dry eye model, corneal epithelial cell damage was assessed through corneal fluorescein staining scores and TUNEL assays. Protein expression levels were examined via western blotting and immunofluorescence staining, while mRNA expression was analyzed using quantitative RT-PCR. Activation of the NLRP3 inflammasome was evaluated by measuring IL-1β protein cleavage and the formation of ASC speckles.

RESULTS

In the DED model, activation of the NLRP3 inflammasome was detected in corneal epithelial cells, along with increased expression of PIEZO1. The PIEZO1-specific agonist Yoda1 induced upregulation of NLRP3 inflammasome-related gene expression and triggered NLRP3 inflammasome activation. Conversely, silencing PIEZO1 using siRNA or inhibiting its activity suppressed hyperosmotic stress-induced changes in NLRP3 inflammasome-related gene expression and activation. In vivo, PIEZO1 inhibition effectively prevented NLRP3 inflammasome activation in corneal epithelial cells and restored the damaged phenotype associated with dry eye disease.

CONCLUSION

Hyperosmotic stress-induced activation of the NLRP3 inflammasome in corneal epithelial cells is mediated through PIEZO1 activation. The identification of PIEZO1's role in this DED-related pathophysiological response highlights its potential as a therapeutic target for mitigating inflammation in clinical settings.

Body roundness index and the risk of knee osteoarthritis: evidence from the China Health and Retirement Longitudinal Study

Objective

Previous cross-sectional studies have demonstrated that the body roundness index (BRI) is associated with knee osteoarthritis (KOA). However, no longitudinal studies have confirmed this association. This study aims to explore the link between BRI and KOA risk in the Chinese population through longitudinal analysis and to evaluate its utility in early diagnosis and risk prediction.

Methods

This study utilizes data from the China Health and Retirement Longitudinal Study (CHARLS). A total of 7,318 participants who were followed from 2015 to 2020 were included. BRI was calculated using physical examinations and questionnaire data, and participants were categorized by quartiles. The relationship between BRI and KOA risk was assessed using multivariate weighted regression models and trend tests, while subgroup and sensitivity analyses were conducted to ensure the robustness of the findings.

Results

After 5 years of follow-up, 1,035 participants (14.14%) were diagnosed with KOA. Findings indicate a positive correlation between BRI and KOA risk (HR = 1.08, 95% CI: 1.02-1.13, p = 0.0039), with an increasing trend in KOA risk across BRI quartiles (p for trend = 0.0033). Subgroup analysis reveals that the association is particularly strong among individuals aged 50-59, males, those living in rural areas, and those without cardiovascular disease.

Conclusion

This study establishes that an increase in BRI significantly elevates KOA risk. These findings suggest that BRI could be an effective tool for KOA risk assessment and could contribute to the development of personalized prevention strategies. Additionally, BRI is valuable in elucidating the potential mechanisms linking body fat distribution and inflammatory responses in KOA progression.

Metformin-Loaded Tannic Acid Nanoparticles Attenuate Osteoarthritis by Promoting Chondrocyte Mitochondria Homeostasis Based on Mitocytosis

The oxidative stress microenvironment and mitochondrial dysfunction in chondrocytes are key mechanisms in the development of osteoarthritis (OA). Metformin (Met) has demonstrated multiple effects on mitochondria and is regarded as a potential therapeutic agent for OA. The low blood flow characteristics in the joint cavity make targeted local delivery of metformin crucial for its clinical application. In this study, tannic acid (TA), with its natural antioxidant and anti-inflammatory properties, was used to prepare self-assemble Met-loaded TA nanoparticles (NPs). The NPs exhibit excellent reactive oxygen scavenging capability, stability in various media, and an acid-responsive release of Met. In Vitro experiments showed that NPs possess excellent biocompatibility, effectively protecting chondrocyte viability in OA's pathological environment and preventing the senescence phenotype. In addition, NPs promoted the expression of antioxidant elements in chondrocytes, restored mitochondrial membrane potential, and enhanced mitocytosis to improve mitochondrial quality. In vivo experiments further confirmed that intra-articular injection of NPs in rats with post-traumatic OA improves cartilage matrix degradation, osteophyte formation, and subchondral bone sclerosis over 8 weeks. Tissue staining further confirmed the protective effects of NPs on chondrocyte mitochondria. Importantly, both in vivo and in vitro experiments revealed that NPs provided superior cellular protection compared to TA or Met alone. Overall, this study demonstrates that NPs effectively against OA cartilage degeneration, with the advantages of easy preparation, high efficiency, and biosafety.

The Mechanism by Which Estrogen Level Affects Knee Osteoarthritis Pain in Perimenopause and Non-Pharmacological Measures

Perimenopausal women have fluctuating estrogen levels, which often trigger a range of symptoms of perimenopausal syndromes as estrogen levels decrease. Changes in perimenopausal estrogen levels are closely related to pain in knee osteoarthritis (KOA), which has long been a research area of great interest in perimenopausal women. In recent years, it has been found that perimenopausal estrogen levels have an important role in KOA pain, namely, that estrogen can affect KOA pain through the regulation of inflammatory responses, inhibition of cellular senescence and apoptosis, and modulation of neurotransmitters, which may provide new ideas for KOA treatment. This study aims to describe the mechanism of estrogen level on knee osteoarthritis pain in perimenopause and related non-pharmacological measures, such as physical therapy, physical factor therapy, traditional Chinese medicine, and diet, which can provide a reference for the study and treatment of pain in perimenopausal women with KOA.

Chondrocyte Ferritinophagy as a Molecular Mechanism of Arthritis-A Narrative Review

Osteoarthritis (OA) is a prevalent joint disease affecting orthopedic patients. Its incidence is steadily increasing, causing great economic hardship for individuals and society as a whole. OA is connected with risk factors such as genetics, obesity, and joint diseases; yet, its pathophysiology is still largely understood. At present, several cell death pathways govern the initiation and advancement of OA. It has been discovered that the onset and progression of OA are strongly associated with pyroptosis, senescence, apoptosis, ferroptosis, and autophagy. Ferroptosis and autophagy have not been well studied in OA, and elucidating their molecular mechanisms in chondrocytes is important for the diagnosis of OA. For this reason, we aim was reviewed recent national and international developments and provided an initial understanding of the molecular pathways underlying autophagy and ferroptosis in OA. We determined the reference period to be the last five years by searching for the keywords "osteoarthritis, mechanical stress, Pizeo1, ferroptosis, autophagy, ferritin autophagy" in the three databases of PUBMED, Web of Science, Google Scholar. We then screened irrelevant literature by reading the abstracts. Ferroptosis is a type of programmed cell death that is dependent on reactive oxygen species and Fe2+. It is primarily caused by processes linked to amino acid metabolism, lipid peroxidation, and iron metabolism. Furthermore, Piezoelectric mechanically sensitive ion channel assembly 1 (PIEZO1), which is triggered by mechanical stress, has been revealed to be intimately associated with ferroptosis events. It was found that mechanical injury triggers changes in the intracellular environment of articular chondrocytes (e.g., elevated levels of oxidative stress and increased inflammation) through PIEZO1, ultimately leading to iron death in chondrocytes. Therefore, we believe that PIEZO1 is a key initiator protein of iron death in chondrocytes. Widely present in eukaryotic cells, autophagy is a lysosome-dependent, evolutionarily conserved catabolic process that carries misfolded proteins, damaged organelles, and other macromolecules to lysosomes for breakdown and recycling. Throughout OA, autophagy is activated to differing degrees, indicating that autophagy may play a role in the development of OA. According to recent research, autophagy is a major factor in the process that leads cells to ferroptosis. Despite the notion of ferritinophagy being put forth, not much research has been done to clarify the connection between ferroptosis and autophagy in OA.

Potential and challenges of utilizing exosomes in osteoarthritis therapy (Review)

Exosomes are integral to the pathophysiology of osteoarthritis (OA) due to their roles in mediating intercellular communication and regulating inflammatory processes. Exosomes are integral to the transport of bioactive molecules, such as proteins, lipids and nucleic acids, which can influence chondrocyte behavior and joint homeostasis. Given their properties of regeneration and ability to target damaged tissues, exosomes represent a promising therapeutic avenue for OA treatment. Exosomes have potential in promoting cartilage repair, reducing inflammation and improving overall joint function. However, several challenges remain, including the need for standardized isolation and characterization methods, variability in exosomal content, and regulatory hurdles. The present review aims to provide a comprehensive overview of the current understanding of exosome mechanisms in OA and their therapeutic potential, while also addressing the ongoing challenges faced in translating these findings into clinical practice. By consolidating existing research, the present review aims to pave the way for future studies aimed at optimizing exosome‑based therapies for effective OA management.

Molecular Mechanisms of Immunoinflammatory Infiltration and Ferroptosis in Arthritis Revealed by a Combination of Bioinformatics and Single-Cell Analysis

Background

Osteoarthritis (OA) is a widespread chronic inflammatory disease in orthopedics, and its molecular mechanisms are still poorly understood.

Objective

The purpose of this work was to detect the immunological infiltration of OA and the manner of cell death utilizing bioinformatics and single-cell analysis in order to provide guidelines for clinical therapy and medicine.

Methods

Ferroptosis -associated genes were sourced from the ferroptosis Database, single-cell and bioinformatic expression profiles were chosen from the Gene Expression Comprehensive Database, and OA gene information was taken from GeneCards. To ascertain the categorization status of OA cells, single-cell analysis was conducted. Protein-protein interaction networks were established by SRING analysis, and functional enrichment was examined in the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases. The important proteins of immune-ferroptosis death in OA were elucidated through co-analysis. Last but not least, network pharmacology and molecular docking support the mechanism by which resveratrol controls Ferroptosis in OA.

Results

The development of OA was found to be tightly related to chondrocytes and immune cells, particularly T and macrophage cells, according to single-cell analysis profile. In patients with OA, immune infiltration also revealed a notable infiltration of T cells, B cells, NK cells, monocytes, and macrophages. The hub genes were shown to be enriched in immunological responses, chemokine-mediated signaling pathways, and inflammatory responses, according to enrichment analysis. The main signaling pathways included autophagy, ferroptosis, the HIF-1 signaling pathway, the PI3K-Akt signaling pathway, and the FoxO signaling pathway. Ferroptosis is a significant cell death mechanism that contributes to the advancement of osteoarthritis. Ferroptosis in chondrocytes is lessened by resveratrol regulation of GPX4, TFRC, and SLC7A11.

Conclusion

Various immune cell infiltrates, especially T cells and macrophages, play an important role in the progression of OA, and resveratrol ameliorates OA by modulating chondrocyte ferroptosis.

Shining light on knee osteoarthritis: an overview of vitamin D supplementation studies

Background

The impact of knee osteoarthritis on individuals' daily functioning is significant. In recent years, Vitamin D supplements cure osteoarthritis has garnered attention from medical professionals and patients due to its simplicity and portability. Several systematic reviews (SRs) and meta-analyses (MAs) have examined the efficacy of vitamin D supplementation for knee osteoarthritis, yet there is variability in their methodology and quality.

Objective

To search, gather, and analyze data on the characteristics and quantitative results of SR/MA in patients with KOA treated with Vitamin D supplementation, and objectively evaluate the efficacy of supplements. Then, provides clinical evidence and recommendations the clinical use of vitamin D supplementation.

Methods

Two individuals reviewed and collected data from four databases until October 2023. AMSTAR-2, ROBIS, PRISMA 2020, and GRADE tools were used to evaluate the methodological quality, bias risk, reporting quality, and evidence strength of all SR/MA. Additionally, we applied the corrected covered area (CCA) method to measure overlap in randomized controlled trials (RCTs) cited among the SR/MA.

Results

3 SRs and 6 MAs were included in the analysis: 3 studies were low quality by AMSTAR-2, and 6 studies were very low quality. According to ROBIS, 6 studies were high-risk and 3 were low-risk. In PRISMA 2020 reporting quality, most studies showed deficiencies in comprehensive literature search strategy, reasons for literature exclusion, data preprocessing for meta-analysis, exploration of reasons for heterogeneity, sensitivity analysis, publication bias, and disclosure of funding and conflicts of interest. Grading the quality of evidence in GRADE consisted of 5 items of moderate quality, 14 items of low quality, and 10 items of very low quality. Bias risk and imprecision were the main factors for downgrading. The calculation of RCT overlap between SR/MA using CCA showed a high degree of overlap.

Conclusion

Vitamin D supplementation may show potential efficacy in ameliorating symptoms of KOA. The evidence indicates that Vitamin D supplements for knee osteoarthritis can improve patients' Total WOMAC scores and synovial fluid volume in the joints. Nevertheless, due to the generally low quality of current studies, future research should prioritize improving the quality of primary studies to establish the efficacy of vitamin D supplementation for KOA with more robust scientific evidence.

Systematic review registration

The protocol of this overview was registered in the International Prospective Register of Systematic Reviews (PROSPERO) (https://www.crd.york.ac.uk/PROSPERO/) with the registration number CRD42024535841.

Unveiling MiR-3085-3p as a modulator of cartilage degeneration in facet joint osteoarthritis: A novel therapeutic target

Background

Low back pain (LBP) is generally caused by lumbar degeneration without effective treatment. Lumbar degeneration is influenced by aberrant axial mechanical stress (MS), with facet joint osteoarthritis (FJOA) representing one of its primary pathological manifestations. MicroRNA (miRNA), functioning as an early intermediate in the transcription process, has frequently been demonstrated to serve as a critical mediator linking mechanical stress perception with cellular processes such as growth, development, aging, and apoptosis. We hypothesized that miR-3085-3p regulates chondrocyte apoptosis under mechanical stress, influencing FJOA and serving as a key regulator.

Methods

The severity of cartilage degeneration in bipedal standing models (BSM) was established and validated through micro-CT and histopathology. Cyclic tensile strain experiments (CTS) were conducted on the ATDC5 cell line to simulate MS. In situ hybridization was utilized to assess the expression levels of miR-3085-3p in degraded facet articular cartilage. The role of miR-3085-3p and its interaction with the downstream mRNA target Hspb6 were investigated through a combination of bioinformatic analysis, quantitative real-time polymerase chain reaction, western blotting, immunofluorescence, and luciferase assay. In vivo experiments on BSM, the functional impact of miR-3085-3p was further examined through transfection with adeno-associated virus (AAV).

Results

It was observed that miR-3085-3p induced endoplasmic reticulum (ER) stress and apoptosis in chondrocytes and cartilage tissues under MS. The detrimental impact of miR-3085-3p was associated with the downregulation of Hspb6 expression, resulting in disruption of endoplasmic reticulum folding function. Additionally, intra-articular transfection of AAV miR-3085-3p mimics in mice facet joints led to spontaneous cartilage loss, while AAV miRNA-3085-3p sponge administration mitigated FJOA in the murine BSM model.

Conclusion

Mechanical stress-regulated miR-3085-3p up regulation induced the ER stress and aggravates FJOA development through targeting HSPB6, suggesting miR-3085-3p may be a novel therapeutic target for FJOA.Translational potential of this article: Our study confirmed the elevated expression of miR-3085-3p in lumbar facet joints following mechanical stress loading, suggesting that miR-3085-3p may serve as a biomarker for the clinical management of FJOA. Additionally, we demonstrated that the knockdown of miR-3085-3p in animal facet joints mitigated facet joint degeneration, thereby identifying a potential therapeutic target for FJOA.

Anxiety and depression as potential risk factors for limited pain management in patients with elderly knee osteoarthritis: a cross-lagged study

BACKGROUND

Pain management for knee osteoarthritis (KOA) patients is challenging. Pain arises from both physiological and psychological interactions, with anxiety and depression potentially contributing as risk factors that hinder effective pain management in KOA patients.

METHODS

Before treatment(T1), A total of 206 elderly inpatients with KOA were enrolled based on initial screening criteria. After treatment (T2), patients were selected based on inclusion and exclusion criteria, and completed follow-up through phone or online questionnaires. The interval between T1 and T2 was three months. Outcome measures included the Visual Analogue Scale (VAS) for pain intensity, Beck Anxiety Inventory (BAI) for anxiety, and Geriatric Depression Scale (GDS) for depression. Descriptive and bivariate analyses were used to evaluate the pain, anxiety and depression of the participants. A cross-lagged model was used to examine the temporal and causal associations among pain, anxiety, and depression.

RESULTS

91% of elderly patients with KOA experienced at least mild depression. Furthermore, 31% of patients reported mild or higher levels of anxiety. At the same time, pain, depression, and anxiety were significantly correlated and mutually predictive(all p < 0.01). Across the different time points, Depression and anxiety at T1 positively predicted pain at T2,with correlation coefficients of 0.19 (p < 0.05) and 0.07 (p < 0.05), respectively.

CONCLUSIONS

Anxiety and depression may be potential risk factors limiting the effectiveness of pain management in KOA patients. Clinical treatment should regularly evaluate anxiety and depression levels and integration of psychological interventions or appropriate antianxiety and antidepressant medications.

CLINICAL TRIAL NUMBER

Not applicable, for the investigative research nature of the study.

The Molecular Mechanism Investigation of HBP-A Slows Down Meniscus Hypertrophy and Mineralisation by the Damage Mechanical Model

HBP-A is the main active component of a traditional Chinese medicine Huaizhen Yanggan Capsule, for the remarkable treatment of knee osteoarthritis (KOA). This study aimed to elucidate the ameliorative effect of HBP-A on meniscus hypertrophy and mineralisation in KOA and the molecular mechanism of its action. An Hartley guinea pig model of KOA that underwent anterior cruciate ligament transection (ACLT) and a model of rat primary meniscus fibrochondrocytes (PMFs) were used to investigate the ameliorative effect of HBP-A on meniscal hypertrophy and calcification and its signal transduction mechanism of action. The results show that Guinea pig's meniscus width, as well as the area of meniscus calcification and meniscus and articular cartilage injury score, were significantly reduced in the HBP-A intervention group compared to the ACLT group. The expression levels of mtrix metalloproteinase 13 (MMP13), runt-related transcription factor 2 (Runx2), Indian hedgehog (Ihh), alkaline phosphatase (ALP), and ankylosis homologue (ANKH) at the protein and gene level significantly decreased in the HBP-A intervention group compared to the ACLT group. In vitro study, apoptosis, hypertrophy, and calcification of rat PMFs after 10% stretch force were significantly improved with HBP-A intervention. Western blot and RT-qPCR showed that hypertrophy, calcification, and p38 MAPK signalling pathway-related markers of PMFs were incredibly depressed in the HBP-A intervention group compared to the 10% stretch force group. In conclusion, HBP-A can slow down meniscus hypertrophy and mineralisation induced by abnormal mechanical loading, and its mechanism of action may be through the p38-MAPK signalling pathway.

Effects of the umbilical cord mesenchymal stem cells in the treatment of knee osteoarthritis: A systematic review and meta-analysis

BACKGROUND

This study aimed to evaluate the effects of umbilical cord mesenchymal stem cells (UC-MSCs) in the treatment of knee osteoarthritis.

METHODS

PubMed, Web of Science, Cochrane Library, Embase, Chinese National Knowledge Infrastructure and Wanfang databases were searched from inception to March 31, 2024. RevMan 5.3 was used to conduct meta-analyses of the final included studies.

RESULTS

Three randomized controlled studies were conducted. Western Ontario and McMaster Universities Osteoarthritis Index was reduced in the UC-MSCs group compared that in to the control group (mean difference: -25.85; 95% confidence interval: -41.50, -10.20; P = .001). Knee Lysholm Score was improved in the UC-MSCs group compared with the control group (mean difference: 18.33; 95% confidence interval: 12.89, 23.77; P < .00001). Egger test showed P = .583, indicating no publication bias. Sensitivity analysis indicated that the results were stable.

CONCLUSION

Intra-articular injection of UC-MSCs improved function and reduced pain in patients with knee osteoarthritis. However, the number of included studies was small and more studies are needed to confirm this.

Identification of genetic association between mitochondrial dysfunction and knee osteoarthritis through integrating multi-omics: a summary data-based Mendelian randomization study

OBJECTIVE

Association between mitochondrial dysfunction and osteoarthritis (OA) has been consistently investigated, yet their genetic association remains obscure. In this study, mitochondrial-related genes were used as instrumental variables to proxy for mitochondrial dysfunction, and summary data of knee OA (KOA) were used as outcome to examine their genetic association.

METHODS

We obtained 1136 mitochondrial-related genes from the human MitoCarta3.0 database. Genetic proxy instruments for mitochondrial-related genes from studies of corresponding gene expression (n = 31,684) and protein (n = 35,559) quantitative trait locus (eQTLs and pQTLs), respectively. Aggregated data for KOA (62,497 KOA cases and 333,557 controls) were extracted from the largest OA genome-wide association study (GWAS). We integrated QTL data with KOA GWAS data to estimate their genetic association using summary data-based Mendelian randomization analysis (SMR). Additionally, we implemented Bayesian colocalization analysis to reveal whether suggestive mitochondrial-related genes and KOA were driven by a same genetic variant. Finally, to validate the primary findings, replication study (24,955 cases and 378,169 controls) and multi-SNP-based SMR (SMR-multi) test was performed.

RESULTS

Through SMR analysis, we found that the expression levels of 2 mitochondrial-related genes were associated with KOA risk. Specifically, elevated gene expression levels of the IMMP2L (odds ratio [OR] = 1.056; 95% confidence interval [CI] = 1.030-1.082; P-FDR = 0.004) increased the risk of KOA. Conversely, increased gene expression levels of AKAP10 decreased the risk of KOA (OR = 0.955; 95% CI, 0.934-0.977; P-FDR = 0.019). Colocalization analysis demonstrated that AKAP10 (PP.H4 = 0.84) and IMMP2L (PP.H4 = 0.91) shared the same genetic variant with KOA. In addition, consistent results were found in replication study and SMR-multi test, further demonstrating the reliability of our findings.

CONCLUSIONS

In summary, our analyses revealed the genetic association between mitochondrial dysfunction proxied by mitochondrial-related genes and KOA, providing new insight into potential pathogenesis of KOA. Furthermore, these identified candidate genes offer the possibility of clinical drug target development for KOA. Key points • This is the first SMR study to explore the genetic association between mitochondrial dysfunction proxied by mitochondrial-related genes and KOA. • Sufficient evidence to support genetic association between the expression levels of AKAP10 and IMMP2L, and KOA • Our MR analysis may provide novel new insight into potential pathogenesis of KOA. • These identified candidate genes offer the possibility of clinical drug target development for KOA.

Ubiquitination and deubiquitination: Implications for the pathogenesis and treatment of osteoarthritis

Osteoarthritis (OA) is a degenerative disease that affects multiple cells and associated extracellular matrix (ECM). Chondrocytes and chondroextracellular matrix together constitute articular cartilage tissue. Any factors that affect the activity of chondrocytes and destroy the metabolic balance of the chondrocyte ECM will lead to the inability of articular cartilage to perform normal functions. The articular subchondral bone and articular cartilage must be coordinated to resist enough friction and mechanical stress, so the articular subchondral bone lesion will aggravate the articular cartilage defect and vice versa. Synoviocytes, including fibroblast-like synoviocytes (FLSs) and synovial macrophages at the joint, are also important factors that cause low-grade chronic progressive inflammation of OA. Regulation of phenotype transformation of synovial macrophages has become another possible target for the clinical treatment of OA. Ubiquitination and deubiquitination are the main post-translational protein modification pathways in the human body, which are widely involved in multiple signaling pathways and physiological processes. Naturally, they also play a very important regulatory role in the occurrence and development of OA. These effects are summarized in this review, including (A) regulating the aging and apoptosis of chondrocytes, FLSs and osteoblasts; (B) regulation of ECM degradation; (C) regulation of macrophage phenotypic transformation; (D) modulation of skeletal muscle and adipose tissues. Ubiquitination targeting drugs for OA treatment are also listed. Depending on the high efficiency of ubiquitination and deubiquitination, understanding OA-related ubiquitination pathways can help design more efficient drugs to treat OA and provide more potential targets for clinical treatment. The Translational Potential of This Article. In this paper, the ubiquitination-related pathways in osteoarthritis (OA), including aging, apoptosis and autophagy in chondrocytes, osteoblasts, FLSs and macrophages were investigated. In particular, several ubiquitination-related targets are expected to be effective approaches for OA clinical treatment. In addition, in the process of OA occurrence and development, the complex relationship between the local joint area and other tissues including skeletal muscle and adipose tissue is also discussed. These myokines and adipokines from musculoskeletal tissues are all expected to become efficient targets for OA treatment apart from the joint itself. In addition, those myokines secreted by cardiovascular tissues would show potential therapeutic effects as well. What if altering the contents for these ubiquitination-related targets in the serum through exercise will provide a new idea for OA therapy or prevent OA from deteriorating continuously?

PDZK1 protects against mechanical overload-induced chondrocyte senescence and osteoarthritis by targeting mitochondrial function

Mechanical overloading and aging are two essential factors for osteoarthritis (OA) development. Mitochondria have been identified as a mechano-transducer situated between extracellular mechanical signals and chondrocyte biology, but their roles and the associated mechanisms in mechanical stress-associated chondrocyte senescence and OA have not been elucidated. Herein, we found that PDZ domain containing 1 (PDZK1), one of the PDZ proteins, which belongs to the Na+/H+ Exchanger (NHE) regulatory factor family, is a key factor in biomechanically induced mitochondrial dysfunction and chondrocyte senescence during OA progression. PDZK1 is reduced by mechanical overload, and is diminished in the articular cartilage of OA patients, aged mice and OA mice. Pdzk1 knockout in chondrocytes exacerbates mechanical overload-induced cartilage degeneration, whereas intraarticular injection of adeno-associated virus-expressing PDZK1 had a therapeutic effect. Moreover, PDZK1 loss impaired chondrocyte mitochondrial function with accumulated damaged mitochondria, decreased mitochondrion DNA (mtDNA) content and increased reactive oxygen species (ROS) production. PDZK1 supplementation or mitoubiquinone (MitoQ) application alleviated chondrocyte senescence and cartilage degeneration and significantly protected chondrocyte mitochondrial functions. MRNA sequencing in articular cartilage from Pdzk1 knockout mice and controls showed that PDZK1 deficiency in chondrocytes interfered with mitochondrial function through inhibiting Hmgcs2 by increasing its ubiquitination. Our results suggested that PDZK1 deficiency plays a crucial role in mediating excessive mechanical load-induced chondrocyte senescence and is associated with mitochondrial dysfunction. PDZK1 overexpression or preservation of mitochondrial functions by MitoQ might present a new therapeutic approach for mechanical overload-induced OA.

Immunoengineering Biomaterials for Musculoskeletal Tissue Repair across Lifespan

Musculoskeletal diseases and injuries are among the leading causes of pain and morbidity worldwide. Broad efforts have focused on developing pro-regenerative biomaterials to treat musculoskeletal conditions; however, these approaches have yet to make a significant clinical impact. Recent studies have demonstrated that the immune system is central in orchestrating tissue repair and that targeting pro-regenerative immune responses can improve biomaterial therapeutic outcomes. However, aging is a critical factor negatively affecting musculoskeletal tissue repair and immune function. Hence, understanding how age affects the response to biomaterials is essential for improving musculoskeletal biomaterial therapies. This review focuses on the intersection of the immune system and aging in response to biomaterials for musculoskeletal tissue repair. The article introduces the general impacts of aging on tissue physiology, the immune system, and the response to biomaterials. Then, it explains how the adaptive immune system guides the response to injury and biomaterial implants in cartilage, muscle, and bone and discusses how aging impacts these processes in each tissue type. The review concludes by highlighting future directions for the development and translation of personalized immunomodulatory biomaterials for musculoskeletal tissue repair.

Ultrasound-guided determination demonstrates influence of age, sex and type of sport on medial femoral condyle cartilage thickness in children and adolescents

PURPOSE

To analyse the reliability of ultrasound-guided measurement of the cartilage thickness at the medial femoral condyle in athletically active children and adolescents before and after mechanical load in relation to age, sex and type of sport.

METHODS

Three successive measurements were performed in 157 participants (median/min-max age: 13.1/6.0-18.0 years, 106 males) before and after mechanical load by squats at the same site of the medial femoral condyle by defined transducer positioning. Test-retest reliability was examined using Cronbach'sα $\alpha $ calculation. Differences in cartilage thickness were analysed with respect to age, sex and type of practiced sports, respectively.

RESULTS

Excellent reliability was achieved both before and after mechanical load by 30 squats with a median cartilage thickness of 1.9 mm (range: 0.5-4.8 mm) before and 1.9 mm (0.4-4.6 mm) after mechanical load. Male cartilages were thicker (p < 0.01) before (median: 2.0 mm) and after (2.0 mm) load when compared to female cartilage (before: 1.6 mm; after: 1.7 mm). Median cartilage thickness was about three times higher in karate athletes (before: 2.3 mm; after: 2.4 mm) than in sports shooters (0.7; 0.7 mm). Cartilage thickness in track and field athletes, handball players and soccer players were found to lay in-between. Sport type related thickness changes after mechanical load were not significant.

CONCLUSION

Medial femoral condyle cartilage thickness in childhood correlates with age, sex and practiced type of sports. Ultrasound is a reliable and simple, pain-free approach to evaluate the cartilage thickness in children and adolescents.

LEVEL OF EVIDENCE

Level III.

The impact of Yoga on patients with knee osteoarthritis: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The objective of this review is to conduct a comprehensive and systematic assessment of the efficacy of Yoga as an intervention for knee osteoarthritis (KOA).

METHODS

We searched PubMed, Cochrane Library, Embase, Web of Science, and PEDro as of January 3, 2024. Retrieved a total of 200 articles. Standardised mean differences (SMDs) and 95% confidence intervals (CI) were calculated.

RESULTS

The study included a total of 8 trials and involved 756 KOA patients. The results indicated that compared to the control group, Yoga exercise showed significant improvements in alleviating pain (SMD = -0.92; 95% CI = -1.64 ~ - 0.20; P = 0.01, I2 = 94%), stiffness (SMD = -0.51; 95% CI = -0.91 ~ -0.12; P = 0.01; I2 = 66%) and physical function (SMD = -0.53; 95% CI = -0.89 ~ -0.17; P = 0.004; I2 = 59%) among KOA patients. However, there was no significant improvement observed in terms of activities of activity of daily living (ADL) (SMD = 1.03; 95% CI = -0.01 ~ 2.07; P = 0.05; I2 = 84%), and quality of life (QOL) (SMD = 0.21; 95% CI = -0.33 ~ 0.74; P = 0.44; I2 = 83%) with the practice of Yoga.

CONCLUSIONS

In general, Yoga has been found to be effective in reducing pain and stiffness in KOA patients, it can also improve the physical function of patients. However, there is limited evidence to suggest significant improvements in terms of ADL and QOL.

Periodic Mechanical Stress Inhibits the Development of Osteoarthritis via Regulating ATF3-Akt Axis

Purpose

The development of osteoarthritis (OA) has been linked to mechanical factors. Studies suggest that periodic mechanical stress (PMS) may be a factor contributing to cartilage repair and the onset of OA. Therefore, this study was designed to explore the effects and underlying mechanisms of PMS on OA development.

Patients and Methods

Firstly, surgery and interleukin (IL)-1β were used for the establishment of rat/cell models of OA, respectively. Subsequently, activating transcription factor (ATF) 3 expression was knocked down in OA rats, and OA chondrocytes were treated with different heights (0, 1, 2, 4, 8 cm) of PMS or si-ATF. Safranin O staining was used to observe the histological changes in the rat knee joint, and enzyme-linked immunosorbent assay (ELISA) was performed to detect levels of tumor necrosis factor (TNF)-α, IL-6, and IL-8 in vivo and in vitro. Further, the expression of extracellular matrix (ECM) proteins in the rat knee joint was assessed immunohistochemistry. Flow cytometry was used to evaluate chondrocyte apoptosis. Lastly, Western blot was performed to detect the expression of related proteins of the protein kinase B (Akt) signaling pathway and ECM.

Results

The OA rat model was successfully constructed. Further experiments indicated that the knockdown of ATF3 not only alleviated joint swelling, pain, inflammatory response and pathological damage, but also promoted ECM synthesis and the phosphorylation of Akt in OA rats. In vitro experiments showed that PMS (4 cm) effectively inhibited cell apoptosis, decreased the levels of TNF-α, IL-6 and IL-8, promoted ECM synthesis, and activated the Akt signaling pathway in osteoarthritic chondrocytes. However, ATF3 overexpression reversed the positive effects of PMS on osteoarthritic chondrocytes.

Conclusion

PMS can effectively inhibit the development of OA, and its protective effects may be attributed to the down-regulation of ATF3 expression and activation of the Akt signaling pathway.