Aging and osteoarthritis: Central role of the extracellular matrix

Role of stem cells in ageing and age-related diseases

Stem cell functions and ageing are deeply interconnected, continually influencing each other in multiple ways. Stem cells play a vital role in organ maintenance, regeneration, and homeostasis, all of which decline over time due to gradual reduction in their self-renewal, differentiation, and growth factor secretion potential. The functional decline is attributed to damaging extrinsic environmental factors and progressively worsening intrinsic genetic and biochemical processes. These ageing-associated deteriorative changes have been extensively documented, paving the way for the discovery of novel biomarkers of ageing for detection, diagnosis, and treatment of age-related diseases. Age-dependent changes in adult stem cells include numerical decline, loss of heterogeneity, and reduced self-renewal and differentiation, leading to a drastic reduction in regenerative potential and thereby driving the ageing process. Conversely, ageing also adversely alters the stem cell niche, disrupting the molecular pathways underlying stem cell homing, self-renewal, differentiation, and growth factor secretion, all of which are critical for tissue repair and regeneration. A holistic understanding of these molecular mechanisms, through empirical research and clinical trials, is essential for designing targeted therapies to modulate ageing and improve health parameters in older individuals.

Vaccarin ameliorates osteoarthritis by suppressing the c-Jun N-terminal kinase (JNK)-serum amyloid A2 (SAA2) pathway mediating chondrocyte senescence

BACKGROUND

Osteoarthritis is a chronic degenerative joint disease marked by chondrocyte senescence and extracellular matrix degradation. Vaccarin, a flavonoid with anti-inflammatory and antioxidant properties, has not been previously investigated for its therapeutic potential in osteoarthritis.

PURPOSE

To evaluate the therapeutic potential of Vaccarin in osteoarthritis and elucidate its underlying mechanisms.

DESIGN AND METHOD

This study utilized in vitro chondrocyte cultures and RNA sequencing to identify relevant pathways, followed by validation at the genetic, protein, and metabolic levels using multiple approaches. Additionally, the therapeutic effects of Vaccarin were assessed in vivo using a destabilization of the medial meniscus (DMM)-induced osteoarthritis mouse model and human cartilage samples from osteoarthritis patients.

RESULTS

Vaccarin effectively ameliorated osteoarthritis both in vivo and in vitro. Transcriptomic sequencing indicated a significant downregulation of serum amyloid A2 (SAA2) expression following Vaccarin treatment. Multi-omics analysis, validated by human specimens, indicated that SAA2 is minimally secreted in healthy articular cartilage but serves as a crucial osteoarthritis biomarker in Asian populations. Mechanistically, Vaccarin inhibits c-Jun N-terminal kinase (JNK) phosphorylation, thereby reducing SAA2 expression and mitigating chondrocyte inflammation and senescence. Notably, inflammatory conditions upregulate SAA2 expression in chondrocytes via the JNK pathway. Elevated SAA2 levels contribute to mitochondrial dysfunction in chondrocytes, leading to increased reactive oxygen species (ROS) production and exacerbating osteoarthritis progression.

CONCLUSION

This study identifies SAA2 as a potential therapeutic target for osteoarthritis and suggests that Vaccarin presents a promising treatment avenue.

DDX3X Activates Chondrocyte Pyroptosis to Promote Osteoarthritis Progression

The RNA-binding protein DDX3X is associated with several biological processes including inflammation and immunity. However, the role of DDX3X in the pathology of inflammation-related osteoarthritis (OA) remains unclear. This study was to explore the action of DDX3X in the progression of OA as well as the underlying mechanisms by using RNA immunoprecipitation (RIP), Immunohistochemical (IHC) and DDX3X knockout mice, etc. We found that DDX3X expression was upregulated in cartilage tissue of OA patient. The in vitro study also showed upregulation of DDX3X in the inflammatory chondrocytes stimulated by LPS. DDX3X overexpression reduced cell viability by inducing pyroptosis in chondrocytes. Knockdown of DDX3X rescued LPS-induced chondrocytes pyroptosis through regulating NLRP3 signaling. In addition, DDX3X deletion attenuates osteoarthritis in vivo. In conclusion, DDX3X promotes OA progression by regulating chondrocytes pyroptosis via the activation of NLRP3 signaling.

Ginsenoside Rh1 attenuates chondrocyte senescence and osteoarthritis via AMPK/PINK1/Parkin-mediated mitophagy

Osteoarthritis (OA) is the most common joint disease characterized by disruption of extracellular matrix (ECM) homeostasis, chronic inflammation, and upregulation of senescent phenotypes. Ginsenoside Rh1 (Rh1) exerted various pharmacological activities, including anti-inflammatory, anti-cancer, and neuroprotective effects. Herein, we aimed to explore the role and mechanism of Rh1 in OA. In IL-1β-induced OA chondrocytes, Rh1 alleviated the imbalance of ECM and senescence phenotypes. Furthermore, we found that Rh1 mitigated mitochondrial damage and the impaired mitophagy of chondrocytes induced by IL-1β, and these effects could be prevented by Mdivi-1 (a mitophagy inhibitor). Knockdown of PINK1 or Parkin partially abolished Rh1-mediated chondroprotection, indicating that Rh1 exerts its therapeutic effects via PINK1/Parkin-dependent mitophagy. Based on molecular docking, Compound C (an AMPK inhibitor), and AMPK siRNA, we found that Rh1 regulated PINK1/Parkin-mediated mitophagy through AMPK. Besides, Rh1 alleviated OA by promoting AMPK-mediated mitophagy in the anterior cruciate ligament transection (ACLT) rats. In conclusion, Rh1 alleviated OA progress by regulating AMPK/PINK1/Parkin-mediated mitophagy and is a potentially effective therapeutic target for age-related OA.

The effect of lactate dehydrogenase B and its mediated histone lactylation on chondrocyte ferroptosis during osteoarthritis

BACKGROUND

Histone lactylation is a novel epigenetic regulator that is reported to participate in gene expression. Ferroptosis is an oxidative form of cell death and chondrocyte ferroptosis crucially impacts the development of osteoarthritis (OA). The study aimed at investigating the effect of lactate dehydrogenase B (LDHB) and its mediated histone lactylation on chondrocyte ferroptosis during OA.

METHODS

Our study focused on the establishment of in vivo mouse model and in vitro interleukin-1β (IL-1β)-induced chondrocytes model and administrated LDHB knockdown (siLDHB). Histopathological assessment of cartilage was conducted via HE staining, while serum levels of cartilage oligomeric matrix protein (COMP) and crosslinked C-telopeptides of type II collagen (CTX-II) were quantified using ELISA to evaluate OA severity. The matrix degradation was further examined by expression of Collagen II and Aggrecan. Levels of total iron, ferrous iron (Fe2+), and lipid reactive oxygen species (ROS) were considered measurements of ferroptosis. Assessment of cell viability and proliferation relied on cell counting kit 8 (CCK-8) together with colony formation assay. Western blotting assay served for detecting the relative expression of proteins and protein lactylation. The epigenetic regulation of ACSL4 by LDHB was determined by chromatin immunoprecipitation (ChIP) and luciferase reporter gene assay.

RESULTS

OA mice presented remarkably elevated protein level of LDHB and H3K18 lactylation in the cartilage versus the sham group. Knockdown of LDHB downregulated the levels of COMP and CTX-II, as well as alleviated chondrocyte ferroptosis in vitro and in vivo. Results from ChIP and luciferase reporter gene assay demonstrated direct histone lactylation of ACSL promoter, and knockdown of LDHB and treatment with LDH inhibitor reduced histone lactylation and expression of ACSL4. ACSL4 overexpression could reverse the impact of LDHB depletion on chondrocyte proliferation and ferroptosis.

CONCLUSION

LDHB promotes ACSL4 by histone lactylation to induce chondrocyte ferroptosis, which further contributes to OA development. The findings in the study assist in understanding the modulating mechanism of LDHB-mediated lactylation against chondrocyte ferroptosis in OA progression.

Atf3 + senescent chondrocytes mediate meniscus degeneration in aging

BACKGROUND

Meniscus degeneration contributes to knee arthritis progression, but the cellular and molecular mechanisms of meniscus aging remain poorly understood. We aimed to characterize age-related changes in the rat meniscus using single-cell RNA sequencing (scRNA-seq) and identify key pathogenic cell populations and pathways.

METHODS

Meniscal tissues from young (12 weeks) and aged (24 months) rats were processed for histology, flow cytometry, and scRNA-seq. Bioinformatics tools, including Seurat, Monocle 2, and CellChat, were used to analyze cellular composition, pseudotime trajectories, and intercellular communication. Senescence-related features and signaling pathways were evaluated.

RESULTS

Knee joint of aged rats exhibited higher Osteoarthritis Research Society International (OARSI) scores and synovial inflammation. scRNA-seq revealed three major chondrocyte subpopulations: Sox9 + stable chondrocytes, Fndc1 + fibrochondrocytes, and Atf3 + senescent chondrocytes. Aging caused a significant increase in Atf3 + senescent chondrocytes, characterized by the expression of senescence markers (Cdkn1a/Cdkn2a) and activation of inflammatory pathways such as tumor necrosis factor (TNF) and nuclear factor-κB (NF-κB). These cells were predominantly located at the endpoint of differentiation trajectories. CellChat analysis identified the ANGPTL4-SDC4 axis as a key signaling pathway mediated by Atf3 + cells. Immunostaining confirmed elevated Angiopoietin-Like Protein 4 (ANGPTL4) expression in aged menisci.

CONCLUSION

We identified Atf3 + senescent chondrocytes as a key pathogenic population in the aging meniscus, driving degeneration via the ANGPTL4 pathway. Targeting Atf3 + cells or ANGPTL4 signaling may offer new therapeutic strategies for age-related meniscus degeneration and arthritis.

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

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

Cellular senescence in age-related musculoskeletal diseases

Aging is typically associated with decreased musculoskeletal function, leading to reduced mobility and increased frailty. As a hallmark of aging, cellular senescence plays a crucial role in various age-related musculoskeletal diseases, including osteoporosis, osteoarthritis, intervertebral disc degeneration, and sarcopenia. The detrimental effects of senescence are primarily due to impaired regenerative capacity of stem cells and the pro-inflammatory environment created by accumulated senescent cells. The secreted senescence-associated secretory phenotype (SASP) can induce senescence in neighboring cells, further amplifying senescent signals. Although the removal of senescent cells and the suppression of SASP factors have shown promise in alleviating disease progression and restoring musculoskeletal health in mouse models, clinical trials have yet to demonstrate significant efficacy. This review summarizes the mechanisms of cellular senescence in age-related musculoskeletal diseases and discusses potential therapeutic strategies targeting cellular senescence.

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.

Therapeutic targets in aging-related osteoarthritis: A focus on the extracellular matrix homeostasis

Osteoarthritis (OA) represents a globally prevalent degenerative bone diseases and is the primary contributors to pain and disability among middle-aged and elderly people, thereby imposing significant social and economic burdens. When articular cartilage is in the aging environment, epigenetic modifications, DNA damage and mitochondrial dysfunction lead to cell senescence. Chondrocyte senescence has been identified as a pivotal event in this metabolic dysregulation of the extracellular matrix (ECM). It can affect the composition and structure of ECM, and the mechanical and biological signals transmitted by ECM to senescent chondrocytes affect their physiology and pathology. Over the past few decades, the role of ECM in aging-related OA has received increasing attention. In this review, we summarize the changes of cartilage's major ECM (type II collagen and aggrecan) and the interaction between aging and ECM in OA, and explore therapeutic strategies targeting cartilagae ECM, such as noncoding RNAs, small-molecule drugs, and mesenchymal stem cell (MSC)-derived extracellular vesicles for OA. The aim of this study was to elucidate the potential benefits of ECM-based therapies as novel strategies for the management of OA diseases.

Stable-Dynamic Hydrogels Mimicking the Pericellular Matrix for Articular Cartilage Repair

Cartilage regeneration requires a specialized biomechanical environment. Macroscopically, cartilage repair requires a protracted, stable mechanical environment, whereas microscopically, it involves dynamic interactions between cells and the extracellular matrix. Therefore, this study aims to design a hydrogel that meets the complex biomechanical requirements for cartilage repair. Dynamic hybrid hydrogels with temporal stability at the macroscale and dynamic properties at the microscale are successfully synthesized. The dynamic hybrid hydrogel simulates the stress relaxation and viscoelasticity of the pericellular matrix, facilitating effective interactions between the extracellular matrix and cells. The in vitro and in vivo experiments demonstrated that the hybrid hydrogel significantly promoted cartilage repair. The dynamic hybrid hydrogel alleviates abnormal actin polymerization, reduces intracellular stress, and increases the volume of individual cells. By modulating the cytoskeleton, the hybrid hydrogel inhibits Notch signal transduction in both the receptor and ligand cells, resulting in an improved cartilage phenotype. This study introduces an effective hybrid hydrogel scaffold that modulates the chondrocyte cytoskeleton and Notch signaling pathways by establishing an appropriate biomechanical environment, thus offering a promising material for cartilage repair.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

SEMA6D modulates extracellular matrix metabolism in osteoarthritis by inhibiting the AGT/AGTR1a/IL-1β axis

The tissue-localized renin-angiotensin system (tRAS) plays a pivotal role in the crosstalk between cardiovascular factors and osteoarthritis (OA). Semaphorin 6D (SEMA6D), a cardiovascular neuroeffector, may contribute to chondrocyte homeostasis; however, its cartilage-specific functions remain unclear. Chondrocytes with altered SEMA6D expression were established via gene transfection. RNA sequencing was performed to identify SEMA6D-related genes and pathways, with preliminary validation in human OA samples. Furthermore, biochemical methods were employed to investigate the role of the AGT/AGTR1a/IL-1β axis in mediating SEMA6D-associated extracellular matrix metabolism (ECM). An AAV5-based lentiviral vector was used to generate OA rat models overexpressing SEMA6D, followed by radiological and histological analyses. SEMA6D overexpression significantly enhanced ECM homeostasis, marked by increased Aggrecan, COL2A1 and decreased COL10A1, MMP13, and Runx2 expression. These SEMA6D-induced genes were enriched in the tRAS pathway, with AGT, AGTR1a, and IL-1β identified as critical targets. Furthermore, the AGT/AGTR1a/IL-1β axis activated ECM degradation in chondrocytes, while SEMA6D overexpression effectively suppressed this signaling. In the OA rat model, elevated SEMA6D expression significantly reduced cartilage degradation. SEMA6D confers chondroprotective effects in OA by modulating the tRAS pathway, likely through inhibition of the AGT/AGTR1a/IL-1β axis, thereby regulating ECM metabolism and chondrocyte hypertrophy. These findings enhance our understanding of cardiovascular influences on cartilage health and reveal tissue-specific regulatory mechanisms in OA.

Metabolic reprogramming of macrophages by a nano-sized opsonization strategy to restore M1/M2 balance for osteoarthritis therapy

Osteoarthritis is a chronic and progressive joint disease accompanied by cartilage degeneration and synovial inflammation. It is associated with an imbalance of synovial macrophage M1/M2 ratio tilting more towards the pro-inflammatory M1 than the anti-inflammatory M2. The M1-macrophages rely on aerobic glycolysis for energy whereas the M2-macrophages derive energy from oxidative phosphorylation. Therefore, inhibiting aerobic glycolysis to induce metabolic reprogramming of macrophages and consequently promote the shift from M1 type to M2 type is a therapeutic strategy for osteoarthritis. Here we developed a macrophage-targeting strategy based on opsonization, using nanoparticles self-assembled to incorporate Chrysin (an anti-inflammatory flavonoid) and V-9302 (an inhibitor of glutamine uptake), and the outer layer modified by immunoglobulin IgG by electrostatic adsorption into IgG/Fe-CV NPs. In vitro studies showed that IgG/Fe-CV NPs effectively target M1 macrophages and inhibit HIF-1α and GLUT-1 essential for aerobic glycolysis and promote polarization from M1 to M2-type macrophages. In vivo, IgG/Fe-CV NPs inhibit inflammation and protect against cartilage damage. The metabolic reprogramming strategy with IgG/Fe-CV NPs to shift macrophage polarization from inflammatory to anti-inflammatory phenotype by inhibiting aerobic glycolysis and glutamine delivery may open up new avenues to treat osteoarthritis.

Identification and validation of hub m7G-related genes and infiltrating immune cells in osteoarthritis based on integrated computational and bioinformatics analysis

BACKGROUND

Osteoarthritis (OA) is a joint disease closely associated with synovial tissue inflammation, with the severity of synovitis impacting disease progression. m7G RNA methylation is critical in RNA processing, metabolism, and function, but its role in OA synovial tissue is not well understood. This study explores the relationship between m7G methylation and immune infiltration in OA.

METHODS

Data were obtained from the GEO database. Hub genes related to m7G were identified using differential expression and LASSO-Cox regression analysis, and a diagnostic model was developed. Functional enrichment, drug target prediction, and target gene-related miRNA prediction were performed for these genes. Immune cell infiltration was analyzed using the CIBERSORT algorithm, and unsupervised clustering analysis was conducted to examine immune infiltration patterns. RT-qPCR was used to validate hub gene expression.

RESULTS

Seven m7G hub genes (SNUPN, RNMT, NUDT1, LSM1, LARP1, CYFIP2, and CYFIP1) were identified and used to develop a nomogram for OA risk prediction. Functional enrichment indicated involvement in mRNA metabolism and RNA transport. Differences in macrophage and T-cell infiltration were observed between OA and normal groups. Two distinct m7G immune infiltration patterns were identified, with significant microenvironment differences between clusters. RT-qPCR confirmed differential hub gene expression.

CONCLUSION

A diagnostic model based on seven m7G hub genes was developed, highlighting these genes as potential biomarkers and significant players in OA pathogenesis.

Blockade of ZMIZ1-GATA4 Axis Regulation Restores Youthfulness to Aged Cartilage

Susceptibility to cartilage degeneration increases in an age-dependent manner and older cartilage exhibits increased catabolic factor expression leading to osteoarthritis (OA). While inhibition of cellular senescence can prevent age-related diseases, the understanding of the regulators governing cartilage senescence and the potential for senolytic intervention remains limited. Here, in vitro and in vivo results are reported, demonstrating for the first time that the transcriptional regulator, ZMIZ1, is upregulated in aged and OA cartilage, and that it acts through GATA4 to accelerate chondrocyte senescence and trigger cartilage deterioration. Furthermore, it is shown that K-7174 interferes with the ZMIZ1-GATA4 interaction and effectively hampers cartilage senescence and OA. It is proposed that inhibition of the ZMIZ1-GATA4 axis could be a valuable strategy for eliminating senescent chondrocytes and impeding OA development and that the relevant inhibitor, K-7174, could potentially be developed as a senolytic drug for managing cartilage senescence and age-related degeneration.

Systemic Lupus Erythematosus Exacerbates Hip Arthritis by Promoting Chondrocyte Pyroptosis in the Femoral Head via Activating the NF-κB Pathway

Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by chronic inflammation and immune dysregulation, significantly impacting multiple organ systems, including the joints. While SLE is known to contribute to musculoskeletal complications, its role in hip arthritis development and the underlying mechanisms remain poorly understood. This study aims to investigate the relationship between SLE and hip arthritis progression using MRL/lpr mice, which exhibit early-onset SLE, compared with MRL/MpJ control mice at 14 weeks of age. Through comprehensive histological, immunohistochemical and molecular analyses, we evaluated articular cartilage (AC) degeneration, extracellular matrix (ECM) metabolism, inflammatory responses, and chondrocyte pyroptosis. Our results demonstrated that MRL/lpr mice developed an accelerated hip arthritis-like phenotype, manifesting as enhanced AC degeneration, impaired chondrocyte proliferation, heightened apoptosis and promoted inflammatory cytokine production. Notably, SLE markedly stimulated chondrocyte pyroptosis by increasing pyroptosis-related proteins, including NLRP3, ASC, CASPASE-1 and GSDMD, via activating the NF-κB pathway. These findings establish a novel mechanistic link between SLE and hip arthritis progression, demonstrating that SLE promotes chondrocyte pyroptosis to exacerbate AC degeneration via NF-κB activation, highlighting chondrocyte pyroptosis as a key driver of SLE-associated hip arthritis and a potential therapeutic target for mitigating SLE-induced joint manifestations.

Effects of Oligomeric Proanthocyanidins on Cadmium-Induced Extracellular Matrix Damage via Inhibiting the ERK1/2 Signaling Pathway in Chicken Chondrocytes

Cadmium (Cd) is a toxic, non-essential metal that primarily enters animal bodies through the digestive and respiratory systems, leading to damage to multiple organs and tissues. Cd can accumulate in cartilage and induce damage to chondrocytes. Procyanidins (PAs), also known as concentrated tannic acid or oligomeric proanthocyanidins (OPCs), exhibit diverse biological and pharmacological activities. However, the mechanism of OPCs alleviates Cd-induced damage to chondrocytes in chickens remains to be further explored in vitro. Chondrocytes were isolated from both ends of the tibia of 17-day-old SPF chicken embryos, and then subsequently treated with various concentrations of Cd (0, 1, 2.5, 5, and 10 μmol/L) or OPCs (0, 5, 10, 20, and 40 μmol/L) to investigate the mechanism underlying extracellular matrix (ECM) degradation and damage. Cd reduced cell viability, glycosaminoglycan (GAG) secretion, and ECM degradation in chondrocytes by decreasing the expression of type II collagen alpha 1 (COL2A1) and aggrecan (ACAN) while increasing the release of cartilage oligomeric matrix protein (COMP), along with elevated levels of matrix-degrading enzymes, such as matrix metalloproteinases 1 (MMP1), MMP10, and MMP13, and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) and ADAMTS5. Cd induced phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) and the expression of matrix-degrading enzymes, impairing ECM synthesis, an effect that could be alleviated by ERK1/2 inhibitor U0126. Chondrocytes were treated with 5 μmol/L Cd and 10 μmol/L OPCs, and it was found that OPCs inhibited the activation of the ERK1/2 signaling pathway and the expression of matrix-degrading enzymes, while promoting ECM synthesis and alleviating Cd-induced ECM damage in chickens. This study provides a theoretical basis for clinical research on OPCs with respect to the prevention and treatment of Cd-induced chondrogenic diseases in poultry.

Immune cells differentiation in osteoarthritic cartilage damage: friends or foes?

Osteoarthritis (OA) is a chronic disease primarily characterized by degenerative changes in articular cartilage and synovitis, for which there are currently no targeted or curative therapies available in clinical practice. In recent years, the in-depth analysis of OA using single-cell sequencing and immunomics technologies has revealed the presence of multiple immune cell subsets, as well as different differentiation states within the same subset, in OA. Through immune-immune and immune-joint tissue interactions, these cells collectively promote or inhibit the progression of arthritis. This complex immune network, where "friends and foes coexist," has made targeted therapeutic strategies aimed at directly eliminating immune cells challenging, highlighting the urgent need for a detailed review of the composition, distribution, functional heterogeneity, therapeutic potential, and potential risks of immune subsets within the joint. Additionally, the similarities and differences between OA and rheumatoid arthritis (RA) in terms of diagnosis and immunotherapy need to be precisely understood, in order to draw lessons from or reject RA-based immunotherapies. To this end, this review summarizes the major triggers of inflammation in OA, the differentiation characteristics of key immune cell subsets, and compares the similarities and differences between OA and RA in diagnosis and treatment. It also outlines the current immunomodulatory strategies for OA and their limitations. Furthermore, we provide a detailed and focused discussion on immune cells that act as "friends or foes" in arthritis, covering the M1/M2 polarization of macrophages, functional heterogeneity of neutrophils, unique roles of dendritic cells at different maturation states, the balance between pro-inflammatory T cells and regulatory T cells (Tregs), and the diverse functions of B cells, plasma cells, and regulatory B cells (Bregs) in OA. By interpreting the roles of these immune cells, this review clarifies the dynamic changes and interactions of immune cells in OA joints, providing a theoretical foundation for more precise targeted interventions in future clinical practice.

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.

Perspectives of exosomal ncRNAs in the treatment of bone metabolic diseases: Focusing on osteoporosis, osteoarthritis, and rheumatoid arthritis

Bone metabolic disorders, constituting a group of prevalent and grave conditions, currently have a scarcity of therapeutic alternatives. Over the recent past, exosomes have been at the forefront of research interest, owing to their nanoparticulate nature and potential for therapeutic intervention. ncRNAs are a class of heterogeneous transcripts that they lack protein-encoding capacity, yet they can modulate the expression of other genes through multiple mechanisms. Mounting evidence underscores the intricate role of exosomes as ncRNAs couriers implicated in the pathogenesis of bone metabolic disorders. In this review, we endeavor to elucidate recent insights into the roles of three ncRNAs - miRNAs, lncRNAs, and circRNAs - in bone metabolic ailments such as osteoporosis, osteoarthritis, and rheumatoid arthritis. Additionally, we examine the viability of exosomal ncRNAs as innovative, cell-free modalities in the diagnosis and therapeutic management of bone metabolic disorders. We aim to uncover the critical function of exosomal ncRNAs within the context of bone metabolic diseases.

Pathological and Inflammatory Consequences of Aging

Aging is a complex, progressive, and irreversible biological process that entails numerous structural and functional changes in the organism. These changes affect all bodily systems, reducing their ability to respond and adapt to the environment. Chronic inflammation is one of the key factors driving the development of age-related diseases, ultimately causing a substantial decline in the functional abilities of older individuals. This persistent inflammatory state (commonly known as "inflammaging") is characterized by elevated levels of pro-inflammatory cytokines, an increase in oxidative stress, and a perturbation of immune homeostasis. Several factors, including cellular senescence, contribute to this inflammatory milieu, thereby amplifying conditions such as cardiovascular disease, neurodegeneration, and metabolic disorders. Exploring the mechanisms of chronic inflammation in aging is essential for developing targeted interventions aimed at promoting healthy aging. This review explains the strong connection between aging and chronic inflammation, highlighting potential therapeutic approaches like pharmacological treatments, dietary strategies, and lifestyle changes.

Redox regulation: mechanisms, biology and therapeutic targets in diseases

Redox signaling acts as a critical mediator in the dynamic interactions between organisms and their external environment, profoundly influencing both the onset and progression of various diseases. Under physiological conditions, oxidative free radicals generated by the mitochondrial oxidative respiratory chain, endoplasmic reticulum, and NADPH oxidases can be effectively neutralized by NRF2-mediated antioxidant responses. These responses elevate the synthesis of superoxide dismutase (SOD), catalase, as well as key molecules like nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH), thereby maintaining cellular redox homeostasis. Disruption of this finely tuned equilibrium is closely linked to the pathogenesis of a wide range of diseases. Recent advances have broadened our understanding of the molecular mechanisms underpinning this dysregulation, highlighting the pivotal roles of genomic instability, epigenetic modifications, protein degradation, and metabolic reprogramming. These findings provide a foundation for exploring redox regulation as a mechanistic basis for improving therapeutic strategies. While antioxidant-based therapies have shown early promise in conditions where oxidative stress plays a primary pathological role, their efficacy in diseases characterized by complex, multifactorial etiologies remains controversial. A deeper, context-specific understanding of redox signaling, particularly the roles of redox-sensitive proteins, is critical for designing targeted therapies aimed at re-establishing redox balance. Emerging small molecule inhibitors that target specific cysteine residues in redox-sensitive proteins have demonstrated promising preclinical outcomes, setting the stage for forthcoming clinical trials. In this review, we summarize our current understanding of the intricate relationship between oxidative stress and disease pathogenesis and also discuss how these insights can be leveraged to optimize therapeutic strategies in clinical practice.

Psoralen remodels the articular cartilage microenvironment by pharmacologically regulating the Nrf2 pathway in osteoarthritis treatment

Osteoarthritis (OA) is a common degenerative joint disease featuring extracellular matrix degradation and apoptosis in the inflammatory microenvironment. Psoralea, a traditional Chinese herb derived from the dried and ripe fruits of the leguminous plant Psoralea corylifolia, possesses anti-inflammatory and antioxidant properties relying on the expression upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2). Psoralen, a compound derived from Psoralea, can be well applied to the treatment of various diseases, while researches have not fully explored its therapeutic effect for OA. Our study aimed to conduct in vivo and in vitro experiments to investigate such effect. According to In vitro experiments, psoralen inhibited interleukin-6-induced chondrocyte inflammation and matrix metalloproteinase 13 production, meanwhile promoting aggrecan and type II collagen to be produced. Mechanistically, psoralen activated the Keap1/ Nrf2/ARE signaling pathway to enhance the antioxidant capacity of chondrocytes. Furthermore, in vivo experiments demonstrated the protective effect of psoralen against OA pathogenesis triggered by destabilized medial meniscus. Collectively, psoralen is considered as a potential candidate specific to OA treatment.

Exploring the Therapeutic Potential of MIR‐140‐3p in Osteoarthritis: Targeting CILP and Ferroptosis for Novel Treatment Strategies

Osteoarthritis (OA) is a prevalent and debilitating joint disorder that affects millions of individuals worldwide, severely impairing mobility, independence, and quality of life. Emerging evidence suggests that ferroptosis is a critical factor in OA pathogenesis. However, its precise involvement and underlying mechanisms remain poorly understood. In this study, we first identified that cartilage intermediate layer protein (CILP) mediates the regulation of ferroptosis‐related genes in OA through hdWGCNA analysis combined with single‐cell RNA sequencing. Further investigation revealed a significant upregulation of CILP protein expression in C28/I2 cells under LPS induction. Mechanistically, bioinformatics analysis identified differentially expressed miRNAs; qRT‐PCR combined with a dual‐luciferase experiment revealed that miR‐140‐3p was downregulated and directly targets CILP. Experimental data further demonstrated that miR‐140‐3p regulates ferroptosis, inflammation, and oxidative stress by targeting CILP. These findings offer valuable insights into the molecular mechanisms of the miR‐140‐3p/CILP axis in regulating ferroptosis, inflammation, and oxidative stress, thus providing a foundation for developing therapeutic strategies 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.

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.

ABCA6 Regulates Chondrogenesis and Inhibits Joint Degeneration via Orchestrated Cholesterol Efflux and Cellular Senescence

Patellar dysplasia (PD) can cause patellar dislocation and subsequent osteoarthritis (OA) development. Herein, a novel ABCA6 mutation contributing to a four-generation family with familiar patellar dysplasia (FPD) is identified. In this study, whole exome sequencing (WES) and genetic linkage analysis across a four-generation lineage presenting with six cases of FPD are conducted. A disease-causing mutation in ABCA6 is identified for FPD. Further analyses reveal a consistent correlation between ABCA6 expression downregulation and PD occurrence, chondrocyte degeneration, and OA onset. Moreover, ABCA6-KO mice demonstrate severe knee joint degeneration and accelerated OA progression. Besides, synovial mesenchymal stem cells (SMSCs) are extracted from WT, ABCA6-/+, and ABCA6-/- mice to create chondrogenic organoids in vitro, confirming ABCA6 deficiency can lead to chondrocyte degeneration via modulating cell cycle and activating cellular senescence. Moreover, transcriptome and metabolomic sequencing analysis on ABCA6-KO chondrocytes unveils that the ABCA6 deficiency inhibits cholesterol efflux, leading to intracellular cholesterol accumulation and subsequent cellular senescence and impaired chondrogenesis.A disease-causing mutation of ABCA6 is identified for FPD. ABCA6 is correlated with PD occurrence and subsequent OA progression. ABCA6 can serve as a potential target in chondrogenesis and OA treatment by orchestrated intracellular cholesterol efflux and delayed cellular senescence.

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.

RNA N6-methyladenosine modification in arthritis: New insights into pathogenesis

The commonest type of eukaryotic RNA modification, N6-methyladenosine (m6A), has drawn increased scrutiny in the context of pathological functioning as well as relevance in determination of RNA stability, splicing, transportation, localization, and translation efficiency. The m6A modification plays an important role in several types of arthritis, especially osteoarthritis and rheumatoid arthritis. Recent studies have reported that m6A modification regulates arthritis pathology in cells, such as chondrocytes and synoviocytes via immune responses and inflammatory responses through functional proteins classified as writers, erasers, and readers. The aim of this review was to highlight recent advances relevant to m6A modification in the context of arthritis pathogenesis and detail underlying molecular mechanisms, regulatory functions, clinical applications, and future perspectives of m6A in arthritis with the aim of providing a foundation for future research directions.

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.

Matrix stiffness regulates mitochondria-lysosome contacts to modulate the mitochondrial network, alleviate the senescence of MSCs

The extracellular microenvironment encompasses the extracellular matrix, neighbouring cells, cytokines, and fluid components. Anomalies in the microenvironment can trigger aging and a decreased differentiation capacity in mesenchymal stem cells (MSCs). MSCs can perceive variations in the firmness of the extracellular matrix and respond by regulating mitochondrial function. Diminished mitochondrial function is intricately linked to cellular aging, and studies have shown that mitochondria-lysosome contacts (M-L contacts) can regulate mitochondrial function to sustain cellular equilibrium. Nonetheless, the influence of M-L contacts on MSC aging under varying matrix stiffness remains unclear. In this study, utilizing single-cell RNA sequencing and atomic force microscopy, we further demonstrate that reduced matrix stiffness in older individuals leads to MSC aging and subsequent decline in osteogenic ability. Mechanistically, augmented M-L contacts under low matrix stiffness exacerbate MSC aging by escalating mitochondrial oxidative stress and peripheral division. Moreover, under soft matrix stiffness, cytoskeleton reorganization facilitates rapid movement of lysosomes. The M-L contacts inhibitor ML282 ameliorates MSC aging by reinstating mitochondrial network and function. Overall, our findings confirm that MSC aging is instigated by disruption of the mitochondrial network and function induced by matrix stiffness, while also elucidating the potential mechanism by which M-L Contact regulates mitochondrial homeostasis. Crucially, this presents promise for cellular anti-aging strategies centred on mitochondria, particularly in the realm of stem cell therapy.

Temporal trends in the burden of musculoskeletal diseases in China from 1990 to 2021 and predictions for 2021 to 2030

BACKGROUND

Musculoskeletal (MSK) diseases represent a significant global public health challenge. Conducting comprehensive research on MSK diseases in China holds profound implications for public health.

METHODS

This study utilized data from the Global Burden of Disease 2021 (GBD 2021) to analyze the incidence rate, prevalence rate, mortality rate, disability-adjusted life years (DALYs), years lived with disability (YLDs), and years of life lost (YLLs) of MSK diseases in China from 1990 to 2021. Trends were evaluated using annual percentage change (APC), average annual percentage change (AAPC), and estimated annual percentage change (EAPC). Future disease trends were predicted using the Bayesian Age-Period-Cohort (BAPC) model.

RESULTS

China had the highest number of DALYs cases globally, totaling 30.4194 million. Low back pain (LBP) represented the largest burden, while hand osteoarthritis exhibited the fastest growth. Differences in disease burden were observed across various genders and age groups. Predictions indicate that between 2021 and 2030, the age-standardized DALYs rate in China will increase annually, reaching 1779.08 per 100,000 population by 2030. Environmental (occupational) factors had the most significant impact on the age-standardized DALYs rate, whereas renal dysfunction had the least impact. The SDI showed a moderately strong positive correlation with the age-standardized DALYs rate of MSK diseases.

CONCLUSION

Over the past 20 years, the prevalence of MSK diseases in China has experienced a slight increase, while other epidemiological burden indicators have shown a downward trend. Projections indicate that the overall disease burden of MSK in China will continue to rise over the next decade, underscoring the need for early intervention strategies. Moreover, substantial differences in MSK disease burden across genders and age groups highlight the importance of developing targeted policy interventions to mitigate this burden.

An Innovative Anoikis Signature With Inflammatory Infiltrates in Osteoarthritis

AIM

To explore the relationship between an innovative anoikis-related gene signature and inflammatory infiltrates in patients with osteoarthritis.

METHODS

Gene expression profiles (GSM1248759 and GSE200843) were curated from the Gene Expression Omnibus database, followed by the construction of a protein-protein interaction network. Functional and genomic enrichment analyses were conducted using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The CIBERSORT method was employed to investigate immune cell infiltration differences between osteoarthritic and control tissues. Additionally, the ConsensusClusterPlus package in R software was utilized to identify distinct anoikis patterns (Cluster C1 and Cluster C2) and conduct molecular biological investigations.

RESULTS

Analysis revealed two distinct anoikis patterns (Cluster C1 and Cluster C2), with Cluster C2 patients exhibiting varying immune cell levels compared to Cluster C1 patients. Molecular investigations identified 84 DEGs enriched in specific pathways such as adipocytokine signaling, cytokine-cytokine receptor interaction, ECM-receptor interaction, and the PPAR signaling pathway. qPCR experiments confirmed the elevated expression levels of specific genes, including SOD2, MAPK14, CEACM3, LAMB3, COL13A1, TLR3, NOTCH3, and KLF12, in the IL-1β-induced group compared with the osteoarthritis group.

CONCLUSION

This study highlights the role of anoikis-related genes and immune infiltration differences in osteoarthritis, enhancing our understanding of its development.

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.

Identification and Validation of Pivotal Genes in Osteoarthritis Combined with WGCNA Analysis

Introduction

The prevalence of osteoarthritis (OA), the most common chronic joint condition, is increasing due to the aging population and escalating obesity rates, leading to a significant impact on human health and well-being. Thus, analyzing the key targets of OA through bioinformatics can help discover new biomarkers to improve its diagnosis.

Methods

The microarray and RNA-seq results were screened from the Gene Expression Omnibus (GEO) database. Functional enrichment analyses, protein-protein interaction (PPI) analysis, and weighted gene co-expression network analysis (WGCNA) of the DEGs were performed. RT-qPCR and WB were further performed to verify the hub gene expression in OA rat.

Results

In this study, 35 key genes were identified through differential expression analysis and weighted gene co-expression network analysis (WGCNA) using the GSE169077 and GSE114007 datasets. Enrichment analysis revealed that these key genes were predominantly enriched in the HIF-1 signaling pathway, ECM-receptor interaction, and FoxO signaling pathway. Through the integration of protein-protein interaction (PPI) analysis, validation in animal models and ROC curve analysis, four pivotal genes (GADD45B, CLDN5, HILPDA and CDKN1B) were finally identified.

Conclusion

In conclusion, these identified key genes could serve as novel targets for predicting and treating OA, offering fresh insights into its etiology and pathogenesis.

Substrate stiffness regulates the proliferation and inflammation of chondrocytes and macrophages through exosomes

Osteoarthritis (OA) progression is characterized by decreased cartilage stiffness and degradation of the extracellular matrix (ECM), which significantly influence cartilage behavior and fate. In contrast, processes such as chondrocyte calcification and aging often result in increased stiffness. Despite extensive studies on how ECM stiffness regulates cellular functions, the impact of substrate stiffness on the cartilage microenvironment and intercellular communications remains not well understood. Using tunable stiffness Gelatin methacryloyl (GelMA) hydrogel, we demonstrated that a potential optimal substrate stiffness can promote maximal chondrocyte proliferation and exosome secretion. The exogenous addition of stiffness-tuned exosomes induced significant changes in chondrocyte morphology, proliferation, migration, and inflammation. Notably, blocking Yes-associated protein (YAP) synthesis negated the proliferation enhancement induced by exosomes from chondrocytes cultured on medium stiffness substrates (ExoMedium), confirming that substrate stiffness regulates cell proliferation through exosomes by modulating YAP expression and its nuclear localization. Moreover, our study revealed that exosomes from medium stiffness substrates-mimicking normal cartilage stiffness-not only reduce inflammation in chondrocytes but also shift macrophage polarization from M1 to M2. Conversely, exosomes from soft stiffness substrates, akin to osteoarthritic tissue, exacerbate chondrocytes inflammation and M1 macrophage polarization. These findings highlight the crucial role of stiffness-tuned exosomes in OA progressing, affecting chondrocyte proliferation, migration, inflammation and macrophage polarization, and provide new insights into the potential novel treatment strategies using engineered scaffolds and exosomes. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by decreased cartilage stiffness and degradation of the extracellular matrix (ECM). While some studies suggest that increased substrate stiffness enhances cell proliferation, others have reported the opposite effect. Whether there exists an optimal matrix stiffness that promotes chondrocytes anabolism and how matrix stiffness regulates the cartilage microenvironment and intercellular communications remain unclear. Utilizing tunable stiffness Gelatin methacryloyl (GelMA) hydrogel, this study demonstrated that a potential optimal substrate stiffness can maximize chondrocyte proliferation and exosome secretion. The introduction of stiffness-tuned exosomes induced significant changes in chondrocyte and macrophage proliferation, migration, and inflammation, offering new insights into OA progression and highlighting their potential as a promising therapeutic strategy for osteoarthritis treatment and tissue regeneration.

Microfluidic Synthesis of miR-200c-3p Lipid Nanoparticles: Targeting ZEB2 to Alleviate Chondrocyte Damage in Osteoarthritis

Introduction

Osteoarthritis (OA) is a degenerative joint disease characterized by articular cartilage degeneration. Chondrocyte inflammation, apoptosis, and extracellular matrix degradation accelerated OA progression. MicroRNA (miRNA) has the potential to be a therapeutic method for osteoarthritis. However, it is difficult to penetrate the cell to exercise its biological function, and its extracellular effect is unclear.

Methods

lipo-AgPEI-miR-200c-3p was created by combining miR-200c-3p with silver nitrate polyvinylimine nanoparticles on a microfluidic device. The drug release curve, stability, temperature sensitivity, cytotoxicity, and the impact of lipo-AgPEI-miR-200c-3p on the expression of proteins linked to matrix disintegration, apoptosis, and inflammatory factors were all detected.

Results

Results showed that the particle size of Lipo-AgPEI-miR-200c-3p was about 130 nm, the Zeta potential was lowered to 1.08±0.12 mV. Lipo-AgPEI-miR-200c-3p could increase cell viability, prevent cell apoptosis, and decrease the expression levels of TNF-α, IL-6, IL-1β, and MCP-1 in ADTC5 cells following LPS stimulation. MMP3, MMP13, and ADAMTS-4 expression was downregulated whereas collagen II expression was upregulated. The ZEB2 expression was greatly elevated following LPS stimulation and dramatically decreased following transfection of miR-200c-3p. Collagen II expression rose following transfection of si-ZEB2, whereas the expression levels of inflammatory factors, apoptosis-related proteins, MMP3, MMP13, and ADAMTS-4 decreased. The dual luciferase experiment demonstrated that ZEB2 was the target gene of miR-200c-3p.

Conclusion

The synergistic effect of AgPEI and miR-200c-3p can inhibit the inflammatory response, apoptosis, and matrix degradation of chondrocytes. Lipo-AgPEI-miR-200c-3p can also improve transfection efficiency and obtain good physicochemical properties of drugs. miR-200c-3p may be crucial in the development of OA and can influence the target gene ZEB2, control the inflammatory response, apoptosis, and chondrocyte matrix breakdown.

AM1241 inhibits chondrocyte inflammation and ECM degradation through the Nrf2/HO-1 and NF-κB pathways and alleviates osteoarthritis in mice

BACKGROUND

This study aimed to investigate the impact of AM1241 on lipopolysaccharide (LPS)-induced chondrocyte inflammation in mice and its potential mechanism for improving osteoarthritis (OA).

METHODS

The OA mice model was established employing the refined Hulth method. The impact of different concentrations of AM1241 on mice chondrocyte activity was detected using CCK-8. Changes in the levels of LPS-induced inflammatory factors and cartilage extracellular matrix (ECM) degradation in chondrocytes were determined by western blot, RT-qPCR, ELISA, and immunofluorescence assays, respectively. The specific action modes and binding sites of AM1241 with NEMO/IκB kinases (IKKs) in the NF-κB pathway and Keap1 protein in the Nrf2 pathway were predicted via molecular docking and molecular dynamics simulation, and the NF-κB and Nrf2 pathways were detected using western blot and immunofluorescence. In vivo, the impact of AM1241 on OA mice was analyzed through safranin-fast green staining, IHC staining, Mankin score, and microCT.

RESULTS

AM1241 inhibited the levels of LPS-induced transforming growth factor-β (TGF-β1), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), matrix metalloproteinase-13 (MMP-13), and a disintegrin and metalloproteinase with thrombospondin motif 5 (ADAMTS-5) and diminished the degradation of type II collagen and Aggrecan. For the mechanism, AM1241 regulated the NF-kB and Nrf2/HO-1 signaling pathways by binding to NEMO/IKKβ and Keap1 target proteins and suppressed the activation of the NF-κB signaling pathway by activating the Nrf2 in chondrocytes. In vivo, AM1241 inhibited bone anabolism, mitigated articular cartilage hyperplasia and wear, and reduced the Mankin score in mice, thereby hindering the development of OA.

CONCLUSION

AM1241 inhibited activation of the NF-κB signaling pathway via activating Nrf2. It suppressed the expression of inflammation factors and the degradation of ECM in vitro, and improved OA in mice in vivo, suggesting its potential as an effective drug candidate for the treatment of OA. The remarkable efficacy of AM1241 in alleviating murine OA positions it as a potential therapeutic strategy in the clinical management of OA diseases.

Integrative analyses of mendelian randomization and bioinformatics reveal casual relationship and genetic links between COVID-19 and knee osteoarthritis

BACKGROUND

Clinical and epidemiological analyses have found an association between coronavirus disease 2019 (COVID-19) and knee osteoarthritis (KOA). Infection with COVID-19 may increase the risk of developing KOA.

OBJECTIVES

This study aimed to investigate the potential causal relationship between COVID-19 and KOA using Mendelian randomization (MR) and to explore the underlying mechanisms through a systematic bioinformatics approach.

METHODS

Our investigation focused on exploring the potential causal relationship between COVID-19, acute upper respiratory tract infection (URTI) and KOA utilizing a bidirectional MR approach. Additionally, we conducted differential gene expression analysis using public datasets related to these three conditions. Subsequent analyses, including transcriptional regulation analysis, immune cell infiltration analysis, single-cell analysis, and druggability evaluation, were performed to explore potential mechanisms and prioritize therapeutic targets.

RESULTS

The results indicate that COVID-19 has a one-way impact on KOA, while URTI does not play a causal role in this association. Ribosomal dysfunction may serve as an intermediate factor connecting COVID-19 with KOA. Specifically, COVID-19 has the potential to influence the metabolic processes of the extracellular matrix, potentially impacting the joint homeostasis. A specific group of genes (COL10A1, BGN, COL3A1, COMP, ACAN, THBS2, COL5A1, COL16A1, COL5A2) has been identified as a shared transcriptomic signature in response to KOA with COVID-19. Imatinib, Adiponectin, Myricetin, Tranexamic acid, and Chenodeoxycholic acid are potential drugs for the treatment of KOA patients with COVID-19.

CONCLUSIONS

This study uniquely combines Mendelian randomization and bioinformatics tools to explore the possibility of a causal relationship and genetic association between COVID-19 and KOA. These findings are expected to provide novel perspectives on the underlying biological mechanisms that link COVID-19 and KOA.

Wharton's Jelly Mesenchymal Stem Cells: Shaping the Future of Osteoarthritis Therapy with Advancements in Chitosan-Hyaluronic Acid Scaffolds

This review explores the potential of Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) in cartilage regeneration and osteoarthritis treatment. It covers key factors influencing chondrogenesis, including growth factors, cytokines, and hypoxia, focusing on precise timing. The effectiveness of three-dimensional cultures and scaffold-based strategies in chondrogenic differentiation is discussed. Specific biomaterials such as chitosan and hyaluronic acid are highlighted for tissue engineering. The document reviews clinical applications, incorporating evidence from animal research and early trials and molecular and histological assessments of chondrogenic differentiation processes. It addresses challenges and strategies for optimizing MSC-derived chondrocyte therapy, emphasizing the immunomodulatory properties of these cells. The review concludes as a comprehensive road map for future research and clinical applications in regenerative medicine.

M13, an anthraquinone compound isolated from Morinda officinalis alleviates the progression of the osteoarthritis via the regulation of STAT3

BACKGROUND

Osteoarthritis (OA) is characterized by the progressive deterioration of articular cartilage, leading to joint pain and functional impairment. OA severely impacts quality of life and presents a substantial societal burden. Currently, effective treatment options remain limited. Morinda officinalis (MO), a traditional Chinese herb, is commonly used to treat rheumatoid arthritis and alleviate joint pain. M13, an anthraquinone extracted from MO, has shown significant anti-inflammatory properties, making it a promising candidate for the treatment of OA. However, its role in inhibiting OA progression and the mechanisms involved remain poorly understood.

PURPOSE

The objective of this study is to examine the impact of M13 on osteoarthritis and uncover the mechanisms.

METHODS

The effects of M13 on OA were assessed using TNF-α induced chondrocyte models and mice with destabilization of the medial meniscus (DMM). Celecoxib was used as a positive control. We evaluated the expression of factors related to chondrocyte degeneration and inflammation through qRT-PCR, immunoblotting, and immunofluorescence. Chondrocyte viability was measured using CCK-8 assays, EdU staining, and flow cytometry. Molecular docking, molecular dynamics simulations and isothermal titration calorimetry (ITC) were performed to evaluate the binding efficacy of target proteins. Additionally, the therapeutic effects of M13 in OA mice were confirmed through in vivo experiments.

RESULTS

In primary murine chondrocytes, M13 rescued TNF-α-induced matrix degradation and loss of vitality while suppressing ROS generation. Mechanistically, STAT3 was identified as a target protein of M13, through which M13 mitigated OA by inhibiting the STAT3 signaling pathway. Further in vivo experiments demonstrated that M13 reduced the scores of the Osteoarthritis Research Society International (OARSI), alleviating cartilage impairment. M13 enhanced levels of collagen II and aggrecan in cartilage tissue while decreasing the amounts of cartilage-degrading proteins ADAMTS-5 and MMP13.

CONCLUSION

This is the first study to validate that M13 mitigates the inflammation and damage in cartilage tissue by blocking the STAT3 signaling pathway. These findings hold promise for enhancing innovative clinical interventions targeting OA.

Therapeutic Controlled Release Strategies for Human Osteoarthritis

Osteoarthritis is a progressive, irreversible debilitating whole joint disease that affects millions of people worldwide. Despite the availability of various options (non-pharmacological and pharmacological treatments and therapy, orthobiologics, and surgical interventions), none of them can definitively cure osteoarthritis in patients. Strategies based on the controlled release of therapeutic compounds via biocompatible materials may provide powerful tools to enhance the spatiotemporal delivery, expression, and activities of the candidate agents as a means to durably manage the pathological progression of osteoarthritis in the affected joints upon convenient intra-articular (injectable) delivery while reducing their clearance, dissemination, or side effects. The goal of this review is to describe the current knowledge and advancements of controlled release to treat osteoarthritis, from basic principles to applications in vivo using therapeutic recombinant molecules and drugs and more innovatively gene sequences, providing a degree of confidence to manage the disease in patients in a close future.

Therapeutic Ultrasound Modulates Cell Proliferation and Proinflammatory Cytokine Levels in Osteoarthritic Chondrocytes

The development and progression of osteoarthritis (OA) are believed to involve inflammation. This study aimed to investigate the effects of applying therapeutic ultrasound (US) to human osteoarthritic chondrocytes in continuous and pulsed modes on cell proliferation and proinflammatory cytokine levels. Human osteoarthritic chondrocytes (HC-OA 402OA-05a) were proliferated in appropriate media and then seeded into culture plates. The plates were grouped and exposed to underwater continuous, pulsed and control US at 0.1 W/cm2 and 1 MHz for 10 min daily for 10 days. Cell viability/proliferation was assessed using the MTT assay, total protein was measured by ELISA and cytokine levels per protein were determined. Cells were photographed using microscopic analysis. Both continuous and pulsed US groups showed a significant increase in viability compared to the control group. No significant difference was found between the continuous and pulsed US groups for IL-1β, TNF-α and IL-6 levels. Both groups showed significant cytokine reduction compared to the control group. For IL-17 and IL-32 levels, both US groups had reduced cytokine levels compared to the control group, but the results were not significant. Underwater US at 0.1 W/cm2 and 1 MHz stimulated cell proliferation and reduced proinflammatory cytokine levels in osteoarthritic chondrocyte cell cultures. This study extensively focused on proinflammatory IL levels, and the meaningful results may inspire future in vivo/in vitro studies. While adapting in vitro data to in vivo conditions poses challenges, our results could guide future in vivo studies and clinical applications.

Polyphyllin I Mitigated IL-1β-Induced Chondrocytes Damage through Downregulating TWIST1 Expression

BACKGROUND

Osteoarthritis (OA) is a chronic joint disease characterized by the degradation of articular cartilage. Polyphyllin I (PPI) has anti-inflammatory effects in many diseases. However, the mechanism of PPI in OA remains unclear.

METHODS

HC-a cells treated with IL-1β were identified by immunofluorescence staining and microscopic observation. The expression of collagen II and DAPI in HC-a cells was detected by immunofluorescence. The effects of gradient concentration of PPI on IL-1β-induced cell viability, apoptosis, senescence, and inflammatory factor release were detected by MTT, flow cytometry, SA-β-Gal assay and ELISA, respectively. Expressions of apoptosis-related genes, extracellular matrix (ECM)- related genes, and TWIST1 were determined by qRT-PCR and western blot as needed. The above-mentioned experiments were conducted again after TWIST1 overexpression in IL-1β-induced chondrocytes.

RESULTS

IL-1β reduced the number of chondrocytes and the density of collagen II. PPI (0.25, 0.5, 1 μmol/L) had no effect on cell viability, but it dose-dependently elevated the inhibition of cell viability regulated by IL-1β. The elevation of cell apoptosis, senescence and expression of IL-6 and TNF-α were suppressed by PPI in a dosedependent manner. Additionally, PPI reduced the expression of cleaved caspase-3, bax, MMP-3, and MMP-13 and promoted the expression of collagen II. TWIST1 expression was diminished by PPI. TWIST1 overexpression reversed the abovementioned effects of PPI on chondrocytes.

CONCLUSION

PPI suppressed apoptosis, senescence, inflammation, and ECM degradation of OA chondrocytes by downregulating the expression of TWIST1.

The genetic and observational nexus between diabetes and arthritis: a national health survey and mendelian randomization analysis

BACKGROUND

Diabetes mellitus (DM) and arthritis are prevalent conditions worldwide. The intricate relationship between these two conditions, especially in the context of various subtypes of arthritis, remains a topic of interest.

OBJECTIVE

To investigate the relationship between diabetes and arthritis, with a focus on Rheumatoid Arthritis (RA), using data from the National Health and Nutrition Examination Survey (NHANES) and Mendelian Randomization (MR) analysis.

METHODS

Data from six consecutive NHANES cycles from 2007 to 2018 were analyzed, involving 30,062 participants after applying exclusion criteria. The association between diabetes and arthritis was assessed using logistic regression. MR was employed to determine the causal relationship between the two conditions using Genome-Wide Association Study (GWAS) data.

RESULTS

The prevalence of arthritis in diabetic patients was almost twice that of non-diabetic patients. Logistic regression showed a significant gross association between arthritis and diabetes with an OR of 2.90 (95% CI: 2.66-3.16). After adjusting for age, gender, race, and other factors, the association yielded an OR of 1.14 (95% CI: 1.00-1.29, p < 0.05). MR analyses indicated a significant association between Type 1 Diabetes and RA (OR = 1.407, p = 0.002), but no significant correlation was observed for Type 2 Diabetes.

CONCLUSION

There is an association between diabetes and arthritis, with potential genetic links between Type 1 Diabetes and RA.

Isoliensinine suppresses chondrocytes pyroptosis against osteoarthritis via the MAPK/NF-κB signaling pathway

BACKGROUND

Isoliensinine is an active compound derived from Nelumbo nucifera which has long been used for its anti-inflammatory properties. However, the mechanism of Isoliensinine in the treatment of osteoarthritis is poorly known.

PURPOSE

The present study aims to investigate whether Isoliensinine could alleviate osteoarthritis by regulating MAPK/NF-κB signaling pathway-mediated pyroptosis.

METHODS

Network pharmacology and KEGG enrichment analysis were used to identify the therapeutic targets of Isoliensinine for OA. Molecular docking was used to confirm the binding ability of Isoliensinine and related proteins. In vitro, chondrocytes were stimulated with IL-1β to construct an inflammatory model and treated with Isoliensinine. The viability of the cells was assessed using the CCK-8 kit. The apoptosis rate of cells was measured using Annexin V-FITC/PI assay. And assessed the levels of ROS, lipid-ROS, and mitochondrial membrane potential. Corresponding assay kits were utilized to measure the levels of MDA and SOD. Subsequently, the anabolic and catabolic markers in chondrocytes, alongside inflammatory targets were measured by RT-PCR and Western blot. The expression level of pyroptosis and MAPK/NF-κB signaling pathway-related targets was examined. Furthermore, we constructed a rat osteoarthritis model using ACLT surgery. We then assessed the progression of osteoarthritis by Micro-CT, H&E staining, S&F staining and immunohistochemistry.

RESULTS

Enrichment analysis showed that Isoliensinine treatment of osteoarthritis may be through the MAPK/NF-κB pathway, and molecular docking showed that Isoliensinine and MAPK/NF-κB pathway proteins had a good binding ability. Data showed that Isoliensinine could reduce ECM degradation and inflammation, and inhibit IL-1β-induced apoptosis. It also mitigated ROS and LPO activation, regulated mitochondrial dysfunction, and reduced intracellular oxidative stress levels. Furthermore, Western blot showed that Isoliensinine also inhibited the activation of the MAPK/NF-κB pathway, thereby inhibiting the pyroptosis of chondrocytes. In vivo, Micro-CT, H&E staining and S&F staining results showed that Isoliensinine could effectively improve joint damage caused by osteoarthritis. And IHC analyses indicated NLRP3, MMP3 protein expression were significantly diminished and Collagen II expression was increased in the Isoliensinine treatment groups.

CONCLUSION

In conclusion, our study suggested that Isoliensinine mitigates ECM degradation, oxidative stress, chondrocytes apoptosis, and pyroptosis through the inhibition of the MAPK and NF-κB pathways, thereby delaying the progression of osteoarthritis.

Coronal Plane Alignment of the Knee (CPAK) Type Shifts Toward Constitutional Varus with Increasing Kellgren and Lawrence Grade: A Radiographic Analysis of 17,365 Knees

BACKGROUND

Studies investigating constitutional alignment across various grades of osteoarthritis (OA) are limited. This study explored the distribution of Coronal Plane Alignment of the Knee (CPAK) types and associated radiographic parameters with increasing OA severity.

METHODS

In this retrospective cross-sectional study, 17,365 knees were analyzed using deep learning software for radiographic measurements. Knees were categorized on the basis of the Kellgren and Lawrence (KL) grade and CPAK type. Radiographic measurements were the hip-knee-ankle angle (HKAA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), arithmetic HKAA (aHKA), joint line obliquity (JLO), and joint line convergence angle (JLCA). Age-stratified analysis was performed to differentiate the impact of age on OA severity.

RESULTS

A shift in the most common CPAK type from II to I was found with increasing KL grade (p < 0.05). Furthermore, there was a corresponding increase in LDFA and JLCA with increasing KL grade, while HKAA, MPTA, and aHKA decreased after KL grade 2. Age exhibited limited association with LDFA and MPTA, suggesting that OA severity is the dominant factor related to the CPAK distribution.

CONCLUSIONS

The study found a shift in CPAK type with worsening OA. It is possible that constitutional varus types are more susceptible to OA, or that their increased OA prevalence is related to anatomical changes. This analysis offers new insights into alterations in CPAK type that occur with OA and underscores the importance of understanding pre-arthritic anatomy when performing joint reconstruction.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Injectable microspheres filled with copper-containing bioactive glass improve articular cartilage healing by regulating inflammation and recruiting stem cells

Osteoarthritis (OA) is a frequent chronic illness in orthopedics that poses a major hazard to patient health. In situ cell therapy is emerging as a therapeutic option, but its efficacy is influenced by both the inflammatory milieu and the amount of stem cells, limiting its use. In this study, we designed a novel injectable porous microsphere (PM) based on microfluidic technology that can support in situ mesenchymal stem cells (MSCs) therapy by combining polylactic-glycolic acid copolymer, kartogenin, polydopamine, stromal cell-derived factor-1, and copper-doped bioactive glass (CuBG). The ex vivo tests demonstrated that PMs@CuBG microspheres were biocompatible and facilitated the transformation of synovial macrophages from pro-inflammatory M1 to anti-inflammatory M2 phenotypes by releasing CuBG to reduce joint inflammation. At the same time, the microspheres are able to recruit MSCs into the joint cavity and encourage their differentiation into chondrocytes, thereby treating articular cartilage injury. The in vivo rat experimental results show that intra-articular injection of PMs@CuBG in rats with OA improves OARSI scores, aggrecan content and the ratio of col-2α-positive cells, indicating a reparative effect on damaged cartilage within the joint. As a result, PMs@CuBG microspheres are predicted to provide a novel and successful approach to in situ cell therapy for OA.

Nuciferine ameliorates osteoarthritis: An in vitro and in vivo study

Osteoarthritis (OA) is the most common musculoskeletal disease and a leading cause of pain and disability. A key hallmark of OA is cartilage degradation, which occurs due to an imbalance between the synthesis and degradation of the extracellular matrix (ECM). Interleukin-1β(IL-1β) has been reported to regulate ECM metabolism. Nuciferine (Nuc), a natural peptide extracted from the lotus leaf, possesses several significant pharmacological properties. However, the anti-inflammation of Nuc in OA has not been reported. In this study, ELISA and Western blot analyses were used to measure the production of inflammatory mediators in IL-1β-Induced mouse chondrocytes. Additionally, mice with or without surgical destabilization of the medial meniscus (DMM) were treated with intra-articular injection of Nuc. We found that Nuc significantly reduces the level of iNOS, PEG2, and IL-6 in IL-1β-induced chondrocytes. Furthermore, Nuc can ameliorate the development of OA in mice. Mechanistically, we found that the chondrocyte-protective effects of Nuc occur via the PTEN/NF-κB pathway. These findings suggest that Nuc could be a potential therapeutic agent for improving OA development.