Cartilage Homeostasis and Osteoarthritis

Liensinine inhibits IL-1β-stimulated inflammatory response in chondrocytes and attenuates papain-induced osteoarthritis in rats

Osteoarthritis (OA) is a joint disease caused by inflammation of cartilage and synovial tissue. Suppressing the process of inflammatory reaction and the generation of oxidative stress is an effective strategy to alleviate the progression of OA. Liensinine is one of the main components of lotus seeds, which has anti-hypertensive and anti-arrhythmia activities. In this study, we aimed to determine the anti-inflammatory effect of liensinine in an OA. Here, we found that liensinine significantly inhibited the inflammatory response of SW1353 cells and primary chondrocytes by inhibiting the release of inflammatory cytokines and oxidative stress. Moreover, we showed that liensinine was able to inhibit the activation of the NF-κB signaling pathway in IL-1β-induced SW1353 cells. Lastly, we found that liensinine significantly ameliorated cartilage damage and inflammatory response in papain-induced rats. Our study demonstrated a significant protective effect of liensinine against OA, which might be by inhibiting the activation of the NF-κB signaling pathway, and provide a new insight for the treatment of OA using liensinine.

Non-coding RNAs as Regulators of Autophagy in Chondrocytes: Mechanisms and Implications for Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease with multiple causative factors such as aging, mechanical injury, and obesity. Autophagy is a complex dynamic process that is involved in the degradation and modification of intracellular proteins and organelles under different pathophysiological conditions. Autophagy, as a cell survival mechanism under various stress conditions, plays a key role in regulating chondrocyte life cycle metabolism and cellular homeostasis. Non-coding RNAs (ncRNAs) are heterogeneous transcripts that do not possess protein-coding functions, but they can act as effective post-transcriptional and epigenetic regulators of gene and protein expression, thus participating in numerous fundamental biological processes. Increasing evidence suggests that ncRNAs, autophagy, and their crosstalk play crucial roles in OA pathogenesis. Therefore, we summarized the complex role of autophagy in OA chondrocytes and focused on the regulatory role of ncRNAs in OA-associated autophagy to elucidate the complex pathological mechanisms of the ncRNA-autophagy network in the development of OA, thus providing new research targets for the clinical diagnosis and treatment of OA.

Identification and Construction of a Disulfidptosis-Mediated Diagnostic Model and Associated Immune Microenvironment of Osteoarthritis from the Perspective of PPPM

Background

Osteoarthritis (OA) is a major cause of human disability. Despite receiving treatment, patients with the middle and late stage of OA have poor survival outcomes. Therefore, within the framework of predictive, preventive, and personalized medicine (PPPM/3PM), early personalized diagnosis of OA is particularly prominent. PPPM aims to accurately identify disease by integrating multiple omic techniques; however, the efficiency of currently available methods and biomarkers in predicting and diagnosing OA should be improved. Disulfidptosis, a novel programmed cell death mechanism and appeared in particular metabolic status, plays a mysterious characteristic in the occurrence and development of OA, which warrants further investigation.

Methods

In this study, we integrated three public datasets from the Gene Expression Omnibus (GEO) database, including 26 OA samples and 20 normal samples. Via a series of bioinformatic analysis and machine learning, we identified the diagnostic biomarkers and several subtypes of OA. Moreover, the expression of these biomarkers were verified in our in-house cohort and the single cell dataset.

Results

Three significant regulators of disulfidptosis (NCKAP1, OXSM, and SLC3A2) were identified through differential expression analysis and machine learning. And a nomogram constructed based on these three regulators exhibited ideal efficiency in predicting early- and late-stage OA. Furthermore, based on the expression of three regulators, we identified two disulfidptosis-related subtypes of OA with different infiltration of immune cells and personalized expression level of immune checkpoints. Notably, the expression of the three regulators was demonstrated in a single-cell RNA profile and verified in the synovial tissue in our in-house cohort including 6 OA patients and 6 normal people. Finally, an efficient disulfidptosis-mediated diagnostic model was constructed for OA, with the AUC value of 97.6923% in the training set and 93.3333% and 100% in two validation sets.

Conclusion

Overall, with regard to PPPM, this study provided novel insights into the role of disulfidptosis regulators in the personalized diagnosis and treatment of OA.

Cartilage oligomeric matrix protein as a potential biomarker for knee osteoarthritis

Aims

This study aimed to determine the expression and clinical significance of a cartilage protein, cartilage oligomeric matrix protein (COMP), in knee osteoarthritis (OA) patients.

Methods

A total of 270 knee OA patients and 93 healthy controls were recruited. COMP messenger RNA (mRNA) and protein levels in serum, synovial fluid, synovial tissue, and fibroblast-like synoviocytes (FLSs) of knee OA patients were determined using enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and immunohistochemistry.

Results

COMP protein levels were significantly elevated in serum and synovial fluid of knee OA patients, especially those in the advanced stages of the disease. Serum COMP was significantly correlated with radiological severity as well as measures of body composition, physical performance, knee pain, and disability. Receiver operating characteristic curve analysis unveiled a diagnostic value of serum COMP as a biomarker of knee OA (41.64 ng/ml, area under the curve (AUC) = 1.00), with a sensitivity of 99.6% and a specificity of 100.0%. Further analysis uncovered that COMP mRNA expression was markedly upregulated in the inflamed synovium of knee OA, consistent with immunohistochemical staining revealing localization of COMP protein in the lining and sub-lining layers of knee OA inflamed synovium. Most notably, relative COMP mRNA expression in knee OA synovium was positively associated with its protein levels in serum and synovial fluid of knee OA patients. In human knee OA FLSs activated with tumour necrosis factor-alpha, COMP mRNA expression was considerably up-regulated in a time-dependent manner.

Conclusion

All results indicate that COMP might serve as a supportive diagnostic marker for knee OA in conjunction with the standard diagnostic methods.

Electrical Stimulation of Mesenchymal Stem Cells as a Tool for Proliferation and Differentiation in Cartilage Tissue Engineering: A Scaffold-Based Approach

Electrical stimulation (ES) is a widely discussed topic in the field of cartilage tissue engineering due to its ability to induce chondrogenic differentiation (CD) and proliferation. It shows promise as a potential therapy for osteoarthritis (OA). In this study, we stimulated mesenchymal stem cells (MSCs) incorporated into collagen hydrogel (CH) scaffolds, consisting of approximately 500,000 cells each, for 1 h per day using a 2.5 Vpp (119 mV/mm) 8 Hz sinusoidal signal. We compared the cell count, morphology, and CD on days 4, 7, and 10. The results indicate proliferation, with an increase ranging from 1.86 to 9.5-fold, particularly on day 7. Additionally, signs of CD were observed. The stimulated cells had a higher volume, while the stimulated scaffolds showed shrinkage. In the ES groups, up-regulation of collagen type 2 and aggrecan was found. In contrast, SOX9 was up-regulated in the control group, and MMP13 showed a strong up-regulation, indicating cell stress. In addition to lower stress levels, the control groups also showed a more spheroidic shape. Overall, scaffold-based ES has the potential to achieve multiple outcomes. However, finding the appropriate stimulation pattern is crucial for achieving successful chondrogenesis.

Novel insights into the role of ubiquitination in osteoarthritis

Ubiquitination (Ub) and deubiquitination are crucial post-translational modifications (PTMs) that precisely regulate protein degradation. Under the catalysis of a cascade of E1-E2-E3 ubiquitin enzymes, ubiquitination extensively regulates protein degradation exerting direct impact on various cellular processes, while deubiquitination opposes the effect of ubiquitination and prevents proteins from degradation. Notably, such dynamic modifications have been widely investigated to be implicated in cell cycle, transcriptional regulation, apoptosis and so on. Therefore, dysregulation of ubiquitination and deubiquitination could lead to certain diseases through abnormal protein accumulation and clearance. Increasing researches have revealed that the dysregulation of catalytic regulators of ubiquitination and deubiquitination triggers imbalance of cartilage homeostasis that promotes osteoarthritis (OA) progression. Hence, it is now believed that targeting on Ub enzymes and deubiquitinating enzymes (DUBs) would provide potential therapeutic pathways. In the following sections, we will summarize the biological role of Ub enzymes and DUBs in the development and progression of OA by focusing on the updating researches, with the aim of deepening our understanding of the underlying molecular mechanism of OA pathogenesis concerning ubiquitination and deubiquitination, so as to explore novel potential therapeutic targets of OA treatment.

Recent Trends in Adipose Tissue-Derived Injectable Therapies for Osteoarthritis: A Scoping Review of Animal Models

Background and Objectives: This scoping review investigates recent trends in adipose tissue-derived injectable therapies for osteoarthritis (OA) in animal models, focusing on minimally manipulated or lightly processed adipose tissue. By evaluating and examining the specific context in which these therapies were investigated across diverse animal OA models, this review aims to provide valuable insights that will inform and guide future research and clinical applications in the ongoing pursuit of effective treatments for osteoarthritis. Materials and Methods: This research conducted a comprehensive literature review of PubMed and Embase to determine studies about minimally manipulated adipose tissue-derived injectable therapies for osteoarthritis investigated using animal models. The primary search found 530 results. After excluding articles that focused on spontaneous osteoarthritis; on transfected, preconditioned, cultured, or co-cultured adipose-derived stem cells; and articles with unavailable full text, we included 11 articles in our review. Results: The examined therapies encompassed mechanical micro-fragmented adipose tissue (MFAT) and stromal vascular fraction (SVF) obtained via collagenase digestion and centrifugation. These interventions were evaluated across various animal models, including mice, rats, rabbits, and sheep with induced OA. Notably, more studies concentrated on surgically induced OA rather than chemically induced OA. The assessment of these therapies focused on elucidating their protective immunomodulatory, anti-inflammatory, and chondroregenerative potential through comprehensive evaluations, including macroscopic assessments, histological analyses, immunohistochemical examinations, and biochemical assays. Conclusions: This review provides a comprehensive analysis of adipose tissue-derived injectable therapies for osteoarthritis across diverse animal models. While revealing potential benefits and insights, the heterogeneity of data and the limited number of studies highlight the need for further research to formulate conclusive recommendations for clinical applications.

Senolytic therapeutics: An emerging treatment modality for osteoarthritis

Osteoarthritis (OA), a chronic joint disease affecting millions of people aged over 65 years, is the main musculoskeletal cause of diminished joint mobility in the elderly. It is characterized by lingering pain and increasing deterioration of articular cartilage. Aging and accumulation of senescent cells (SCs) in the joints are frequently associated with OA. Apoptosis resistance; irreversible cell cycle arrest; increased p16INK4a expression, secretion of senescence-associated secretory phenotype factors, senescence-associated β-galactosidase levels, secretion of extracellular vesicles, and levels of reactive oxygen and reactive nitrogen species; and mitochondrial dysregulation are some common changes in cellular senescence in joint tissues. Development of OA correlates with an increase in the density of SCs in joint tissues. Senescence-associated secretory phenotype has been linked to OA and cartilage breakdown. Senolytics and therapeutic pharmaceuticals are being focused upon for OA management. SCs can be selectively eliminated or killed by senolytics to halt the pathogenesis and progression of OA. Comprehensive understanding of how aging affects joint dysfunction will benefit OA patients. Here, we discuss age-related mechanisms associated with OA pathogenesis and senolytics as an emerging modality in the management of age-related SCs and pathogenesis of OA in preclinical and clinical studies.

Gentiopicroside ameliorates the lipopolysaccharide-induced inflammatory response and hypertrophy in chondrocytes

PURPOSE

This study aimed to evaluate the protective effects of gentiopicroside against lipopolysaccharide-induced chondrocyte inflammation.

METHODS

SW 1353 chondrosarcoma cells were stimulated with LPS (5 μg/ml) for 24 h and treated with different concentrations of gentiopicroside (GPS) for 24 h. The toxic effects of GPS on chondrocytes were determined using a CCK-8 assay and EdU staining. Western blotting, qPCR, and immunofluorescence analysis were used to examine the protective effect of GPS against the inflammatory response in chondrocytes induced by lipopolysaccharide (LPS). One-way ANOVA was used to compare the differences between the groups (significance level of 0.05).

RESULTS

The CCK-8 results showed that 10, 20 and 40 μM GPS had no significant toxic effects on chondrocytes; GPS effectively reduced the production of IL-1β and PGE2, reversed LPS-induced extracellular matrix degradation in cartilage by inhibiting the Stat3/Runx2 signaling pathway, and suppressed the hypertrophic transformation of SW 1353 chondrosarcoma cells.

CONCLUSION

Our study demonstrated that GPS significantly inhibited the LPS-induced inflammatory response and hypertrophic cellular degeneration in SW 1353 chondrosarcoma cells and is a valuable traditional Chinese medicine for the treatment of knee osteoarthritis.

The dysregulated autophagy in osteoarthritis: Revisiting molecular profile

The risk factors of osteoarthritis (OA) are different and obesity, lifestyle, inflammation, cell death mechanisms and diabetes mellitus are among them. The changes in the biological mechanisms are considered as main regulators of OA pathogenesis. The dysregulation of autophagy is observed in different human diseases. During the pathogenesis of OA, the autophagy levels (induction or inhibition) change. The supportive and pro-survival function of autophagy can retard the progression of OA. The protective autophagy prevents the cartilage degeneration. Moreover, autophagy demonstrates interactions with cell death mechanisms and through inhibition of apoptosis and necroptosis, it improves OA. The non-coding RNA molecules can regulate autophagy and through direct and indirect control of autophagy, they dually delay/increase OA pathogenesis. The mitochondrial integrity can be regulated by autophagy to alleviate OA. Furthermore, therapeutic compounds, especially phytochemicals, stimulate protective autophagy in chondrocytes to prevent cell death. The protective autophagy has ability of reducing inflammation and oxidative damage, as two key players in the pathogenesis of OA.

Cardamonin inhibits osteogenic differentiation by downregulating Wnt/beta-catenin signaling and alleviates subchondral osteosclerosis in osteoarthritic mice

Osteoarthritis (OA) is a common degenerative joint disease, and subchondral osteosclerosis is an important pathological change that occurs in its late stages. Cardamonin (CD) is a natural flavonoid isolated from Alpinia katsumadai that has anti-inflammatory activity. The objectives of this study were to investigate the therapeutic effects and potential mechanism of CD in regulating OA subchondral osteosclerosis at in vivo and in vitro settings. Eight-week-old male C57BL/6J mice were randomly divided into four groups: sham operation, anterior cruciate ligament transection (ACLT)-induced OA model, low-dose and high-dose CD treated ACLT-OA model groups. Histological assessment and immunohistochemical examinations for chondrocyte metabolism-related markers metalloproteinase-13, ADAMTS-4, Col II, and Sox-9 were performed. Microcomputed tomography was used to assess the sclerosis indicators in subchondral bone. Further, MC3T3-E1 (a mouse calvarial preosteoblast cell line) cells were treated with various concentrations of CD to reveal the influence and potential molecular pathways of CD in osteogenic differentiations. Animal studies suggested that CD alleviated the pathological changes in OA mice such as maintaining integrity and increasing the thickness of hyaline cartilage, decreasing the thickness of calcified cartilage, decreasing the Osteoarthritis Research Society International score, regulating articular cartilage metabolism, and inhibiting subchondral osteosclerosis. In vitro investigation indicated that CD inhibited alkaline phosphatase expression and production of calcium nodules during osteogenic differentiation of MC3T3-E1 cells. In addition, CD inhibited the expression of osteogenic differentiation-related indicators and Wnt/β-catenin pathway-related proteins. In conclusion, CD inhibits osteogenic differentiation by downregulating Wnt/β-catenin signaling and alleviating subchondral osteosclerosis in a mouse model of OA.

Regulation of Oxygen Tension as a Strategy to Control Chondrocytic Phenotype for Cartilage Tissue Engineering and Regeneration

Cartilage defects and osteoarthritis are health problems which are major burdens on health care systems globally, especially in aging populations. Cartilage is a vulnerable tissue, which generally faces a progressive degenerative process when injured. This makes it the 11th most common cause of global disability. Conservative methods are used to treat the initial phases of the illness, while orthopedic management is the method used for more progressed phases. These include, for instance, arthroscopic shaving, microfracturing and mosaicplasty, and joint replacement as the final treatment. Cell-based implantation methods have also been developed. Despite reports of successful treatments, they often suffer from the non-optimal nature of chondrocyte phenotype in the repair tissue. Thus, improved strategies to control the phenotype of the regenerating cells are needed. Avascular tissue cartilage relies on diffusion for nutrients acquisition and the removal of metabolic waste products. A low oxygen content is also present in cartilage, and the chondrocytes are, in fact, well adapted to it. Therefore, this raises an idea that the regulation of oxygen tension could be a strategy to control the chondrocyte phenotype expression, important in cartilage tissue for regenerative purposes. This narrative review discusses the aspects related to oxygen tension in the metabolism and regulation of articular and growth plate chondrocytes and progenitor cell phenotypes, and the role of some microenvironmental factors as regulators of chondrocytes.

LncRNA-mediated cartilage homeostasis in osteoarthritis: a narrative review

Osteoarthritis (OA) is a degenerative disease of cartilage that affects the quality of life and has increased in morbidity and mortality in recent years. Cartilage homeostasis and dysregulation are thought to be important mechanisms involved in the development of OA. Many studies suggest that lncRNAs are involved in cartilage homeostasis in OA and that lncRNAs can be used to diagnose or treat OA. Among the existing therapeutic regimens, lncRNAs are involved in drug-and nondrug-mediated therapeutic mechanisms and are expected to improve the mechanism of adverse effects or drug resistance. Moreover, targeted lncRNA therapy may also prevent or treat OA. The purpose of this review is to summarize the links between lncRNAs and cartilage homeostasis in OA. In addition, we review the potential applications of lncRNAs at multiple levels of adjuvant and targeted therapies. This review highlights that targeting lncRNAs may be a novel therapeutic strategy for improving and modulating cartilage homeostasis in OA patients.

TSP-1 increases autophagy level in cartilage by upregulating HSP27 which delays progression of osteoarthritis

This study aimed to determine whether Thrombospondin-1 (TSP-1) can be used as a biomarker to diagnose early osteoarthritis (OA) and whether it has a chondroprotective effect against OA. We examined TSP-1 expression in cartilage, synovial fluid, and serum at different time points after anterior cruciate ligament transection (ACLT) surgery in rats. Subsequently, TSP-1 was overexpressed or silenced to detect its effects on extracellular matrix (ECM) homeostasis, autophagy level, proliferation and apoptosis in chondrocytes. Adenovirus encoding TSP-1 was injected into the knee joints of ACLT rats to test its effect against OA. Combined with proteomic analysis, the molecular mechanism of TSP-1 in cartilage degeneration was explored. Intra-articular injection of an adenovirus carrying the TSP-1 sequence showed chondroprotective effects against OA. Moreover, TSP-1 expression decreases with OA progression and can effectively promote cartilage proliferation, inhibit apoptosis, and helps to sustain the balance between ECM anabolism and catabolism. Overexpression of TSP-1 also can increase autophagy by upregulating Heat Shock Protein 27 (HSP27, hspb1), thereby enhancing its effect as a stimulator of autophagy. TSP-1 is a hopeful strategy for OA treatment.

Screening of diagnostic biomarkers for ferroptosis-related osteoarthritis and construction of a risk-prognosis model

Background

Osteoarthritis (OA) is the most prevalent and commonly chronic joint disease that frequently develops among the elderly population. It is not just a single tissue that is affected, but rather a pathology involving the entire joint. Among them, synovitis is a key pathological change in OA. Ferroptosis is a newly discovered form of cell death that results from the buildup of lipid peroxidation. However, the role and impact of it in OA are yet to be explored.

Objective

The key to this work is to uncover the mechanisms of ferroptosis-related OA pathogenesis and develop more novel diagnostic biomarkers to facilitate the diagnostic and therapeutic of OA.

Materials and methods

Download ferroptosis-related genes and OA synovial chip datasets separately from the FerrDB and Gene Expression Omnibus databases. Identify ferroptosis differentially expressed genes using R software, obtain the intersection genes through two machine learning algorithms, and obtain diagnostic biomarkers after logistic regression analysis. Verify the diagnostic and therapeutic efficacy of specific genes for OA through the construction of clinical risk prognostic models using ROC curves and nomogram. Simultaneously, correlations between specific genes and OA immune cell infiltration co-expression were constructed. Finally, verify the differential presentation of specific genes in OA and health control synovium.

Results

Obtain 38 ferroptosis differentially expressed genes through screening. Based on machine learning algorithms and logistic regression analysis, select AGPS, BRD4, RBMS1, and EGR1 as diagnostic biomarker genes. The diagnostic and therapeutic efficacy of the four specific genes for OA has been validated by ROC curves and nomogram of clinical risk prognostic models. The analysis of immune cell infiltration and correlation suggests a close association between specific genes and OA immune cell infiltration. Further revealing the diagnostic value of specific genes for OA by the differential presentation analysis of their differential presentation in synovial tissue from OA and health control.

Conclusion

This study identified four diagnostic biomarkers for OA that are associated with iron death. The establishment of a risk-prognostic model is conducive to the premature diagnosis of OA, evaluating functional recovery during rehabilitation, and guidance for subsequent treatment.

Sakuranetin reduces inflammation and chondrocyte dysfunction in osteoarthritis by inhibiting the PI3K/AKT/NF-κB pathway

Osteoarthritis (OA) is a prevalent degenerative disease that impairs limb function, and its pathogenesis is closely related to inflammation. Sakuranetin (SK) is a cherry flavonoid phytoalexin with potent anti-inflammatory, anti-oxidant, and ant-ifungal properties. In recent studies, flavonoid and phytoalexin-related medicines have shown promise in the treatment of OA. However, the effects of SK on chondrocyte inflammation and the chondrogenesis process have remained unexplored, as have its functions in OA treatment. This study sought to confirm the therapeutic effects of SK in the OA rat model and reveal the potential mechanisms for protecting chondrocytes. The relevant mechanisms of SK were analyzed by network pharmacology analysis. Chondrocytes were subjected to IL-1β intervention to simulate an inflammatory environment and received SK treatment. Then, anabolism, catabolism, and inflammatory markers were detected by western blot, qPCR, elisa, and immunofluorescence. Chondrogenic ability was evaluated by micromass and 3D culture assays. The rats were treated with destabilization of the medial meniscus (DMM) surgery to establish an OA model and SK intra-articular injections subsequently. Histological staining, immunohistochemistry, and micro-CT were performed to analyze the structural and morphological changes of cartilage and subchondral bone. In chondrocytes, IL-1β treatment reduced chondrogenic ability, promoted catabolism, and exacerbated inflammation by triggering the PI3K/AKT/NF-κB pathway, whereas SK treatment partially rescued these negative effects. In vivo, SK treatment effectively alleviated the degeneration of cartilage and subchondral bone, thereby delaying the progression of OA. In summary, SK alleviates chondrocyte inflammation and promotes chondrogenesis by inhibiting the PI3K/AKT/NF-κB pathway, thereby improving OA progression.

The protective effect of Ergolide in osteoarthritis: In vitro and in vivo studies

Osteoarthritis (OA), a prevalent degenerative condition, occurs due to the deterioration of joint tissues and cells. Consequently, safeguarding chondrocytes against damage caused by inflammation is an area of future research emphasis. There is growing evidence that Ergolide (ERG) has multiple biological functions. Nevertheless, it is still uncertain whether it can hinder the advancement of OA. In this study, we investigate the ERG's potential to reduce inflammation and protect cartilage. ERG treatment in vitro effectively inhibited the excessive production of pro-inflammatory substances, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and tumor necrosis factor-α (TNF-α), leading to their complete suppression. Furthermore, ERG suppressed the production of matrix-degrading enzymes (ADAMTS-5) and matrix metalloproteinase 13 (MMP13), consequently impeding the breakdown of extracellular matrix (ECM) and restraining the synthesis of collagenase II and Aggrecan. Through the P38/MAPK pathway, we discovered that ERG hinders the activation of NF-κB in chondrocytes induced by IL-1β. The protective effect of ERG was enhanced by the p38 MAPK inhibitor SB203580. In vivo, ERG further demonstrated protective effects on cartilage in animal models of DMM. In conclusion, the study has discovered that ERG exhibits innovative therapeutic potential in the context of OA.

Biological functions and applications of LncRNAs in the regulation of the extracellular matrix in osteoarthritis

Osteoarthritis (OA) is a major cause of disability, characterized by chronic pain, irreversible destruction, and loss of function of the articular cartilage. The integrity and arrangement of the composition and structure of the extracellular matrix (ECM) are essential for maintaining the elasticity, integrity, and mechanical support function of the cartilage tissue. Osteoarthritis causes substantial changes in the ECM, driving the progression of the disease. Recent studies have shown that the ECM plays a critical role in the development of cartilage tissue as well as the occurrence and development of osteoarthritis by directly or indirectly regulating chondrocyte proliferation, apoptosis, differentiation, and gene expression. Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs derived from large transcripts. Mutations and disorders of lncRNAs are closely related to the development of osteoarthritis. Abnormal expression of lncRNAs in osteoarthritic cartilage regulates the synthesis and decomposition of the cartilaginous ECM. Therefore, the use of lncRNAs as nucleic acid drugs that regulate their targets may reduce ECM degradation, thereby delaying the pathological progression of osteoarthritis. In this review, the regulatory effects of lncRNAs on ECM in different cell behaviors related to OA are summarized. The roles of lncRNAs in the proliferation, apoptosis, differentiation, and ECM-related gene activity of chondrocytes, as well as the application of lncRNAs as potential gene therapy drugs for the repair and regeneration of osteoarthritic tissue, are also reviewed. A better understanding of the roles of lncRNAs in guiding chondrocyte behavior and ECM metabolism is critical for their future applications in osteoarthritis therapy and regenerative medicine.

Single‑cell sequencing, genetics, and epigenetics reveal mesenchymal stem cell senescence in osteoarthritis (Review)

Osteoarthritis (OA) is a chronic joint disease characterized by articular cartilage degeneration, secondary bone hyperplasia, inadequate extracellular matrix synthesis and degeneration of articular cartilage. Mesenchymal stem cells (MSCs) can self‑renew and undergo multidirectional differentiation; they can differentiate into chondrocytes. Aging MSCs have a weakened ability to differentiate, and release various pro‑inflammatory cytokines, which may contribute to OA progression; the other mechanism contributing to OA is epigenetic regulation (for instance, DNA methylation, histone modification and regulation of non‑coding RNA). Owing to the self‑renewal and differentiation ability of MSCs, various MSC‑based exogenous cell therapies have been developed to treat OA. The efficacy of MSC‑based therapy is mainly attributed to cytokines, growth factors and the paracrine effect of exosomes. Recently, extensive studies have been conducted on MSC‑derived exosomes. Exosomes from MSCs can deliver a variety of DNA, RNA, proteins and lipids, thereby facilitating MSC migration and cartilage repair. Therefore, MSC‑derived exosomes are considered a promising therapy for OA. The present review summarized the association between MSC aging and OA in terms of genetics and epigenetics, and characteristics of MSC‑derived exosomes, and the mechanism to alleviate OA cartilage damage.

Wnt5a deficiency in osteocalcin-expressing cells could not alleviate the osteoarthritic phenotype in a mouse model of post-traumatic osteoarthritis

Objectives

Wnt5a, which regulates the activities of osteoblasts and osteoclasts, is reportedly overexpressed in osteoarthritis (OA) tissues. The purpose of this study was to elucidate its role in the development of OA by deleting Wnt5a in osteocalcin (OCN)-expressing cells.

Materials and Methods

Knee OA was induced by anterior cruciate ligament transection (ACLT) in OCN-Cre;Wnt5afl/fl knockout (Wnt5a-cKO) mice and control littermates. Eight weeks after surgery, histological changes, cell apoptosis, and matrix metabolism of cartilage were evaluated by toluidine blue, TUNEL staining, and im-immunohistochemistry analyses, respectively. In addition, the subchondral bone microarchitecture of mice was examined by micro-computed tomography (micro-CT).

Results

Histological scores show substantial cartilage degeneration occurred in ACLT knees, coupled with decreased collagen type II expression and enhanced matrix metalloproteinase 13 expression, as well as higher proportions of apoptotic cells. Micro-CT results show that ACLT resulted in decreased bone mineral density, bone volume/trabecular volume, trabecular number, and structure model index of subchondral bones in both Wnt5a-cKO and control littermates; although Wnt5a-cKO mice display lower BMD and BV/TV values, no significant difference was observed between Wnt5a-cKO and control mice for any of these values.

Conclusion

Our findings indicate that Wnt5a deficiency in OCN-expressing cells could not prevent an osteoarthritic phenotype in a mouse model of post-traumatic OA.

Osteoarthritis in the Elderly Population: Preclinical Evidence of Nutrigenomic Activities of Flavonoids

Osteoarthritis (OA) is a degenerative joint disease that is age-related and progressive. It causes the destruction of articular cartilage and underlying bone, often aggravated by inflammatory processes and oxidative stresses. This pathology impairs the quality of life of the elderly, causing pain, reduced mobility, and functional disabilities, especially in obese patients. Phytochemicals with anti-inflammatory and antioxidant activities may be used for long-term treatment of OA, either in combination with current anti-inflammatories and painkillers, or as an alternative to other products such as glucosamine and chondroitin, which improve cartilage structure and elasticity. The current systematic review provides a comprehensive understanding of the use of flavonoids. It highlights chondrocyte, cartilage, and subchondral bone activities, with a particular focus on their nutrigenomic effects. The molecular mechanisms of these molecules demonstrate how they can be used for the prevention and treatment of OA in the elderly population. However, clinical trials are still needed for effective use in clinical practice.

Bioinformatics analysis of hub genes as osteoarthritis prognostic biomarkers

Osteoarthritis (OA) is a progressive cartilage degradation disease, concomitant with synovitis, osteophyte formation, and subchondral bone sclerosis. Over 37% of the elderly population is affected by OA, and the number of cases is increasing as the global population ages. Therefore, the objective of this study was to identify and analyze the hub genes of OA combining with comprehensive bioinformatics analysis tools to provide theoretical basis in further OA effective therapies. Two sample sets of GSE46750 contained 12 pairs OA synovial membrane and normal samples harvested from patients as well as GSE98918 including 12 OA and non-OA patients were downloaded from the Gene Expression Omnibus database (GEO) database. Differentially expressed genes (DEGs) were identified using Gene Expression Omnibus 2R (GEO2R), followed by functional enrichment analysis, protein-protein interaction networks construction. The hub genes were identified and evaluated. An OA rat model was constructed, hematoxylin and eosin staining, safranin O/fast green staining, cytokines concentrations of serum were used to verify the model. The hub genes expression level in the knee OA samples were verified using RT-qPCR. The top 20 significantly up-regulated and down-regulated DEGs were screened out from the two datasets, respectively. The top 18 GO terms and 10 KEGG pathways were enriched. Eight hub genes were identified, namely MS4A6A, C1QB, C1QC, CD74, CSF1R, HLA-DPA1, HLA-DRA and ITGB2. Among them, the hub genes were all up-regulated in in vivo OA rat model, compared with healthy controls. The eight hub genes identified (MS4A6A, C1QB, C1QC, CD74, CSF1R, HLA-DPA1, HLA-DRA and ITGB2) were shown to be associated with OA. These genes can serve as disease markers to discriminate OA patients from healthy controls.

Unraveling cartilage degeneration through synergistic effects of hydrostatic pressure and biomimetic temperature increase

Cartilage degeneration, typically viewed as an irreversible, vicious cycle, sees a significant reduction in two essential biophysical cues: the well-established hydrostatic pressure (HP) and the recently discovered transient temperature increase. Our study aimed to evaluate the combined influence of these cues on maintaining cartilage homeostasis. To achieve this, we developed a customized bioreactor, designed to mimic the specific hydrostatic pressure and transient thermal increase experienced during human knee physiological activities. This system enabled us to investigate the response of human 3D-cultured chondrocytes and human cartilage explants to either isolated or combined hydrostatic pressure and thermal stimuli. Our study found that chondroinduction (SOX9, aggrecan, and sulfated glycosaminoglycan) and chondroprotection (HSP70) reached maximum expression levels when hydrostatic pressure and transient thermal increase acted in tandem, underscoring the critical role of these combined cues in preserving cartilage homeostasis. These findings led us to propose a refined model of the vicious cycle of cartilage degeneration.

Cucurbitacin E reduces IL-1β-induced inflammation and cartilage degeneration by inhibiting the PI3K/Akt pathway in osteoarthritic chondrocytes

BACKGROUND

Osteoarthritis is a degenerative joint disease. Cartilage degeneration is the earliest and most important pathological change in osteoarthritis, and persistent inflammation is one of the driving factors of cartilage degeneration. Cucurbitacin E, an isolated compound in the Cucurbitacin family, has been shown to have anti-inflammatory effects, but its role and mechanism in osteoarthritic chondrocytes are unclear.

METHODS

For in vitro experiments, human chondrocytes were stimulated with IL-1β, and the expression of inflammatory genes was measured by Western blotting and qPCR. The expression of extracellular matrix proteins was evaluated by immunofluorescence staining, Western blotting and saffron staining. Differences in gene expression between cartilage from osteoarthritis patients and normal cartilage were analysed by bioinformatics methods, and the relationship between Cucurbitacin E and its target was analysed by a cellular thermal shift assay, molecular docking analysis and molecular dynamics simulation. For in vivo experiments, knee osteoarthritis was induced by DMM in C57BL/6 mouse knee joints, and the effect of Cucurbitacin E on knee joint degeneration was evaluated.

RESULTS

The in vitro experiments confirmed that Cucurbitacin E effectively inhibited the production of the inflammatory cytokine interleukin-1β(IL-1β) and cyclooxygenase-2 (COX-2) by IL-1β-stimulated chondrocytes and alleviates extracellular matrix degradation. The in vivo experiments demonstrated that Cucurbitacin E had a protective effect on the knee cartilage of C57BL/6 mice with medial meniscal instability in the osteoarthritis model. Mechanistically, bioinformatic analysis of the GSE114007 and GSE117999 datasets showed that the PI3K/AKT pathway was highly activated in osteoarthritis. Immunohistochemical analysis of PI3K/Akt signalling pathway proteins in pathological slices of human cartilage showed that the level of p-PI3K in patients with osteoarthritis was higher than that in the normal group. PI3K/Akt were upregulated in IL-1β-stimulated chondrocytes, and Cucurbitacin E intervention reversed this phenomenon. The cellular thermal shift assay, molecular docking analysis and molecular dynamics experiment showed that Cucurbitacin E had a strong binding affinity for the inhibitory target PI3K. SC79 activated Akt phosphorylation and reversed the effect of Cucurbitacin E on IL-1β-induced chondrocyte degeneration, demonstrating that Cucurbitacin E inhibits IL-1β-induced chondrocyte inflammation and degeneration by inhibiting the PI3K/AKT pathway.

CONCLUSION

Cucurbitacin E inhibits the activation of the PI3K/AKT pathway, thereby alleviating the progression of OA. In summary, we believe that Cucurbitacin E is a potential drug for the treatment of OA.

Tranexamic Acid Causes Chondral Injury Through Chondrocytes Apoptosis Induced by Activating Endoplasmic Reticulum Stress

PURPOSE

To investigate whether tranexamic acid (TXA) is cytotoxic in chondrocyte and cartilage tissues, as well as explore the mechanisms behind the possible toxicity in detail.

METHODS

We detected the cell viability of chondrocytes in vitro and the change of morphology and specific in vivo contents of cartilage after TXA treatment. Furthermore, we detected apoptosis in cartilage. We used apoptosis-specific staining, reactive oxygen species detection, mitochondrial membrane potential detection, flow cytometry, and western blot for apoptosis detection. Finally, we detected the activation of endoplasmic reticulum stress (ERS) in TXA-treated chondrocytes to clarify the mechanism behind chondrocyte apoptosis.

RESULTS

TXA presented an increasing toxic effect with increasing concentrations, especially in the 100 mg/mL group. In addition, we found that 50 mg/mL and 100 mg/mL TXA significantly increased apoptosis in cartilage and subchondral bone. TXA could induce chondrocyte apoptosis in cell and protein levels with reactive oxygen species generation and mitochondrial membrane depolarization. An apoptosis inhibitor could inhibit the induced apoptosis. Next, TXA induced calcium overload in chondrocytes and increased ERS-specific protein expression, whereas ERS inhibitor blocked ERS activation and further inhibited chondrocyte apoptosis.

CONCLUSIONS

We concluded that TXA had a toxic effect on chondrocytes by inducing apoptosis through ERS activation, especially in 50 mg/mL and 100 mg/mL groups. We recommend TXA concentrations of less than 50 mg/mL in joint surgeries.

CLINICAL RELEVANCE

It is still unclear whether TXA has a toxic effect on cartilage when topically used in joint surgeries. The concentration also varies. This study provides additional evidence that TXA at high concentrations will cause cartilage damage, which will help to provide a new understanding of the clinical administration of TXA.

Epigenetic modification and exosome effects on autophagy in osteoarthritis

Osteoarthritis (OA) is a degenerative disease that leads to joint pain and stiffness and is one of the leading causes of disability and pain worldwide. Autophagy is a highly conserved self-degradation process, and its abnormal function is closely related to human diseases, including OA. Abnormal autophagy regulates cell aging, matrix metalloproteinase metabolism, and reactive oxygen metabolism, which are key in the occurrence and development of OA. There is evidence that drugs directly or indirectly targeting autophagy significantly hinder the progress of OA. In addition, the occurrence and development of autophagy in OA are regulated by many factors, including epigenetic modification, exosomes, crucial autophagy molecules, and signaling pathway regulation. Autophagy, as a new therapeutic target for OA, has widely influenced the pathological mechanism of OA. However, determining how autophagy affects OA pathology and its use in the treatment and diagnosis of targets still need further research.

Mucopolysaccharidosis IVA: Current Disease Models and Drawbacks

Mucopolysaccharidosis IVA (MPS IVA) is a rare disorder caused by mutations in the N-acetylgalactosamine-6-sulfate-sulfatase (GALNS) encoding gene. GALNS leads to the lysosomal degradation of the glycosaminoglyccreasans keratan sulfate and chondroitin 6-sulfate. Impaired GALNS enzymes result in skeletal and non-skeletal complications in patients. For years, the MPS IVA pathogenesis and the assessment of promising drugs have been evaluated using in vitro (primarily fibroblasts) and in vivo (mainly mouse) models. Even though value information has been raised from those studies, these models have several limitations. For instance, chondrocytes have been well recognized as primary cells affected in MPS IVA and responsible for displaying bone development impairment in MPS IVA patients; nonetheless, only a few investigations have used those cells to evaluate basic and applied concepts. Likewise, current animal models are extensively represented by mice lacking GALNS expression; however, it is well known that MPS IVA mice do not recapitulate the skeletal dysplasia observed in humans, making some comparisons difficult. This manuscript reviews the current in vitro and in vivo MPS IVA models and their drawbacks.

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

Knee osteoarthritis (KOA) is a common chronic disease in orthopedics, which brings great pain to patients' life and spirit. Therefore, it is necessary to elucidate the pathogenesis of KOA. The pathophysiology of KOA has been linked to numerous factors, including oxidative stress, apoptosis, cellular senescence, mitochondrial dysfunction, and inflammatory factors. Cellular senescence has grown in importance as a topic of study for age-related illnesses recently. KOA has also been discovered to be closely related to human aging, a process in which chondrocyte senescence may be crucial. Numerous researches have looked at the pathogenesis of KOA from the perspectives of mechanical stress abnormalities, oxidative stress, inflammatory overexpression, and mitochondrial dysfunction. Many studies have discovered that the primary pathogenesis of KOA is inflammatory overexpression and chondrocyte death brought on by an imbalance in the joint microenvironment. And abnormal mechanical stress is the initiating cause of oxidative stress, inflammation, and mitochondrial disorders. However, few findings have been reported in the literature on the relationship between these factors, especially for mechanical stress abnormalities, and chondrocyte senescence. This time, in order to better understand the pathogenesis of KOA and identify potential connections between chondrocyte senescence and these microenvironments in KOA, as well as oxidative stress, inflammatory overexpression, and mitochondrial dysfunction microenvironmental dysfunctions, we will use chondrocyte senescence as a starting point. This will allow us to develop new therapeutic approaches for KOA.

PLXNC1 interference alleviates the inflammatory injury, apoptosis and extracellular matrix degradation of IL-1β-exposed chondrocytes via suppressing GRP78 expression

BACKGROUND

Osteoarthritis (OA) is a frequently encountered debilitating joint disorder. Whether plexin C1 (PLXNC1) is implicated in OA is far from being investigated despite its well-documented pro-inflammatory property in human diseases. The goal of this study is to expound the specific role of PLXNC1 in OA and elaborate the probable action mechanism.

METHODS

Firstly, PLXNC1 expression in the cartilage tissues of patients with OA was examined with GEO database. In interleukin-1beta (IL-1β)-induced OA cell model, RT-qPCR and western blotting tested the expression of PLXNC1, glucose-regulating protein 78 (GRP78) and extracellular matrix (ECM) degradation-related factors. Cell viability and inflammation were respectively judged by CCK-8 assay and RT-qPCR. TUNEL and western blotting estimated cell apoptosis. The potential binding between PLXNC1 and GRP78 was corroborated by Co-IP assay. Western blotting also tested the expression of endoplasmic reticulum stress (ERS)-associated proteins.

RESULTS

As it turned out, PLXNC1 expression was elevated in the cartilage tissues of patients with OA and IL-1β-treated chondrocytes. When PLXNC1 was depleted, the viability injury, inflammation, apoptosis and ECM degradation of chondrocytes exposed to IL-1β were obstructed. Besides, GRP78 bond to PLXNC1 in IL-1β-treated chondrocytes. The ascending GRP78 expression in the chondrocytes exposed to IL-1β was depleted after PLXNC1 was silenced. Meanwhile, the impacts of PLXNC1 deficiency on the viability, inflammatory response, apoptosis, ECM degradation as well as ERS in IL-1β-exposed chondrocytes were abolished by GRP78 up-regulation.

CONCLUSION

In summary, PLXNC1 silencing might interact with and down-regulate GRP78 to mitigate the apoptosis, inflammation, and ECM degradation of IL-1β-insulted chondrocytes in OA.

MicroRNA as Possible Mediators of the Synergistic Effect of Celecoxib and Glucosamine Sulfate in Human Osteoarthritic Chondrocyte Exposed to IL-1β

This study investigated the role of a pattern of microRNA (miRNA) as possible mediators of celecoxib and prescription-grade glucosamine sulfate (GS) effects in human osteoarthritis (OA) chondrocytes. Chondrocytes were treated with celecoxib (1.85 µM) and GS (9 µM), alone or in combination, for 24 h, with or without interleukin (IL)-1β (10 ng/mL). Cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, apoptosis and reactive oxygen species (ROS) by cytometry, nitric oxide (NO) by Griess method. Gene levels of miRNA, antioxidant enzymes, nuclear factor erythroid (NRF)2, and B-cell lymphoma (BCL)2 expressions were analyzed by quantitative real time polymerase chain reaction (real time PCR). Protein expression of NRF2 and BCL2 was also detected at immunofluorescence and western blot. Celecoxib and GS, alone or in combination, significantly increased viability, reduced apoptosis, ROS and NO production and the gene expression of miR-34a, -146a, -181a, -210, in comparison to baseline and to IL-1β. The transfection with miRNA specific inhibitors significantly counteracted the IL-1β activity and potentiated the properties of celecoxib and GS on viability, apoptosis and oxidant system, through nuclear factor (NF)-κB regulation. The observed effects were enhanced when the drugs were tested in combination. Our data confirmed the synergistic anti-inflammatory and chondroprotective properties of celecoxib and GS, suggesting microRNA as possible mediators.

An inducible long noncoding RNA, LncZFHX2, facilitates DNA repair to mediate osteoarthritis pathology

Cartilage homeostasis is essential for chondrocytes to maintain proper phenotype and metabolism. Because adult articular cartilage is avascular, chondrocytes must survive in low oxygen conditions, and changing oxygen tension can significantly affect metabolism and proteoglycan synthesis in these cells. However, whether long noncoding RNA participate in cartilage homeostasis under hypoxia has not been reported yet. Here, we first identified LncZFHX2 as a lncRNA upregulated under physiological hypoxia in cartilage, specifically by HIF-1α. LncZFHX2 knockdown simultaneously accelerated cellular senescence, targeted multiple components of extracellular matrix metabolism, and increased DNA damage in chondrocytes. Through a series of in vitro and in vivo experiments, we identified that LncZFHX2 performed a novel function that regulated RIF1 expression through forming a transcription complex with KLF4 and promoting chondrocyte DNA repair. Moreover, chondrocyte-conditional knockout of LncZFHX2 accelerated injury-induced cartilage degeneration in vivo. In conclusion, we identified a hypoxia-activated DNA repair pathway that maintains matrix homeostasis in osteoarthritis cartilage.

Clinical Potential of Cellular Material Sources in the Generation of iPSC-Based Products for the Regeneration of Articular Cartilage

Inflammatory joint diseases, among which osteoarthritis and rheumatoid arthritis are the most common, are characterized by progressive degeneration of the cartilage tissue, resulting in the threat of limited or lost joint functionality in the absence of treatment. Currently, treating these diseases is difficult, and a number of existing treatment and prevention measures are not entirely effective and are complicated by the patients' conditions, the multifactorial nature of the pathology, and an incomplete understanding of the etiology. Cellular technologies based on induced pluripotent stem cells (iPSCs) can provide a vast cellular resource for the production of artificial cartilage tissue for replacement therapy and allow the possibility of a personalized approach. However, the question remains whether a number of etiological abnormalities associated with joint disease are transmitted from the source cell to iPSCs and their chondrocyte derivatives. Some data state that there is no difference between the iPSCs and their derivatives from healthy and sick donors; however, there are other data indicating a dissimilarity. Therefore, this topic requires a thorough study of the differentiation potential of iPSCs and the factors influencing it, the risk factors associated with joint diseases, and a comparative analysis of the characteristics of cells obtained from patients. Together with cultivation optimization methods, these measures can increase the efficiency of obtaining cell technology products and make their wide practical application possible.

Biomimetic Hyaluronic Acid-Based Brush Polymers Modulate Chondrocyte Homeostasis via ROS/Ca2+/TRPV4

Bionic mimics using natural cartilage matrix molecules can modulate the corresponding metabolic activity by improving the microenvironment of chondrocytes. A bionic brush polymer, HA/PX, has been found to reverse the loss of cartilage extracellular matrix (ECM) and has promising applications in the clinical treatment of osteoarthritis (OA). However, the unknown bioremediation mechanism of HA/PX severely hinders its clinical translation. In OA, the massive loss of the ECM may be attributed to a decrease in transient receptor potential vanilloid 4 (TRPV4) activity, which affects reactive oxygen species (ROS) clearance and [Ca2+]i signaling, initiating downstream catabolic pathways. In this study, we investigated the bioremediation mechanism of HA/PX in a model of interleukin 1β (IL-1β)-induced inflammation. Through TRPV4, HA/PX reduced ROS accumulation in chondrocytes and enhanced [Ca2+]i signaling, reflecting a short-term protection capacity for chondrocytes. In addition, HA/PX balanced the metabolic homeostasis of chondrocytes via TRPV4, including promoting the secretion of type II collagen (Col-II) and aggrecan, the major components of the ECM, and reducing the expression of matrix metal-degrading enzyme (MMP-13), exerting long-term protective effects on chondrocytes. Molecular dynamics (MD) simulations showed that HA/PX could act as a TRPV4 activator. Our results suggest that HA/PX can regulate chondrocyte homeostasis via ROS/Ca2+/TRPV4, thereby improving cartilage regeneration. Because the ECM is a prevalent feature of various cell types, HA/PX holds promising potential for improving regeneration and disease modification for not only cartilage-related healthcare but many other tissues and diseases.

Identification of EGFR as an essential regulator in chondrocytes ferroptosis of osteoarthritis using bioinformatics, in vivo, and in vitro study

Objective

The mechanisms of chondrocytes ferroptosis in osteoarthritis (OA) have not yet been fully elucidated. This study aimed to identify key ferroptosis related genes (FRGs) involved in chondrocytes ferroptosis.

Methods

LASSO, SVM-RFE, and receiver operating characteristic curve (ROC) were performed to screen key differentially expressed FRGs (DEFRGs). Functional analyses were conducted using GO, and KEGG analyses. Unsupervised clustering analysis was used to identify ferroptosis related patterns. The CeRNA network was constructed to predict the upstream miRNAs and lncRNAs. Finally, we validated the role of EGFR in chondrocytes ferroptosis using in vivo and in vitro experiments.

Results

A total of 42 DEFRGs were identified between OA and normal cartilages. GO and KEGG analyses indicated that these DEFRGs were significantly engaged in ferroptosis related biological processes and pathways, such as cellular response to oxidative stress, positive regulation of programmed cell death, MAPK and PI3K-Akt signaling pathways. Moreover, four key DEFRGs, including ACSF2, AURKA, EGFR, and KLHL24, were considered as potential biomarkers of OA. Moreover, two distinct ferroptosis related patterns were determined, and a total of 882 differentially expressed genes were identified which might participate in extracellular matrix degradation and inflammatory response. In addition, the CeRNA network showed that EGFR could be competitively regulated by 3 lncRNAs and 4 miRNAs. Significantly, the expression of EGFR was downregulated in human OA cartilages, OA mouse model, and erastin induced chondrocytes. EGFR inhibition could induce the occurrence of chondrocytes ferroptosis and ECM degradation which could be reversed by the addition of Ferrostatin-1.

Conclusion

Our study has identified ACSF2, AURKA, EGFR, and KLHL24 as ferroptosis-related biomarkers in OA. Furthermore, we have conducted a preliminary investigation into the role of EGFR in regulating chondrocytes ferroptosis. These findings offer novel insights into the molecular mechanisms underlying OA.

Incorporation of kartogenin and silk fibroin scaffolds promotes rat articular cartilage regeneration through enhancement of antioxidant functions

Treating articular cartilage defects in patients remains a challenging task due to the absence of blood vessels within the cartilage tissue. The regenerative potential is further compromised by an imbalance between anabolism and catabolism, induced by elevated levels of reactive oxygen species. However, the advent of tissue engineering introduces a promising strategy for cartilage regeneration, offering viable solutions such as mechanical support and controlled release of chondrogenic molecules or cytokines. In this study, we developed an antioxidant scaffold by incorporating natural silk fibroin (SF) and kartogenin (KGN)-loaded liposomes (SF-Lipo@KGN). The scaffold demonstrated appropriate pore size, connectivity, and water absorption and the sustained release of KGN was achieved through the encapsulation of liposomes. In vitro experiments revealed that the SF-Lipo@KGN scaffolds exhibited excellent biocompatibility, as evidenced by enhanced cell adhesion, migration, and proliferation of chondrocytes. The SF-Lipo@KGN scaffolds were found to stimulate cartilage matrix synthesis through the activation of the nuclear factor erythroid-2-related factor 2/heme oxygenase-1 antioxidant signaling pathway. In vivo experiments demonstrated the effective promotion of articular cartilage regeneration by the SF-Lipo@KGN scaffolds, which enhanced extracellular matrix anabolism and restored the intrinsic redox homeostasis. Overall, this study successfully developed biomimetic KGN-loaded scaffolds that restore cartilage redox homeostasis, indicating promising prospects for cartilage tissue engineering.

Hsa_circ_0007292 promotes chondrocyte injury in osteoarthritis via targeting the miR-1179/HMGB1 axis

BACKGROUND

Circular RNAs (circRNAs) have been demonstrated to participate in the progression of osteoarthritis (OA). This study aimed to investigate the role and molecular mechanism of hsa_circ_0007292 in OA.

METHODS

Hsa_circ_0007292 was identified by analyzing a circRNA microarray from the Gene Expression Omnibus (GEO) database, and its expression was detected by real-time PCR in OA cartilage tissues and interleukin (IL)-1β-induced two human chondrocytes (CHON-001 and C28/I2), the OA cell models. The effects of hsa_circ_0007292 knockdown and miR-1179 overexpression on IL-1β-induced chondrocyte injury were examined by CCK-8, BrdU, flow cytometry, ELISA, and western blot. RNA pull-down assay and dual-luciferase reporter gene assay were used to analyze the interaction between hsa_circ_0007292 and miR-1179. Rescue experiments were carried out to determine the correlations among hsa_circ_0007292, miR-1179 and high mobility group box-1 (HMGB1).

RESULTS

Hsa_circ_0007292 expression was upregulated in OA tissues and IL-1β-induced chondrocytes. Both downregulation of hsa_circ_0007292 and miR-1179 overexpression increased the proliferation and Aggrecan expression, suppressed apoptosis, matrix catabolic enzyme MMP13 expression and inflammatory factor (TNF-α, IL-6, and IL-8) levels. There was a negative correlation between hsa_circ_0007292 and miR-1179, and a positive correlation between hsa_circ_0007292 and HMGB1 in OA tissues. The mechanistic study showed that hsa_circ_0007292 prevented HMGB1 downregulation by sponging miR-1179. Upregulation of HMGB1 could reverse the influence of hsa_circ_0007292 downregulation on IL-1β-induced chondrocyte injury.

CONCLUSIONS

Downregulation of hsa_circ_0007292 relieved apoptosis, extracellular matrix degradation and inflammatory response in OA via the miR-1179/HMGB1 axis, suggesting that hsa_circ_0007292 might be a potential therapeutic target for OA treatment.

A comprehensive analysis of biomarkers associated with synovitis and chondrocyte apoptosis in osteoarthritis

Introduction

Osteoarthritis (OA) is a chronic disease with high morbidity and disability rates whose molecular mechanism remains unclear. This study sought to identify OA markers associated with synovitis and cartilage apoptosis by bioinformatics analysis.

Methods

A total of five gene-expression profiles were selected from the Gene Expression Omnibus database. We combined the GEO with the GeneCards database and performed Gene Ontology and Kyoto Encyclopedia of Genes and Genome analyses; then, the least absolute shrinkage and selection operator (LASSO) algorithm was used to identify the characteristic genes, and a predictive risk score was established. We used the uniform manifold approximation and projection (UMAP) method to identify subtypes of OA patients, while the CytoHubba algorithm and GOSemSim R package were used to screen out hub genes. Next, an immunological assessment was performed using single-sample gene set enrichment analysis and CIBERSORTx.

Results

A total of 56OA-related differential genes were selected, and 10 characteristic genes were identified by the LASSO algorithm. OA samples were classified into cluster 1 and cluster 2 subtypes byUMAP, and the clustering results showed that the characteristic genes were significantly different between these groups. MYOC, CYP4B1, P2RY14, ADIPOQ, PLIN1, MFAP5, and LYVE1 were highly expressed in cluster 2, and ANKHLRC15, CEMIP, GPR88, CSN1S1, TAC1, and SPP1 were highly expressed in cluster 1. Protein-protein interaction network analysis showed that MMP9, COL1A, and IGF1 were high nodes, and the differential genes affected the IL-17 pathway and tumor necrosis factor pathway. The GOSemSim R package showed that ADIPOQ, COL1A, and SPP1 are closely related to the function of 31 hub genes. In addition, it was determined that mmp9 and Fos interact with multiple transcription factors, and the ssGSEA and CIBERSORTx algorithms revealed significant differences in immune infiltration between the two OA subtypes. Finally, a qPCR experiment was performed to explore the important genes in rat cartilage and synovium tissues; the qPCR results showed that COL1A and IL-17A were both highly expressed in synovitis tissues and cartilage tissues of OA rats, which is consistent with the predicted results.

Discussion

In the future, common therapeutic targets might be found forsimultaneous remissions of both phenotypes of OA.

Automated Prediction of Osteoarthritis Level in Human Osteochondral Tissue Using Histopathological Images

Osteoarthritis (OA) is the most common arthritis and the leading cause of lower extremity disability in older adults. Understanding OA progression is important in the development of patient-specific therapeutic techniques at the early stage of OA rather than at the end stage. Histopathology scoring systems are usually used to evaluate OA progress and the mechanisms involved in the development of OA. This study aims to classify the histopathological images of cartilage specimens automatically, using artificial intelligence algorithms. Hematoxylin and eosin (HE)- and safranin O and fast green (SafO)-stained images of human cartilage specimens were divided into early, mild, moderate, and severe OA. Five pre-trained convolutional networks (DarkNet-19, MobileNet, ResNet-101, NasNet) were utilized to extract the twenty features from the last fully connected layers for both scenarios of SafO and HE. Principal component analysis (PCA) and ant lion optimization (ALO) were utilized to obtain the best-weighted features. The support vector machine classifier was trained and tested based on the selected descriptors to achieve the highest accuracies of 98.04% and 97.03% in HE and SafO, respectively. Using the ALO algorithm, the F1 scores were 0.97, 0.991, 1, and 1 for the HE images and 1, 0.991, 0.97, and 1 for the SafO images for the early, mild, moderate, and severe classes, respectively. This algorithm may be a useful tool for researchers to evaluate the histopathological images of OA without the need for experts in histopathology scoring systems or the need to train new experts. Incorporating automated deep features could help to improve the characterization and understanding of OA progression and development.

HTRA1 from OVX rat osteoclasts causes detrimental effects on endplate chondrocytes through NF-κB

Endplate osteochondritis is considered one of the major causes of intervertebral disc degeneration (IVDD) and low back pain. Menopausal women have a higher rate of endplate cartilage degeneration than similarly aged men, but the related mechanisms are still unclear. Subchondral bone changes, mainly mediated by osteoblasts and osteoclasts, are considered an important reason for the degeneration of cartilage. This work explored the role of osteoclasts in endplate cartilage degeneration, as well as its underlying mechanisms. A rat ovariectomy (OVX) model was used to induce estrogen deficiency. Our experiments indicated that OVX significantly promoted osteoclastogenesis and anabolism and catabolism changes in endplate chondrocytes. OVX osteoclasts cause an imbalance between anabolism and catabolism in endplate chondrocytes, as shown by a decrease in anabolic markers such as Aggrecan and Collagen II, and an increase in catabolic markers such as a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) and matrix metalloproteinases (MMP13). Osteoclasts were also confirmed in this study to be able to secrete HtrA serine peptidase 1 (HTRA1), which resulted in increased catabolism in endplate chondrocytes through the NF-κB pathway under estrogen deficiency. This study demonstrated the involvement and mechanism of osteoclasts in the anabolism and catabolism changes of endplate cartilage under estrogen deficiency, and proposed a new strategy for the treatment of endplate osteochondritis and IVDD by targeting HTRA1.

Osteoarthritis genetic risk acting on the galactosyltransferase gene COLGALT2 has opposing functional effects in articulating joint tissues

BACKGROUND

Investigation of cartilage and chondrocytes has revealed that the osteoarthritis risk marked by the independent DNA variants rs11583641 and rs1046934 mediate  their effects by decreasing the methylation status of CpG dinucleotides in enhancers and increasing the expression of shared target gene COLGALT2. We set out to investigate if these functional effects operate in a non-cartilaginous joint tissue.

METHODS

Nucleic acids were extracted from the synovium of osteoarthritis patients. Samples were genotyped, and DNA methylation was quantified by pyrosequencing at CpGs within the COLGALT2 enhancers. CpGs were tested for enhancer effects using a synovial cell line and a reporter gene assay. DNA methylation was altered using epigenetic editing, with the impact on gene expression determined using quantitative polymerase chain reaction. In silico analysis complemented laboratory experiments.

RESULTS

The rs1046934 genotype did not associate with DNA methylation or COLGALT2 expression in the synovium, whereas the rs11583641 genotype did. Surprisingly, the effects for rs11583641 were opposite to those previously observed in cartilage. Epigenetic editing in synovial cells revealed that enhancer methylation is causally linked to COLGALT2 expression.

CONCLUSIONS

This is the first direct demonstration for osteoarthritis genetic risk of a functional link between DNA methylation and gene expression operating in opposite directions between articular joint tissues. It highlights pleiotropy in the action of osteoarthritis risk and provides a cautionary note in the application of future genetically based osteoarthritis therapies: an intervention that decreases the detrimental effect of a risk allele in one joint tissue may inadvertently increase its detrimental effect in another joint tissue.

Dihydrocaffeic acid improves IL-1β-induced inflammation and cartilage degradation via inhibiting NF-κB and MAPK signalling pathways

Aims

Osteoarthritis (OA) is a prevalent joint disorder with inflammatory response and cartilage deterioration as its main features. Dihydrocaffeic acid (DHCA), a bioactive component extracted from natural plant (gynura bicolor), has demonstrated anti-inflammatory properties in various diseases. We aimed to explore the chondroprotective effect of DHCA on OA and its potential mechanism.

Methods

In vitro, interleukin-1 beta (IL-1β) was used to establish the mice OA chondrocytes. Cell counting kit-8 evaluated chondrocyte viability. Western blotting analyzed the expression levels of collagen II, aggrecan, SOX9, inducible nitric oxide synthase (iNOS), IL-6, matrix metalloproteinases (MMPs: MMP1, MMP3, and MMP13), and signalling molecules associated with nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Immunofluorescence analysis assessed the expression of aggrecan, collagen II, MMP13, and p-P65. In vivo, a destabilized medial meniscus (DMM) surgery was used to induce mice OA knee joints. After injection of DHCA or a vehicle into the injured joints, histological staining gauged the severity of cartilage damage.

Results

DHCA prevented iNOS and IL-6 from being upregulated by IL-1β. Moreover, the IL-1β-induced upregulation of MMPs could be inhibited by DHCA. Additionally, the administration of DHCA counteracted IL-1β-induced downregulation of aggrecan, collagen II, and SOX9. DHCA protected articular cartilage by blocking the NF-κB and MAPK pathways. Furthermore, DHCA mitigated the destruction of articular cartilage in vivo.

Conclusion

We present evidence that DHCA alleviates inflammation and cartilage degradation in OA chondrocytes via suppressing the NF-κB and MAPK pathways, indicating that DHCA may be a potential agent for OA treatment.

Cite this article: Bone Joint Res 2023;12(4):259–273.

A chemo-mechano-biological modeling framework for cartilage evolving in health, disease, injury, and treatment

BACKGROUND AND OBJECTIVE

Osteoarthritis (OA) is a pervasive and debilitating disease, wherein degeneration of cartilage features prominently. Despite extensive research, we do not yet understand the cause or progression of OA. Studies show biochemical, mechanical, and biological factors affect cartilage health. Mechanical loads influence synthesis of biochemical constituents which build and/or break down cartilage, and which in turn affect mechanical loads. OA-associated biochemical profiles activate cellular activity that disrupts homeostasis. To understand the complex interplay among mechanical stimuli, biochemical signaling, and cartilage function requires integrating vast research on experimental mechanics and mechanobiology-a task approachable only with computational models. At present, mechanical models of cartilage generally lack chemo-biological effects, and biochemical models lack coupled mechanics, let alone interactions over time.

METHODS

We establish a first-of-its kind virtual cartilage: a modeling framework that considers time-dependent, chemo-mechano-biologically induced turnover of key constituents resulting from biochemical, mechanical, and/or biological activity. We include the "minimally essential" yet complex chemical and mechanobiological mechanisms. Our 3-D framework integrates a constitutive model for the mechanics of cartilage with a novel model of homeostatic adaptation by chondrocytes to pathological mechanical stimuli, and a new application of anisotropic growth (loss) to simulate degradation clinically observed as cartilage thinning.

RESULTS

Using a single set of representative parameters, our simulations of immobilizing and overloading successfully captured loss of cartilage quantified experimentally. Simulations of immobilizing, overloading, and injuring cartilage predicted dose-dependent recovery of cartilage when treated with suramin, a proposed therapeutic for OA. The modeling framework prompted us to add growth factors to the suramin treatment, which predicted even better recovery.

CONCLUSIONS

Our flexible framework is a first step toward computational investigations of how cartilage and chondrocytes mechanically and biochemically evolve in degeneration of OA and respond to pharmacological therapies. Our framework will enable future studies to link physical activity and resulting mechanical stimuli to progression of OA and loss of cartilage function, facilitating new fundamental understanding of the complex progression of OA and elucidating new perspectives on causes, treatments, and possible preventions.

Siraitia grosvenorii Residual Extract Inhibits Inflammation in RAW264.7 Macrophages and Attenuates Osteoarthritis Progression in a Rat Model

Osteoarthritis (OA) is a degenerative joint disease characterised by cartilage degeneration and chondrocyte inflammation. We investigated the anti-inflammatory effects of the Siraitia grosvenorii residual extract (SGRE) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages in vitro and its anti-osteoarthritic effects in a monosodium iodoacetate (MIA)-induced OA rat model. SGRE dose-dependently decreased nitric oxide (NO) production in LPS-induced RAW264.7 cells. Moreover, SGRE reduced the pro-inflammatory mediator (cyclooxygenase-2 (COX2), inducible NO synthase (iNOS), and prostaglandin E2 (PGE2)) and pro-inflammatory cytokine (interleukin-(IL)-1β, IL-6, and tumour necrosis factor (TNF-α)) levels. SGRE suppressed nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathway activation in RAW264.7 macrophages, thus reducing inflammation. Rats were orally administered SGRE (150 or 200 mg/kg) or the positive control drug JOINS (20 mg/kg) 3 days before MIA injection, and once daily for 21 days thereafter. SGRE elevated the hind paw weight-bearing distribution, thus relieving pain. It also reduced inflammation by inhibiting inflammatory mediator (iNOS, COX-2, 5-LOX, PGE2, and LTB4) and cytokine (IL-1β, IL-6, and TNF-α) expression, downregulating cartilage-degrading enzymes, such as MMP-1, -2, -9, and -13. SGRE significantly reduced the SOX9 and extracellular matrix component (ACAN and COL2A1) levels. Therefore, SGRE is a potential therapeutic active agent against inflammation and OA.

Synovial mesenchymal stem cell-derived exosomal microRNA-320c facilitates cartilage damage repair by targeting ADAM19-dependent Wnt signalling in osteoarthritis rats

OBJECTIVE

Our previous study revealed that synovial mesenchymal stem cell (SMSC)-derived exosomal microRNA-302c enhanced chondrogenesis by targeting a disintegrin and metalloproteinase 19 (ADAM19) in vitro. This study aimed to validate the potential of SMSC-derived exosomal microRNA-302c for the treatment of osteoarthritis in vivo.

METHODS

After 4 weeks of destabilization of the medial meniscus surgery (DMM) to establish an osteoarthritis model, the rats received weekly articular cavity injection of SMSCs with or without GW4869 treatment (exosome inhibitor) or exosomes from SMSCs with or without microRNA-320c overexpression for another 4 weeks.

RESULTS

SMSCs and SMSC-derived exosomes reduced the Osteoarthritis Research Society International (OARSI) score, improved cartilage damage repair, suppressed cartilage inflammation, suppressed extracellular matrix (ECM) degradation, and inhibited chondrocyte apoptosis in DMM rats. However, these effects were largely hampered in rats that were injected with GW4869-treated SMSCs. Moreover, exosomes from microRNA-320c-overexpressing SMSCs exerted a better effect than exosomes from negative control SMSCs on decreasing the OARSI score, enhancing cartilage damage repair, suppressing cartilage inflammation, and inhibiting ECM degradation and chondrocyte apoptosis. Mechanistically, exosomes from microRNA-320c-overexpressing SMSCs reduced the levels of ADAM19, as well as β-catenin and MYC, which are two critical proteins in Wnt signalling.

CONCLUSION

SMSC-derived exosomal microRNA-320c suppresses ECM degradation and chondrocyte apoptosis to facilitate cartilage damage repair in osteoarthritis rats by targeting ADAM19-dependent Wnt signalling.

Proteomics identifies novel biomarkers of synovial joint disease in a canine model of mucopolysaccharidosis I

Mucopolysaccharidosis I is a lysosomal storage disorder characterized by deficient alpha-L-iduronidase activity, leading to abnormal accumulation of glycosaminoglycans in cells and tissues. Synovial joint disease is prevalent and significantly reduces patient quality of life. There is a critical need for improved understanding of joint disease pathophysiology in MPS I, including specific biomarkers to predict and monitor joint disease progression, and response to treatment. The objective of this study was to leverage the naturally-occurring MPS I canine model and undertake an unbiased proteomic screen to identify systemic biomarkers predictive of local joint disease in MPS I. Synovial fluid and serum samples were collected from MPS I and healthy dogs at 12 months-of-age, and protein abundance characterized using liquid chromatography tandem mass spectrometry. Stifle joints were evaluated postmortem using magnetic resonance imaging (MRI) and histology. Proteomics identified 40 proteins for which abundance was significantly correlated between serum and synovial fluid, including markers of inflammatory joint disease and lysosomal dysfunction. Elevated expression of three biomarker candidates, matrix metalloproteinase 19, inter-alpha-trypsin inhibitor heavy-chain 3 and alpha-1-microglobulin, was confirmed in MPS I cartilage, and serum abundance of these molecules was found to correlate with MRI and histological degenerative grades. The candidate biomarkers identified have the potential to improve patient care by facilitating minimally-invasive, specific assessment of joint disease progression and response to therapeutic intervention.

MicroRNAs and long non-coding RNAs in cartilage homeostasis and osteoarthritis

During the last decade, osteoarthritis (OA) has become one of the most prevalent musculoskeletal diseases worldwide. OA is characterized by progressive loss of articular cartilage, abnormal remodeling of subchondral bone, hyperplasia of synovial cells, and growth of osteophytes, which lead to chronic pain and disability. The pathological mechanisms underlying OA initiation and progression are still poorly understood. Non-coding RNAs (ncRNAs) constitute a large portion of the transcriptome that do not encode proteins but function in numerous biological processes. Cumulating evidence has revealed a strong association between the changes in expression levels of ncRNA and the disease progression of OA. Moreover, loss- and gain-of-function studies utilizing transgenic animal models have demonstrated that ncRNAs exert vital functions in regulating cartilage homeostasis, degeneration, and regeneration, and changes in ncRNA expression can promote or decelerate the progression of OA through distinct molecular mechanisms. Recent studies highlighted the potential of ncRNAs to serve as diagnostic biomarkers, prognostic indicators, and therapeutic targets for OA. MiRNAs and lncRNAs are two major classes of ncRNAs that have been the most widely studied in cartilage tissues. In this review, we focused on miRNAs and lncRNAs and provided a comprehensive understanding of their functional roles as well as molecular mechanisms in cartilage homeostasis and OA pathogenesis.

Autophagy: An important target for natural products in the treatment of bone metabolic diseases

Bone homeostasis depends on a precise dynamic balance between bone resorption and bone formation, involving a series of complex and highly regulated steps. Any imbalance in this process can cause disturbances in bone metabolism and lead to the development of many associated bone diseases. Autophagy, one of the fundamental pathways for the degradation and recycling of proteins and organelles, is a fundamental process that regulates cellular and organismal homeostasis. Importantly, basic levels of autophagy are present in all types of bone-associated cells. Due to the cyclic nature of autophagy and the ongoing bone metabolism processes, autophagy is considered a new participant in bone maintenance. Novel therapeutic targets have emerged as a result of new mechanisms, and bone metabolism can be controlled by interfering with autophagy by focusing on certain regulatory molecules in autophagy. In parallel, several studies have reported that various natural products exhibit a good potential to mediate autophagy for the treatment of metabolic bone diseases. Therefore, we briefly described the process of autophagy, emphasizing its function in different cell types involved in bone development and metabolism (including bone marrow mesenchymal stem cells, osteoblasts, osteocytes, chondrocytes, and osteoclasts), and also summarized research advances in natural product-mediated autophagy for the treatment of metabolic bone disease caused by dysfunction of these cells (including osteoporosis, rheumatoid joints, osteoarthritis, fracture nonunion/delayed union). The objective of the study was to identify the function that autophagy serves in metabolic bone disease and the effects, potential, and challenges of natural products for the treatment of these diseases by targeting autophagy.