Inflammation and epigenetic regulation in osteoarthritis

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.

Triptolide attenuates LPS-induced chondrocyte inflammation by inhibiting inflammasome activation via the Wnt/β-catenin and NF-κB signaling pathways

Osteoarthritis (OA) is a common form of arthritis characterized by subchondral bone proliferation and articular cartilage degeneration. Recently, the Nod-like receptor pyrin domain 3 (NLRP3) inflammasome has gained attention due to its association with synovial inflammation in OA. Triptolide (TP), known for its immunosuppressive and anti-inflammatory effects, has been studied in various diseases. However, the specific impact of TP on OA and its underlying mechanism remains largely unexplored. In this study, chondrocytes were treated with a specific concentration of TP, and subsequent analysis through Western blotting and immunofluorescence staining revealed decreased expression levels of MMP-13, NLRP3, Caspase-1, ASC, β-catenin, p-p65, and IκB compared to the model group. ELISA results demonstrated significantly lower levels of IL-1β, IL-18, and TNF-α in the TP treatment group compared to the model group. In addition, triptolide ameliorates the degradation of the extracellular matrix (ECM) by enhancing the expression of collagen-II. In conclusion, our findings suggest that TP exhibits anti-inflammatory effects on chondrocytes in the presence of LPS-induced inflammation by inhibiting the activation of the NLRP3 inflammasome via the Wnt/β-catenin and NF-κB pathway. These results contribute to a better understanding of TP's potential therapeutic benefits in managing OA.

A natural polyphenolic nanoparticle--knotted hydrogel scavenger for osteoarthritis therapy

Exploring highly efficient and cost-effective biomaterials for osteoarthritis (OA) treatment remains challenging, as current therapeutic strategies are difficult to eradicate the excessive reactive oxygen species (ROS) and nitric oxide (NO) at damaged sites. Tea polyphenol (TP) nanoparticles (NPs), a nature-inspired antioxidant in combination with 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), a NO scavenger, could provide maximized positive therapeutic effects on OA by eradicating both ROS and NO. Notably, this combination not only improves the half-life of the TP monomer and the drug loading efficiency of carboxy-PTIO but also prevents nitrite from being harmful to tissue. Moreover, the protonation ability of carboxy-PTIO allows smart acid-responsive release in response to environmental pH, which provides conditioned treatment strategies for OA. In in vitro experiments, TP/PTIO NPs downregulated proinflammatory cytokine release via synergistic removal of ROS and NO and suppression of ROS/NF-κB and iNOS/NO/Caspase-3 signaling. For in vivo experiments, NPs were cross-linked with 4-arm-PEG-SH to form an injectable hydrogel system. The release of TP and carboxy-PTIO from the system efficiently prevents cartilage inflammation and damage via similar signaling pathways. Overall, the proposed system provides an efficient approach for OA therapy.

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.

Enrichment of H3S28p and H3K9me2 Epigenetic Marks on Inflammatory-Associated Gene Promoters in Response to Severe Burn Injury

BACKGROUND

Severe burns activate systemic inflammation and lead to an increase in cytokine levels. Epigenetic elements are key regulators of inflammation; however, their involvement in severe burns has not been studied. In this work, we aimed to unveil the histone H3 posttranslational modifications (PTM) profile and their enrichment in promoters of inflammatory genes in response to severe burns.

METHODS

The levels of H3 PTMs were analyzed by ELISA assays in circulating cells from burn patients. ChIP assays were conducted to evaluate the enrichment of H3K9me2 and H3S28p at the promoter of CXCL8, IL-17, TNFA, IL-6, FOS, and IL-1B genes.

RESULTS

We found that eight H3 PTMs decreased at 5 days post-burn. Burn patients showed a decreased enrichment of H3K9me2 in CXCL8, IL-17, and TNFA promoters, whereas IL-6, FOS, and IL-1B promoters displayed an H3S28p enrichment diminution during the first 10 days post-burn. Interestingly, burn-injured septic patients exhibited an increased enrichment of H3K9me2 in TNFA, IL-1B, CXCL8, and IL-17 promoters, whereas H3S28p was increased in promoters of TNFA and IL-1B at 1 dpb.

CONCLUSION

Severe burns trigger epigenetic changes and differential H3 PTM enrichment at inflammation gene promoters. Epigenetic misregulation of H3 may be involved in sepsis occurrence after severe burn injury.

The role and current research status of resveratrol in the treatment of osteoarthritis and its mechanisms: a narrative review

Osteoarthritis (OA) is a chronic degenerative disease caused by various factors such as aging, obesity, trauma, and genetics. It is a challenging condition faced by orthopedic doctors in clinical practice and places a heavy burden on patients and their families. Currently, the treatment of OA primarily focuses on symptomatic relief and lacks ideal therapeutic methods. Resveratrol is a natural polyphenolic compound with anti-inflammatory and antioxidant properties, and in recent years, it has gained attention as a candidate drug for OA treatment. This article provides an overview of the research status on the role and mechanisms of resveratrol in treating OA. It has been found that resveratrol can prevent the development of OA by inhibiting inflammatory responses, protecting chondrocytes, maintaining cartilage homeostasis, promoting autophagy, and has shown certain therapeutic effects. This process may be related to the regulation of signaling pathways such as nuclear factor-kappa B (NF-κB), Toll-like receptor 4 (TLR4), and silent information regulator 1 (SIRT1). We summarize the current molecular mechanisms of resveratrol in treating OA, hoping to provide a reference for further research and application of resveratrol in OA treatment.

Deciphering the Role of LncRNAs in Osteoarthritis: Inflammatory Pathways Unveiled

Long non-coding RNA (LncRNA), with transcripts over 200 nucleotides in length, play critical roles in numerous biological functions and have emerged as significant players in the pathogenesis of osteoarthritis (OA), an inflammatory condition traditionally viewed as a degenerative joint disease. This review comprehensively examines the influence of LncRNA on the inflammatory processes driving OA progression, focusing on their role in regulating gene expression, cellular activities, and inflammatory pathways. Notably, LncRNAs such as MALAT1, H19, and HOTAIR are upregulated in OA and exacerbate the inflammatory milieu by modulating key signaling pathways like NF-κB, TGF-β/SMAD, and Wnt/β-catenin. Conversely, LncRNA like MEG3 and GAS5, which are downregulated in OA, show potential in dampening inflammatory responses and protecting against cartilage degradation by influencing miRNA interactions and cytokine production. By enhancing our understanding of LncRNA' roles in OA inflammation, we can better leverage them as potential biomarkers for the disease and develop innovative therapeutic strategies for OA management. This paper aims to delineate the mechanisms by which LncRNA influence inflammatory responses in OA and propose them as novel targets for therapeutic intervention.

A point-of-research decision in synovial tissue engineering: Mesenchymal stromal cells, tissue derived fibroblast or CTGF-mediated mesenchymal-to-fibroblast transition

Rheumatoid arthritis (RA) and osteoarthritis (OA) are prevalent inflammatory joint diseases characterized by synovitis, cartilage, and bone destruction. Fibroblast-like synoviocytes (FLSs) of the synovial membrane are a decisive factor in arthritis, making them a target for future therapies. Developing novel strategies targeting FLSs requires advanced in vitro joint models that accurately replicate non-diseased joint tissue. This study aims to identify a cell source reflecting physiological synovial fibroblasts. Therefore, we newly compared the phenotype and metabolism of "healthy" knee-derived FLSs from patients with ligament injuries (trauma-FLSs) to mesenchymal stromal cells (MSCs), their native precursors. We differentiated MSCs into fibroblasts using connective tissue growth factor (CTGF) and compared selected protein and gene expression patterns to those obtained from trauma-FLSs and OA-FLSs. Based on these findings, we explored the potential of an MSC-derived synovial tissue model to simulate a chronic inflammatory response akin to that seen in arthritis. We have identified MSCs as a suitable cell source for synovial tissue engineering because, despite metabolic differences, they closely resemble human trauma-derived FLSs. CTGF-mediated differentiation of MSCs increased HAS2 expression, essential for hyaluronan synthesis. It showed protein expression patterns akin to OA-FLSs, including markers of ECM components and fibrosis, and enzymes leading to a shift in metabolism towards increased fatty acid oxidation. In general, cytokine stimulation of MSCs in a synovial tissue model induced pro-inflammatory and pro-angiogenic gene expression, hyperproliferation, and increased glucose consumption, reflecting cellular response in human arthritis. We conclude that MSCs can serve as a proxy to study physiological synovial processes and inflammatory responses. In addition, CTGF-mediated mesenchymal-to-fibroblast transition resembles OA-FLSs. Thus, we emphasize MSCs as a valuable cell source for tools in preclinical drug screening and their application in tissue engineering.

Nutritional Epigenomics: Bioactive Dietary Compounds in the Epigenetic Regulation of Osteoarthritis

Nutritional epigenomics is exceptionally important because it describes the complex interactions among food compounds and epigenome modifications. Phytonutrients or bioactive compounds, which are secondary metabolites of plants, can protect against osteoarthritis by suppressing the expression of inflammatory and catabolic mediators, modulating epigenetic changes in DNA methylation, and the histone or chromatin remodelling of key inflammatory genes and noncoding RNAs. The combination of natural epigenetic modulators is crucial because of their additive and synergistic effects, safety and therapeutic efficacy, and lower adverse effects than conventional pharmacology in the treatment of osteoarthritis. In this review, we have summarized the chondroprotective properties of bioactive compounds used for the management, treatment, or prevention of osteoarthritis in both human and animal studies. However, further research is needed into bioactive compounds used as epigenetic modulators in osteoarthritis, in order to determine their potential value for future clinical applications in osteoarthritic patients as well as their relation with the genomic and nutritional environment, in order to personalize food and nutrition together with disease prevention.

CRISPR-mediated Sox9 activation and RelA inhibition enhance cell therapy for osteoarthritis

Osteoarthritis (OA) is a painful and debilitating disease affecting over 500 million people worldwide. Intraarticular injection of mesenchymal stromal cells (MSCs) shows promise for the clinical treatment of OA, but the lack of consistency in MSC preparation and application makes it difficult to further optimize MSC therapy and to properly evaluate the clinical outcomes. In this study, we used Sox9 activation and RelA inhibition, both mediated by the CRISPR-dCas9 technology simultaneously, to engineer MSCs with enhanced chondrogenic potential and downregulated inflammatory responses. We found that both Sox9 and RelA could be fine-tuned to the desired levels, which enhances the chondrogenic and immunomodulatory potentials of the cells. Intraarticular injection of modified cells significantly attenuated cartilage degradation and palliated OA pain compared with the injection of cell culture medium or unmodified cells. Mechanistically, the modified cells promoted the expression of factors beneficial to cartilage integrity, inhibited the production of catabolic enzymes in osteoarthritic joints, and suppressed immune cells. Interestingly, a substantial number of modified cells could survive in the cartilaginous tissues including articular cartilage and meniscus. Together, our results suggest that CRISPR-dCas9-based gene regulation is useful for optimizing MSC therapy for OA.

A potential link between inflammatory profiles, clinical pain, pain catastrophizing and long-term outcomes after total knee arthroplasty surgery

BACKGROUND

Chronic postoperative pain after total knee replacement (TKR) is a major clinical problem. It is still unclear if specific inflammatory mediators are associated with long-term postoperative pain complications. The current exploratory study aimed to (1) evaluate a multiplex of inflammatory mediators 5 years after TKR surgery in patients with different degrees of postoperative pain intensities and (2) study any association of the markers with clinical pain intensity, cognitive and functional outcomes.

METHODS

Plasma samples were collected 5 years after TKR surgery from 76 knee patients (43 females; 33 males) and analysed for 44 inflammatory markers. Pain (using visual analogue scale, VAS), the pain catastrophizing scale (PCS) and the Oxford knee score (OKS) were evaluated. Patients were categorized as high or low groups based on VAS, PCS and OKS scores. Associations between inflammatory markers, VAS, PCS and OKS were analysed and the marker expressions were compared between groups.

RESULTS

Pearson's correlations found 12 biomarkers associated with VAS (p < 0.05), 4 biomarkers with PCS and 3 biomarkers with OKS (p < 0.05). Four markers were altered in patients suffering from high compared to low chronic postoperative pain, three markers were altered in high compared to low catastrophizers and three markers were altered in patients with poor functional scores (p < 0.05).

CONCLUSIONS

The present exploratory study suggests that low-grade inflammation might be present in a subset of patients with high pain, high catastrophizing and low function 5 years after TKR. These exploratory results provide insights into some of the long-term postoperative complications after TKR surgery.

SIGNIFICANCE STATEMENT

This exploratory study evaluated a subset of inflammatory markers and the association to clinical pain intensity, knee function and pain catastrophizing in patients 5 years after total knee replacement surgery. Our results provide insights into the understanding of the underlying mechanisms that may drive the long experience of pain after TKR surgery.

Bibliometric analysis of synovial in osteoarthritis in the last 10 years

Background

Our aim was to examine trends in the bibliometric analysis of synovial for osteoarthritis over the last 10 years.

Methods

Publications relevant to synovial in osteoarthritis from 2013 to 2022 were retrieved from the Science Citation Index Expanded (SCI-E), Social Sciences Citation Index (SSCI), and Web of Science Core Collection (WoSCC) databases. The countries/regions, institutions, authors, journals, references, and keywords related to this topic were extracted using Citespace and Vosviewer. Citespace and Vosviewer were also used to identify and analyze this field's research hotspots and trends.

Results

Over the past 10 years, 5738 articles addressing the role of synovium in osteoarthritis have been published. Between 2013 and 2022, 2021 had the highest amount of published articles (a total of 756 published articles, or 13.18 % of the total articles) covering synovial in osteoarthritis. China was the country that published the most articles, while Duke University was the institution that published the most articles. Osteoarthritis and Cartilage was the journal with the most publications related to the study of Synovium in osteoarthritis. The National Nature Science Foundation of China provided the most funding. According to the analysis of keyword burst detection, human cartilage, control experiment, and exosomes were the most searched at different points in time.

Conclusion

In the last ten years, both the number of citations and the article discussing synovial in osteoarthritis have increased. The top 10 most searched keywords were "osteoarthritis","synovial fluid", "inflammation", "cartilage", "expression","rheumatoid arthritis","articular cartilage", "knee osteoarthritis", "synovial", "knee". According to the timeline view of co-citation clustering, synovial components and their expressions have emerged as hotspots of research associated with synovial osteoarthritis.

Protein crotonylation: Basic research and clinical diseases

Crotonylation is an importantly conserved post-translational modification, which is completely different from acetylation. In recent years, it has been confirmed that crotonylation occurs on histone and non-histone. Crotonylated Histone primarily affects gene expression through transcriptional regulation, while non-histone Crotonylation mainly regulates protein functions including protein activity, localization, and stability, as well as protein-protein interactions. The change in protein expression and function will affect the physiological process of cells and even cause disease. Reviewing previous studies, this article summarizes the mechanisms of histone and non-histone crotonylation in regulating diseases and cellular physiological processes to explore the possibility of precise regulation of crotonylation sites as potential targets for disease treatment.

Unveiling inflammatory and prehypertrophic cell populations as key contributors to knee cartilage degeneration in osteoarthritis using multi-omics data integration

OBJECTIVES

Single-cell and spatial transcriptomics analysis of human knee articular cartilage tissue to present a comprehensive transcriptome landscape and osteoarthritis (OA)-critical cell populations.

METHODS

Single-cell RNA sequencing and spatially resolved transcriptomic technology have been applied to characterise the cellular heterogeneity of human knee articular cartilage which were collected from 8 OA donors, and 3 non-OA control donors, and a total of 19 samples. The novel chondrocyte population and marker genes of interest were validated by immunohistochemistry staining, quantitative real-time PCR, etc. The OA-critical cell populations were validated through integrative analyses of publicly available bulk RNA sequencing data and large-scale genome-wide association studies.

RESULTS

We identified 33 cell population-specific marker genes that define 11 chondrocyte populations, including 9 known populations and 2 new populations, that is, pre-inflammatory chondrocyte population (preInfC) and inflammatory chondrocyte population (InfC). The novel findings that make this an important addition to the literature include: (1) the novel InfC activates the mediator MIF-CD74; (2) the prehypertrophic chondrocyte (preHTC) and hypertrophic chondrocyte (HTC) are potentially OA-critical cell populations; (3) most OA-associated differentially expressed genes reside in the articular surface and superficial zone; (4) the prefibrocartilage chondrocyte (preFC) population is a major contributor to the stratification of patients with OA, resulting in both an inflammatory-related subtype and a non-inflammatory-related subtype.

CONCLUSIONS

Our results highlight InfC, preHTC, preFC and HTC as potential cell populations to target for therapy. Also, we conclude that profiling of those cell populations in patients might be used to stratify patient populations for defining cohorts for clinical trials and precision medicine.

Astaxanthin reduces inflammation and promotes a chondrogenic phenotype by upregulating SIRT1 in osteoarthritis

OBJECTIVE

To investigate the effects of astaxanthin (AST) on mouse osteoarthritis (OA) and lipopolysaccharide (LPS)-induced ATDC5 cell damage and to explore whether SIRT1 protein plays a role.

METHODS

In this study, some mouse OA models were constructed by anterior cruciate ligament transection (ACLT). Imaging, molecular biology and histopathology methods were used to study the effect of AST administration on traumatic OA in mice. In addition, LPS was used to stimulate ATDC5 cells to mimic the inflammatory response of OA. The effects of AST on the cell activity, inflammatory cytokines, matrix metalloproteinases and collagen type II levels were studied by CCK8 activity assay, reverse transcription polymerase chain reaction and protein imprinting. The role of SIRT1 protein was also detected.

RESULTS

In the mouse OA model, the articular surface collapsed, the articular cartilage thickness and cartilage matrix protein abundance were significantly decreased, while the expression of inflammatory cytokines and matrix metalloproteinases was increased; but AST treatment reversed these effects. Meanwhile, AST pretreatment could partially reverse LPS-induced ATDC5 cell damage and upregulate SIRT1 expression, but this protective effect of AST was attenuated by concurrent administration of the SIRT1 inhibitor Ex527.

CONCLUSION

AST can protect against the early stages of OA by affecting SIRT1 signalling, suggesting that AST might be a potential therapeutic agent for OA treatment.

Systematic review and network meta-analysis on the efficacy and safety of parmacotherapy for hand osteoarthritis

OBJECTIVE

Hand osteoarthritis poses a significant health challenge globally due to its increasing prevalence and the substantial burden on individuals and the society. In current clinical practice, treatment options for hand osteoarthritis encompass a range of approaches, including biological agents, antimetabolic drugs, neuromuscular blockers, anti-inflammatory drugs, hormone medications, pain relievers, new synergistic drugs, and other medications. Despite the diverse array of treatments, determining the optimal regimen remains elusive. This study seeks to conduct a network meta-analysis to assess the effectiveness and safety of various drug intervention measures in the treatment of hand osteoarthritis. The findings aim to provide evidence-based support for the clinical management of hand osteoarthritis.

METHODS

We performed a comprehensive search across PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials was conducted until September 15th, 2022, to identify relevant randomized controlled trials. After meticulous screening and data extraction, the Cochrane Handbook's risk of bias assessment tool was applied to evaluate study quality. Data synthesis was carried out using Stata 15.1 software.

RESULTS

21 studies with data for 3965 patients were meta-analyzed, involving 20 distinct Western medicine agents. GCSB-5, a specific herbal complex that mainly regulate pain in hand osteoarthritis, showed the greatest reduction in pain [WMD = -13.00, 95% CI (-26.69, 0.69)]. CRx-102, s specific medication characterized by its significant effect for relieving joint stiffness symptoms, remarkably mitigated stiffness [WMD = -7.50, 95% CI (-8.90, -6.10)]. Chondroitin sulfate displayed the highest incidence of adverse events [RR = 0.26, 95% CI (0.06, 1.22)]. No substantial variation in functional index for hand osteoarthritis score improvement was identified between distinct agents and placebo.

CONCLUSIONS

In summary, GCSB-5 and CRx-102 exhibit efficacy in alleviating pain and stiffness in HOA, respectively. However, cautious interpretation of the results is advised. Tailored treatment decisions based on individual contexts are imperative.

The Efficacy of Platelet-Rich Plasma Injection Therapy in Obese versus Non-Obese Patients with Knee Osteoarthritis: A Comparative Study

Background/Objectives: Obesity is a common comorbidity in knee osteoarthritis (KOA) patients. Platelet-Rich Plasma (PRP) injection therapy may mitigate KOA. To further clarify potential patient selection for PRP injection therapy, we compared the outcomes in patients with different body mass index (BMI). Methods: A total of 91 patients with mild to moderate KOA were treated with three intra-articular PRP injections at 10 to 14-day intervals. Range of motion (ROM), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Visual Analogue Scale (VAS) were documented before and after the injections at 15 days, 6 months, 12 months, and at the last follow-up. Outcomes were compared between patients with a BMI over 30 kg/m2 (obese, n = 34) and under 30 kg/m2 (non-obese, n = 57). Results: Significant difference during the follow-up was detected in WOMAC score at the last follow-up favouring BMI under 30 group [17.8 ± 18.8 versus 10.5 ± 11.7, p = 0.023]. The odds ratio (OR) in BMI over 30 kg/m2 group for total knee arthroplasty was 3.5 (95% CI 0.3-40.1, p = 0.553), and OR for any arthroplasty was 7.5 (95% CI 0.8-69.8, p = 0.085) compared to non-obese patients. Conclusions: Obese patients benefitted from PRP injections in KOA but there is a minimal difference favouring non-obese patients in symptom alleviation in follow-up stages after 12 months. The risk of arthroplasty is higher for obese KOA patients.

Exploration beyond osteoarthritis: the association and mechanism of its related comorbidities

Osteoarthritis is the most prevalent age-related degenerative joint disease and a leading cause of pain and disability in aged people. Its etiology is multifaceted, involving factors such as biomechanics, pro-inflammatory mediators, genetics, and metabolism. Beyond its evident impact on joint functionality and the erosion of patients' quality of life, OA exhibits symbiotic relationships with various systemic diseases, giving rise to various complications. This review reveals OA's extensive impact, encompassing osteoporosis, sarcopenia, cardiovascular diseases, diabetes mellitus, neurological disorders, mental health, and even cancer. Shared inflammatory processes, genetic factors, and lifestyle elements link OA to these systemic conditions. Consequently, recognizing these connections and addressing them offers opportunities to enhance patient care and reduce the burden of associated diseases, emphasizing the need for a holistic approach to managing OA and its complications.

Exploring causal correlations between inflammatory cytokines and knee osteoarthritis: a two-sample Mendelian randomization

Objectives

Knee osteoarthritis (KOA) and certain inflammatory cytokines (such as interleukin 1 [IL-1] and tumor necrosis factor alpha [TNF-a]) are related; however, the causal relationship remains unclear. Here, we aimed to assess the causal relationship between 41 inflammatory cytokines and KOA using Mendelian randomization (MR).

Methods

Two-sample bidirectional MR was performed using genetic variation data for 41 inflammatory cytokines that were obtained from European Genome-Wide Association Study (GWAS) data (n=8293). KOA-related genetic association data were also obtained from European GWAS data (n=40,3124). Inverse variance weighting (IVW), MR, heterogeneity, sensitivity, and multiple validation analyses were performed.

Results

Granulocyte colony-stimulating factor (G-CSF) or colony-stimulating factor 3 (CSF-3) levels were negatively associated with the risk of developing KOA (OR: 0.93, 95%CI:0.89-0.99, P=0.015). Additionally, macrophage inflammatory protein-1 alpha (MIP-1A/CCL3) was a consequence of KOA (OR: 0.72, 95%CI:0.54-0.97, P=0.032). No causal relationship was evident between other inflammatory cytokines and KOA development.

Conclusion

This study suggests that certain inflammatory cytokines may be associated with KOA etiology. G-CSF exerts an upstream influence on KOA development, whereas MIP-1A (CCL-3) acts as a downstream factor.

MiR-98-5p plays suppressive effects on IL-1β-induced chondrocyte injury associated with osteoarthritis by targeting CASP3

BACKGROUND

This study aims to explore how miR-98-5p affects osteoarthritis, focusing on its role in chondrocyte inflammation, apoptosis, and extracellular matrix (ECM) degradation.

METHODS

Quantitative real-time PCR was used to measure miR-98-5p and CASP3 mRNA levels in OA cartilage tissues and IL-1β-treated CHON-001 cells. We predicted miR-98-5p and CASP3 binding sites using TargetScan and confirmed them via luciferase reporter assays. Chondrocyte viability was analyzed using CCK-8 assays, while pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) were quantified via ELISA. Caspase-3 activity was examined to assess apoptosis, and Western blotting was conducted for protein marker quantification.

RESULTS

Our results showed lower miR-98-5p levels in both OA cartilage and IL-1β-stimulated cells. Increasing miR-98-5p resulted in reduced pro-inflammatory cytokines, decreased caspase-3 activity, and improved cell viability. Furthermore, miR-98-5p overexpression hindered IL-1β-induced ECM degradation, evident from the decline in MMP-13 and β-catenin levels, and an increase in COL2A1 expression. MiR-98-5p's impact on CASP3 mRNA directly influenced its expression. Mimicking miR-98-5p's effects, CASP3 knockdown also inhibited IL-1β-induced inflammation, apoptosis, and ECM degradation. In contrast, CASP3 overexpression negated the suppressive effects of miR-98-5p.

CONCLUSIONS

In conclusion, our data collectively suggest that miR-98-5p plays a protective role against IL-1β-induced damage in chondrocytes by targeting CASP3, highlighting its potential as a therapeutic target for OA.

Pathological progression of osteoarthritis: a perspective on subchondral bone

Osteoarthritis (OA) is a degenerative bone disease associated with aging. The rising global aging population has led to a surge in OA cases, thereby imposing a significant socioeconomic burden. Researchers have been keenly investigating the mechanisms underlying OA. Previous studies have suggested that the disease starts with synovial inflammation and hyperplasia, advancing toward cartilage degradation. Ultimately, subchondral-bone collapse, sclerosis, and osteophyte formation occur. This progression is deemed as "top to bottom." However, recent research is challenging this perspective by indicating that initial changes occur in subchondral bone, precipitating cartilage breakdown. In this review, we elucidate the epidemiology of OA and present an in-depth overview of the subchondral bone's physiological state, functions, and the varied pathological shifts during OA progression. We also introduce the role of multifunctional signal pathways (including osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B ligand (RANKL)/receptor activator of nuclear factor-kappa B (RANK), and chemokine (CXC motif) ligand 12 (CXCL12)/CXC motif chemokine receptor 4 (CXCR4)) in the pathology of subchondral bone and their role in the "bottom-up" progression of OA. Using vivid pattern maps and clinical images, this review highlights the crucial role of subchondral bone in driving OA progression, illuminating its interplay with the condition.

Baicalin Maintains Articular Cartilage Homeostasis and Alleviates Osteoarthritis by Activating FOXO1

Baicalin has been acknowledged for its anti-inflammatory properties. However, its potential impact on osteoarthritis (OA) has not yet been explored. Therefore, our study aimed to examine the effects of Baicalin on OA, both in laboratory and animal models. To evaluate its efficacy, human chondrocytes affected by OA were treated with interleukin-1β and/or Baicalin. The effects were then assessed through viability tests using the cell counting kit-8 (CCK-8) method and flow cytometry. In addition, we analyzed the expressions of various factors such as FOXO1, autophagy, apoptosis, and cartilage synthesis and breakdown to corroborate the effects of Baicalin. We also assessed the severity of OA through analysis of tissue samples. Our findings demonstrate that Baicalin effectively suppresses inflammatory cytokines and MMP-13 levels caused by collagenase-induced osteoarthritis, while simultaneously preserving the levels of Aggrecan and Col2. Furthermore, Baicalin has been shown to enhance autophagy. Through the use of FOXO1 inhibitors, lentivirus-mediated knockdown, and chromatin immunoprecipitation, we verified that Baicalin exerts its protective effects by activating FOXO1, which binds to the Beclin-1 promoter, thereby promoting autophagy. In conclusion, our results show that Baicalin has potential as a therapeutic agent for treating OA (Clinical Trial Registration number: 2023-61).

[miR-515-5p targeting Toll-like receptor 4 regulates myeloid differentiation primary response gene 88/nuclear factor-kappa B pathway to inhibit apoptosis and inflammatory response of osteoarthritis chondrocytes]

Objective

To explore the molecular mechanism of miR-515-5p in inhibiting chondrocyte apoptosis and alleviating inflammatory response in osteoarthritis (OA).

Methods

Human cartilage cell line C28/I2 was cultured in vitro and treated with 10 ng/mL interleukin 1β (IL-1β) for 24 hours to construct an in vitro OA model. C28/I2 cells were transfected with miR mimics, mimics negative control (NC), over expression (oe)-NC, and oe-Toll-like receptor 4 (TLR4), respectively, and then treated with 10 ng/mL IL-1β for 24 hours to establish OA model. Cell proliferation capacity was detected by cell counting kit 8 and 5-Ethynyl-2'-deoxyuridine, cell apoptosis and cell cycle were detected by flow cytometry, and B-cell lymphoma 2 protion (Bcl-2), Bcl-2-associated X protein (Bax), cleaved-Caspase-3, TLR4, myeloid differentiation primary response gene 88 (MyD88), p65 and phosphorylated p65 (p-p65) protein expression levels were detected by Western blot. Real-time fluorescence quantitative PCR was used to detect mRNA expression levels of miR-515-5p and TLR4, and ELISA was used to detect pro-inflammatory factor prostaglandin E2 (PGE2), tumor necrosis factor α (TNF -α), and IL-6 levels in cell supernatant. The potential binding sites between miR-515-5p and TLR4 were predicted by BiBiServ2 database, and the targeting relationship between miR-515-5p and TLR4 was verified by dual luciferase reporting assay.

Results

After the treatment of C28/I2 cells with IL-1β, the expressions of miR-515-5p and Bcl-2 protein and the proliferation ability of C28/I2 cells significantly reduced. The expression levels of Bax and cleaved-Caspase-3 protein, the levels of pro-inflammatory factors (PGE2, TNF-α, IL-6) in the supernatant of C28/I2 cells, and the apoptosis of C28/I2 cells significantly increased. In addition, the proportion of the cells at S phase and G 2 phase decreased significantly, and the proportion of cells at G 1 phase increased significantly, suggesting that the cell cycle was blocked after IL-1β treatment. After transfection with miR mimics, the expression level of miR-515-5p in the cells significantly up-regulated, partially reversing the apoptosis of OA chondrocytes induced by IL-1β, and alleviating the cycle arrest and inflammatory response of OA chondrocytes. After treating C28/I2 cells with IL-1β, the mRNA and protein levels of TLR4 significantly increased. Overexpression of miR-515-5p targeted inhibition of TLR4 expression and blocked activation of MyD88/nuclear factor κB (NF-κB) pathway. Overexpression of TLR4 could partially reverse the effect of miR mimics on IL-1β-induced apoptosis and inflammation of OA chondrocytes.

Conclusion

miR-515-5p negatively regulates the expression of TLR4, inhibits the activation of MyD88/NF-κB pathway and apoptosis of OA chondrocytes, and effectively alleviates the inflammatory response of the cells.

Maternal exposure to E 551 during pregnancy leads to genome-wide DNA methylation changes and metabolic disorders in the livers of pregnant mice and their fetuses

The widespread use of nanoparticles in the food industry has raised concerns regarding their potential adverse effects on human health, particularly in vulnerable populations, including pregnant mothers and fetuses. However, studies evaluating the reproductive and developmental toxicity of food-grade nanomaterials are limited. This study investigated the potential risks of prenatal dietary exposure to food-grade silica nanoparticles (E 551) on maternal health and fetal growth using conventional toxicological and epigenetic methods. The results showed that prenatal exposure to a high-dose of E 551 induces fetal resorption. Moreover, E 551 significantly accumulates in maternal and fetal livers, triggering a hepatic inflammatory response. At the epigenetic level, global DNA methylation is markedly altered in the maternal and fetal livers. Genome-wide DNA methylation sequencing revealed affected mCG, mCHG, and mCHH methylation landscapes. Subsequent bioinformatic analysis of the differentially methylated genes suggests that E 551 poses a risk of inducing metabolic disorders in maternal and fetal livers. This is further evidenced by impaired glucose tolerance in pregnant mice and altered expression of key metabolism-related genes and proteins in maternal and fetal livers. Collectively, the results of this study highlighted the importance of epigenetics in characterizing the potential toxicity of maternal exposure to food-grade nanomaterials during pregnancy.

Role of epigenetically regulated inflammation in renal diseases

In recent decades, renal disease research has witnessed remarkable advances. Experimental evidence in this field has highlighted the role of inflammation in kidney disease. Epigenetic dynamics and immunometabolic reprogramming underlie the alterations in cellular responses to intrinsic and extrinsic stimuli; these factors determine cell identity and cell fate decisions and represent current research hotspots. This review focuses on recent findings and emerging concepts in epigenetics and inflammatory regulation and their effect on renal diseases. This review aims to summarize the role and mechanisms of different epigenetic modifications in renal inflammation and injury and provide new avenues for future research on inflammation-related renal disease and drug development.

DNA hypomethylation ameliorates erosive inflammatory arthritis by modulating interferon regulatory factor-8

Epigenetic regulation plays a crucial role in the pathogenesis of autoimmune diseases such as inflammatory arthritis. DNA hypomethylating agents, such as decitabine (DAC), have been shown to dampen inflammation and restore immune homeostasis. In the present study, we demonstrate that DAC elicits potent anti-inflammatory effects and attenuates disease symptoms in several animal models of arthritis. Transcriptomic and epigenomic profiling show that DAC-mediated hypomethylation regulates a wide range of cell types in arthritis, altering the differentiation trajectories of anti-inflammatory macrophage populations, regulatory T cells, and tissue-protective synovial fibroblasts (SFs). Mechanistically, DAC-mediated demethylation of intragenic 5'-Cytosine phosphate Guanine-3' (CpG) islands of the transcription factor Irf8 (interferon regulatory factor 8) induced its re-expression and promoted its repressor activity. As a result, DAC restored joint homeostasis by resetting the transcriptomic signature of negative regulators of inflammation in synovial macrophages (MerTK, Trem2, and Cx3cr1), TREGs (Foxp3), and SFs (Pdpn and Fapα). In conclusion, we found that Irf8 is necessary for the inhibitory effect of DAC in murine arthritis and that direct expression of Irf8 is sufficient to significantly mitigate arthritis.

Epigenetic alterations dictating the inflammation: A view through pancreatitis

Pancreatitis is a severe inflammation in the pancreas and accounts for one of the leading gastrointestinal disorders worldwide, and presently pacing up with the morbidity and mortality rates. It has been noted that severe recurrences of acute pancreatitis lead to chronic inflammation and fibrosis of the pancreas which may further result to a long-term risk of pancreatic carcinogenesis which has a lower survival rate and worse prognosis. Several genetic and epigenetic mechanisms have been reported to orchestrate disease development. Intriguingly, concurrent epigenetic alterations can also control the genes responsible for the pathophysiology of several inflammatory pathways. Deciphering how epigenetic changes affect the inflammatory processes in pancreatitis and body's response to various therapeutic modalities may help to manage the condition more effectively. The current review will concentrate on several epigenetic changes in general and how specifically they are implicated in pancreatitis pathogenesis. Further, this review summarizes the involvement of inflammation in pancreatitis from an epigenetic perspective.

Genomic Determinants of Knee Joint Biomechanics: An Exploration into the Molecular Basis of Locomotor Function, a Narrative Review

In recent years, the nexus between genetics and biomechanics has garnered significant attention, elucidating the role of genomic determinants in shaping the biomechanical attributes of human joints, specifically the knee. This review seeks to provide a comprehensive exploration of the molecular basis underlying knee joint locomotor function. Leveraging advancements in genomic sequencing, we identified specific genetic markers and polymorphisms tied to key biomechanical features of the knee, such as ligament elasticity, meniscal resilience, and cartilage health. Particular attention was devoted to collagen genes like COL1A1 and COL5A1 and their influence on ligamentous strength and injury susceptibility. We further investigated the genetic underpinnings of knee osteoarthritis onset and progression, as well as the potential for personalized rehabilitation strategies tailored to an individual's genetic profile. We reviewed the impact of genetic factors on knee biomechanics and highlighted the importance of personalized orthopedic interventions. The results hold significant implications for injury prevention, treatment optimization, and the future of regenerative medicine, targeting not only knee joint health but joint health in general.

Inflammatory biomarkers in patients with painful knee osteoarthritis: exploring the potential link to chronic postoperative pain after total knee arthroplasty-a secondary analysis

ABSTRACT

Total knee arthroplasty (TKA) is the end-stage treatment of knee osteoarthritis (OA), and approximately 20% of patients experience chronic postoperative pain. Studies indicate that inflammatory biomarkers might be associated with pain in OA and potentially linked to the development of chronic postoperative pain after TKA. This study aimed to (1) evaluate preoperative serum levels of inflammatory biomarkers in patients with OA and healthy control subjects, (2) investigate preoperative differences of inflammatory biomarker profiles in subgroups of patients, and (3) compare subgroups of patients with and without postoperative pain 12 months after surgery. Serum samples from patients with OA scheduled for TKA (n = 127) and healthy participants (n = 39) were analyzed. Patients completed the Knee-injury-and-Osteoarthritis-Outcome-Score (KOOS) questionnaire and rated their clinical pain intensity using a visual analog scale (VAS) before and 12 months after TKA. Hierarchical cluster analysis and Orthogonal Partial Least Squares Discriminant Analysis were used to compare groups (patients vs control subjects) and to identify subgroups of patients in relation to postoperative outcomes. Difference in preoperative and postoperative VAS and KOOS scores were compared across subgroups. Twelve inflammatory markers were differentially expressed in patients when compared with control subjects. Cluster analysis identified 2 subgroups of patients with 23 proteins being significantly different ( P < 0.01). The 12-months postoperative VAS and KOOS scores were significantly different between subgroups of patients ( P < 0.05). This study identified differences in specific inflammatory biomarker profiles when comparing patients with OA and control subjects. Cluster analysis identified 2 subgroups of patients with OA, with one subgroup demonstrating comparatively worse 12-month postoperative pain intensity and function scores.

Therapeutic targets and potential delivery systems of melatonin in osteoarthritis

Osteoarthritis (OA) is a highly prevalent age-related musculoskeletal disorder that typically results in chronic pain and disability. OA is a multifactorial disease, with increased oxidative stress, dysregulated inflammatory response, and impaired matrix metabolism contributing to its onset and progression. The neurohormone melatonin, primarily synthesized by the pineal gland, has emerged as a promising therapeutic agent for OA due to its potential to alleviate inflammation, oxidative stress, and chondrocyte death with minimal adverse effects. The present review provides a comprehensive summary of the current understanding regarding melatonin as a promising pharmaceutical agent for the treatment of OA, along with an exploration of various delivery systems that can be utilized for melatonin administration. These findings may provide novel therapeutic strategies and targets for inhibiting the advancement of OA.

Anti-Inflammatory Activity of APPA (Apocynin and Paeonol) in Human Articular Chondrocytes

Osteoarthritis (OA) is a chronic joint disease leading to cartilage loss and reduction in the joint space which results in pain. The current pharmacological treatment of OA is inadequate and pharmacological interventions focus on symptom management. APPA, a combination of apocynin (AP) and paeonol (PA), is a potential drug for treating OA. The aim of this study was to analyze the effects of APPA on the modulation of the inflammatory response in chondrocytes. Samples were incubated with IL-1β and APPA, and their responses to proinflammatory cytokines, catabolic mediators and redox responses were then measured. The effect of APPA on mitogenesis was also evaluated. Results show that APPA attenuated the expression of IL-8, TNF-α, MMP-3, MMP-13, SOD-2 and iNOS, resulting in the protection of human articular cartilage. APPA decreased PGC-1α gene expression induced by IL-1β. APPA did not modulate the gene expression of Mfn2, Sirt-1 or Sirt-3. The overall findings indicate that APPA may be an effective treatment for OA by targeting several of the pathways involved in OA pathogenesis.

[Effects of VX765 on osteoarthritis and chondrocyte inflammation in rats]

Objective

To investigate the effects and underlying mechanisms of VX765 on osteoarthritis (OA) and chondrocytes inflammation in rats.

Methods

Chondrocytes were isolated from the knee joints of 4-week-old Sprague Dawley (SD) rats. The third-generation cells were subjected to cell counting kit 8 (CCK-8) analysis to assess the impact of various concentrations (0, 1, 5, 10, 20, 50, 100 μmol/L) of VX765 on rat chondrocyte activity. An in vitro lipopolysaccharide (LPS) induced cell inflammation model was employed, dividing cells into control group, LPS group, VX765 concentration 1 group and VX765 concentration 2 group without obvious cytotoxicity. Western blot, real-time fluorescence quantitative PCR, and ELISA were conducted to measure the expression levels of inflammatory factors-transforming growth factor β 1 (TGF-β 1), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α). Additionally, Western blot and immunofluorescence staining were employed to assess the expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1). Thirty-two SD rats were randomly assigned to sham surgery group (group A), OA group (group B), OA+VX765 (50 mg/kg) group (group C), and OA+VX765 (100 mg/kg) group (group D), with 8 rats in each group. Group A underwent a sham operation with a medial incision, while groups B to D underwent additional transverse incisions to the medial collateral ligament and anterior cruciate ligament, with removal of the medial meniscus. One week post-surgery, groups C and D were orally administered 50 mg/kg and 100 mg/kg VX765, respectively, while groups A and B received an equivalent volume of saline. Histopathological examination using HE and safranin-fast green staining was performed, and Mankin scoring was utilized for evaluation. Immunohistochemical staining technique was employed to analyze the expressions of matrix metalloproteinase 13 (MMP-13) and collagen type Ⅱ.

Results

The CCK-8 assay indicated a significant decrease in cell viability at VX765 concentrations exceeding 10 μmol/L ( P<0.05), so 4 μmol/L and 8 μmol/L VX765 without obvious cytotoxicity were selected for subsequent experiments. Following LPS induction, the expressions of TGF-β 1, IL-6, and TNF-α in cells significantly increased when compared with the control group ( P<0.05). However, intervention with 4 μmol/L and 8 μmol/L VX765 led to a significant decrease in expression compared to the LPS group ( P<0.05). Western blot and immunofluorescence staining demonstrated a significant upregulation of Nrf2 pathway-related molecules Nrf2 and HO-1 protein expressions by VX765 ( P<0.05), indicating Nrf2 pathway activation. Histopathological examination of rat knee joint tissues and immunohistochemical staining revealed that, compared to group B, treatment with VX765 in groups C and D improved joint structural damage in rat OA, alleviated inflammatory reactions, downregulated MMP-13 expression, and increased collagen type Ⅱ expression.

Conclusion

VX765 can improve rat OA and reduce chondrocyte inflammation, possibly through the activation of the Nrf2 pathway.

Epigenetic Dysregulation in Endometriosis: Implications for Pathophysiology and Therapeutics

Endometriosis is a prevalent gynecological condition associated with pelvic pain and infertility. Despite more than a century of research, the etiology of endometriosis still eludes scientific consensus. This lack of clarity has resulted in suboptimal prevention, diagnosis, and treatment options. Evidence of genetic contributors to endometriosis is interesting but limited; however, significant progress has been made in recent years in identifying an epigenetic role in the pathogenesis of endometriosis through clinical studies, in vitro cell culture experiments, and in vivo animal models. The predominant findings include endometriosis-related differential expression of DNA methyltransferases and demethylases, histone deacetylases, methyltransferases, and demethylases, and regulators of chromatin architecture. There is also an emerging role for miRNAs in controlling epigenetic regulators in the endometrium and endometriosis. Changes in these epigenetic regulators result in differential chromatin organization and DNA methylation, with consequences for gene expression independent of a genetic sequence. Epigenetically altered expression of genes related to steroid hormone production and signaling, immune regulation, and endometrial cell identity and function have all been identified and appear to play into the pathophysiological mechanisms of endometriosis and resulting infertility. This review summarizes and critically discusses early seminal findings, the ever-growing recent evidence of epigenetic contributions to the pathophysiology of endometriosis, and implications for proposed epigenetically targeted therapeutics.

Inotodiol ameliorates the progression of osteoarthritis: An in vitro and in vivo study

Osteoarthritis is a common chronic degenerative disease, of which the essence is the degenerative changes of bone and joint cartilage, involving damage in multiple structures such as bone, synovium and joints. In the mechanism of arthritis inflammation is closely related, and therefore the exploration to inhibit inflammatory mediators is crucial for the clinical prevention and treatment of osteoarthritis. Inotodiol is a lanostane triterpenoid isolated from Inonotus obliquus, which had been extensively reported to be an anti-inflammatory agent, but its effect on arthritis remains unknown. In this study, we firstly demonstrated that inotodiol significantly reduced IL-1β-induced chondrocyte injury and inhibited the release of inflammatory factors. At the same time, experiments in vivo showed that inotodiol could effectively improve the symptoms of joint injury in mice and reduce the area of cartilage destruction, indicating that inotodiol may be a potential therapeutic drug for osteoarthritis.

Electrical stimulation of the auricular branch of the vagus nerve potentiates analgesia induced by physical exercise in mice with peripheral inflammation

Objective

This study evaluated the antihyperalgesic and anti-inflammatory effects of percutaneous vagus nerve electrical stimulation (pVNS) associated with physical exercise, i.e., swimming, in mice with peripheral inflammation.

Methods

The pain model was induced by intraplantar (i.pl.) injection of Freund's complete adjuvant (CFA). Sixty-four male Swiss mice (35-40 g) received an i.pl. of CFA and underwent behavioral tests, i.e., mechanical hyperalgesia, edema, and paw temperature tests. Additionally, cytokine levels, specifically interleukin-6 (IL-6) and interleukin-10 (IL-10), were determined by enzyme-linked immunosorbent assay. Mice were treated with swimming exercise for 30 min alone or associated with different time protocols (10, 20, or 30 min) of stimulation in the left ear with random frequency during four consecutive days.

Results

pVNS for 20 min prolonged the antihyperalgesic effect for up to 2 h, 24 h after CFA injection. pVNS for 30 min prolonged the antihyperalgesic effect for up to 7 h, 96 h after CFA injection. However, it did not alter the edema or temperature at both analyzed times (24 and 96 h). Furthermore, the combination of pVNS plus swimming exercise, but not swimming exercise alone, reduced IL-6 levels in the paw and spinal cord, as well as IL-10 levels in the spinal cord.

Conclusion

pVNS potentiates the analgesic effect induced by swimming, which may be, at least in part, mediated by the modulation of inflammatory cytokines in the periphery (paw) and central nervous system (spinal cord). Therefore, the combination of these therapies may serve as an important adjunctive treatment for persistent inflammatory pain.

SNIP1 reduces extracellular matrix degradation and inflammation via inhibiting the NF-κB signaling pathway in osteoarthritis

Osteoarthritis (OA), the most common joint disease, is characterized by inflammation and cartilage degradation. Previous studies illustrated that Smad nuclear-interacting protein 1 (SNIP1) is an inhibitor of the TGF-β signal transduction pathway and SNIP1 has been reported as an anti-inflammatory factor. This study aimed to explore the role of SNIP1 in OA progression. In this study, the SNIP1 expression was evaluated in OA human and OA mice tissue and interleukin-1 beta (IL-1β)-induced chondrocytes. The Safranin-O (SO) staining and osteoarthritis research society international (OARSI) scoring system was used to evaluate cartilage injury. The gain- and loss-of-function studies for SNIP1 were performed in chondrocytes. The SNIP1 overexpression adenovirus was injected into mice by intra-articular injection. The SNIP1 expression was decreased in OA patients, OA mice, and IL-1β-stimulated chondrocytes. The cartilage injury of medial meniscus-induced OA (DMM-OA) mice at 8 weeks showed more severe than that at 4 weeks. The expression of SNIP1 was lower at 8 weeks than that at 4 weeks. In IL-1β-stimulated chondrocytes, SNIP1 overexpression reduced the expression of TNF-α and IL-6, alleviated ECM degradation, reduced the phosphorylation levels of p65 and IκBα, and decreased the p65 level in nuclear. Moreover, overexpression of SNIP1 alleviated cartilage injury in DMM-OA mice. In brief, our study suggested that SNIP1 alleviated OA and repressed inflammation by inhibiting the activation of NF-κB. This study might provide a new insight into OA treatment.

Exposure of Tissue-Engineered Cartilage Analogs to Synovial Fluid Hematoma After Ankle Fracture Is Associated With Chondrocyte Death and Altered Cartilage Maintenance Gene Expression

BACKGROUND

The first stage of fracture healing consists of hematoma formation with recruitment of proinflammatory cytokines and matrix metalloproteinases. Unfortunately, when there is an intra-articular fracture, these inflammatory mediators are not retained at the fracture site, but instead, envelop the healthy cartilage of the entire joint via the synovial fluid fracture hematoma (SFFH). These inflammatory cytokines and matrix metalloproteinases are known factors in the progression of osteoarthritis and rheumatoid arthritis. Despite the known inflammatory contents of the SFFH, little research has been done on the effects of the SFFH on healthy cartilage with regard to cell death and alteration in gene expression that could lead to posttraumatic osteoarthritis (PTOA).

METHODS

SFFH was collected from 12 patients with intraarticular ankle fracture at the time of surgery. Separately, C20A4 immortalized human chondrocytes were 3-dimensionally cultured to create scaffold-free cartilage tissue analogs (CTAs) to simulate healthy cartilage. Experimental CTAs (n = 12) were exposed to 100% SFFH for 3 days, washed, and transferred to complete media for 3 days. Control CTAs (n = 12) were simultaneously cultured in complete medium without exposure to SFFH. Subsequently, CTAs were harvested and underwent biochemical, histological, and gene expression analysis.

RESULTS

Exposure of CTAs to ankle SFFH for 3 days significantly decreased chondrocyte viability by 34% (P = .027). Gene expression of both COL2A1 and SOX9 were significantly decreased after exposure to SFFH (P = .012 and P = .0013 respectively), while there was no difference in COL1A1, RUNX2, and MMP13 gene expression. Quantitative analysis of Picrosirius red staining demonstrated increased collagen I deposition with poor ultrastructural organization in SFFH-exposed CTAs.

CONCLUSION

Exposure of an organoid model of healthy cartilage tissue to SFFH after intraarticular ankle fracture resulted in decreased chondrocyte viability, decreased expression of genes regulating normal chondrocyte phenotype, and altered matrix ultrastructure indicating differentiation toward an osteoarthritis phenotype.

CLINICAL RELEVANCE

The majority of ankle fracture open reduction and internal fixation does not occur immediately after fracture. In fact, typically these fractures are treated several days to weeks later in order to let the swelling subside. This means that the healthy innocent bystander cartilage not involved in the fracture is exposed to SFFH during this time. In this study, the SFFH caused decreased chondrocyte viability and specific altered gene expression that might have the potential to induce osteoarthritis. These data suggest that early intervention after intraarticular ankle fracture could possibly mitigate progression toward PTOA.

The effects of platelet-rich plasma injections in different stages of knee osteoarthritis

PURPOSE

Platelet-rich plasma (PRP) injections are challenging the current treatment options for knee osteoarthritis (KOA). Targeting the treatment to optimal stage of the symptomatic KOA may be crucial in the success and failure of treatment. The aim of this study is to compare the outcomes of PRP injections at different stages of KOA in order to determine the optimal stage of the KOA for PRP injection treatments.

METHODS

A total of 89 consecutive patients with symptomatic KOA Kellgren-Lawrence grade 1 to 3 (Group A grade 1, group B grade 2 and group C grade 3) were given three intra-articular injections of PRP with 2 weeks interval between injections. Visual Analogue Scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Range of Motion were measured before injection, at 15 days, 6 months, 12 months and, at last follow-up. Intergroup outcomes were compared.

RESULTS

The comparison of groups A and C showed that WOMAC scores were significantly higher in group C at 15 days [p = 0.047] and at last follow-up [p = 0.008] than in group A, as well as VAS scores at 6 months [p = 0.031] and at last follow-up [p = 0.008]. The overall WOMAC and VAS scores showed decrease in all the groups in minimum follow-up of 14 months. The other comparisons did not show significant differences in outcomes.

CONCLUSION

All the groups showed decrease in WOMAC and VAS, but patients with mild KOA benefit significantly more from the treatments than patients with more severe KOA.

MATN3 delivered by exosome from synovial mesenchymal stem cells relieves knee osteoarthritis: Evidence from in vitro and in vivo studies

Background

Synovial mesenchymal stem cell (SMSC) exerts chondroprotective effects in osteoarthritis (OA) clinical models. However, the regulatory potentials of SMSC-derived exosomes (SMSC-Exo) in OA still need to be discovered, which attracted our attention.

Methods

The destabilization of the medial meniscus surgery was performed on the knee joints of a mouse OA model, followed by injection of SMSC-Exo. In addition, SMSC-Exo was administrated to mouse chondrocytes to observe the functional and molecular alterations.

Results

Both of SMSC-Exo and overexpression of Matrilin-3 (MATN3) alleviated cartilage destruction and suppressed degradation of extracellular matrix (ECM) in the OA rat model. In addition, assays concerning the in vitro OA model induced by IL-1β showed that SMSC-Exo could promote chondrocyte viability and inhibit autophagy defects. Furthermore, SMSC-Exo achieved the chondroprotective effects through the delivery of MATN3/IL-17A, and MATN3 could suppress the activation of PI3K/AKT/mTOR signaling through IL-17A.

Conclusion

SMSC-Exo exerts beneficial therapeutic effects on OA by preventing ECM degradation and autophagy defects by delivering MATN3/IL-17A.

The Translational Potential of this Article

The translational potential of this study is not only limited to the treatment of knee osteoarthritis but also provides new insights for the treatment of other joint diseases by exploring the mechanism of MATN3. In addition, SMSCExo, as a novel drug carrier, has great potential for treating and diagnosing other diseases. With further research, these findings will provide new directions for developing personalized and innovative treatment options.

Engineering Inflammation-Resistant Cartilage: Bridging Gene Therapy and Tissue Engineering

Articular cartilage defects caused by traumatic injury rarely heal spontaneously and predispose into post-traumatic osteoarthritis. In the current autologous cell-based treatments the regenerative process is often hampered by the poor regenerative capacity of adult cells and the inflammatory state of the injured joint. The lack of ideal treatment options for cartilage injuries motivated the authors to tissue engineer a cartilage tissue which would be more resistant to inflammation. A clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 knockout of TGF-β-activated kinase 1 (TAK1) gene in polydactyly chondrocytes provides multivalent protection against the signals that activate the pro-inflammatory and catabolic NF-κB pathway. The TAK1-KO chondrocytes encapsulate into a hyaluronan hydrogel deposit copious cartilage extracellular matrix proteins and facilitate integration onto native cartilage, even under proinflammatory conditions. Furthermore, when implanted in vivo, compared to WT fewer pro-inflammatory M1 macrophages invade the cartilage, likely due to the lower levels of cytokines secreted by the TAK1-KO polydactyly chondrocytes. The engineered cartilage thus represents a new paradigm-shift for the creation of more potent and functional tissues for use in regenerative medicine.

Study of hydrogen sulfide biosynthesis in synovial tissue from diabetes-associated osteoarthritis and its influence on macrophage phenotype and abundance

Type 2 diabetes (DB) is an independent risk factor for osteoarthritis (OA). However, the mechanisms underlying the connection between both diseases remain unclear. Synovial macrophages from OA patients with DB present a marked pro-inflammatory phenotype. Since hydrogen sulphide (H₂S) has been previously described to be involved in macrophage polarization, in this study we examined H₂S biosynthesis in synovial tissue from OA patients with DB, observing a reduction of H₂S-synthetizing enzymes in this subset of individuals. To elucidate these findings, we detected that differentiated TPH-1 cells to macrophages exposed to high levels of glucose presented a lower expression of H₂S-synthetizing enzymes and an increased inflammatory response to LPS, showing upregulated expression of markers associated with M1 phenotype (i.e., CD11c, CD86, iNOS, and IL-6) and reduced levels of those related to M2 fate (CD206 and CD163). The co-treatment of the cells with a slow-releasing H₂S donor, GYY-4137, attenuated the expression of M1 markers, but failed to modulate the levels of M2 indicators. GYY-4137 also reduced HIF-1α expression and upregulated the protein levels of HO-1, suggesting their involvement in the anti-inflammatory effects of H₂S induction. In addition, we observed that intraarticular administration of H₂S donor attenuated synovial abundance of CD68⁺ cells, mainly macrophages, in an in vivo model of OA. Taken together, the findings of this study seem to reinforce the key role of H₂S in the M1-like polarization of synovial macrophages associated to OA and specifically its metabolic phenotype, opening new therapeutic perspectives in the management of this pathology.

CKLF1 interference alleviates IL‑1β‑induced inflammation, apoptosis and degradation of the extracellular matrix in chondrocytes via CCR5

Osteoarthritis (OA) is a type of joint disease with a rising prevalence and incidence among the elderly across the global population. Chemokine-like factor 1 (CKLF1) is a human cytokine, which has been demonstrated to be involved in the progression of multiple human diseases. However, little attention has been paid to the impact of CKLF1 on OA. The present study was designed to identify the role of CKLF1 in OA and to clarify the regulatory mechanism. The expression levels of CKLF1 and its receptor CC chemokine receptor 5 (CCR5) were examined by reverse transcription-quantitative PCR (RT-qPCR) and western blotting. A Cell Counting Kit-8 assay was used to estimate cell viability. The levels and expression of inflammatory factors were determined by ELISA and RT-qPCR, respectively. Apoptosis was investigated by TUNEL assays and the protein levels of apoptosis-related factors were analyzed by western blotting. RT-qPCR and western blotting were used to examine the expression of extracellular matrix (ECM) degradation-associated proteins and ECM components. Dimethylmethylene blue analysis was used to analyze the production of soluble glycosamine sulfate additive. A co-immunoprecipitation assay was used to confirm the protein interaction between CKLF1 and CCR5. The results revealed that CKLF1 expression was increased in IL-1β-exposed murine chondrogenic ATDC5 cells. Furthermore, CKLF1 silencing enhanced the viability of IL-1β-induced ATDC5 cells, while inflammation, apoptosis and degradation of the ECM were reduced. Additionally, CKLF1 knockdown led to decreased CCR5 expression in IL-1β-challenged ATDC5 cells, and CKLF1 bound with CCR5. The enhanced viability, as well as the suppressed inflammation, apoptosis and degradation of the ECM, following CKLF1 knockdown in the IL-1β-induced ATDC5 cells were all restored after CCR5 was overexpressed. In conclusion, CKLF1 might serve a detrimental role in the development of OA by targeting its receptor CCR5.

The role of genetic polymorphisms of interleukin-1 (IL-1R1 and IL-1RN) in primary knee osteoarthritis in Indonesia

This study aimed to evaluate the association of SNPs of the IL-1 family with the clinical severity of knee OA. This case‒control study was performed among 100 healthy knees and 130 osteoarthritis (OA) knees of people aged ≥ 50 years with a BMI ≥ 25 kg/m². The possible correlations among clinical findings, radiographic evaluations, serum levels of IL-1R1 and IL-1Ra, and genotype analyses were evaluated. Three SNPs of IL-1R1, rs871659, rs3771202, and rs3917238, were associated with primary knee OA. Females with IL-1R1 SNP rs871659 allele A had a higher prevalence of primary knee OA. No correlation was found between SNPs of IL-1R1 and IL-1RN and clinical or radiologic severity or serum concentrations of IL-1R1 and IL-1Ra (p > 0.05). BMI and IL-1R1 rs3917238 genotype C/C were correlated with moderate-severe VAS scores. A correlation was also found between the EQ-5D-3L self-care dimension and obesity and between the EQ-5D-3L pain and usual activity dimensions and age ≥ 60 and obesity (p < 0.05). Radiologic severity was only associated with age ≥ 60 years (p < 0.05). We found the IL-1R1 SNPs rs871659, rs3771202, and rs3917238 to be predisposing factors for primary knee osteoarthritis. The clinical findings, radiographic severity, and serum concentrations of IL-1R1 and IL-1Ra were not correlated with these gene polymorphisms.

Inflammaging and Osteoarthritis

Osteoarthritis is a highly prevalent disease particularly in subjects over 65 years of age worldwide. While in the past it was considered a mere consequence of cartilage degradation leading to anatomical and functional joint impairment, in recent decades, there has been a more dynamic view with the synovium, the cartilage, and the subchondral bone producing inflammatory mediators which ultimately lead to cartilage damage. Inflammaging is defined as a chronic, sterile, low-grade inflammation state driven by endogenous signals in the absence of infections, occurring with aging. This chronic status is linked to the production of reactive oxygen species and molecules involved in the development of age-related disease such as cancer, diabetes, and cardiovascular and neurodegenerative diseases. Inflammaging contributes to osteoarthritis development where both the innate and the adaptive immune response are involved. Elevated systemic and local inflammatory cytokines and senescent molecules promote cartilage degradation, and antigens derived from damaged joints further trigger inflammation through inflammasome activation. B and T lymphocyte populations also change with inflammaging and OA, with reduced regulatory functions, thus implicating self-reactivity as an additional mechanism of joint damage. The discovery of the underlying pathogenic pathways may help to identify potential therapeutic targets for the management or the prevention of osteoarthritis. We will provide a comprehensive evaluation of the current literature on the role of inflammaging in osteoarthritis and discuss the emerging therapeutic strategies.

Silencing of IRF7 ameliorates osteoarthritis by inhibiting chondrocyte pyroptosis via targeting FGF21

Osteoarthritis (OA) is the most common joint disease which can lead to serious disability. Interferon regulatory factor 7 (IRF7) is a member of the interferon regulatory factor family. This study aimed to explore the function and potential mechanism of IRF7 in OA. Our results found that IRF7 was increased in LPS-stimulated C28/I2 chondrocytes and in OA mice established with medial menisco-tibial ligament (MMTL) transection. IRF7 silencing enhanced cell viability, reduced IL-18 and IL-1β levels and suppressed cell apoptosis. IRF7 knockdown decreased ROS and LDH levels, and inhibited pyroptosis in LPS-treated chondrocytes. IRF7 negatively regulated FGF21 expression. FGF21 overexpression alleviated pyroptosis in LPS-stimulated chondrocytes. Knockdown of IRF7 improved OA injury in mice. In conclusion, our study demonstrates that silencing of IRF7 alleviates OA by inhibiting chondrocyte pyroptosis via upregulation of FGF21.

The Bcr-Abl inhibitor DCC-2036 inhibits necroptosis and ameliorates osteoarthritis by targeting RIPK1 and RIPK3 kinases

Osteoarthritis (OA) is a chronic progressive degenerative joint disease. Owing to its complex pathogenesis, OA treatment is typically challenging. Necroptosis is a form of programmed cell death mainly mediated by the serine/threonine kinases, RIPK1 and RIPK3, and mixed lineage kinase-like domain (MLKL). In this study, we found that the multi-targeted kinase inhibitor DCC-2036 can inhibit TSZ (TNF-α, Smac mimetic, and z-VAD-FMK)-induced necroptosis of chondrocytes and synovial fibroblast cells (SFs). In addition, we found that oral DCC-2036 inhibited chondrocyte damage in a rat model of OA induced by intra-articular injection of monosodium iodoacetate (MIA). A mechanistic study showed that DCC-2036 directly inhibited the activities of RIPK1 and RIPK3 kinases to block necroptosis, inhibiting the inflammatory response and protecting chondrocytes. In summary, our research suggests that DCC-2036, a new necroptosis inhibitor targeting RIPK1 and RIPK3 kinase activity, may be useful for the clinical treatment of OA and provides a new direction for the research and treatment of OA.

Osteoarthritis year in review: genetics, genomics and epigenetics

This "year in review" provides a summary of the research findings on the topic of genetics, genomics and epigenetics for osteoarthritis (OA) between Mar 2021-Apr 2022. A search routine of the literature in PubMed for the keyword, osteoarthritis, together with topics on genetics, genomics, epigenetics, polymorphism, DNA methylation, noncoding RNA, lncRNA, proteomics, and single cell RNA sequencing, returned key research articles and relevant reviews. Following filtering of duplicates across search routines, 695 unique research articles and 112 reviews were identified. We manually curated these articles and selected 90 as references for this review. However, we were unable to refer to all these articles, and only used selected articles to highlight key outcomes and trends. The trend in genetics is on the meta-analysis of existing cohorts with comparable genetic and phenotype characterisation of OA; in particular, clear definition of endophenotypes to enhance the genetic power. Further, many researchers are realizing the power of big data and multi-omics approaches to gain molecular insights for OA, and this has opened innovative approaches to include transcriptomics and epigenetics data as quantitative trait loci (QTLs). Given that most of the genetic loci for OA are not located within coding regions of genes, implying the impact is likely to be on gene regulation, epigenetics is a hot topic, and there is a surge in studies relating to the role of miRNA and long non-coding RNA on cartilage biology and pathology. The findings are exciting and new insights are provided in this review to summarize a year of research and the road map to capture all new innovations to achieve the desired goal in OA prevention and treatment.

Protective effects of Tripterygium glycoside on IL-1β-induced inflammation and apoptosis of rat chondrocytes via microRNA-216a-5p/TLR4/NF-κB axis

BACKGROUND

This study is designed to fill the research gap concerning the efficacy of Tripterygium glycoside (TG) on Interleukin-1β (IL-1β)-induced inflammation and injury in chondrocytes.

METHODS

Chondrocytes were isolated from Sprague-Dawley rats. After the treatment with IL-1β and TG and transfection, the viability and apoptosis of chondrocytes were determined via Cell Counting Kit-8 (CCK-8) assay and flow cytometry. The levels of inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-8 were determined by enzyme-linked immunosorbent assay (ELISA). Relative expression levels of potential microRNAs (miRNAs, miRs) that may target toll-like receptor 4 (TLR4), as well as apoptosis- and TLR4/nuclear factor-κB (TLR4/NF-κB) pathway-associated factors were quantified using quantitative real-time (qRT) PCR and western blot. The targeting relationship between miR-216a-5p and TLR4 was predicted by TargetScan and further confirmed by dual-luciferase reporter assay.

RESULTS

The viability was reduced yet the apoptosis and inflammation were promoted in IL-1β-treated chondrocytes, where upregulation of Bax, Cleaved caspase 3, TLR4, Myeloid differentiation factor 88 (MyD88), phosphorylation of P65 and IκBα yet downregulation of Bcl-2 and IκBα were evidenced. Strikingly, the above changes were reversed by TG. TG also offset the effects of IL-1β on repressing the expression of miR-216a-5p, the miRNA targeting TLR4. Additionally, TLR4 overexpression neutralized the impacts of TG upon viability, apoptosis, and TLR4 expression in IL-1β-treated chondrocytes, while all these effects induced by TLR4 overexpression could be restored by miR-216a-5p.

CONCLUSIONS

TG protects chondrocytes against IL-1β-induced inflammation and apoptosis via miR-216a-5p/TLR4/NF-κB axis.

Plantamajoside suppresses the activation of NF-κB and MAPK and ameliorates the development of osteoarthritis

Osteoarthritis (OA) is a common degenerative bone and joint disorder characterized by progressive cartilage degeneration and secondary synovial inflammation. It is a common chronic joint disorder that affects people of all ages (especially the old). Plantamajoside is a phenylpropanoside derived from plantain. It has a variety of biological properties, including antioxidant, anti-malignant cell proliferation, and anti-inflammatory properties. In this study, the latent mechanism of plantamajoside was explored by slowing the in-vivo and in-vitro progression of osteoarthritis. The results revealed that plantamajoside pre-conditioning inhibited IL-1β induced pro-inflammatory factors like COX-2, iNOS, IL-6, and TNF-α. Moreover, plantamajoside also reversed the IL-1 β mediated type II collagen and aggrecan degradation within the extracellular matrix (ECM). The protective effects of plantamajoside have been attributed to the inhibition of both MAPK and NF-κB pathways. Furthermore, our in-vivo research found that plantamajoside could slow the progression of OA in mice. Finally, all findings point to plantamajoside as a potential anti-OA therapeutic candidate.

Epigenetics as a Therapeutic Target in Osteoarthritis

Osteoarthritis (OA) is a heterogenous, complex disease affecting the integrity of diarthrodial joints that, despite its high prevalence worldwide, lacks effective treatment. In recent years it has been discovered that epigenetics may play an important role in OA. Our objective is to review the current knowledge of the three classical epigenetic mechanisms-DNA methylation, histone post-translational modifications (PTMs), and non-coding RNA (ncRNA) modifications, including microRNAs (miRNAs), circular RNAs (circRNAs), and long non-coding RNAs (lncRNAs)-in relation to the pathogenesis of OA and focusing on articular cartilage. The search for updated literature was carried out in the PubMed database. Evidence shows that dysregulation of numerous essential cartilage molecules is caused by aberrant epigenetic regulatory mechanisms, and it contributes to the development and progression of OA. This offers the opportunity to consider new candidates as therapeutic targets with the potential to attenuate OA or to be used as novel biomarkers of the disease.