Pathophysiological landscape of osteoarthritis

Arthritis increases the risk of erectile dysfunction: Results from the NHANES 2001-2004

Objective

This study assessed the association between erectile dysfunction (ED) and arthritis.

Methods

Weighted logistic regression and subgroup analyses were used to investigate the association between arthritis incidence and ED among participants in the 2001-2004 National Health and Nutrition Examination Survey database.

Results

Among the participants, 27.8% and 18.5% had a self-reported history of ED and arthritis, respectively. ED was associated with arthritis (odds ratio [OR]=4.00; 95% confidence interval [CI]: 3.20-4.99; p<0.001], which remained significant after adjustment (OR=1.42, 95% CI: 1.00-1.96; p<0.001). Stratified by type of arthritis, after full adjustment, osteoarthritis remained significant (OR=1.11; 95% CI: 1.03-1.20; p=0.017), and rheumatoid arthritis (OR=1.03, 95% CI: 0.93-1.13; p= 0.5) and other arthritis (OR=1.04, 95% CI: 0.98-1.11; p=0.2) were not significantly correlated with ED. Multiple inference analyses confirmed the robustness of the results.

Conclusion

Our study showed that arthritis was strongly associated with ED. There is an urgent need to raise awareness and conduct additional research on the reasons behind this association in order to implement more scientific and rational treatment programs for patients with ED and arthritis.

Melatonin Delays Arthritis Inflammation and Reduces Cartilage Matrix Degradation through the SIRT1-Mediated NF-κB/Nrf2/TGF-β/BMPs Pathway

Cartilage, a flexible and smooth connective tissue that envelops the surfaces of synovial joints, relies on chondrocytes for extracellular matrix (ECM) production and the maintenance of its structural and functional integrity. Melatonin (MT), renowned for its anti-inflammatory and antioxidant properties, holds the potential to modulate cartilage regeneration and degradation. Therefore, the present study was devoted to elucidating the mechanism of MT on chondrocytes. The in vivo experiment consisted of three groups: Sham (only the skin tissue was incised), Model (using the anterior cruciate ligament transection (ACLT) method), and MT (30 mg/kg), with sample extraction following 12 weeks of administration. Pathological alterations in articular cartilage, synovium, and subchondral bone were evaluated using Safranin O-fast green staining. Immunohistochemistry (ICH) analysis was employed to assess the expression of matrix degradation-related markers. The levels of serum cytokines were quantified via Enzyme-linked immunosorbent assay (ELISA) assays. In in vitro experiments, primary chondrocytes were divided into Control, Model, MT, negative control, and inhibitor groups. Western blotting (WB) and Quantitative RT-PCR (q-PCR) were used to detect Silent information regulator transcript-1 (SIRT1)/Nuclear factor kappa-B (NF-κB)/Nuclear factor erythroid-2-related factor 2 (Nrf2)/Transforming growth factor-beta (TGF-β)/Bone morphogenetic proteins (BMPs)-related indicators. Immunofluorescence (IF) analysis was employed to examine the status of type II collagen (COL2A1), SIRT1, phosphorylated NF-κB p65 (p-p65), and phosphorylated mothers against decapentaplegic homolog 2 (p-Smad2). In vivo results revealed that the MT group exhibited a relatively smooth cartilage surface, modest chondrocyte loss, mild synovial hyperplasia, and increased subchondral bone thickness. ICH results showed that MT downregulated the expression of components related to matrix degradation. ELISA results showed that MT reduced serum inflammatory cytokine levels. In vitro experiments confirmed that MT upregulated the expression of SIRT1/Nrf2/TGF-β/BMPs while inhibiting the NF-κB pathway and matrix degradation-related components. The introduction of the SIRT1 inhibitor Selisistat (EX527) reversed the effects of MT. Together, these findings suggest that MT has the potential to ameliorate inflammation, inhibit the release of matrix-degrading enzymes, and improve the cartilage condition. This study provides a new theoretical basis for understanding the role of MT in decelerating cartilage degradation and promoting chondrocyte repair in in vivo and in vitro cultured chondrocytes.

Bioactive components and potential mechanisms of Biqi Capsule in the treatment of osteoarthritis: based on chondroprotective and anti-inflammatory activity

Cartilage damage and synovial inflammation are vital pathological changes in osteoarthritis (OA). Biqi Capsule, a traditional Chinese medicine formula used for the clinical treatment of arthritis in China, yields advantages in attenuating OA progression. The drawback here is that the bioactive components and pharmacological mechanisms by which Biqi Capsule exerts its anti-inflammatory and chondroprotective effects have yet to be fully clarified. For in vivo studies, a papain-induced OA rat model was established to explore the pharmacological effects and potential mechanisms of Biqi Capsule against OA. Biqi Capsule alleviated articular cartilage degeneration and chondrocyte damage in OA rats and inhibited the phosphorylation of NF-κB and the expression of pro-inflammatory cytokines in synovial tissue. Network pharmacology analysis suggested that the primary biological processes regulated by Biqi Capsule are inflammation and oxidative stress, and the critical pathway regulated is the PI3K/AKT signaling pathway. The result of this analysis was later verified on SW1353 cells. The in vitro studies demonstrated that Glycyrrhizic Acid and Liquiritin in Biqi Capsule attenuated H2O2-stimulated SW1353 chondrocyte damage via activation of PI3K/AKT/mTOR pathway. Moreover, Biqi Capsule alleviated inflammatory responses in LPS-stimulated RAW264.7 macrophages via the NF-κB/IL-6 pathway. These observations were suggested to have been facilitated by Brucine, Liquiritin, Salvianolic Acid B, Glycyrrhizic Acid, Cryptotanshinone, and Tanshinone ⅡA. Put together, this study partially clarifies the pharmacological mechanisms and the bioactive components of Biqi capsules against OA and suggests that it is a promising therapeutic option for the treatment of OA. Chemical compounds studied in this article. Strychnine (Pubchem CID:441071); Brucine (Pubchem CID:442021); Liquiritin (Pubchem CID:503737); Salvianolic Acid B (Pubchem CID:6451084); Glycyrrhizic Acid (Pubchem CID:14982); Cryptotanshinone (Pubchem CID:160254); Tanshinone ⅡA (Pubchem CID:164676).

Effect of l-Carnitine Supplementation on Osteoarthritis: A Systematic Review

SCOPE

Comprehensive assessment of l-carnitine's safety and effectiveness in reducing inflammatory markers in osteoarthritis (OA) patients.

METHODS AND RESULTS

Journal articles on l-carnitine for OA are gathered using computer searches of PubMed, Embase, the Cochrane Library, and Web of Science. The kind of literature that is found is restricted to clinical randomized controlled trials (RCTs). The Cochrane Handbook risk of bias assessment tool RevMan 5.4 software is used to conduct a meta-analysis. The systematic assessment comprises eight trials totaling 619 patients; the included studies' quality is mediocre. The study's findings demonstrate that OA patients' Western Ontario and McMaster University (WOMAC) function improves and that treatment efficacy outperforms that of the control group (mean difference [MD] = -7.75, 95% CI [-14.63, -0.86]; Z = 2.21; p = 0.03), WOMAC total (MD = -10.24, 95% CI [-18.97, -1.51]; Z = 2.30; p = 0.02), and visual analogue scale (VAS) pain (MD = -14.01, 95% CI [-16.16, -11.85]; Z = 12.74; p < 0.00001). The studies that are methodically reviewed also discover heterogeneity, which may have resulted from the created pooled data and requires more analysis.

CONCLUSION

In patients with OA, l-carnitine effectively decreases clinical signs and symptoms, inflammatory markers, pain, and stiffness indicators, and significantly improves WOMAC and VAS scores.

Potential therapeutic strategies for osteoarthritis via CRISPR/Cas9 mediated gene editing

Osteoarthritis (OA) is an incapacitating and one of the most common physically degenerative conditions with an assorted etiology and a highly complicated molecular mechanism that to date lacks an efficient treatment. The capacity to design biological networks and accurately modify existing genomic sites holds an apt potential for applications across medical and biotechnological sciences. One of these highly specific genomes editing technologies is the CRISPR/Cas9 mechanism, referred to as the clustered regularly interspaced short palindromic repeats, which is a defense mechanism constituted by CRISPR associated protein 9 (Cas9) directed by small non-coding RNAs (sncRNA) that bind to target DNA through Watson-Crick base pairing rules where subsequent repair of the target DNA is initiated. Up-to-date research has established the effectiveness of the CRISPR/Cas9 mechanism in targeting the genetic and epigenetic alterations in OA by suppressing or deleting gene expressions and eventually distributing distinctive anti-arthritic properties in both in vitro and in vivo osteoarthritic models. This review aims to epitomize the role of this high-throughput and multiplexed gene editing method as an analogous therapeutic strategy that could greatly facilitate the clinical development of OA-related treatments since it's reportedly an easy, minimally invasive technique, and a comparatively less painful method for osteoarthritic patients.

Extracellular vesicles derived from mesenchymal stem cells mediate extracellular matrix remodeling in osteoarthritis through the transport of microRNA-29a

BACKGROUND

Knee osteoarthritis (KOA) is a common orthopedic condition with an uncertain etiology, possibly involving genetics and biomechanics. Factors like changes in chondrocyte microenvironment, oxidative stress, inflammation, and immune responses affect KOA development. Early-stage treatment options primarily target symptom relief. Mesenchymal stem cells (MSCs) show promise for treatment, despite challenges. Recent research highlights microRNAs (miRNAs) within MSC-released extracellular vesicles that can potentially promote cartilage regeneration and hinder KOA progression. This suggests exosomes (Exos) as a promising avenue for future treatment. While these findings emphasize the need for effective KOA progression management, further safety and efficacy validation for Exos is essential.

AIM

To explore miR-29a's role in KOA, we'll create miR-29a-loaded vesicles, testing for early treatment in rat models.

METHODS

Extraction of bone marrow MSC-derived extracellular vesicles, preparation of engineered vesicles loaded with miR-29a using ultrasonication, and identification using quantitative reverse transcription polymerase chain reaction; after establishing a rat model of KOA, rats were randomly divided into three groups: Blank control group injected with saline, normal extracellular vesicle group injected with normal extracellular vesicle suspension, and engineered extracellular vesicle group injected with engineered extracellular vesicle suspension. The three groups were subjected to general behavioral observation analysis, imaging evaluation, gross histological observation evaluation, histological detection, and immunohistochemical detection to compare and evaluate the progress of various forms of arthritis.

RESULTS

General behavioral observation results showed that the extracellular vesicle group and engineered extracellular vesicle group had better performance in all four indicators of pain, gait, joint mobility, and swelling compared to the blank control group. Additionally, the engineered extracellular vesicle group had better pain relief at 4 wk and better knee joint mobility at 8 wk compared to the normal extracellular vesicle group. Imaging examination results showed that the blank control group had the fastest progression of arthritis, the normal extracellular vesicle group had a relatively slower progression, and the engineered extracellular vesicle group had the slowest progression. Gross histological observation results showed that the blank control group had the most obvious signs of arthritis, the normal extracellular vesicle group showed signs of arthritis, and the engineered extracellular vesicle group showed no significant signs of arthritis. Using the Pelletier gross score evaluation, the engineered extracellular vesicle group had the slowest progression of arthritis. Results from two types of staining showed that the articular cartilage of rats in the normal extracellular vesicle and engineered extracellular vesicle groups was significantly better than that of the blank control group, and the engineered extracellular vesicle group had the best cartilage cell and joint surface condition. Immunohistochemical detection of type II collagen and proteoglycan showed that the extracellular matrix of cartilage cells in the normal extracellular vesicle and engineered extracellular vesicle groups was better than that of the blank control group. Compared to the normal extracellular vesicle group, the engineered extracellular vesicle group had a better regulatory effect on the extracellular matrix of cartilage cells.

CONCLUSION

Engineered Exos loaded with miR-29a can exert anti-inflammatory effects and maintain extracellular matrix stability, thereby protecting articular cartilage, and slowing the progression of KOA.

Metabolic syndrome and arthritis among Mexican American older adults: findings from a 23-year follow-up

PURPOSE

To examine the sex differences in the relationship of metabolic syndrome (MetS) criteria with arthritis and symptomatic arthritis among Mexican American older adults aged ≥ 65 without self-reported arthritis at baseline over 23-years of follow-up.

METHODS

Participants (N = 1447) were from the Hispanic Established Population for the Epidemiologic Study of the Elderly (1993/94-2016). Measures included MetS criteria, arthritis defined as self-reported physician-diagnosed arthritis, socio-demographics, morbidities, depressive symptoms, pain on weight-bearing, cognitive and physical function, handgrip strength, mobility, and activities of daily living (ADLs) limitations. Symptomatic arthritis was defined as self-reported arthritis and having ≥ 1 of the following: pain, mobility limitation, or limited ADLs.

RESULTS

At baseline, the mean age was 72.6 years and 730 (50.5%) of our participants were females. Female participants with 2 and 3 MetS criteria had greater odds of arthritis [odds ratio (OR) = 1.77, 95% Confidence Interval (Cl) = 1.28-2.45 and OR = 2.68, 95% CI = 1.69-4.27, respectively) and symptomatic arthritis (OR = 1.74, 95% Cl = 1.24-2.44 and OR = 3.27, 95% CI = 2.04-5.26, respectively) after controlling for covariates. Male participants with 2 and 3 MetS criteria had greater odds of arthritis (OR = 1.65, 95% Cl = 1.14-2.39 and OR = 2.52, 95% CI = 1.51-4.19, respectively) and symptomatic arthritis (OR = 1.93, 95% Cl = 1.30-2.86 and OR = 2.98, 95% CI = 1.62-5.47, respectively) after controlling for covariates. Both females and males with pain on weight-bearing had greater odds of arthritis than those without pain.

CONCLUSIONS

At 23-years of follow-up, Mexican American older adults with MetS have an increased risk of arthritis and symptomatic arthritis. Early MetS screening and management may reduce arthritis in this population at high risk of disability.

Carveol alleviates osteoarthritis progression by acting on synovial macrophage polarization transformation: An in vitro and in vivo study

Osteoarthritis (OA) is a heterogeneous disease that affects the entire joint. Its pathogenesis involves hypertrophy and hyperplasia of synovial cells and polarization infiltration of macrophages, in which macrophages, as a potential target, can delay the progression of the disease by improving the immune microenvironment in OA. To investigate the role and regulatory mechanism of Carveol in cartilage and synovial macrophage reprogramming and crosstalk during the development of OA. RAW264.7 mouse macrophage cell line was mainly used to stimulate macrophages to polarization towards M1 and M2 by LPS, IL4+IL13, respectively. Different concentrations of Carveol were given to intervene, and macrophage culture medium was collected to intervene mouse C57BL6J chondrocytes. ROS assay kit, western blotting, cellular immunofluorescence, scanning microscope and section histology were used to evaluate the effect of Carveol on anti-M1-polarization, M2-polarization promotion and cartilage protection. The mouse destabilization of medial meniscus (DMM) model was observed by micro-CT scan and histology. We found that CA could inhibit the increase of macrophage inflammation level under the intervention of LPS and promote the production of M2 anti-inflammatory substances under the intervention of IL-4+IL13. In addition, Carveol activated NRF2/HO-1/NQO1 pathway and enhanced ROS clearance in chondrocytes under the intervention of macrophage culture medium. The phosphorylation of I-κBα is inhibited, which further reduces the phosphorylation of P65 downstream of nuclear factor-κB (NF-κB) signaling pathway. In addition, Carveol inhibits mitogen activated protein kinase (MAPK) signaling molecules P-JNK, P-ERK and P-P38, and inhibits the production of inflammatory mediators. In vivo, Carveol can reduce osteophytes and bone spurs induced by DMM, reduce hypertrophy of synovial cells, reduce infiltration of macrophages, inhibit subchondral bone destruction, and reduce articular cartilage erosion. Our study suggests that synovial macrophages are potential targets for OA treatment, and Carveol is an effective candidate for OA treatment.

A microfluidic organ-on-a-chip: into the next decade of bone tissue engineering applied in dentistry

A comprehensive understanding of the complex physiological and pathological processes associated with alveolar bones, their responses to different therapeutics strategies, and cell interactions with biomaterial becomes necessary in precisely treating patients with severe progressive periodontitis, as a bone-related issue in dentistry. However, existing monolayer cell culture or pre-clinical models have been unable to mimic the complex physiological, pathological and regeneration processes in the bone microenvironment in response to different therapeutic strategies. In this point, 'organ-on-a-chip' (OOAC) technology, specifically 'alveolar-bone-on-a-chip', is expected to resolve the problems by better imitating infection site microenvironment and microphysiology within the oral tissues. The OOAC technology is assessed in this study toward better approaches in disease modeling and better therapeutics strategy for bone tissue engineering applied in dentistry.

Exploration of effective biomarkers and infiltrating Immune cells in Osteoarthritis based on bioinformatics analysis

Osteoarthritis (OA) is a multi-factorial chronic joint disease mainly identified by synovial inflammation, cartilage damage, and degeneration. Our study applied bioinformatics analysis to uncover the immunity in OA and tried to explore the underlying immune-related molecular mechanism. First, OA-related gene-expression profiling data were retrieved from GEO database. Then, we analysed a series of datadata with using the xCell algorithm, GEO2R, enrichment analysis of SangerBox website, CytoHubba, ROC logistic regression and correlation analysis. Finally, Nine infiltrating immune cells with differential abundance between OA and normal samples were obtained. There were 42 IODEGs in OA, and their functions were associated with immune cells and corresponding biological processes. Moreover, 5 hub genes, including GREM1, NRP1, VEGFA, FYN and IL6R, were identified. Correlation analysis demonstrated that NRP1 was negatively associated with NKT cells, NRP1 and GREM1 were positively associated with aDC, VEGFA was positively associated with CD8+ naïve T cells, while VEGFA, FYN and IL6R were negatively associated with Macrophages M1. The 5 hub genes could be employed as effective diagnostic biomarkers for OA. In addition, they may participate in OA pathogenesis via interactions with infiltrating immune cells.

Research and publication trends on knee osteoarthritis and cellular senescence: a bibliometric analysis

Background: Cellular senescence is associated with age-related pathological changes, senescent cells promote the development of knee osteoarthritis. A better understanding between knee osteoarthritis and cellular senescence may enhance the effectiveness of therapies that aim to slow or stop the progression of this disease. Purpose: This study aimed to systematically analyze and visualize the publication trends, research frontiers and current research hotspots of knee osteoarthritis and cellular senescence by using bibliometrics. Methods: The publication search was performed on the Web of Science Core Collection database for documents published from 1992 to 2023. VOSviewer, Citespace, R package Bibliometrix and Microsoft Office Excel were used to study the characteristics of the publications. The publication number, countries, institutions, authors, journals, citations and co-citations, keywords were analyzed. Results: A total of 1,074 publications were analyzed, with an average annual growth rate of 29.89%. United States accounted for the biggest contributor, ranked first in publications and citations. Publications of this field were published in 420 journals, OSTEOARTHRITIS and CARTILAGE was the most influential. A total of 5,657 authors contributed to this research. The most productive author was Lotz, MK (n = 31, H-index = 22, Total citation = 2,619), followed by Loeser, R.F (n = 16, H-index = 14, Total citation = 2,825). However, the collaboration between authors was relatively weak. Out of the 1,556 institutions involved, 60% were from the United States. Scripps Research ranked first with 25 papers and a total of 2,538 citations. The hotspots of this field had focused on the pathomechanisms (e.g., expression, inflammation, apoptosis, autophagy, oxidative stress) and therapeutics (e.g., stem cell, platelet-rich plasma, transplantation, autologous chondrocytes, repair), and the exploration of Senolytics might be the important direction of future research. Conclusion: Research on the cross field of knee osteoarthritis and cellular senescence is flourishing. Age-related pathomechanism maps of various cells in the joint and the targeted medicines for the senescent cells may be the future trends. This bibliometric study provides a comprehensive analysis of this cross field and new insights into future research.

Mechanism of Nrf2/miR338-3p/TRAP-1 pathway involved in hyperactivation of synovial fibroblasts in patients with osteoarthritis

Our previous study has confirmed that miR338-3p/TRAP-1 axis was involved in regulation of hyperactivation in human synovial fibroblasts (HFLS) of patients with osteoarthritis (OA). Here, we aim to further investigate the underlying causes of the abnormal activation miR338-3p/TRAP-1 at the molecular level. Our results showed that the decrease of NF-E2-related factor 2(Nrf2) was the direct cause of downregulation of miR338-3p and upregulation of TRAP-1 protein expression in HFLS of OA patients. Furthermore, we also found that the phosphorylation and nuclear entry of Nrf2 protein were significantly reduced in HFLS of OA patients than that of normal individuals, and both of them were positively correlated with miR338-3p levels. Bioinformatics analysis, luciferase assay, and CHIP experiment together indicated that Nrf2 could positively regulate the transcription of miR338-3p by binding to the Transcription Factor Binding Sites (TFBS) on its promoter. It was confirmed by in vitro assays that oltipraz (agonists of Nrf2) treatment effectively inhibited the hyperactivation of HFLS induced by TGF-β1, and the effects of oltipraz could be reversed by the exogenous TRAP-1. In short, our research has revealed for the first time that Nrf2/miR338-3p/TRAP-1 pathway was involved in hyperactivation of HFLS in OA patients, Nrf2 has the potential to be used as therapy and new drug target of OA.

Dapagliflozin suppress endoplasmic reticulum stress mediated apoptosis of chondrocytes by activating Sirt1

OBJECTIVE

Osteoarthritis (OA) is a common joint disease characterized by inflammation and cartilage degeneration. Accumulating evidences support that endoplasmic reticulum (ER) stress induced OA chondrocytes apoptosis. The hypoglycemic and anti-inflammatory properties render Dapagliflozin (DAPA) effective in reducing ER stress on cells. However, its impact and potential mechanisms on the OA pathology are still obscure. The present study aimed to investigate whether DAPA attenuates ER stress in chondrocytes by activating sirt1 and delays the progression of OA.

METHODS

In vitro, we first investigated the effect of DAPA on chondrocytes viability with IL-1β or not for 24 or 48 h. Then, chondrocytes were treated with 10 ng/ml IL-1β and 10 μM dapagliflozin with10 μM thapsigargin, 5 μM SRT1460 or not. Chondrocytes apoptosis in each group were detected by Tunel staining and flow cytometric. Immunofluorescence staining was applied to quantify the expression levels of cleaved caspase-3, Sirt1 and CHOP in chondrocytes. Inhibition of ER stress in chondrocytes associated with sirt1 activation were verified by PCR and western blotting. In addition, the effects of DAPA on cartilage were validated by a series of experiments in OA rat model, such as micro-CT, histological and immunohistochemical assay.

RESULTS

The data demonstrated that DAPA alleviates IL-1β induced ER stress related chondrocytes apoptosis, and PCR and western blotting data confirmed that DAPA inhibits the PERK-eIF2α-CHOP pathway by activating Sirt1. Besides, immunohistochemical results showed that DAPA enhanced the expression of Sirt1 and Collagen II in OA rats, and inhibited the expression of CHOP and cleaved caspase-3. Meanwhile, histological staining and micro-CT photography also confirmed that DAPA alleviated inflammation and cartilage degeneration in OA rat.

CONCLUSIONS

The study demonstrated the relationship of ER stress and inflammation in the progression of OA, and verified that DAPA could inhibit PERK-eIF2α-CHOP axis of the ER stress response by activating Sirt1 in IL-1β treated rat chondrocytes and potentially prevent the OA development.

PSD95 as a New Potential Therapeutic Target of Osteoarthritis: A Study of the Identification of Hub Genes through Self-Contrast Model

Osteoarthritis (OA) is a worldwide joint disease. However, the precise mechanism causing OA remains unclear. Our primary aim was to identify vital biomarkers associated with the mechano-inflammatory aspect of OA, providing potential diagnostic and therapeutic targets for OA. Thirty OA patients who underwent total knee arthroplasty were recruited, and cartilage samples were obtained from both the lateral tibial plateau (LTP) and medial tibial plateau (MTP). GO and KEGG enrichment analyses were performed, and the protein-protein interaction (PPI) assessment was conducted for hub genes. The effect of PSD95 inhibition on cartilage degeneration was also conducted and analyzed. A total of 1247 upregulated and 244 downregulated DEGs were identified. Significant differences were observed between MTP and LTP in mechanical stress-related genes and activated sensory neurons based on a self-contrast model of human knee OA. Cluster analysis identified DLG4 as the hub gene. Cyclic loading stress increased PSD95 (encoded by DLG4) expression in LTP cartilage, and PSD95 inhibitors could alleviate OA progression. This study suggests that inhibiting PSD95 could be a potential therapeutic strategy for preventing articular cartilage degradation.

Differential Metabolites in Osteoarthritis: A Systematic Review and Meta-Analysis

(1) Many studies have attempted to utilize metabolomic approaches to explore potential biomarkers for the early detection of osteoarthritis (OA), but consistent and high-level evidence is still lacking. In this study, we performed a systematic review and meta-analysis of differential small molecule metabolites between OA patients and healthy individuals to screen promising candidates from a large number of samples with the aim of informing future prospective studies. (2) Methods: We searched the EMBASE, the Cochrane Library, PubMed, Web of Science, Wan Fang Data, VIP Date, and CNKI up to 11 August 2022, and selected relevant records based on inclusion criteria. The risk of bias was assessed using the Newcastle-Ottawa quality assessment scale. We performed qualitative synthesis by counting the frequencies of changing directions and conducted meta-analyses using the random effects model and the fixed-effects model to calculate the mean difference and 95% confidence interval. (3) Results: A total of 3798 records were identified and 13 studies with 495 participants were included. In the 13 studies, 132 kinds of small molecule differential metabolites were extracted, 58 increased, 57 decreased and 17 had direction conflicts. Among them, 37 metabolites appeared more than twice. The results of meta-analyses among four studies showed that three metabolites increased, and eight metabolites decreased compared to healthy controls (HC). (4) Conclusions: The main differential metabolites between OA and healthy subjects were amino acids (AAs) and their derivatives, including tryptophan, lysine, leucine, proline, phenylalanine, glutamine, dimethylglycine, citrulline, asparagine, acetylcarnitine and creatinine (muscle metabolic products), which could be potential biomarkers for predicting OA.

Research Progress on the Pathogenesis of Knee Osteoarthritis

Knee osteoarthritis (KOA) is a chronic joint bone disease characterized by inflammatory destruction and hyperplasia of bone. Its main clinical symptoms are joint mobility difficulties and pain, severe cases can lead to limb paralysis, which poses major pressure to the quality of life and mental health of patients, but also brings serious economic burden to society. The occurrence and development of KOA is influenced by many factors, including systemic factors and local factors. The joint biomechanical changes caused by aging, trauma and obesity, abnormal bone metabolism caused by metabolic syndrome, the effects of cytokines and related enzymes, genetic and biochemical abnormalities caused by plasma adiponectin, etc. all directly or indirectly lead to the occurrence of KOA. However, there is little literature that systematically and comprehensively integrates macro- and microscopic KOA pathogenesis. Therefore, it is necessary to comprehensively and systematically summarize the pathogenesis of KOA in order to provide a better theoretical basis for clinical treatment.

Diagnostic value and immune infiltration characterization of YTHDF2 as a critical m6A regulator in osteoarthritic synovitis

BACKGROUND

N6-methyladenosine (m6A) is a universal RNA modification pattern regulated by multiple m6A regulators. In osteoarthritis (OA), m6A regulators influence disease progression by regulating cartilage degradation. However, the function of m6A regulators in synovial tissue remains unclear. In this work, we investigated the biological significance of m6A regulators in osteoarthritic synovitis.

METHODS

Datasets were acquired from Gene Expression Omnibus. Differential analysis of merged data identified the differentially expressed m6A regulators. Machine learning models were used to evaluate genetic importance. To predict disease risk, a nomogram was constructed based on above m6A regulators. Cluster analysis divided the OA sample into different subgroups. Immune infiltration revealed the immune m6A regulators, which were validated using clinical samples. Eventually, a competing endogenous RNA (ceRNA) network was constructed.

RESULTS

We acquired five differentially expressed m6A regulators and a random forest model. The nomogram accurately predicted disease risk. We identified 122 differentially expressed genes between two m6A subgroups. The analysis of immune infiltration showed that YTHDF2 was an immune-related m6A regulator closely related with macrophages. In clinical samples, the protein and mRNA contents of YTHDF2 were consistent with the results of bioinformatic analysis. The ceRNA network based on YTHDF2 revealed 75 lncRNA nodes and 19 miRNA nodes.

CONCLUSION

YTHDF2 has a high diagnostic value in the synovitis of OA and significantly influences the immune status of patients. Hence, YTHDF2, a critical m6A regulator, may provide a biomarker for diagnosis and immune therapy of osteoarthritic synovitis.

Detrimental alteration of mesenchymal stem cells by an articular inflammatory microenvironment results in deterioration of osteoarthritis

BACKGROUND

Articular injection of mesenchymal stem cells (MSCs) has been applied to treat knee osteoarthritis (kOA), but its clinical outcomes are controversial. This study investigated whether an articular inflammatory microenvironment (AIM) impacts MSC-based therapy in a rat model of kOA.

METHODS

The biological change of MSCs and the functional change of MSCs on chondrocytes were evaluated under AIM. The key mediator and mechanism for the AIM impact on MSC therapy were explored via gain- and loss-of-function approaches.

RESULTS

The results showed that MSCs exerted potent anti-kOA effects in vivo and in vitro, but that this therapy become chondrodestructive if a chronic AIM was present. Mechanistically, the overexpression of MMP13 in the injected MSCs via a MAPKs-AP1 signaling axis was revealed as the underlying mechanism for the detriment outcome.

CONCLUSIONS

This study thus clarifies recent clinical findings while also suggesting a means to overcome any detrimental effects of MSC-based therapy while improving its efficacy.

Current Non-surgical Management of Knee Osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative disease. The prevalence tends to increase with age and is influenced by underlying risk factors such as gender, obesity, joint injuries (work/sports activities), and geographic region. OA has a distinctive picture, namely, damage to the joint cartilage and the formation of new bone at the edges of the bones, also called osteophytes, due to biochemical, metabolic, physiological, and pathological changes in the joint cartilage and subchondral bone. Symptoms that can be caused include joint pain, inhibition of joint movement, crepitus, deformity, asymmetrical swelling of the joints, signs of inflammation, and changes in gait. Currently, there are various methods of managing OA in terms of reducing pain, including regeneration and non-regeneration therapy. Non-regeneration treatments include physiotherapy (exercise, biomechanical intervention, electrotherapy, diathermy), pharmacology, intra-articular injections (corticosteroids, hyaluronic acid, geniculate nerve blocks), extra-articular injections, and radiofrequency. In comparison, regeneration management includes laser and intra-articular injection (prolotherapy and PRP).

Phytochemicals in the treatment of inflammation-associated diseases: the journey from preclinical trials to clinical practice

Advances in biomedical research have demonstrated that inflammation and its related diseases are the greatest threat to public health. Inflammatory action is the pathological response of the body towards the external stimuli such as infections, environmental factors, and autoimmune conditions to reduce tissue damage and improve patient comfort. However, when detrimental signal-transduction pathways are activated and inflammatory mediators are released over an extended period of time, the inflammatory process continues and a mild but persistent pro-inflammatory state may develop. Numerous degenerative disorders and chronic health issues including arthritis, diabetes, obesity, cancer, and cardiovascular diseases, among others, are associated with the emergence of a low-grade inflammatory state. Though, anti-inflammatory steroidal, as well as non-steroidal drugs, are extensively used against different inflammatory conditions, they show undesirable side effects upon long-term exposure, at times, leading to life-threatening consequences. Thus, drugs targeting chronic inflammation need to be developed to achieve better therapeutic management without or with a fewer side effects. Plants have been well known for their medicinal use for thousands of years due to their pharmacologically active phytochemicals belonging to diverse chemical classes with a number of these demonstrating potent anti-inflammatory activity. Some typical examples include colchicine (alkaloid), escin (triterpenoid saponin), capsaicin (methoxy phenol), bicyclol (lignan), borneol (monoterpene), and quercetin (flavonoid). These phytochemicals often act via regulating molecular mechanisms that synergize the anti-inflammatory pathways such as increased production of anti-inflammatory cytokines or interfere with the inflammatory pathways such as to reduce the production of pro-inflammatory cytokines and other modulators to improve the underlying pathological condition. This review describes the anti-inflammatory properties of a number of biologically active compounds derived from medicinal plants, and their mechanisms of pharmacological intervention to alleviate inflammation-associated diseases. The emphasis is given to information on anti-inflammatory phytochemicals that have been evaluated at the preclinical and clinical levels. Recent trends and gaps in the development of phytochemical-based anti-inflammatory drugs have also been included.

Trimanganese Tetroxide Nanozyme protects Cartilage against Degeneration by Reducing Oxidative Stress in Osteoarthritis

Osteoarthritis, a chronic degenerative cartilage disease, is the leading cause of movement disorders among humans. Although the specific pathogenesis and associated mechanisms remain unclear, oxidative stress-induced metabolic imbalance in chondrocytes plays a crucial role in the occurrence and development of osteoarthritis. In this study, a trimanganese tetroxide (Mn₃ O₄ ) nanozyme with superoxide dismutase (SOD)-like and catalase (CAT)-like activities is designed to reduce oxidative stress-induced damage and its therapeutic effect is investigated. In vitro, Mn₃ O₄ nanozymes are confirmed to reprogram both the imbalance of metabolism in chondrocytes and the uncontrolled inflammatory response stimulated by hydrogen peroxide. In vivo, a cross-linked chondroitin sulfate (CS) hydrogel is designed as a substrate for Mn₃ O₄ nanozymes to treat osteoarthritis in mouse models. As a result, even in the early stage of OA (4 weeks), the therapeutic effect of the Mn₃ O₄ @CS hydrogel is observed in both cartilage metabolism and inflammation. Moreover, the Mn₃ O₄ @CS hydrogel maintained its therapeutic effects for at least 7 days, thus revealing a broad scope for future clinical applications. In conclusion, these results suggest that the Mn₃ O₄ @CS hydrogel is a potentially effective therapeutic treatment for osteoarthritis, and a novel therapeutic strategy for osteoarthritis based on nanozymes is proposed.

Potential Therapeutic Mechanism of Radix Angelicae Biseratae and Dipsaci Radix Herb Pair against Osteoarthritis: Based on Network Pharmacology and Molecular Docking

Background

A major contributor to older disability is osteoarthritis. Radix Angelicae Biseratae (known as Duhuo in China, DH, the dried rhizome of Angelica pubescens) and Dipsaci Radix (known as Xuduan in China, XD, the dried rhizome of Dipsacus asper Wall) herb pair (DXHP) is widely used to treat osteoarthritis, but the underlying molecular mechanisms still have not been revealed. This research aimed to illustrate the therapeutic mechanism of DXHP against osteoarthritis through the techniques of network pharmacology and molecular docking.

Methods

Gene targets for osteoarthritis and active ingredients for DXHP were screened based on the pharmacology public database and the gene-disease target database. The software program Cytoscape was used to visualize the active chemical target-disease gene network. The STRING biological information website was used to investigate protein interactions. On the Metascape bioinformatics website, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were carried out. The molecular docking of the important chemicals and primary targets identified by the aforementioned screening was performed using Autodock software.

Results

Twenty-six active substances from the DXHP that had strong connections to 138 osteoarthritis-related targets were screened out. According to network analysis, TNF, GAPDH, IL-6, AKT-1, IL-1B, and VEGFA are prospective therapeutic targets, while osthole, cauloside A, ammidin, angelicone, beta-sitosterol, and asperosaponin VI may be significant active components. 1705 biological processes (BP), 155 molecular functions (MF), and 89 cellular components (CC) were identified by GO analysis. KEGG analysis indicated that IL-17, NF-kappa B, HIF-1, MAPK, and AGE-RAGE signaling pathways are potentially involved. Molecular docking showed that cauloside A, osthole, and β-sitosterol have excellent binding activity with main targets.

Conclusions

This study comprehensively illuminated the active ingredients, potential targets, primary pharmacological effects, and relevant mechanisms of the DXHP in the treatment of OA. These findings provide fresh thoughts into the therapeutic mechanisms of the main active ingredients of DXHP and provide a reference for further exploration and clinical applications of DXHP.

Healthy and Osteoarthritis-Affected Joints Facing the Cellular Crosstalk

Osteoarthritis (OA) is a chronic, progressive, severely debilitating, and multifactorial joint disease that is recognized as the most common type of arthritis. During the last decade, it shows an incremental global rise in prevalence and incidence. The interaction between etiologic factors that mediate joint degradation has been explored in numerous studies. However, the underlying processes that induce OA remain obscure, largely due to the variety and complexity of these mechanisms. During synovial joint dysfunction, the osteochondral unit undergoes cellular phenotypic and functional alterations. At the cellular level, the synovial membrane is influenced by cartilage and subchondral bone cleavage fragments and extracellular matrix (ECM) degradation products from apoptotic and necrotic cells. These "foreign bodies" serve as danger-associated molecular patterns (DAMPs) that trigger innate immunity, eliciting and sustaining low-grade inflammation in the synovium. In this review, we explore the cellular and molecular communication networks established between the major joint compartments-the synovial membrane, cartilage, and subchondral bone of normal and OA-affected joints.

Identification and validation of hub genes and potential drugs involved in osteoarthritis through bioinformatics analysis

Purpose: Osteoarthritis (OA) is a common degenerative disease, which still lacks specific therapeutic drugs. Synovitis is one of the most important pathological process in OA. Therefore, we aim to identify and analyze the hub genes and their related networks of OA synovium with bioinformatics tools to provide theoretical basis for potential drugs. Materials and methods: Two datasets were obtained from GEO. DEGs and hub genes of OA synovial tissue were screened through Gene Ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment as well as protein-protein interaction (PPI) network analysis. Subsequently, the correlation between expression of hub genes and ferroptosis or pyroptosis was analyzed. CeRNA regulatory network was constructed after predicting the upstream miRNAs and lncRNAs. The validation of hub genes was undertook through RT-qPCR and ELISA. Finally, potential drugs targeting pathways and hub genes were identified, followed by the validation of the effect of two potential drugs on OA. Results: A total of 161 commom DEGs were obtained, of which 8 genes were finally identified as hub genes through GO and KEGG enrichment analysis as well as PPI network analysis. Eight genes related to ferroptosis and pyroptosis respectively were significantly correlated to the expression of hub genes. 24 miRNAs and 69 lncRNAs were identified to construct the ceRNA regulatory network. The validation of EGR1, JUN, MYC, FOSL1, and FOSL2 met the trend of bioinformatics analysis. Etanercept and Iguratimod reduced the secretion of MMP-13 and ADAMTS5 of fibroblast-like synoviocyte. Conclusion: EGR1, JUN, MYC, FOSL1, and FOSL2 were identified as hub genes in the development of OA after series of bioinformatics analysis and validation. Etanercept and Iguratimod seemed to have opportunities to be novel drugs for OA.

Implication of Cellular Senescence in Osteoarthritis: A Study on Equine Synovial Fluid Mesenchymal Stromal Cells

Osteoarthritis (OA) is described as a chronic degenerative disease characterized by the loss of articular cartilage. Senescence is a natural cellular response to stressors. Beneficial in certain conditions, the accumulation of senescent cells has been implicated in the pathophysiology of many diseases associated with aging. Recently, it has been demonstrated that mesenchymal stem/stromal cells isolated from OA patients contain many senescent cells that inhibit cartilage regeneration. However, the link between cellular senescence in MSCs and OA progression is still debated. In this study, we aim to characterize and compare synovial fluid MSCs (sf-MSCs), isolated from OA joints, with healthy sf-MSCs, investigating the senescence hallmarks and how this state could affect cartilage repair. Sf-MSCs were isolated from tibiotarsal joints of healthy and diseased horses with an established diagnosis of OA with an age ranging from 8 to 14 years. Cells were cultured in vitro and characterized for cell proliferation assay, cell cycle analysis, ROS detection assay, ultrastructure analysis, and the expression of senescent markers. To evaluate the influence of senescence on chondrogenic differentiation, OA sf-MSCs were stimulated in vitro for up to 21 days with chondrogenic factors, and the expression of chondrogenic markers was compared with healthy sf-MSCs. Our findings demonstrated the presence of senescent sf-MSCs in OA joints with impaired chondrogenic differentiation abilities, which could have a potential influence on OA progression.

Biological Functions of Selenoprotein Glutathione Peroxidases (GPXs) and their Expression in Osteoarthritis

Purpose

In order to further study the biological functions of glutathione peroxidases (GPXs) and their expression level in patients with osteoarthritis (OA), we fully explored the potential relationship between GPXs and OA. This will provide new ideas for basic biological studies and therapeutic strategies for OA patients.

Patients and Methods

In this study, bioinformatics techniques were used to explore the biological functions of five GPXs. The core genes related to the biological functions of GPXs were identified by constructing a protein-protein interaction network (PPI). In addition, we utilized microarray data in public databases to analyze the expression levels of GPXs in OA patients and healthy controls. Finally, we used quantitative real-time polymerase chain reaction (qRT-PCR) to detect the expression of GPXs in OA patients and controls to validate our bioinformatic analysis results.

Results

Enrichment analysis showed GPXs were mainly enriched in the glutathione metabolic pathway and participate in the biological process of oxidative stress response, and further play an antioxidant role. The PPI network indicated that superoxide dismutase 1 (SOD1), superoxide dismutase 2(SOD2) and catalase (CAT) were the core proteins of this network. GPX1 was regulated by the greatest number of miRNAs. Experiments showed that the expression of GPX1 was elevated in OA patients compared with controls.

Conclusion

GPXs play an important antioxidant role in oxidative stress response. The expression of GPX1 was elevated in peripheral blood mononuclear cells (PBMCs) of OA patients. The changes of GPXs in OA patients may regulate the level of oxidative stress, which may influence synovial lesions and chondrocyte apoptosis.

Resveratrol Improves the Progression of Osteoarthritis by Regulating the SIRT1-FoxO1 Pathway-Mediated Cholesterol Metabolism

Osteoarthritis (OA) is considered a metabolic disorder. This study investigated the effect of resveratrol (RES) on cholesterol accumulation in osteoarthritic articular cartilage via the silent information regulator 1 (SIRT1)/forkhead transcription factor (FoxO1) pathway. Interleukin (IL)-1β-treated chondrocytes that mimic OA chondrocytes were used in in vitro experiments. The optimal RES concentration was selected based on the results of chondrocyte proliferation in the Cell Counting Kit-8 assay. Western blotting, immunofluorescence, and reverse transcription-quantitative polymerase chain reaction were performed. For the animal experiments, mice were randomly divided into the RES group (n = 15), medial meniscus destabilization group (n = 15), and sham group (n = 15), and each group received the same dose of RES or saline. Articular cartilage tissue was obtained eight weeks after surgery for relevant histological analysis. Clinical tissue test results suggest that downregulation of the SIRT1/FoxO1 pathway is associated with cholesterol buildup in OA chondrocytes. For the in vitro studies, RES increased the expression of SIRT1 and phosphorylation of FoxO1 in IL-1β-treated chondrocytes, promoted the expression of cholesterol efflux factor liver X receptor alpha (LXRα), and inhibited the expression of cholesterol synthesis-associated factor sterol-regulatory element binding proteins 2 (SREBP2). This reduced IL-1β-induced chondrocytes cholesterol accumulation. SIRT1 inhibition prevented the RES-mediated reduction in cholesterol buildup. Inhibiting FoxO1 but not SIRT1 reduced FoxO1 phosphorylation and increased cholesterol buildup in cultured chondrocytes. Additionally, in vivo experiments have shown that RES can alleviate cholesterol buildup and pathological changes in OA cartilage. Our findings suggest that RES regulates cholesterol buildup in osteoarthritic articular cartilage via the SIRT1/FoxO1 pathway, thereby improving the progression of OA.

Phenotypic and functional characterisation of synovial fluid-derived neutrophils in knee osteoarthritis and knee infection

OBJECTIVE

An increase in the number of neutrophils (NEUs) has long been associated with infections in the knee joints; however, their impact on knee osteoarthritis (KOA) pathophysiology remains largely unexplored.

DESIGN

This study compared the phenotypic and functional characteristics of synovial fluid (SF)-derived NEUs in KOA and knee infection (INF).

RESULTS

KOA NEUs were characterised by a lower expression of CD11b, CD54, and CD64 and higher expression of CD62L, TLR2, and TLR4 compared with INF NEUs. Except for CCL2, lower levels of inflammatory mediators and proteases were detected in KOA SF than in INF SF. Functionally, KOA NEUs displayed increased reactive oxygen species production and phagocytic activity compared with INF NEUs. Moreover, KOA and INF NEUs differed in cell sizes, histological characteristics of the surrounding synovial tissues, and their effects on the endothelial cells assessed by human umbilical vein endothelial cells. When KOA patients were subdivided based on the SF NEU abundance, patients with high NEUs (10%-60%) were characterised by i) elevated SF protein levels of TNF-α, IL-1RA, MMP-9, sTREM-1, VILIP-1 and ii) lower CD54, CD64, TLR2 and TLR4 expression compared to patients with low NEUs (<10%). Analysis of paired SF samples suggests that low or high NEU percentages, respectively, persist throughout the course of disease.

CONCLUSIONS

Our findings suggest that NEU may play a significant role in KOA pathophysiology. Further studies should explore the mechanisms that contribute to the increased number of NEUs in SF and the clinical consequences of neutrophilic phenotype in KOA.

The protective activity of natural flavonoids against osteoarthritis by targeting NF-κB signaling pathway

Osteoarthritis (OA) is a typical joint disease associated with chronic inflammation. The nuclear factor-kappaB (NF-κB) pathway plays an important role in inflammatory activity and inhibiting NF-κB-mediated inflammation can be a potential strategy for treating OA. Flavonoids are a class of naturally occurring polyphenols with anti-inflammatory properties. Structurally, natural flavonoids can be divided into several sub-groups, including flavonols, flavones, flavanols/catechins, flavanones, anthocyanins, and isoflavones. Increasing evidence demonstrates that natural flavonoids exhibit protective activity against the pathological changes of OA by inhibiting the NF-κB signaling pathway. Potentially, natural flavonoids may suppress NF-κB signaling-mediated inflammatory responses, ECM degradation, and chondrocyte apoptosis. The different biological actions of natural flavonoids against the NF-κB signaling pathway in OA chondrocytes might be associated with the differentially substituted groups on the structures. In this review, the efficacy and action mechanism of natural flavonoids against the development of OA are discussed by targeting the NF-κB signaling pathway. Potentially, flavonoids could become useful inhibitors of the NF-κB signaling pathway for the therapeutic management of OA.

Synovial Fluid in Knee Osteoarthritis Extends Proinflammatory Niche for Macrophage Polarization

Macrophage polarization is a steering factor of osteoarthritis (OA) progression. Synovial fluid (SF) obtained from OA patients with different Kellgren-Lawrence grades (KL grades) holds several proinflammatory factors and was hypothesized to induce macrophage differentiation and polarization by providing the needed microenvironment. U937 cells and peripheral-blood-mononuclear-cell-derived monocytes (PBMC-derived CD14+ cells) were induced with SFs of progressive KL grades for 48 h, and the status of the differentiated cells was evaluated by cell surface markers representing M1 and M2 macrophage phenotypes. Functional viability assessment of the differentiated cells was performed by cytokine estimation. The fraction of macrophages and their phenotypes were estimated by immunophenotyping of SF-isolated cells of different KL grades. A grade-wise proteome analysis of SFs was performed in search of the factors which are influential in macrophage differentiation and polarization. In the assay on U937 cells, induction with SF of KL grade III and IV showed a significant increase in M1 type (CD86+). The percentage of M2 phenotype (CD163+) was significantly higher after the induction with SF of KL grade II. A Significantly higher M1/M2 ratio was estimated in the cells induced with KL grade III and IV. The cell differentiation pattern in the assay on PBMC-derived CD14+ cells showed a grade-wise decline in both M1 (CD11C+, CD86+) and M2 phenotype (CD163+). Cytokine estimation specific to M1 (TNF-α, IL-6, IL-1β, IFN-γ) and M2 (IL-4 and IL-10) macrophages corelated with the differentiation pattern in the U937 cell assay, while it did not reveal any significant changes in the PBMC-derived CD14+ cells assay. SF cells' immunophenotyping showed the highest percentage of CD14+ macrophages in KL grade II; CD86+ and CD163+ cells were minimal in all KL grades' SFs. The proteome analysis revealed significantly expressed MIF, CAPG/MCP, osteopontin, and RAS-related RAB proteins in KL grade III and IV samples, which are linked with macrophages' movement, polarization, and migration-behavior. In conclusion, this study demonstrated that SF in OA joints acts as a niche and facilitates M1 phenotype polarization by providing a proinflammatory microenvironment.

Osteoarthritis: New Insight on Its Pathophysiology

Understanding of the basis of osteoarthritis (OA) has seen some interesting advancements in recent years. It has been observed that cartilage degeneration is preceded by subchondral bone lesions, suggesting a key role of this mechanism within the pathogenesis and progression of OA, as well as the formation of ectopic bone and osteophytes. Moreover, low-grade, chronic inflammation of the synovial lining has gained a central role in the definition of OA physiopathology, and central immunological mechanisms, innate but also adaptive, are now considered crucial in driving inflammation and tissue destruction. In addition, the role of neuroinflammation and central sensitization mechanisms as underlying causes of pain chronicity has been characterized. This has led to a renewed definition of OA, which is now intended as a complex multifactorial joint pathology caused by inflammatory and metabolic factors underlying joint damage. Since this evidence can directly affect the definition of the correct therapeutic approach to OA, an improved understanding of these pathophysiological mechanisms is fundamental. To this aim, this review provides an overview of the most updated evidence on OA pathogenesis; it presents the most recent insights on the pathophysiology of OA, describing the interplay between immunological and biochemical mechanisms proposed to drive inflammation and tissue destruction, as well as central sensitization mechanisms. Moreover, although the therapeutic implications consequent to the renewed definition of OA are beyond this review scope, some suggestions for intervention have been addressed.

Innovative immune mechanisms and antioxidative therapies of intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the basic pathological process of many degenerative diseases of the spine, characterized by series of symptoms, among which low back pain (LBP) is the most common symptom that patients suffer a lot, which not only makes patients and individual families bear a huge pain and psychological burden, but also consumes a lot of medical resources. IDD is usually thought to be relevant with various factors such as genetic predisposition, trauma and aging, and IDD progression is tightly relevant with structural and functional alterations. IDD processes are caused by series of pathological processes, including oxidative stress, matrix decomposition, inflammatory reaction, apoptosis, abnormal proliferation, cell senescence, autophagy as well as sepsis process, among which the oxidative stress and inflammatory response are considered as key link in IDD. The production and clearance of ROS are tightly connected with oxidative stress, which would further simulate various signaling pathways. The phenotype of disc cells could change from matrix anabolism-to matrix catabolism- and proinflammatory-phenotype during IDD. Recent decades, with the relevant reports about oxidative stress and inflammatory response in IDD increasing gradually, the mechanisms researches have attracted much more attention. Consequently, this study focused on the indispensable roles of the oxidative stress and inflammatory response (especially macrophages and cytokines) to illustrate the origin, development, and deterioration of IDD, aiming to provide novel insights in the molecular mechanisms as well as significant clinical values for IDD.

Mitophagy—A New Target of Bone Disease

Bone diseases are usually caused by abnormal metabolism and death of cells in bones, including osteoblasts, osteoclasts, osteocytes, chondrocytes, and bone marrow mesenchymal stem cells. Mitochondrial dysfunction, as an important cause of abnormal cell metabolism, is widely involved in the occurrence and progression of multiple bone diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis, and osteosarcoma. As selective mitochondrial autophagy for damaged or dysfunctional mitochondria, mitophagy is closely related to mitochondrial quality control and homeostasis. Accumulating evidence suggests that mitophagy plays an important regulatory role in bone disease, indicating that regulating the level of mitophagy may be a new strategy for bone-related diseases. Therefore, by reviewing the relevant literature in recent years, this paper reviews the potential mechanism of mitophagy in bone-related diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis, and osteosarcoma, to provide a theoretical basis for the related research of mitophagy in bone diseases.

A discovery of clinically approved Panlongqi Tablet for repositioning to treat osteoarthritis by inhibiting PI3K/AKT activation

BACKGROUND

Panlongqi Tablet (PLQT) is a Chinese patent drug composed of 29 kinds of traditional Chinese medicines. Clinical practice has shown that PLQT can relieve osteoarthritis-caused joint pain, but its effects and mechanisms in other pathological links of osteoarthritis have not been characterized.

PURPOSE

The purpose of this study is to reposition the pharmacodynamic effects of PLQT through network pharmacology analysis combined with experimental validation, and also to preliminarily explore its possible mechanism.

METHODS

On the basis of integrating the relevant targets of PLQT in multiple drug databases and osteoarthritis-related targets in the disease database, an interaction network of related genes was constructed. The hub candidate targets of PLQT in the treatment of osteoarthritis were determined by calculating the main network topological characteristics, The specific functions and pathways of these targets acting on osteoarthritis were modularly analyzed. In addition, the modified Hulth-induced rat model of osteoarthritis and IL-1β-induced in vitro model of osteoarthritis were established to further validate the potential efficacy and possible mechanism of PLQT.

RESULTS

A total of 138 key targets related to osteoarthritis were selected based on topological parameters, and their biological functions were mainly enriched in four over-expressed modules of cartilage degeneration, inflammatory response, immune response, and subchondral bone metabolism. The hub candidate targets had the highest enrichment degree in the TLR4-RAC1-PIK3CA-Akt-NFκB signaling axis of the PI3K/Akt signaling pathway. In vivo results showed that PLQT treatment significantly inhibited the degeneration of proteoglycan and collagen in the cartilage of osteoarthritis rats, suppressed chondrocyte apoptosis, and reduced the Mankin score of joints. Moreover, PLQT alleviated synovial inflammation, reduced the Krenn score of synovium, inhibited the formation of osteophytes in osteoarthritis rats, reduced the bone mineral density (BMD), fractional bone volume (BV/TV), and trabecular thickness (Tb.Th.), as well as increased the trabecular separation (Tb.Sp.) of subchondral bone and the thickness of the subchondral bone plate (SBP.Th.). PLQT suppressed the expressions of TLR4, RAC1, PIK3CA, p-Akt, MMP-13, and ADAMTS-5 in the cartilage, and inhibited the expression of NFκB p65 in the chondrogenic nucleus. Meanwhile, as downstream effector factors of the predictive pathways, the levels of serum interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), nitric oxide (NO), and prostaglandin E₂ (PGE₂) were decreased after PLQT treatment. In vitro results also showed that PLQT could inhibit the expression of key proteins and downstream effector factors of the signaling axis, and this inhibition disappeared when pathway agonists were added.

CONCLUSION

PLQT exerted pharmacological effects on the key pathological links of osteoarthritis including chondrocyte apoptosis, extracellular matrix degradation, inflammation, and subchondral bone metabolism by inhibiting the TLR4-RAC1-PIK3CA-Akt-NFκB axis-related proteins.

Medicinal plants and their secondary metabolites in alleviating knee osteoarthritis: A systematic review

BACKGROUND

With the increasing ages of the general population, the incidence of knee osteoarthritis (KOA) is also rising, and KOA has become a major health problem worldwide. Recently, medicinal plants and their secondary metabolites have gained interest due to their activity in treating KOA. In this paper, a comprehensive systematic review of the literature was performed concerning the effects of medicinal plant extracts and natural compounds against KOA in recent years. The related molecular pathways of natural compounds against KOA were summarized, and the possible crosstalk among components in chondrocytes was discussed to propose possible solutions for the current situation of treating KOA.

PURPOSE

This review focused on the molecular mechanisms by which medicinal plants and their secondary metabolites act against KOA.

METHODS

Literature searches were performed in the PUBMED, Embase, Science Direct, and Web of Science databases for a 10-year period from 2011 to 2022 with the search terms "medicinal plants," "bioactive compounds," "natural products," "phytochemical," "knee osteoarthritis," "knee joint osteoarthritis," "knee osteoarthritis," "osteoarthritis of the knee," and "osteoarthritis of knee joint."

RESULTS

According to the results, substantial plant extracts and secondary metabolites show a positive effect in fighting KOA. Plant extracts and their secondary metabolites can affect the diagnostic and prognostic biomarkers of KOA. Natural products inhibit the expression of MMP1, MMP3, MMP19, syndecan IV, ADAMTS-4, ADAMTS-5, iNOS, COX-2, collagenases, IL-6, IL-1β, and TNF-α in vitro and in vivo and . Cytokines also upregulate the expression of collagen II and aggrecan. The main signaling pathways affected by the extracts and isolated compounds include AMPK, SIRT, NLRP3, MAPKs, PI3K/AKT, mTOR, NF-κB, WNT/β-catenin, JAK/STAT3, and NRF2, as well as the cell death modes apoptosis, autophagy, pyroptosis, and ferroptosis.

CONCLUSION

The role of secondary metabolites in different signaling pathways supplies a better understanding of their potential to develop further curative options for KOA.

Nanoarchitectonics of Cartilage-Targeting Hydrogel Microspheres with Reactive Oxygen Species Responsiveness for the Repair of Osteoarthritis

Clinically, intra-articular administration can hardly achieve the truly targeted therapy, and the drugs are usually insufficient to show local and long-term therapeutic effects because of their rapid clearance. Herein, inspired by the phenomenon that bees track the scent of flowers to collect nectar, we developed cartilage-targeting hydrogel microspheres with reactive oxygen species (ROS)-responsive ability via combining the microfluidic method and photopolymerization processes to integrate cartilage-targeting peptides and ROS-responsive nanoparticles in the hydrogel matrix. The hydrogel microspheres with cartilage-targeting properties promoted better retention in the joint cavity and enhanced cellular uptake of the nanoparticles. Moreover, the ROS-responsive nanoparticles could react with osteoarthritis (OA)-induced intracellular ROS, resulting in the depolymerization of nanoparticles, which could not only eliminate excess ROS and reduce inflammation but also promote the release of dexamethasone (Dex) and kartogenin (KGN) in situ, realizing effective OA therapy. It was demonstrated that this hydrogel microsphere showed favorable ROS-responsive ability and enhanced chondrogenic differentiation as well as the downregulation of pro-inflammatory factors in vitro. Additionally, the hydrogel microspheres, similar to bees, could target and effectively repair cartilage in the OA model. Thus, the injectable hydrogel microspheres exerted an excellent potential to repair OA and may also provide an effective avenue for inflammatory bowel disease therapy.

The Nrf2 antioxidant defense system in intervertebral disc degeneration: Molecular insights

Intervertebral disc degeneration (IDD) is a common degenerative musculoskeletal disorder and is recognized as a major contributor to discogenic lower back pain. However, the molecular mechanisms underlying IDD remain unclear, and therapeutic strategies for IDD are currently limited. Oxidative stress plays pivotal roles in the pathogenesis and progression of many age-related diseases in humans, including IDD. Nuclear factor E2-related factor 2 (Nrf2) is a master antioxidant transcription factor that protects cells against oxidative stress damage. Nrf2 is negatively modulated by Kelch-like ECH-associated protein 1 (Keap1) and exerts important effects on IDD progression. Accumulating evidence has revealed that Nrf2 can facilitate the transcription of downstream antioxidant genes in disc cells by binding to antioxidant response elements (AREs) in promoter regions, including heme oxygenase-1 (HO-1), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and NADPH quinone dehydrogenase 1 (NQO1). The Nrf2 antioxidant defense system regulates cell apoptosis, senescence, extracellular matrix (ECM) metabolism, the inflammatory response of the nucleus pulposus (NP), and calcification of the cartilaginous endplates (EP) in IDD. In this review, we aim to discuss the current knowledge on the roles of Nrf2 in IDD systematically.

Insights into the activity of a protein that regulates gene expression and protects cells against oxidative stress could yield novel treatments for lower back pain. Intervertebral disc degeneration (IDD) is a common cause of lower back pain, but the molecular mechanisms underlying IDD are unclear, meaning treatment options are limited. Oxidative stress is implicated in IDD, and scientists have begun exploring the role of nuclear factor E2-related factor 2 (Nrf2), a master regulator of the body’s antioxidant responses, in regulating IDD progression. In a review of recent research, Weishi Li at Peking University Third Hospital, Beijing, China, and co-workers point out that boosting the activity of Nrf2-related signaling pathways alleviates oxidative stress in intervertebral disc cells. The researchers suggest that therapies based on non-coding RNAs may prove valuable in activating Nrf2 in IDD patients.

HIF-1α in Osteoarthritis: From Pathogenesis to Therapeutic Implications

Osteoarthritis is a common age-related joint degenerative disease. Pain, swelling, brief morning stiffness, and functional limitations are its main characteristics. There are still no well-established strategies to cure osteoarthritis. Therefore, better clarification of mechanisms associated with the onset and progression of osteoarthritis is critical to provide a theoretical basis for the establishment of novel preventive and therapeutic strategies. Chondrocytes exist in a hypoxic environment, and HIF-1α plays a vital role in regulating hypoxic response. HIF-1α responds to cellular oxygenation decreases in tissue regulating survival and growth arrest of chondrocytes. The activation of HIF-1α could regulate autophagy and apoptosis of chondrocytes, decrease inflammatory cytokine synthesis, and regulate the chondrocyte extracellular matrix environment. Moreover, it could maintain the chondrogenic phenotype that regulates glycolysis and the mitochondrial function of osteoarthritis, resulting in a denser collagen matrix that delays cartilage degradation. Thus, HIF-1α is likely to be a crucial therapeutic target for osteoarthritis via regulating chondrocyte inflammation and metabolism. In this review, we summarize the mechanism of hypoxia in the pathogenic mechanisms of osteoarthritis, and focus on a series of therapeutic treatments targeting HIF-1α for osteoarthritis. Further clarification of the regulatory mechanisms of HIF-1α in osteoarthritis may provide more useful clues to developing novel osteoarthritis treatment strategies.

Intra-Articular Injection of Adipose-Derived Stem Cells Ameliorates Pain and Cartilage Anabolism/Catabolism in Osteoarthritis: Preclinical and Clinical Evidences

Background: Osteoarthritis (OA) is the most common joint disorder, lacking disease-modifying treatments. Adipose-derived mesenchymal stem cells (ADSCs) are adult multipotent stromal cells obtained from fat tissue, which holds great potential in treating OA. This study aimed to evaluate the anti-OA efficacy of ADSCs from preclinical and clinical facets and explore the underlying mechanism of action.

Methods:In vivo, a single dose of 5 × 10⁵ ADSCs was injected into the knee joints of monoiodoacetate-induced OA rat model. The levels of metabolic and hypertrophic molecules (MMP13, Collagen II, Collagen X) of chondrocytes were measured by immunohistochemistry. In vitro, cell viability assay was conducted to detect the proliferation ability of chondrocytes treated with ADSCs conditioned medium (ADSCs-CM). Quantitative real-time polymerase chain reaction and Western blot assays were applied to explore the mechanism of action of ADSCs. Moreover, a retrospective analysis was conducted to determine the clinical efficacy and safety of ADSCs on OA patients.

Results: The animal study showed that ADSCs significantly alleviated OA cartilage lesions in rats, as was confirmed by downregulation of the MMP13 and Collagen X and upregulation of the Collagen II. In vitro data showed that ADSCs-CM promoted the proliferation of chondrocytes, and significantly restored the IL-1β-induced abnormal expressions of molecular markers IL-6, Aggrecan, MMP3, MMP13, Collagen II, Collagen X, ADAMTS5, ADAMTS9, SOX6, and SOX9 in chondrocytes. Such regulatory effects of ADSCs-CM on the proliferation and these anabolic, catabolic, and hypertrophic markers of chondrocytes suggested a paracrine-based mode of action of ADSCs. Furthermore, the clinical data showed that ADSCs reduced pain and repaired cartilage damage in OA patients, with no adverse events.

Conclusion: This study demonstrated the anti-OA efficacy, safety, and a paracrine-based mechanism of ADSCs, providing a promising cell-based therapeutic option for OA treatment.

The immune microenvironment in cartilage injury and repair

The ability of articular cartilage to repair itself is limited because it lacks blood vessels, nerves, and lymph tissue. Once damaged, it can lead to joint swelling and pain, accelerating the progression of osteoarthritis. To date, complete regeneration of hyaline cartilage exhibiting mechanical properties remains an elusive goal, despite the many available technologies. The inflammatory milieu created by cartilage damage is critical for chondrocyte death and hypertrophy, extracellular matrix breakdown, ectopic bone formation, and progression of cartilage injury to osteoarthritis. In the inflammatory microenvironment, mesenchymal stem cells (MSCs) undergo aberrant differentiation, and chondrocytes begin to convert or dedifferentiate into cells with a fibroblast phenotype, thereby resulting in fibrocartilage with poor mechanical qualities. All these factors suggest that inflammatory problems may be a major stumbling block to cartilage repair. To produce a milieu conducive to cartilage repair, multi-dimensional management of the joint inflammatory microenvironment in place and time is required. Therefore, this calls for elucidation of the immune microenvironment of cartilage repair after injury. This review provides a brief overview of: (1) the pathogenesis of cartilage injury; (2) immune cells in cartilage injury and repair; (3) effects of inflammatory cytokines on cartilage repair; (4) clinical strategies for treating cartilage defects; and (5) strategies for targeted immunoregulation in cartilage repair. STATEMENT OF SIGNIFICANCE: Immune response is increasingly considered the key factor affecting cartilage repair. It has both negative and positive regulatory effects on the process of regeneration and repair. Proinflammatory factors are secreted in large numbers, and necrotic cartilage is removed. During the repair period, immune cells can secrete anti-inflammatory factors and chondrogenic cytokines, which can inhibit inflammation and promote cartilage repair. However, inflammatory factors persist, which accelerate the degradation of the cartilage matrix. Furthermore, in an inflammatory microenvironment, MSCs undergo abnormal differentiation, and chondrocytes begin to transform or dedifferentiate into fibroblast-like cells, forming fibrocartilage with poor mechanical properties. Consequently, cartilage regeneration requires multi-dimensional regulation of the joint inflammatory microenvironment in space and time to make it conducive to cartilage regeneration.

Mast Cells Differentiated in Synovial Fluid and Resident in Osteophytes Exalt the Inflammatory Pathology of Osteoarthritis

Introduction: Osteophytes are a prominent feature of osteoarthritis (OA) joints and one of the clinical hallmarks of the disease progression. Research on osteophytes is fragmentary and modes of its contribution to OA pathology are obscure. Aim: To elucidate the role of osteophytes in OA pathology from a perspective of molecular and cellular events. Methods: RNA-seq of fully grown osteophytes, collected from tibial plateau of six OA patients revealed patterns corresponding to active extracellular matrix re-modulation and prominent participation of mast cells. Presence of mast cells was further confirmed by immunohistochemistry, performed on the sections of the osteophytes using anti-tryptase alpha/beta-1 and anti-FC epsilon RI antibodies and the related key up-regulated genes were validated by qRT-PCR. To test the role of OA synovial fluid (SF) in mast cell maturation as proposed by the authors, hematopoietic stem cells (HSCs) and ThP1 cells were cultured in a media supplemented with 10% SF samples, obtained from various grades of OA patients and were monitored using specific cell surface markers by flow cytometry. Proteomics analysis of SF samples was performed to detect additional markers specific to mast cells and inflammation that drive the cell differentiation and maturation. Results: Transcriptomics of osteophytes revealed a significant upregulation of mast cells specific genes such as chymase 1 (CMA1; 5-fold) carboxypeptidase A3 (CPA3; 4-fold), MS4A2/FCERI (FCERI; 4.2-fold) and interleukin 1 receptor-like 1 (IL1RL1; 2.5-fold) indicating their prominent involvement. (In IHC, anti-tryptase alpha/beta-1 and anti- FC epsilon RI-stained active mast cells were seen populated in cartilage, subchondral bone, and trabecular bone.) Based on these outcomes and previous learnings, the authors claim a possibility of mast cells invasion into osteophytes is mediated by SF and present in vitro cell differentiation assay results, wherein ThP1 and HSCs showed differentiation into HLA-DR+/CD206+ and FCERI+ phenotype, respectively, after exposing them to medium containing 10% SF for 9 days. Proteomics analysis of these SF samples showed an accumulation of mast cell-specific inflammatory proteins. Conclusions: RNA-seq analysis followed by IHC study on osteophyte samples showed a population of mast cells resident in them and may further accentuate inflammatory pathology of OA. Besides subchondral bone, the authors propose an alternative passage of mast cells invasion in osteophytes, wherein OA SF was found to be necessary and sufficient for maturation of mast cell precursor into effector cells.

Identification of transcription factors and construction of a novel miRNA regulatory network in primary osteoarthritis by integrated analysis

Backgrounds

As osteoarthritis (OA) disease-modifying therapies are not available, novel therapeutic targets need to be discovered and prioritized. Here, we aim to identify miRNA signatures in patients to fully elucidate regulatory mechanism of OA pathogenesis and advance in basic understanding of the genetic etiology of OA.

Methods

Six participants (3 OA and 3 controls) were recruited and serum samples were assayed through RNA sequencing (RNA-seq). And, RNA-seq dataset was analysed to identify genes, pathways and regulatory networks dysregulated in OA. The overlapped differentially expressed microRNAs (DEMs) were further screened in combination with the microarray dataset GSE143514. The expression levels of candidate miRNAs were further validated by quantitative real-time PCR (qRT-PCR) based on the GEO dataset (GSE114007).

Results

Serum samples were sequenced interrogating 382 miRNAs. After screening of independent samples and GEO database, the two comparison datasets shared 19 overlapped candidate micRNAs. Of these, 9 up-regulated DEMs and 10 down-regulated DEMs were detected, respectively. There were 236 target genes for up-regulated DEMs and 400 target genes for those down-regulated DEMs. For up-regulated DEMs, the top 10 hub genes were KRAS, NRAS, CDC42, GDNF, SOS1, PIK3R3, GSK3B, IRS2, GNG12, and PRKCA; for down-regulated DEMs, the top 10 hub genes were NR3C1, PPARGC1A, SUMO1, MEF2C, FOXO3, PPP1CB, MAP2K1, RARA, RHOC, CDC23, and CREB3L2. Mir-584-5p-KRAS, mir-183-5p-NRAS, mir-4435-PIK3R3, and mir-4435-SOS1 were identified as four potential regulatory pathways by integrated analysis.

Conclusions

We have integrated differential expression data to reveal putative genes and detected four potential miRNA-target gene pathways through bioinformatics analysis that represent new mediators of abnormal gene expression and promising therapeutic targets in OA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04894-2.

IL-38-mediated NLRP3/caspase-1 inhibition is a disease-modifying treatment for TMJ inflammation

Recently, interleukin-38 (IL-38) was identified as an important anti-inflammatory and immunosuppressive factor, but its functional role in temporomandibular joint (TMJ) inflammation remains unknown. This study aimed to elucidate how IL-38 affects chondrocytes and the underlying mechanism that contributes to anti-inflammatory processes in the TMJ. Western blotting, quantitative real-time PCR, enzyme-linked immunosorbent assay, and immunofluorescence analysis were used to verify that IL-38 has anti-inflammatory effects on chondrocytes, and the related key pathways were analyzed by western blotting. SiRNA-IL-38, siRNA-NLRP3, and MCC950 were used to investigate the mechanism underlying the anti-inflammatory effects of IL-38. Inflammation models were induced by injection of complete Freund's adjuvant in TMJ with mouse recombinant IL-38 in in vivo studies. Histological and immunohistochemical analyses were used to investigate histological changes in the cartilage. The results showed that IL-38 inhibited the expression of inflammatory cytokines and MMPs. IL-38 limited inflammation by inhibiting the expression of MAPKs/NF-κB and the NLRP3/caspase-1 pathway. In vivo, IL-38 reduced chondrocyte inflammation and limited cartilage degeneration. This study shows for the first time that IL-38 plays a protective role in TMJ cartilage. IL-38 exerts anti-inflammatory effects through the NLRP3/caspase-1 pathway and may be a promising agent for treating TMJ inflammation.

Synovium-Synovial Fluid Axis in Osteoarthritis Pathology: A Key Regulator of the Cartilage Degradation Process

Failure of conventional anti-inflammatory therapies in osteoarthritis (OA) underlines the insufficient knowledge about inflammatory mechanisms, patterns and their relationship with cartilage degradation. Considering non-linear nature of cartilage loss in OA, a better understanding of inflammatory milieu and MMP status at different stages of OA is required to design early-stage therapies or personalized disease management. For this, an investigation based on a synovium-synovial fluid (SF) axis was planned to study OA associated changes in synovium and SF along the progressive grades of OA. Gene expressions in synovial-biopsies from different grades OA patients (N = 26) revealed a peak of IL-1β, IL-15, PGE2 and NGF in early OA (Kellgren-Lawrence (KL) grade-I and II); the highest MMP levels were found in advanced stages (KL grade-III and IV). MMPs (MMP-1, 13, 2 and 9) abundance and FALGPA activity estimated in forty SFs of progressive grades showed the maximum protein levels and activity in KL grade-II and III. In an SF challenge test, SW982 and THP1 cells were treated with progressive grade SFs to study the dynamics of MMPs modulation in inflammatory microenvironment; the test yielded a result pattern, which matched with FALGPA and the protein-levels estimation. Inflammatory mediators in SFs served as steering factor for MMP up-regulation. A correlation-matrix of IL-1β and MMPs revealed expressional negative correlation.

MicroRNA-10a-3p Improves Cartilage Degeneration by Regulating CH25H-CYP7B1-RORα Mediated Cholesterol Metabolism in Knee Osteoarthritis Rats

Osteoarthritis (OA) is a worldwide degenerative joint disease that seriously impaired the quality of life of patients. OA has been established as a disease with metabolic disorder. Cholesterol 25-hydroxylase (CH25H) was proved to play a key role in cartilage cholesterol metabolism. However, the biological function and mechanism of CH25H in OA remains further investigation. Growing researches have proved the vital roles of miRNAs in OA progression. In this study, we screened out miR-10a-3p through high-throughput miRNA sequencing which may bind to CH25H. Molecular mechanism investigation indicated that miR-10a-3p is an upstream target of CH25H. Functional exploration revealed miR-10a-3p suppressed the inflammatory responses, cholesterol metabolism and extracellular matrix (ECM) degradation in primary chondrocytes. Moreover, rescue assays implied that miR-10a-3p reversed CH25H plasmids induced inflammatory cytokine production and ECM degradation. Furthermore, the OA rat model was established to explore the function of miR-10a-3p in vivo. The results showed that miR-10a-3p can recover the OA features through targeting CH25H/CYP7B1/RORα axis. In conclusion, these findings implied a crucial role of miR-10a-3p/CH25H/CYP7B1/RORα axis in OA, which may provide a promising therapeutic strategy for OA.

Dextrose prolotherapy in knee osteoarthritis: A systematic review and meta-analysis

OBJECTIVE

To summarize the evidence for dextrose prolotherapy in knee osteoarthritis.

DATA SOURCES

The authors searched PubMed and Embase from inception to September 2020. All publications in the English language were included without demographic limits.

STUDY SELECTION

Randomized clinical trials comparing the effects of any active interventions or placebo versus dextrose prolotherapy in patients with knee osteoarthritis were included.

DATA EXTRACTION

Potential articles were screened for eligibility, and data was extracted independently. The risk of bias was assessed using the Cochrane Risk of Bias tool. Meta-analysis was performed on clinical trials with similar parameters. The Strength of Recommendation Taxonomy (SORT) was used for evaluating the strength of recommendations.

DATA SYNTHESIS

In total, eleven articles (n = 837 patients) met the search criteria and were included. The risk-of-bias analysis revealed two studies to be of low risk. The overall effectiveness was calculated using a meta-analysis method. Prolotherapy was no different from platelet-rich plasma on the pain subscale at the 6-month time point. Prolotherapy was inferior to platelet-rich plasma at 6 months (MD 0.45, 95% CI 0.06-0.85, p = 0.03) on the stiffness subscale. Prolotherapy was found to be safe with no major adverse effects.

CONCLUSION

Prolotherapy in knee osteoarthritis confers potential benefits for pain but the studies are at high risk of bias. Based on two well-designed studies, dextrose prolotherapy may be considered in knee osteoarthritis (strength of recommendation B). This treatment is safe and may be considered in patients with limited alternative options (strength of recommendation C).

Mechanistic insights into AMPK-SIRT3 positive feedback loop-mediated chondrocyte mitochondrial quality control in osteoarthritis pathogenesis

Osteoarthritis (OA) is a major cause of disability in the elderly population and represents a significant public health problem and socioeconomic burden worldwide. However, no disease-modifying therapeutics are currently available for OA due to an insufficient understanding of the pathogenesis of this disability. As a unique cell type in cartilage, chondrocytes are essential for cartilage homeostasis and play a critical role in OA pathogenesis. Mitochondria are important metabolic centers in chondrocytes and contribute to cell survival, and mitochondrial quality control (MQC) is an emerging mechanism for maintaining cell homeostasis. An increasing number of recent studies have demonstrated that dysregulation of the key processes of chondrocyte MQC, which involve mitochondrial redox, biogenesis, dynamics, and mitophagy, is associated with OA pathogenesis and can be regulated by the chondroprotective molecules 5' adenosine monophosphate-activated protein kinase (AMPK) and sirtuin 3 (SIRT3). Moreover, AMPK and SIRT3 regulate each other, and their expression and activity are always consistent in chondrocytes, which suggests the existence of an AMPK-SIRT3 positive feedback loop (PFL). Although the precise mechanisms are not fully elucidated and need further validation, the current literature indicates that this AMPK-SIRT3 PFL regulates OA development and progression, at least partially by mediating chondrocyte MQC. Therefore, understanding the mechanisms of AMPK-SIRT3 PFL-mediated chondrocyte MQC in OA pathogenesis might yield new ideas and potential targets for subsequent research on the OA pathomechanism and therapeutics.