Association of synovial fluid and urinary C2C-HUSA levels with surgical outcomes post-total knee arthroplasty.

OBJECTIVES: After total knee arthroplasty (TKA), ∼30% of knee osteoarthritis (KOA) patients show little symptomatic improvement. Earlier studies have correlated urinary (u) type 2 collagen C terminal cleavage peptide assay (C2C-HUSA), which detects a fragment of cartilage collagen breakdown, with KOA progression. This study determines whether C2C levels in urine, synovial fluid, or their ratio, are associated with post-surgical outcomes. METHODS: From a large sample of 489 subjects, diagnosed with primary KOA undergoing TKA, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function scores were collected at baseline (time of surgery) and one-year post-TKA. Baseline urine (u) and synovial fluid (sf) were analysed using the IBEX-C2C-HUSA assay, with higher values indicating higher amounts of cartilage degradation. For urine, results were normalised to creatinine. Furthermore, subjects' changes in WOMAC scores were categorised based on percent reduction in pain or improvement in function, compared to baseline, such that >66.7%, >33.3 to ≤66.7%, and ≤33.3% denoted "strong", "moderate" and "mild/worse" responses, respectively. Associations of individual biofluid C2C-HUSA levels, or their ratio, with change in WOMAC pain and function scores up to one-year post-TKA, or category of change, were analysed by linear, logistic, or cumulative odds models. RESULTS: Higher baseline uC2C-HUSA levels or a lower ratio of baseline sfC2C-HUSA to uC2C-HUSA were associated with improvements in WOMAC pain by linear multivariable modelling [odds ratio -0.40 (95% confidence interval -0.76, -0.05) p = 0.03; 0.36 (0.01, 0.71), p = 0.04, respectively], while sfC2C-HUSA alone was not. However, lower ratios of sfC2C-HUSA to uC2C-HUSA were associated with improvements in WOMAC function [1.37 (0.18, 2.55), p = 0.02], while sfC2C-HUSA and uC2C-HUSA alone were not. Lower ratios of sfC2C-HUSA to uC2C-HUSA were also associated with an increased likelihood of a subject being categorised in a group where TKA was beneficial in both univariable [pain, 0.81 (0.68, 0.96), p = 0.02; function, 0.92 (0.85, 0.99), p = 0.035] and multivariable [pain, 0.81 (0.68, 0.97) p = 0.02; function, 0.92 (0.85, 1.00), p = 0.043] ordinal modelling, while sfC2C-HUSA and uC2C-HUSA alone were not. CONCLUSIONS: Overall, ratios of baseline sfC2C-HUSA to uC2C-HUSA, and baseline uC2C-HUSA, may play an important role in studying post-TKA surgical outcomes.

DDIT3 aggravates TMJOA cartilage degradation via Nrf2/HO-1/NLRP3-mediated autophagy.

OBJECTIVE: DNA damage-inducible transcript 3 (DDIT3), as a downstream transcription factor of endoplasmic reticulum stress, is reported to regulate chondrogenic differentiation under physiological and pathological state. However, the specific involvement of DDIT3 in the degradation of condylar cartilage of temporomandibular joint osteoarthritis (TMJOA) is unclarified. DESIGN: The expression patterns of DDIT3 in condylar cartilage from monosodium iodoacetate-induced TMJOA mice were examined to uncover the potential role of DDIT3 in TMJOA. The Ddit3 knockout (Ddit3-/-) mice and their wildtype littermates (Ddit3+/+) were used to clarify the effect of DDIT3 on cartilage degradation. Primary condylar chondrocytes and ATDC5 cells were applied to explore the mechanisms of DDIT3 on autophagy and extracellular matrix (ECM) degradation in chondrocytes. The autophagy inhibitor chloroquine (CQ) was used to determine the effect of DDIT3-inhibited autophagy in vivo. RESULTS: DDIT3 were highly expressed in condylar cartilage from TMJOA mice. Ddit3 knockout alleviated condylar cartilage degradation and subchondral bone loss, compared with their wildtype littermates. In vitro study demonstrated that DDIT3 exacerbated ECM degradation in chondrocytes induced by TNF-α through inhibiting autophagy. The intraperitoneal injection of CQ further confirmed that Ddit3 knockout alleviated cartilage degradation in TMJOA through activating autophagy in vivo. CONCLUSIONS: Our findings identified the crucial role of DDIT3-inhibited autophagy in condylar cartilage degradation during the development of TMJOA.

A new ex vivo human model of osteoarthritis cartilage calcification.

OBJECTIVE: Cartilage pathologic calcification is a hallmark of osteoarthritis (OA). Here, we aimed to describe a new ex vivo human model to study the progression of cartilage calcification. METHOD: Cartilage explants (n = 11), as well as primary chondrocytes (n = 3), were obtained from OA patients undergoing knee replacement. Explants and chondrocytes were cultured in control (NT) or calcification (CM) medium (supplemented with ascorbic acid and ß-glycerophosphate). Calcification was evaluated by micro-CT scan at day 0 and 21 in explants, and by Alizarin red staining in chondrocyte monolayers. Raman spectrometry allowed characterization of the crystal type. Interleukin-6 (IL-6) secretion in explant and cell supernatants was measured by ELISA. Finally, matrix degradation was evaluated by Safranin-O staining of explant sections and by glycosaminoglycans (GAG) release in supernatants. RESULTS: Micro-CT scan showed calcifications in all explants at baseline (day 0), which in the CM group increased significantly in number and size after 21 days compared with the NT group. Raman spectrometry revealed that crystals were exclusively basic calcium phosphate crystals (carbonated hydroxyapatite) both in NT and CM. IL-6 secretion was significantly increased in calcifying conditions. Finally, CM significantly increased cartilage catabolism as assessed by decreased Safranin-O staining of tissue explants and increased GAG release in supernatants. CM effects (enhanced calcification, IL-6 secretion and proteoglycans turn-over) were recapitulated in vitro in OA chondrocytes. CONCLUSIONS: We have described a new ex vivo human model of cartilage calcification that can summurize the triad of events seen during osteoarthritis progression, i.e. calcification, inflammation, and cartilage degradation. This model will allow the identification of new anti-calcification compounds.

Quercitrin attenuates the progression of osteoarthritis via inhibiting NF-κB signaling pathways and enhance glucose transport capacity.

Osteoarthritis (OA) is a common musculoskeletal disorder that impairs function and reduces the quality of life. Extracellular matrix (ECM) degradation and inflammatory mechanisms are crucial to the progression of OA. In this study, we aimed to investigate the anti-inflammatory activity, anti-ECM degradation property, and glucose transport capacity of quercitrin (QCT) on IL-1ß-treated rat primary chondrocytes. Rat primary chondrocytes were treated with IL-1ß to simulate inflammatory environmental conditions and OA in vitro. We examined the effects of QCT at concentrations ranging from 0 to 200 µM on the viability of rat chondrocytes and selected 5 µM for further study. Using qRT-PCR, immunofluorescent, immunocytochemistry, and western blotting techniques, we identified the potential molecular mechanisms and signaling pathways that are responsible for these effects. We established an OA rat model through anterior cruciate ligament transection (ACLT). The animals were then periodically injected with QCT into the knee articular cavity. Our in vivo and in vitro study showed that QCT could inhibit IL-1ß-activated inflammation and ECM degradation in chondrocyte. Furthermore, QCT could inhibit the NF-κB signal pathway and enhance glucose transport capacity in the IL-1ß-stimulated chondrocytes. In vivo study proved that QCT attenuates OA progression in rats. Overall, QCT inhibited the activation of NF-κB and enhanced glucose transport capacity to alleviate the progression of OA.

Anti-inflammatory and anti-oxidant activities of mesenchymal stem cells in chemically induced arthritic rats.

BACKGROUND: Mesenchymal stem cells (MSCs) have been extensively used as cell-based treatments for decades due to their anti-inflammatory, immunomodulatory, and healing abilities. The intent of our study was to determine the efficacy of MSCs in alleviating rheumatoid arthritis (RA) induced by Complete Freund's adjuvant (CFA) and to investigate the anti-inflammatory and antioxidant characteristics of MSCs. METHODS AND RESULTS: Intrapedally injecting 0.1 ml of CFA directly into the footpad of the right hind paw daily for 2 days was used to induce RA. Arthritic rats received four doses of MSCs (1 × 106 cells/rat/dose) intravenously through the lateral tail vein. Our results showed that arthritic rats treated with MSCs exhibited reduced levels of paw edema. Furthermore, arthritic rats treated with MSCs exhibited a significant decrease in the levels of RF, CRP, IL-1ß, TNF-α, IL-17 and ADAMTS-5, along with a significant increase in the levels of IL-4 and TIMP-3. Additionally, MSCs significantly reduced the expression of TGF-ß. Both the glutathione (GSH) content and antioxidant activity of GST were enhanced by MSCs, while LPO levels were suppressed. CONCLUSION: These findings provide further evidence that MSCs are valuable in treating RA, possibly due to their anti-inflammatory and anti-oxidative properties. Thus, MSCs have potential as a more effective therapeutic strategy for treating RA.

Post-Transcriptional Regulator RBM47 Stabilizes FBXO2 mRNA to Advance Osteoarthritis Development: WGCNA Analysis and Experimental Validation.

Osteoarthritis (OA) is a common chronic joint degenerative disease and a major cause of disability in the elderly. However, the current intervention strategies cannot effectively improve OA, and the pathogenesis of OA remains elusive. The present study identified RNA binding motif protein 47 (RBM47) as an upstream modulator of key dysregulation gene co-expression module based on weighted gene co-expression network analysis (WGCNA) analysis and least absolute shrinkage and selection operator (Lasso) modeling. Subsequently, data from real-time quantitative PCR and western blot analysis revealed that RBM47 was upregulated in OA models in vivo and in vitro compared with normal controls. Functional analysis results from the MTT assay, flow cytometry, evaluation of LDH activities and inflammatory mediators, and western blot analysis of extracellular matrix (ECM) proteins, showed that RBM47 knockdown significantly alleviated inflammation, apoptosis, and ECM degradation in interleukin 1ß (IL-1ß)-treated chondrocytes. Mechanistically, RBM47 bound to F box only protein 2 (FBXO2) and stabilized FBXO2 messenger RNA (mRNA) to promote the phosphorylation of signal transducer and activator of transcription 3 (STAT3) in chondrocytes. Results from the recovery assay showed that the re-activation of STAT3 signaling by overexpressing FBXO2 or STAT3 counteracted the alleviating effect of RBM47 downregulation on IL-1ß-induced inflammation, apoptosis, and ECM degradation. Altogether, our findings illustrate that RBM47 stabilizes FBXO2 mRNA to advance OA development by activating STAT3 signaling, which enhances our understanding of the molecular regulatory mechanisms underlying the development of OA.

Therapeutic Nanodiamonds Containing Icariin Ameliorate the Progression of Osteoarthritis in Rats.

In present study, icariin (ICA)/tannic acid (TA)-nanodiamonds (NDs) were prepared as follows. ICA was anchored to ND surfaces with absorbed TA (ICA/TA-NDs) and we evaluated their in vitro anti-inflammatory effects on lipopolysaccharide (LPS)-activated macrophages and in vivo cartilage protective effects on a rat model of monosodium iodoacetate (MIA)-induced osteoarthritis (OA). The ICA/TA-NDs showed prolonged release of ICA from the NDs for up to 28 days in a sustained manner. ICA/TA-NDs inhibited the mRNA levels of pro-inflammatory elements, including matrix metalloproteinases-3 (MMP-3), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and increased the mRNA levels of anti-inflammatory factors (i.e., IL-4 and IL-10) in LPS-activated RAW 264.7 macrophages. Animal studies exhibited that intra-articular injection of ICA/TA-NDs notably suppressed levels of IL-6, MMP-3, and TNF-α and induced level of IL-10 in serum of MIA-induced OA rat models in a dose-dependent manner. Furthermore, these noticeable anti-inflammatory effects of ICA/TA-NDs remarkably contributed to the protection of the progression of MIA-induced OA and cartilage degradation, as exhibited by micro-computed tomography (micro-CT), gross findings, and histological investigations. Accordingly, in vitro and in vivo findings suggest that the prolonged ICA delivery of ICA/TA-NDs possesses an excellent latent to improve inflammation as well as defend against cartilage disorder in OA.

Th17 lymphocyte-dependent degradation of joint cartilage by synovial fibroblasts in a humanized mouse model of arthritis and reversal by secukinumab.

How T-helper (Th) lymphocyte subpopulations identified in synovial fluid from patients with juvenile idiopathic arthritis (JIA) (Th17, classic Th1, or nonclassic Th1) drive joint damage is of great interest for the possible use of biological drugs that inhibit the specific cytokines. Our objective was to clarify the role of such Th subpopulations in the pathogenesis of articular cartilage destruction by synovial fibroblasts (SFbs), and the effect of Th17 blockage in an animal model. SFbs were isolated from healthy subjects and patients with JIA, and peripheral blood Th lymphocytes subsets were obtained from healthy subjects. Fragments of human cartilage from healthy subjects in a collagen matrix containing JIA or normal SFbs grafted underskin in SCID mice were used to measure cartilage degradation under the effects of Th supernatants. JIA SFbs overexpress MMP9 and MMP2 and Th17 induce both MMPs in normal SFbs, while nonclassic Th1 upregulate urokinase plasminogen activator (uPA) activity. In vitro invasive phenotype of normal SFbs is stimulated with conditioned medium of Th17 and nonclassic-Th1. In the in vivo "inverse wrap" model, normal SFbs stimulated with supernatants of Th17-lymphocytes and nonclassic Th1 produced a cartilage invasion and degradation similar to JIA SFbs. Secukinumab inhibits the cartilage damage triggered by factors produced by Th17.

Association between osteoarthritis-related serum biochemical markers over 11 years and knee MRI-based imaging biomarkers in middle-aged adults.

OBJECTIVE: To describe the associations between osteoarthritis (OA)-related biochemical markers (COMP, MMP-3, HA) and MRI-based imaging biomarkers in middle-aged adults over 10-13 years. METHODS: Blood serum samples collected during the Childhood Determinants of Adult Health (CDAH)-1 study (year:2004-06; n = 156) and 10-13 year follow-up at CDAH-3 (n = 167) were analysed for COMP, MMP-3, and HA using non-isotopic ELISA. Knee MRI scans obtained during the CDAH-knee study (year:2008-10; n = 313) were assessed for cartilage volume and thickness, subchondral bone area, cartilage defects, and BML. RESULTS: In a multivariable linear regression model describing the association of baseline biochemical markers with MRI-markers (assessed after 4-years), we found a significant negative association of standardised COMP with medial femorotibial compartment cartilage thickness (ß:-0.070; 95%CI:-0.138,-0.001), and standardised MMP-3 with patellar cartilage volume (ß:-141.548; 95%CI:-254.917,-28.179) and total bone area (ß:-0.729; 95%CI:-1.340,-0.118). In multivariable Tobit regression model, there was a significant association of MRI-markers with biochemical markers (assessed after 6-9 years); a significant negative association of patellar cartilage volume (ß:-0.001; 95%CI:-0.002,-0.00004), and total bone area (ß:-0.158; 95%CI-0.307,-0.010) with MMP-3, and total cartilage volume (ß:-0.001; 95%CI:-0.001,-0.0001) and total bone area (ß:-0.373; 95%CI:-0.636,-0.111) with COMP. No significant associations were observed between MRI-based imaging biomarkers and HA. CONCLUSION: COMP and MMP-3 levels were negatively associated with knee cartilage thickness and volume assessed 4-years later, respectively. Knee cartilage volume and bone area were negatively associated with COMP and MMP-3 levels assessed 6-9 years later. These results suggest that OA-related biochemical markers and MRI-markers are interrelated in early OA.

Hypoxia-inducible factor expression is related to apoptosis and cartilage degradation in temporomandibular joint osteoarthritis.

BACKGROUND: It remains unclear etiology of cartilaginous tissues in osteoarthritis (OA) lesions. In this study, we hypothesized the accumulation of hypoxia-inducible factor (HIF) and activated apoptosis relate to condylar cartilage degeneration in vivo. METHODS: Malocclusion stress was applied for 2 weeks, 4 weeks and 8 weeks to induce an OA-like lesion animal model in rats. Histological analysis was performed by H&E staining and Safranin O/fast green staining. The expression levels of protein in condylar cartilage were examined by immunostaining to evaluate cartilage degeneration. RESULTS: We found apparent histological phenotypes associated with degeneration in the occlusion disorder (OD) stress group. The OD group at 4 weeks and 8 weeks had obviously reduced expression of Aggrecan (Acan) and type II collagen (Col II) in cartilage. In contrast, the OD groups had higher levels of ADAM metallopeptidase with thrombospondin type 5 (ADAMTS5) and matrix metallopeptidase 13 (MMP13) in the condylar cartilage than the control group. Moreover, the OD group cartilage had prominent degenerative changes with reduced levels of hypoxia inducible factor 1 alpha (HIF1α) and increased levels of hypoxia inducible factor 2 alpha (HIF2α) and the apoptosis factor Caspase3 in condylar cartilage at 8 weeks. CONCLUSION: Thus, abnormal hypoxic conditions inducing Occlusion disorder stress results in cartilage degeneration. opposite expression patterns of HIF1α and HIF2α could be involved in the pathogenesis of condylar cartilage degeneration and chondrocyte apoptosis. HIF2α may provide a potential negative feedback mechanism for HIF1α during cartilage damage.

Chaenomeles Fructus (CF), the Fruit of Chaenomeles sinensis Alleviates IL-1ß Induced Cartilage Degradation in Rat Articular Chondrocytes.

Osteoarthritis (OA) causes persistent pain, joint dysfunction, and physical disability. It is the most prevalent type of degenerative arthritis, affecting millions of people worldwide. OA is currently treated with a focus on pain relief, inflammation control, and artificial joint surgery. Hence, a therapeutic agent capable of preventing or delaying the progression of OA is needed. OA is strongly associated with the degeneration of the articular cartilage and changes in the ECM, which are primarily associated with a decrease in proteoglycan and collagen. In the progress of articular cartilage degradation, catabolic enzymes, such as matrix metalloproteinases (MMPs), are activated by IL-1ß stimulation. Given the tight relationship between IL-1ß and ECM (extra-cellular matrix) degradation, this study examined the effects of Chaenomeles Fructus (CF) on IL-1ß-induced OA in rat chondrocytes. The CF treatment reduced IL-1ß-induced MMP3/13 and ADAMTS-5 production at the mRNA and protein levels. Similarly, CF enhanced col2a and aggrecan accumulation and chondrocyte proliferation. CF inhibited NF-κB (nuclear factor kappa B) activation, nuclear translocation induced by IL-1ß, reactive oxygen species (ROS) production, and ERK phosphorylation. CF demonstrated anti-OA and articular regeneration effects on rat chondrocytes, thus, suggesting that CF is a viable and fundamental therapeutic option for OA.

The circadian clock: a central mediator of cartilage maintenance and osteoarthritis development?

The circadian clock is a specialized cell signalling pathway present in all cells. Loss of clock function leads to tissue degeneration and premature ageing in animal models demonstrating the fundamental importance of clocks for cell, tissue and organism health. There is now considerable evidence that the chondrocyte circadian clock is altered in OA. The purpose of this review is to summarize current knowledge regarding the nature of the change in the chondrocyte clock in OA and the implications of this change for disease development. Expression of the core clock component, BMAL1, has consistently been shown to be lower in OA chondrocytes. This may contribute to changes in chondrocyte differentiation and extracellular matrix turnover in disease. Circadian clocks are highly responsive to environmental factors. Mechanical loading, diet, inflammation and oxidative insult can all influence clock function. These factors may contribute to causing the change in the chondrocyte clock in OA.

MiR-203 regulates estrogen receptor α and cartilage degradation in IL-1ß-stimulated chondrocytes.

INTRODUCTION: Estrogen receptor α (ERα) plays important roles in the etiology of osteoarthritis (OA), in which cartilage degradation and cellular inflammation are involved. MiR-203 is reported to direct target ERα, but its roles in chondrocytes remain uncovered. METHODS: In this study, ELISA showed that the level of estrogen hormone in the serum of postmenopausal OA patients was significantly lower than the one in patients without OA. RT-PCR revealed that the expression level of miR-203 was significantly up-regulated in the OA patients. Furthermore, western blotting demonstrated the lower expression levels of aggrecan, Col2A1, and ERα in the isolated articular cartilage tissues of OA patients. To decipher the association between ERα and miR-203 in the pathogenesis of OA, IL-1ß stimulated cultured chondrocyte cell model was established to measure the cell viability, cellular inflammation, cell injury, as well as cartilage degradation with miR-203 inhibitor and ERα. RESULTS: The results showed that IL-1ß stimulation induced the expression of miR-203, which promoted cellular inflammation and cell injury, and caused down-regulation of aggrecan and Col2A1. Luciferase assay indicated the direct binding between miR-203 and ERα, and ERα-specific SiRNA inversed the protective role of miR-203 inhibitor in the progression of OA in the cell system. CONCLUSIONS: MiR-203 is critical in the onset and progression of OA, at least in part, caused by estrogen deficiency and ERα instability in OA patients, providing a novel therapeutic target for the treatment of OA.

Herbal Composition LI73014F2 Alleviates Articular Cartilage Damage and Inflammatory Response in Monosodium Iodoacetate-Induced Osteoarthritis in Rats.

The aim of this study was to determine the anti-osteoarthritic effects of LI73014F2, which consists of Terminalia chebula fruit, Curcuma longa rhizome, and Boswellia serrata gum resin in a 2:1:2 ratio, in the monosodium iodoacetate (MIA)-induced osteoarthritis (OA) rat model. LI73014F2 was orally administered once per day for three weeks. Weight-bearing distribution and arthritis index (AI) were measured once per week to confirm the OA symptoms. Synovial membrane, proteoglycan layer, and cartilage damage were investigated by histological examination, while synovial fluid interleukin-1ß level was analyzed using a commercial kit. Levels of pro-inflammatory mediators/cytokines and matrix metalloproteinases (MMPs) in the cartilage tissues were investigated to confirm the anti-osteoarthritic effects of LI73014F2. LI73014F2 significantly inhibited the MIA-induced increase in OA symptoms, synovial fluid cytokine, cartilage damage, and expression levels of pro-inflammatory mediators/cytokines and MMPs in the articular cartilage. These results suggest that LI73014F2 exerts anti-osteoarthritic effects by regulating inflammatory cytokines and MMPs in MIA-induced OA rats.

Soybean isoflavone can protect against osteoarthritis in ovariectomized rats.

Osteoarthritis (OA) is a chronic and incurable disease and a leading cause of significant pain and disability that is closely associated with aging and obesity. An appropriate long-term therapy regimen is presently unknown. An estrogen deficiency after menopause increases the incidence and severity of OA in women. Soybean isoflavone have weak estrogenic effects in several organs and have been considered as a potentially safe natural selective estrogen receptor modulator. The present study aimed to determine the effects of isoflavone on cartilage degradation in ovariectomized rats. Six-month-old female Sprague-Dawley (SD) rats (n = 40) were randomly assigned to sham operation (n = 10), ovariectomy (OVX) (n = 15) or OVX + isoflavone (OVXI) (n = 15) groups. The OVXI group was fed with soybean isoflavone (51.0 mg/kg/day) for nine weeks, then knee joints were excised. Cartilage degradation was evaluated by toluidine blue staining joint specimens, and by comparing values for serum C-telopeptides of Type II collagen (CTX-II) and cartilage oligomeric matrix protein (COMP) between baseline and the end of the study. Cartilage damage scored by Toluidine blue staining was significantly lower in the OXVI, than the OVX group (P < 0.016). The CTX-II values before the surgical procedure and the end of experiment, did not significantly differ among the groups. Values for COMP in all samples were below detection limits in all samples. Soy bean isoflavone limited the degeneration of cartilage induced by OVX in rats.

IL-1ß Damages Fibrocartilage and Upregulates MMP-13 Expression in Fibrochondrocytes in the Condyle of the Temporomandibular Joint.

The temporomandibular joint (TMJ), which differs anatomically and biochemically from hyaline cartilage-covered joints, is an under-recognized joint in arthritic disease, even though TMJ damage can have deleterious effects on physical appearance, pain and function. Here, we analyzed the effect of IL-1ß, a cytokine highly expressed in arthritic joints, on TMJ fibrocartilage-derived cells, and we investigated the modulatory effect of mechanical loading on IL-1ß-induced expression of catabolic enzymes. TMJ cartilage degradation was analyzed in 8-11-week-old mice deficient for IL-1 receptor antagonist (IL-1RA-/-) and wild-type controls. Cells were isolated from the juvenile porcine condyle, fossa, and disc, grown in agarose gels, and subjected to IL-1ß (0.1-10 ng/mL) for 6 or 24 h. Expression of catabolic enzymes (ADAMTS and MMPs) was quantified by RT-qPCR and immunohistochemistry. Porcine condylar cells were stimulated with IL-1ß for 12 h with IL-1ß, followed by 8 h of 6% dynamic mechanical (tensile) strain, and gene expression of MMPs was quantified. Early signs of condylar cartilage damage were apparent in IL-1RA-/- mice. In porcine cells, IL-1ß strongly increased expression of the aggrecanases ADAMTS4 and ADAMTS5 by fibrochondrocytes from the fossa (13-fold and 7-fold) and enhanced the number of MMP-13 protein-expressing condylar cells (8-fold). Mechanical loading significantly lowered (3-fold) IL-1ß-induced MMP-13 gene expression by condylar fibrochondrocytes. IL-1ß induces TMJ condylar cartilage damage, possibly by enhancing MMP-13 production. Mechanical loading reduces IL-1ß-induced MMP-13 gene expression, suggesting that mechanical stimuli may prevent cartilage damage of the TMJ in arthritic patients.

Knockdown of PRMT1 suppresses IL-1ß-induced cartilage degradation and inflammatory responses in human chondrocytes through Gli1-mediated Hedgehog signaling pathway.

Osteoarthritis (OA) is characterized by articular cartilage degradation and joint inflammation. The purpose of the present study is to elucidate the role of the specific function of PRMT1 in chondrocytes and its association with the pathophysiology of OA. We observed that the expression of PRMT1 was apparently upregulated in OA cartilage, as well as in chondrocytes stimulated with IL-1ß. Additionally, knockdown of PRMT1 suppressed interleukin 1 beta (IL-1ß)-induced extracellular matrix (ECM) metabolic imbalance by regulating the expression of MMP-13, ADAMTS-5, COL2A1, and ACAN. Furthermore, silencing of PRMT1 dramatically declined the production of prostaglandin E2 (PGE2) and nitric oxide as well as the level of pro-inflammatory cytokine IL-6 and TNF-α. Mechanistic analyses further revealed that IL-1ß-induced activation of the Hedgehog/Gli-1 signaling is suppressed upon PRMT1 knockdown. However, the effects of inhibition of PRMT1-mediated IL-1ß-induced cartilage matrix degradation and inflammatory response in OA chondrocytes were obviously abolished by Hedgehog agonist Purmorphamine (Pur). Our data collectively suggest that silencing of PRMT1 exerts anti-catabolic and anti-inflammatory effects on IL-1ß-induced chondrocytes via suppressing the Gli-1 mediated Hedgehog signaling pathway, indicating that PRMT1 plays a critical role in OA development and serves as a promising therapeutic target for OA.

Suppression of ABCD2 dysregulates lipid metabolism via dysregulation of miR-141:ACSL4 in human osteoarthritis.

Even though increasing evidence indicates the importance of peroxisomal lipid metabolism in regulating biological and pathological events, its involvement in cartilage development has not been well studied. Here, we identified the importance of peroxisomal function, particularly the functional integrity of ABCD2, in the pathogenesis of osteoarthritis (OA). Knockdown of ABCD2 in OA chondrocytes induced the accumulation of very long chain fatty acids (VLCFAs) and apoptotic cell death. Moreover, knockdown of ABCD2 altered profiles of miRNAs that affect the expression level of ACSL4, a known direct regulator of lipid metabolism. Suppression of ACSL4 in human chondrocytes-induced VLCFA accumulation, MMP-13 expression, and apoptotic cell death. In vivo morph-down of the ACSL4 homologue in zebrafish resulted in significant defects in cartilage development and in vivo knockdown of ACSL4 in cartilage tissue of an OA model mice promoted severe cartilage degradation. In summary, to the best of our knowledge, this is the first report suggesting that the regulatory network among peroxisomal ABCD2:ACSL4:VLCFA serves as a novel regulator of cartilage homeostasis, and these data may provide novel insights into the role of peroxisomal fatty acid metabolism in pathogenesis of human OA. SIGNIFICANCE OF THE STUDY: Our study indicates that peroxisomal dysfunction is closely related to OA pathogenesis. Particularly, the functional integrity of ABCD2 may play an important role in OA pathogenesis via the accumulation of VLCFAs and stimulation of apoptotic death through altering profiles of miRNAs that target ACSL4. Our findings suggest that targeting the regulatory network among the peroxisomal ABCD2:ACSL4:VLCFA axis may provide a new potential therapeutic strategy for OA pathogenesis.

Effect of mechanical loading on the metabolic activity of cells in the temporomandibular joint: a systematic review.

OBJECTIVES: The purpose of this systematic review was to elucidate how different modalities and intensities of mechanical loading affect the metabolic activity of cells within the fibro-cartilage of the temporomandibular joint (TMJ). MATERIALS AND METHODS: A systematic review was conducted according to PRISMA guidelines using PubMed, Embase, and Web of Science databases. The articles were selected following a priori formulated inclusion criteria (viz., in vivo and in vitro studies, mechanical loading experiments on TMJ, and the response of the TMJ). A total of 254 records were identified. After removal of duplicates, 234 records were screened by assessing eligibility criteria for inclusion. Forty-nine articles were selected for full-text assessment. Of those, 23 were excluded because they presented high risk of bias or were reviews. Twenty-six experimental studies were included in this systematic review: 15 in vivo studies and 11 in vitro ones. CONCLUSION: The studies showed that dynamic mechanical loading is an important stimulus for mandibular growth and for the homeostasis of TMJ cartilage. When this loading is applied at a low intensity, it prevents breakdown of inflamed cartilage. Yet, frequent overloading at excessive levels induces accelerated cell death and an increased cartilage degradation. CLINICAL SIGNIFICANCE: Knowledge about the way temporomandibular joint (TMJ) fibrocartilage responds to different types and intensities of mechanical loading is important to improve existing treatment protocols of degenerative joint disease of the TMJ, and also to better understand the regenerative pathway of this particular type of cartilage.

Danshen attenuates osteoarthritis-related cartilage degeneration through inhibition of NF-κB signaling pathway in vivo and in vitro.

Danshen (Salvia miltiorrhiza) is a traditional Chinese medicine herb that can alleviate the symptoms of osteoarthritis (OA) (Söder et al. 2006) in animals. However, the underlying mechanisms remain poorly understood and require further investigation. In this study, rabbits with experimentally induced OA were given an intra-articular injection of danshen (0.7 mL/day) for 5 weeks. In addition to attenuating the cartilage degeneration of OA in the rabbits, danshen decreased the expression and activity of matrix metalloproteinase 9 (MMP-9) and MMP-13, and increased the expression of their natural inhibitors: tissue inhibitor of matrix metalloproteinase 1 (TIMP-1) and TIMP-2. Apoptosis in osteoarthritic cartilage tissues was attenuated by danshen, accompanied with increased expression of B cell lymphoma 2 (Bcl-2) and decreased levels of Bcl-2-associated X protein (Bax). Further, danshen inhibited the nuclear accumulation of nuclear factor kappa-B (NF-κB) p65 in osteoarthritic cartilage. The therapeutic effects of danshen in vivo were comparable to that of sodium hyaluronate, which is a drug used clinically for the treatment OA. In vitro, sodium nitroprusside (SNP) was used to stimulate apoptosis in primary rabbit chondrocytes. We found that the SNP-induced apoptosis was mitigated by danshen. BAY11-7028, an inhibitor of the NF-κB pathway, augmented danshen's anti-apoptotic effects in cells exposed to SNP. When these results are considered together, they indicate that danshen alleviates the cartilage injury in rabbit OA through inhibition of the NF-κB signaling pathway.