Long noncoding RNA LINC00671 exacerbates osteoarthritis by promoting ONECUT2-mediated Smurf2 expression and extracellular matrix degradation.

Accumulating evidence has highlighted the remarkable role of long noncoding RNAs (lncRNAs) in the pathogenesis of various diseases including osteoarthritis (OA). Since current treatment available for OA has limited efficacy, it is urgent to elucidate the pathogenesis of OA. Therefore, we aimed at elucidating the specific regulatory role of LINC00671 in OA progression. Differentially expressed lncRNAs were initially screened using the OA profile. LINC00671, ONECUT2, and Smurf2 expression in OA cartilage tissues were determined, while their interaction was verified by RNA-pull down assay, ChIP, and dual-luciferase reporter gene assay. After chondrocytes were transfected with shRNA and overexpressed plasmids, the proliferation and apoptosis were determined. Meanwhile, extracellular matrix (ECM)-related proteins were detected by Western blot analysis. Establishment of the OA model was performed by surgical destabilization of the medial meniscus (DMM) surgery in mice. Upregulation of LINC00671, ONECUT2, and Smurf2 expression were detected in OA cartilage. LINC00671 was bound to ONECUT2 and ONECUT2 was conjugated to Smurf2. Overexpression of LINC00671 resulted in inhibited chondrocytes proliferation, enhanced apoptosis, and ECM degradation, which was readily reversed by silencing ONECUT2 or Smurf2. Furthermore, LINC00671 induced GSK-3ß ubiquitination and upregulated ß-catenin expression through Smurf2. In vivo experiment revealed that silencing of LINC00671 or GSK-3ß activator resulted in alleviated ECM degradation and ameliorated OA progression. Collectively, these data demonstrated that LINC00671 exacerbates OA progression through GSK-3ß ubiquitination by upregulating ONECUT2-mediated Smurf2.

Lnc RNA ZFAS1 regulates the proliferation, apoptosis, inflammatory response and autophagy of fibroblast-like synoviocytes via miR-2682-5p/ADAMTS9 axis in rheumatoid arthritis.

BACKGROUNDS: Rheumatoid arthritis (RA) is a frequent autoimmune disease. Emerging evidence indicated that ZNFX1 antisense RNA1 (ZFAS1) participates in the physiological and pathological processes in RA. However, knowledge of ZFAS1 in RA is limited, the potential work pathway of ZFAS1 needs to be further investigated. METHODS: Levels of ZFAS1, microRNA (miR)-2682-5p, and ADAM metallopeptidase with thrombospondin type 1 motif 9 (ADAMTS9) were estimated using quantitative real-time polymerase chain reaction (qRT-PCR) assay. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was conducted to explore the ability of cell proliferation in fibroblast-like synoviocytes (FLS-RA). Cell apoptosis was measured via flow cytometry. Also, levels of ADAMTS9, apoptosis-related proteins, cleaved-caspase-3 (active large subunit), and autophagy-related proteins were identified adopting Western blot. Enzyme-linked immunosorbent assay (ELISA) was performed to determine the productions of inflammatory cytokines. Beside, the interrelation between miR-2682-5p and ZFAS1 or ADAMTS9 was verified utilizing dual-luciferase reporter assay. RESULTS: High levels of ZFAS1 and ADAMTS9, and a low level of miR-2682-5p were observed in RA synovial tissues and FLS-RA. Knockdown of ZFAS1 led to the curbs of cell proliferation, inflammation, autophagy, and boost apoptosis in FLS-RA, while these effects were abolished via regaining miR-2682-5p inhibition. Additionally, the influence of miR-2682-5p on cell phenotypes and inflammatory response were eliminated by ADAMTS9 up-regulation in FLS-RA. Mechanically, ZFAS1 exerted its role through miR-2682-5p/ADAMTS9 axis in RA. CONCLUSION: ZFAS1/miR-2682-5p/ADAMTS9 axis could modulate the cell behaviors, inflammatory response in FLS-RA, might provide a potential therapeutic target for RA treatment.

Huoxuezhitong capsule ameliorates MIA-induced osteoarthritis of rats through suppressing PI3K/ Akt/ NF-κB pathway.

Huoxuezhitong capsule (HXZT, activating blood circulation and relieving pain capsule), has been applied for osteoarthritis since 1974. It consists of Angelica sinensis (Oliv.) Diels, Panax notoginseng (Burkill) F. H. Chen ex C. H., Boswellia sacra, Borneol, Eupolyphaga sinensis Walker, Pyritum. However, the direct effects of HXZT on osteoarthritis and the underlying mechanisms were poorly understood. In this study, we aimed to explore the analgesia effect of HXZT on MIA-induced osteoarthritis rat and the underlying mechanisms. The analgesia and anti-inflammatory effect of HXZT on osteoarthritis in vivo were tested by the arthritis model rats induced by monosodium iodoacetate (MIA).. Mechanistic studies confirmed that HXZT could inhibit the activation of NF-κB and down-regulate the mRNA expression of related inflammatory factors in LPS-induced RAW264.7 and ATDC5 cells. Furtherly, in LPS-induced RAW264.7 cells, HXZT could suppress NF-κB via inhibiting PI3K/Akt pathway. Taken together, HXZT capsule could ameliorate MIA-induced osteoarthritis of rats through suppressing PI3K/ Akt/ NF-κB pathway.

miR-122/SIRT1 axis regulates chondrocyte extracellular matrix degradation in osteoarthritis.

BACKGROUND/AIMS: MicroRNAs (miRNAs) are involved in the pathogenesis of osteoarthritis (OA). The present study aimed to investigate the potential function of miR-122 in the development of OA and its potential molecular mechanisms. METHODS: The expression of miR-122, silent information regulator 1 (SIRT1), collagen II, aggrecan, matrix metalloproteinase (MMP) 13 (MMP13) and ADAMTS4 in OA cartilage was detected by RT-qPCR. Target gene prediction and screening, luciferase reporter assay were used to verify downstream target genes of miR-122. RESULTS: Compared with osteonecrosis, the expression of miR-122 was significantly increased in OA cartilage, while the expression of SIRT1 was significantly decreased. Overexpression of miR-122 increased the expression of extracellular matrix (ECM) catabolic factors, for example disintegrins, MMPs and metalloproteinases with platelet reaction protein motifs, and inhibited the expression of synthetic metabolic genes such as collagen II and aggregating proteoglycan. Inhibition of miR-122 expression had the opposite effect. Furthermore, SIRT1 was identified as a direct target of miR-122. SIRT1 was significantly inhibited by miR-122 overexpression. Knockdown of SIRT1 reversed the degradation of chondrocyte ECM by miR-122 inhibitors. CONCLUSION: The miR-122/SIRT1 axis can regulate the degradation of ECM in OA, thus providing new insights into the treatment of OA.

Associations of serum citrate levels with knee structural changes and cartilage enzymes in patients with knee osteoarthritis.

OBJECTIVE: The aim of this study was to investigate cross-sectional associations between serum levels of citrate and knee structural changes and cartilage enzymes in patients with knee osteoarthritis (OA). METHOD: A total of 137 subjects with symptomatic knee OA (mean age 55.0 years, range 34-74, 84% female) were included. Knee radiography was used to assess knee osteophytes, joint space narrowing (JSN) and radiographic OA assessed by Kellgren-Lawrence (K-L) grading system. T2-weighted fat-suppressed fast spin echo magnetic resonance imaging (MRI) was used to determine knee cartilage defects, bone marrow lesions (BMLs) and infrapatellar fat pad (IPFP) signal intensity alternations. Colorimetric fluorescence was used to measure the serum levels of citrate. Enzyme-linked immunosorbent assay was used to measure the serum cartilage enzymes including matrix metalloproteinase (MMP)-3 and MMP-13. RESULTS: After adjustment for potential confounders (age, sex, body mass index), serum citrate was negatively associated with knee osteophytes at the femoral site, cartilage defects at medial femoral site, total cartilage defects, and total BMLs (odds ratio [OR] 0.17-0.30, all P < .05). Meanwhile, serum citrate was negatively associated with IPFP signal intensity alteration (OR 0.30, P = .05) in multivariable analyses. Serum citrate was significantly and negatively associated with MMP-13 (ß -3106.37, P < .05) after adjustment for potential confounders. However, citrate was not significantly associated with MMP-3 in patients with knee OA. CONCLUSION: Serum citrate was negatively associated with knee structural changes including femoral osteophytes, cartilage defects, and BMLs and also serum MMP-13 in patients with knee OA, suggesting that low serum citrate may be a potential indicator for advanced knee OA.

Up-regulation of P21-activated kinase 1 in osteoarthritis chondrocytes is responsible for osteoarthritic cartilage destruction.

Osteoarthritis is mainly caused by a degenerative joint disorder, which is characterized by the gradual degradation of articular cartilage and synovial inflammation. The chondrocyte, the unique resident cell type of articular cartilage, is crucial for the development of osteoarthritis. Previous studies revealed that P21-activated kinase-1 (PAK1) was responsible for the initiation of inflammation. The purpose of the present study was to determine the potential role of PAK1 in osteoarthritis. The level of PAK1 expression was measured by Western blot and quantitative real-time PCR in articular cartilage from osteoarthritis model rats and patients with osteoarthritis. In addition, the functional role of aberrant PAK1 expression was detected in the chondrocytes. We found that the expression of PAK1 was significantly increased in chondrocytes treated with osteoarthritis-related factors. Increased expression of PAK1 was also observed in knee articular cartilage samples from patients with osteoarthritis and osteoarthritis model rats. PAK1 was found to inhibit chondrocytes proliferation and to promote the production of inflammatory cytokines in cartilages chondrocytes. Furthermore, we found that PAK1 modulated the production of extracellular matrix and cartilage degrading enzymes in chondrocytes. Results of the present studies demonstrated that PAK1 might play an important role in the pathogenesis of osteoarthritis.

The Oxidative Stress in Knee Osteoarthritis Patients. An Attempt of Evaluation of Possible Compensatory Effects Occurring in the Disease Development.

Background and Objective: Osteoarthritis (OA) is a disorder of the musculoskeletal system resulting in worsening of life condition. The research revealed the involvement of oxidative stress into both OA pathogenesis and the effects of therapeutic agents applied in OA cases. The activities of the most important antioxidant enzymes, namely superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and total antioxidant status (TAS), in blood of the knee OA patients were studied, with the aim of clarifying which enzymatic antioxidants are involved into osteoarthritis (OA)-related oxidative stress and whether any compensatory effects occur. The results were additionally analyzed with regard to gender. Methods: Whole blood SOD (U/mL), plasma GPx (U/L) and CAT (U/mL) activities as well as plasma TAS (mmol/L)) in knee OA patients were investigated. Sixty-seven patients (49 females and 18 males) with primary knee OA were enrolled. The control comprised 21 subjects (10 females and 11 males) free of osteoarthritis or inflammation. Results: TAS was decreased in OA subjects (4.39 0.53 vs. 4.70 0.60), with this effect being more significant in OA females (4.31 0.51 vs. 5.02 0.54). GPx was depressed in all OA patients (518 176 vs. 675 149). In both genders, GPx was decreased, significantly in males (482 185 vs. 715 105). SOD was decreased in all OA patients (109 32 vs. 127 42). CAT showed no difference in all OA subjects vs. control, while in OA females it was depleted (20.2 (11.6-31.6) vs. 38.5 (27.9-46.6)) and in OA men it increased (26.9 (23.3-46.5) vs. 14.0 (7.0-18.6)). Conclusions: The obtained results suggest that in men some compensatory mechanisms towards OA-related oxidative stress occurred. Based on the obtained data, the introduction of antioxidant supplements into OA therapy could be suggested with further research concerning the choice of agents.

High-Temperature Requirement A1 Protease as a Rate-Limiting Factor in the Development of Osteoarthritis.

Preserving the mature articular cartilage of joints is a critical focus in the prevention and treatment of osteoarthritis. We determined whether the genetic inactivation of high-temperature requirement A1 (HtrA1) can significantly attenuate the degradation of articular or condylar cartilage. Two types of mouse models of osteoarthritis were used, a spontaneous mutant mouse model [type XI collagen-haploinsufficient (Col11a1+/-) mice] and two post-traumatic mouse models [destabilization of the medial meniscus (DMM) on the knee and a partial discectomy (PDE) on the temporomandibular joint]. Three different groups of mice were generated: i) HtrA1 was genetically deleted from Col11a1+/- mice (HtrA1-/-;Col11a1+/-), ii) HtrA1-deficient mice (HtrA1-/-) were subjected to DMM, and iii) HtrA1-/- mice were subjected to PDE. Knee and temporomandibular joints from the mice were characterized for evidence of cartilage degeneration. The degradation of articular or condylar cartilage was significantly delayed in HtrA1-/-;Col11a1+/- mice and HtrA1-/- mice after DMM or PDE. The amount of collagen type VI was significantly higher in the articular cartilage in HtrA1-/-;Col11a1+/- mice, compared with that in Col11a1+/- mice. The genetic removal of HtrA1 may delay the degradation of articular or condylar cartilage in mice.

Cdc42 Is Essential for Both Articular Cartilage Degeneration and Subchondral Bone Deterioration in Experimental Osteoarthritis.

Cdc42, a member of Rho family small guanosine triphosphatases (GTPases), is critical for cartilage development. We investigated the roles of Cdc42 in osteoarthritis and explored the potential mechanism underlying Cdc42-mediated articular cartilage degeneration and subchondral bone deterioration. Cdc42 is highly expressed in both articular cartilage and subchondral bone in a mouse osteoarthritis model with surgical destabilization of the medial meniscus (DMM) in the knee joints. Specifically, genetic disruption of Cdc42, knockdown of Cdc42 expression, or inhibition of Cdc42 activity robustly attenuates the DMM-induced destruction, hypertrophy, high expression of matrix metallopeptidase-13 and collagen X, and activation of Stat3 in articular cartilages. Notably, genetic disruption of Cdc42, knockdown of Cdc42 expression or inhibition of Cdc42 activity significantly restored the increased numbers of mesenchymal stem cells, osteoprogenitors, osteoblasts, osteoclasts, and neovascularized vessels, the increased bone mass, and the activated Erk1/2, Smad1/5 and Smad2 in subchondral bone of DMM-operated mice. Mechanistically, Cdc42 mediates interleukin-1ß-induced interleukin-6 production and subsequent Jak/Stat3 activation to regulate chondrocytic inflammation, and also lies upstream of Erk/Smads to regulate subchondral bone remodeling during transform growth factor-ß1 signaling. Cdc42 is apparently required for both articular cartilage degeneration and subchondral bone deterioration of osteoarthritis, thus, interventions targeting Cdc42 have potential in osteoarthritic therapy. © 2018 American Society for Bone and Mineral Research.

Low prevalence of knee chondrocalcinosis and its catabolic association with serum matrix metalloproteinase 3: A rural Japanese population study.

AIM: This study aimed to elucidate the prevalence of radiographic knee chondrocalcinosis (CC) and to clarify whether CC is correlated with self-reported knee symptoms and a serum catabolic biomarker. METHODS: A total of 1278 volunteers participated. Plain radiographs of both knees were obtained. Identification of a linear calcification in the knee joint space was defined as CC. Patients with a Kellgren-Lawrence grade of 2 or more were considered to have knee osteoarthritis (OA). Symptoms were evaluated using the Knee injury and Osteoarthritis Outcome Score (KOOS) Pain scale, and serum matrix metalloproteinase-3 (MMP-3) concentration was determined. Multiple regression analysis was conducted to determine whether CC was correlated with OA, the KOOS Pain scale and MMP-3 concentration. RESULTS: Twenty-eight subjects were found to have CC (2.2%), and 389 had OA (30.4%). CC was correlated with OA (odds ratio: 5.797; P = 0.006). Additionally, CC was correlated with MMP-3 concentration (B = 11.415, ß = 0.059, P = 0.014), but not with KOOS Pain scale. CONCLUSIONS: The prevalence of CC was low in the Japanese population evaluated in this study. While CC was not correlated with self-reported knee symptoms, it was positively correlated with serum MMP-3 concentration.

Estrogen-related receptor γ causes osteoarthritis by upregulating extracellular matrix-degrading enzymes.

The estrogen-related receptor (ERR) family of orphan nuclear receptor is composed of ERRα, ERRß, and ERRγ, which are known to regulate various isoform-specific functions under normal and pathophysiological conditions. Here, we investigate the involvement of ERRs in the pathogenesis of osteoarthritis (OA) in mice. Among ERR family members, ERRγ is markedly upregulated in cartilage from human OA patients and various mouse models of OA. Adenovirus-mediated overexpression of ERRγ in mouse knee joint or transgenic expression of ERRγ in cartilage leads to OA. ERRγ overexpression in chondrocytes directly upregulates matrix metalloproteinase (MMP)-3 and MMP13, which are known to play crucial roles in cartilage destruction in OA. In contrast, genetic ablation of Esrrg or shRNA-mediated downregulation of Esrrg in joint tissues abrogates experimental OA in mice. Our results collectively indicate that ERRγ is a novel catabolic regulator of OA pathogenesis.

Platelets Contribute to the Accumulation of Matrix Metalloproteinase Type 2 in Synovial Fluid in Osteoarthritis.

Inflammation plays a role in the initiation and progression of osteoarthritis (OA), a chronic degenerative joint disorder. Platelets are inflammatory cells, contain and release matrix metalloproteinases (MMPs) and favour the release of these enzymes, key effectors of cartilage and subchondral bone degradation, by other cells; however, their role in OA has not been investigated yet. Our aims were (1) to assess the presence of platelets and of MMP-2 in synovial fluid (SF) of OA patients; (2) to evaluate the contribution of platelets to MMP-2 release by fibroblast-like synoviocytes (FLS); and (3) to investigate if hyaluronic acid (HA) interferes with these processes. SF was collected from 27 OA patients before and after treatment with intra-articular HA (20 mg/2 mL). Moreover, FLS were co-cultured with platelets, and the release of MMP-2 in supernatants was measured. Our results show that platelets are present in OA SF and show markers of activation. OA SF also contains relevant amounts of MMP-2. Co-incubation of platelets with FLS favours the release of MMP-2 by the interaction of platelet surface P-selectin with FLS CD44 by a mechanism involving the activation of pAkt and pSrc in FLS. Administration of HA to OA patients decreased the infiltration of platelets in SF and reduced the levels of MMP-2. The addition of HA in vitro inhibited the release of MMP-2 by FLS triggered by the interaction with platelets. In conclusion, our data show that platelets may contribute to joint degeneration in OA by favouring the accumulation of MMP-2 in SF.

The biomechanical and histological effects of posterior cruciate ligament rupture on the medial tibial plateau.

BACKGROUND: The objective of this study was to investigate the biomechanical and histological effects of the posterior cruciate ligament (PCL) on the medial tibial plateau. METHODS: A total of 12 cadaveric human knee specimens were collected and grouped as follows: the PCL intact group (n = 12), the anterolateral bundle rupture group (n = 6), the postmedial bundle rupture group (n = 6), and the PCL rupture group (n = 12). The strain on the anterior, middle, and posterior parts of the medial tibial plateau with an axial loading force at different flexion angles was measured and analyzed, respectively. Forty-eight rabbits were chosen for animal study: surgery was performed on the one side of each rabbit randomly (experimental group), while the other side was taken as control (control group). Every 12 rabbits were culled at each of the four selected time points to collect the medial tibial plateau for morphological and histological observation. RESULTS: The PCL rupture, either partial or complete, may generate an abnormal load on all the parts of the medial tibial plateau with axial loading at all positions. Noticeable time-dependent degenerative histological changes of the medial tibial plateau were observed in the rabbit models of PCL rupture. Compared with the control group, all the PCL rupture groups exhibited a higher expression of the matrix metalloproteinase-7 (MMP-7) and the tissue inhibitors of metalloproteinase-1 (TIMP-1) at all the time points. CONCLUSIONS: Either partial or complete PCL rupture may generate an abnormal load on all the parts of the medial tibial plateau with axial loading at all the positions and may cause cartilage degeneration on the medial tibial plateau.

Naringenin regulates production of matrix metalloproteinases in the knee-joint and primary cultured articular chondrocytes and alleviates pain in rat osteoarthritis model.

Inflammation of cartilage is a primary symptom for knee-joint osteoarthritis. Matrix metalloproteinases (MMPs) are known to play an important role in the articular cartilage destruction related to osteoarthritis. Naringenin is a plant-derived flavonoid known for its anti-inflammatory properties. We studied the effect of naringenin on the transcriptional expression, secretion and enzymatic activity of MMP-3 in vivo in the murine monosodium iodoacetate (MIA) osteoarthritis model. The assessment of pain behavior was also performed in the MIA rats. The destruction of knee-joint tissues was analyzed microscopically. Moreover, the effect of naringenin was also studied in vitro in IL-1ß activated articular chondrocytes. The transcriptional expression of MMP-3, MMP-1, MMP-13, thrombospondin motifs (ADAMTS-4) and ADAMTS-5 was also studied in primary cultured chondrocytes of rats. Naringenin caused significant reduction in pain behavior and showed marked improvement in the tissue morphology of MIA rats. Moreover, a significant inhibition of MMP-3 expression in MIA rats was observed upon treatment with naringenin. In the in vitro tests, naringenin caused a significant reduction in the transcriptional expression, secretion and enzymatic activity of the studied degradative enzymes. The NF-κB pathway was also found to be inhibited upon treatment with naringenin in vitro. Overall, the study suggests that naringenin alleviated pain and regulated the production of matrix-metalloproteinases via regulation of NF-κB pathway. Thus, naringenin could be a potent therapeutic option for the treatment of osteoarthritis.

Naringenin regulates production of matrix metalloproteinases in the knee-joint and primary cultured articular chondrocytes and alleviates pain in rat osteoarthritis model

Inflammation of cartilage is a primary symptom for knee-joint osteoarthritis. Matrix metalloproteinases (MMPs) are known to play an important role in the articular cartilage destruction related to osteoarthritis. Naringenin is a plant-derived flavonoid known for its anti-inflammatory properties. We studied the effect of naringenin on the transcriptional expression, secretion and enzymatic activity of MMP-3 in vivo in the murine monosodium iodoacetate (MIA) osteoarthritis model. The assessment of pain behavior was also performed in the MIA rats. The destruction of knee-joint tissues was analyzed microscopically. Moreover, the effect of naringenin was also studied in vitro in IL-1β activated articular chondrocytes. The transcriptional expression of MMP-3, MMP-1, MMP-13, thrombospondin motifs (ADAMTS-4) and ADAMTS-5 was also studied in primary cultured chondrocytes of rats. Naringenin caused significant reduction in pain behavior and showed marked improvement in the tissue morphology of MIA rats. Moreover, a significant inhibition of MMP-3 expression in MIA rats was observed upon treatment with naringenin. In the in vitro tests, naringenin caused a significant reduction in the transcriptional expression, secretion and enzymatic activity of the studied degradative enzymes. The NF-κB pathway was also found to be inhibited upon treatment with naringenin in vitro. Overall, the study suggests that naringenin alleviated pain and regulated the production of matrix-metalloproteinases via regulation of NF-κB pathway. Thus, naringenin could be a potent therapeutic option for the treatment of osteoarthritis.

A Disintegrin and Metalloproteinase with Thrombospondin Motifs-5 (ADAMTS-5) Forms Catalytically Active Oligomers.

The metalloproteinase ADAMTS-5 (A disintegrin and metalloproteinase with thrombospondin motifs) degrades aggrecan, a proteoglycan essential for cartilage structure and function. ADAMTS-5 is the major aggrecanase in mouse cartilage, and is also likely to be the major aggrecanase in humans. ADAMTS-5 is a multidomain enzyme, but the function of the C-terminal ancillary domains is poorly understood. We show that mutant ADAMTS-5 lacking the catalytic domain, but with a full suite of ancillary domains inhibits wild type ADAMTS activity, in vitro and in vivo, in a dominant-negative manner. The data suggest that mutant ADAMTS-5 binds to wild type ADAMTS-5; thus we tested the hypothesis that ADAMTS-5 associates to form oligomers. Co-elution, competition, and in situ PLA experiments using full-length and truncated recombinant ADAMTS-5 confirmed that ADAMTS-5 molecules interact, and showed that the catalytic and disintegrin-like domains support these intermolecular interactions. Cross-linking experiments revealed that recombinant ADAMTS-5 formed large, reduction-sensitive oligomers with a nominal molecular mass of ∼ 400 kDa. The oligomers were unimolecular and proteolytically active. ADAMTS-5 truncates comprising the disintegrin and/or catalytic domains were able to competitively block full-length ADAMTS-5-mediated aggrecan cleavage, measured by production of the G1-EGE(373) neoepitope. These results show that ADAMTS-5 oligomerization is required for full aggrecanase activity, and they provide evidence that blocking oligomerization inhibits ADAMTS-5 activity. The data identify the surface provided by the catalytic and disintegrin-like domains of ADAMTS-5 as a legitimate target for the design of aggrecanase inhibitors.

Correlation between senescence-associated beta-galactosidase expression in articular cartilage and disease severity of patients with knee osteoarthritis.

AIM: The purposes of this study were to investigate senescence-associated beta-galactosidase (SA-beta-Gal) levels in articular cartilage of knee osteoarthritis (OA) and the relationship with severity of the disease. METHODS: All the 50 cartilage tissues, including normal (controls) and OA cartilage were ascribed to four groups of normal, mild lesions, moderate lesions and severe lesions on the basis of the modified Mankin score. Immunohistochemistry was used to assess the SA-beta-Gal expression in articular cartilage. RESULTS: No SA-beta-Gal staining was observed in the normal articular cartilage samples. SA-beta-Gal staining was found in a subset of the chondrocytes close to the lesion site of mild, moderate and severe damaged knee OA cartilage. The percentage of SA-beta-Gal-positive chondrocytes in articular cartilage was 0% in controls, 13.00 ± 5.77% in mild lesions, 31.65 ± 6.91% in moderate lesions and 51.95 ± 6.21% in severe lesions. SA-beta-Gal expression in mild lesions, moderate lesions and severe lesions was higher compared with that of controls (P < 0.0001). SA-beta-Gal expression in moderate lesions and severe lesions were higher with respect to mild lesion samples (P < 0.0001). SA-beta-Gal expression in severe lesions was elevated compared with those of moderate lesions (P < 0.0001). Subsequent analysis showed that articular cartilage SA-beta-Gal levels correlated with severity of disease (Spearman's ρ = 0.94, P < 0.0001). CONCLUSION: SA-beta-Gal expression in articular cartilage is associated with progressive knee OA joint damage and is a potential indictor of disease severity.

Deficiency of hyaluronan synthase 1 (Has1) results in chronic joint inflammation and widespread intra-articular fibrosis in a murine model of knee joint cartilage damage.

OBJECTIVE: Articular cartilage defects commonly result from traumatic injury and predispose to degenerative joint diseases. To test the hypothesis that aberrant healing responses and chronic inflammation lead to osteoarthritis (OA), we examined spatiotemporal changes in joint tissues after cartilage injury in murine knees. Since intra-articular injection of hyaluronan (HA) can attenuate injury-induced osteoarthritis in wild-type (WT) mice, we investigated a role for HA in the response to cartilage injury in mice lacking HA synthase 1 (Has1(-/-)). DESIGN: Femoral groove cartilage of WT and Has1(-/-) mice was debrided to generate a non-bleeding wound. Macroscopic imaging, histology, and gene expression were used to evaluate naïve, sham-operated, and injured joints. RESULTS: Acute responses (1-2 weeks) in injured joints from WT mice included synovial hyperplasia with HA deposition and joint-wide increases in expression of genes associated with inflammation, fibrosis, and extracellular matrix (ECM) production. By 4 weeks, some resurfacing of damaged cartilage occurred, and early cell responses were normalized. Cartilage damage in Has1(-/-) mice also induced early responses; however, at 4 weeks, inflammation and fibrosis genes remained elevated with widespread cartilage degeneration and fibrotic scarring in the synovium and joint capsule. CONCLUSIONS: We conclude that the ineffective repair of injured cartilage in Has1(-/-) joints can be at least partly explained by the markedly enhanced expression of particular genes in pathways linked to ECM turnover, IL-17/IL-6 cytokine signaling, and apoptosis. Notably, Has1 ablation does not alter gross HA content in the ECM, suggesting that HAS1 has a unique function in the metabolism of inflammatory HA matrices.

Evaluation of correlation of articular cartilage staining for DDR2 and proteoglycans with histological tissue damage and the results of radiographic assessment in patients with early stages of knee osteoarthritis.

OBJECTIVE: To determine, if staining of articular cartilage for proteoglycans (natural element of healthy and functioning cartilage) and discoidin domain receptor 2 (DDR2) (a protein associated with articular cartilage degradation) is correlated with histological tissue damage or radiographic assessment score in patients with early stages of knee osteoarthritis (OA). METHOD: 40 patients, with early stage OA were enrolled, from whom the biopsies for histological and immunohistochemical studies were obtained from edge of the femoral condyle during the arthroscopy. Semi-quantitative computer based analysis was used to evaluate the proportion of staining in histological sections. RESULTS: No correlation was shown between the proportion of tissue stained for DDR2 and histological score or the results of radiographic assessment of tibiofemoral (TF) joint. There was a negative correlation between the proportion of tissue stained for DDR2 and radiographic grade of patellofemoral (PF) OA (Spearman r=-0.34; 95% CI -0.60 to -0.02; P=0.03). No correlation was shown between the proportion of tissue stained for proteoglycans and histological score or the results of radiographic assessment of TF and PF joints. A negative correlation was found between proportion of tissue stained for DDR2 and proteoglycans. Spearman r=-0.43; 95% CI=-0.66 to -0.12; P=0.006. CONCLUSION: Production of DDR2 in articular cartilage could be related to early stages of OA, as it is significantly correlated to decrease of staining for cartilage proteoglycans. The role of production of DDR2 in cartilage may be decreased in stages, where higher grades of OA are detected on the radiographs.

Expression and significance of MMP3 in synovium of knee joint at different stage in osteoarthritis patients.

OBJECTIVE: To investigate the expression and significance of MMP-3 in synovium of knee joint at different stage in osteoarthritis (OA) patients. METHODS: Knee synovial tissue were collected in 90 OA patients (the OA group). Patients in the OA group was divided into 3 subgroups: grade I subgroup (n=30), grade II subgroup (n=30), grade III; subgroup (n=30). Thirty patients served as control group. Immunohistochemical assay was used to detect the expression of MMP-3 protein in the knee synovial tissue. RESULTS: MMP-3 protein was detected in all knee synovial tissue. The expression of MMP-3 protein in the OA group was significantly higher that in the normal synovium (P<0.05), and the MMP-3 protein was mainly located in the cytoplasm. There was significant difference in the expression of MMP-3 protein between the grade I subgroup and the grade II, grade III subgroups (all P<0.05). The expression of MMP-3 protein was positively related to the severity of OA (r=0.912, P<0.05). CONCLUSIONS: The expression of MMP-3 protein are closely related to pathogenic mechanism of OA. It may be an important indicator of early diagnosis and the activity of the disease of osteoarthritis.