BackgroundOsteoarthritis (OA) is a chronic degenerative disease of the articular cartilage, and its diagnosis is based on symptoms and radiological signs that are only present in the late stages of the disease. Due to the limitations in diagnosing OA before the onset of symptoms, such as pain, little is known about the molecular mechanisms involved in the pathogenesis of OA. Experimental OA models are often used to study the kinetics of the progression of this disease. In this report, we conducted a proteomic study of osteoarthritic cartilage during the early stages of OA using an experimental rat model.ResultsTen proteins that are differentially expressed under early OA conditions were identified by 2-DE and MALDI-TOF/MS. These proteins mediated many processes, such as glycolysis and energy production (Nme2 and Pnp), cartilage matrix (Col2a1), transcription and protein synthesis (Eef1a1 and DJ-1), signal transduction (CaM and Pebp1), transport (Alb and Hba1), and latexin (Lxn). In addition, changes in Lxn expression in early OA were observed and validated by western blot and immunofluorescence analysis.ConclusionsThe proteins that we identified indicate that energy metabolism, cartilage matrix remodelling, and protective cellular mechanisms are associated with early OA. In addition, latexin expression during the early stages of OA could be implicated in cartilage repair.Electronic supplementary materialThe online version of this article (doi:10.1186/s12953-014-0055-0) contains supplementary material, which is available to authorized users.
Purpose: We and others have previously shown that periostin expression is dramatically elevated in human OA cartilage and in three surgical models of OA (medial menisectomy and anterior crucial ligament, partial meniscectomy) in rodents. In vitro periostin promotes collagen and proteoglycan degradation in human chondrocytes via activation of MMP-13 and ADAMTS4 expression. Therefore, we hypothesized that periostin-deficient mice may be protected from surgically-induced posttraumatic OA. Periostin has been shown to control gene expression in bone cells by interacting with avb3 integrin. However, the nature of periostin receptor(s) in chondrocytes is unknown. DDR1, a receptor tyrosine kinase, is highly expressed in chondrocytes and controls MMP-13 expression during chondrogenesis. Therefore, we hypothesized that the effect of periostin on chondrocytes is mediated by DDR1. Methods: Periostin (Postn) knockout (PostnÀ/À) mice were purchased from Jackson Laboratory (B6;129-Postntm1Jmol/J Stock No: 009067). We subjected 3-months old littermates (Postnþ/þ, Postnþ/À and PostnÀ/À) to partial medial menisectomy (PMX) or sham surgery, and harvested the knee joints 8 week post-surgery for histological assessment of OA progression. Human OA cartilage explant cultures were incubated in the presence or absence of the DDR1 inhibitor DDR1-IN-1 dihydrochloridein (100e500 nM) for 2 h before addition of periostin (1 mg/ml) or control vehicle to the culture medium. MMP-13 levels were determined by ELISA-24 h post stimulation. Results: PostnÀ/À deficient mice showed reduced PMX-induced cartilage degeneration and osteophyte formation relative to Postnþ/þ mice. We also observed reduced subchondral bone thickening in both Postnþ/À and PostnÀ/À mice relative to Postnþ/þ controls. In ex vivo studies, pre-incubation of human cartilage explants with the DDR1 inhibitor, DDR1-IN-1 dihydrochloridein, inhibited both constitutive and periostin-induced MMP-13 expression in a dose-dependent manner ( Fig. 1). In contrast, neutralizing antibody to avb3 integrin had no effect on periostin-induced MMP-13 expression. Conclusions: PostnÀ/À mice are protected from surgically-induced post-traumatic OA showing that periostin promotes cartilage degeneration.. DDR1 mediates the stimulatory effect of periostin on MMP-13 expression. Further studies are in progress to investigate the potential of periostin as a druggable target for the treatment of OA. INVESTIGACI ON Y DE ESTUDIOS AVANZADOS DEL INSTITUTO POLIT ECNICO NACIONAL (CINVESTAV-IPN), MEXICO CITY, MexicoPurpose: The aim of this study was to identify the expression of Latexin of chondrocytes from the three zones of the cartilage and their possible role during the OA pathogenesis in an animal model. Methods: We conducted a proteomic study of osteoarthritic cartilage during the early stages of OA using an experimental rat model. Then, we identify and evaluated the presence of Latexin (Lxn) in the three zones of the cartilage during OA pathogenesis. Results: In this work, we performed a proteomic study of oste...
Methods: Synovial fluid (SF) samples were obtained with consent from the knee joints of osteoarthritic patients (n¼12). Samples with a WBC count greater than 2000 cells/mm 3 and a PMN composition over 25% were classified as inflammatory (n¼6), and remaining samples were classified as non-inflammatory (n¼6). Lubricin concentration was quantified using a peanut agglutinin sandwich ELISA with mAb 9G3, and purified lubricin from bovine SF as the standard. Cartilage explants from the femoral condyles of neonatal bovids were bisected, fluorescently stained, and mounted on a test frame on an inverted confocal microscope. While bathed in SF, explants were axially compressed 15% then sheared against glass at a sliding speed of 1 mm/s. Depth-dependent shear strains were calculated from the displacements of photobleached lines perpendicular to the cartilage surface (Fig 1A). Following testing, the SF was mixed in a 1:1 ratio with Hymovis, a modified HA viscosupplement, and the same test was performed on a new cartilage sample. Friction coefficients were calculated as the ratio of shear force divided by axial force. The ratio of time in static friction over one sliding cycle describes the amount of time the tissue is in contact with the glass plate before sliding, and was calculated by dividing the duration the tissue spent in static friction (t m static , Fig 1B) by the period (t cycle). Lubricin concentration, t m static / t cycle , and friction coefficients were compared between SF groups using a t-test. Shear strains were compared between SF groups þ/-HA using a two-way repeated measures ANOVA. Results: For all SF samples þ/-HA, shear strains were highest at the tissue surface and decreased with depth (Fig 2A). The addition of HA to the inflammatory group significantly reduced shear strains in the first 125mm (p<0.01), but did not decrease tissue strains in the noninflammatory group at any depth (p>0.41 for all comparisons). There was no difference in lubricin concentration between inflammatory and non-inflammatory groups (p¼0.93). However, regardless of arthritic phenotype, increased lubricin concentration correlated with decreased shear strains at the tissue surface (Fig 2B, fit to doseresponse curve). Average friction coefficients were greater in inflammatory SFs compared to non-inflammatory, but were not significant (p¼0.09). Ratios of time in static friction (t m static / t cycle) were higher in inflammatory SF compared to non-inflammatory (p<0.05). We find that the coefficient of friction is a weak predictor of strain, while the relative time in static friction is a strong predictor (Fig 2C,D). Conclusions: Our results describe distinct tribological phenotypes of inflammatory and non-inflammatory SF where strains are higher with inflammatory SF as a lubricant. Additionally, viscosupplementation has greater efficacy when combined with inflammatory SF compared to non-inflammatory. While there was no difference in lubricin levels between the arthritic SF phenotypes, lower levels of lubricin correlated with higher stra...
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