Serum adipokines in osteoarthritis; comparison with controls and relationship with local parameters of synovial inflammation and cartilage damage.

OBJECTIVE: Adipose tissue is an endocrine tissue releasing adipokines suggested to be involved in the pathogenesis of osteoarthritis (OA). Nevertheless, their relative contribution and exact mechanisms are still ambiguous. The aim of this study is to compare serum adipokine levels between end-stage knee OA patients and controls and to relate these serum levels to local parameters of cartilage damage and synovial inflammation. METHODS: Serum was collected from 172 severe knee OA patients, shortly before total knee replacement (TKR) surgery and from 132 controls without radiographic knee OA [Kellgren & Lawrence (K&L) = 0]. Serum adiponectin, leptin, and resistin levels were measured by enzyme-linked immunosorbent assay (ELISA). Cartilage and synovial tissue were collected at TKR surgery and assessed for cartilage degeneration and synovial inflammation by histochemistry and biochemical analyses. RESULTS: The adipokine levels were all distinctly higher in OA patients as compared to controls. Especially adiponectin and leptin were associated with female gender (stand beta = 0.239 and 0.467, respectively, P < 0.001) and body mass index (BMI) (stand beta = -0.189 and 0.396, respectively, P < 0.001). No associations between serum levels of adipokines and cartilage damage (histochemistry, proteoglycan content) were found whereas weak but positive associations with synovial inflammation were found [adiponectin and interleukin-1ß (IL-1ß), stand beta = 0.172, P = 0.02; resistin and histology, stand beta = 0.183, P = 0.034, adjusted for demographics]. CONCLUSION: This study suggests an important involvement of adipokines in OA patients considering their high serum levels compared to controls. Associations of systemic adipokines with local synovial tissue inflammation were found, although not represented by similar relations with cartilage damage, suggesting that adipokines are of relevance in the inflammatory component of OA.

In end stage osteoarthritis, cartilage tissue pentosidine levels are inversely related to parameters of cartilage damage.

OBJECTIVES: Age is the most prominent predisposition for development of osteoarthritis (OA). Age-related changes of articular cartilage are likely to play a role. Advanced glycation endproducts (AGEs) accumulate in cartilage matrix with increasing age and adversely affect the biomechanical properties of the cartilage matrix and influence chondrocyte activity. In clinical studies AGEing of cartilage and its relation to actual cartilage damage can only be measured by surrogate markers (e.g., serum, skin or urine AGE levels and imaging or biochemical markers of cartilage damage). In this study actual cartilage AGE levels were directly related to actual cartilage damage by use of cartilage obtained at joint replacement surgery. METHODS: Cartilage and urine samples were obtained from 69 patients undergoing total knee replacement. Samples were analyzed for pentosidine as marker of AGE. Cartilage damage was evaluated macroscopically, histologically, and biochemically. RESULTS: Cartilage and urine pentosidine both increased with increasing age. The higher the macroscopic, histological, and biochemical cartilage damage the lower the cartilage pentosidine levels were. In multiple regression analysis age is not found to be a confounder. CONCLUSION: There is an inverse relation between cartilage AGEs and actual cartilage damage in end-stage OA. This is likely due to ongoing (ineffective) increased turnover of cartilage matrix proteins even in end stage disease.

The chondroprotective effect of selective COX-2 inhibition in osteoarthritis: ex vivo evaluation of human cartilage tissue after in vivo treatment.

OBJECTIVE: Recent in vitro studies showed that celecoxib, a selective cyclooxygenase (COX)-2 inhibitor, protects human osteoarthritic cartilage tissue from degeneration. The objective was to substantiate these beneficial effects in an in vivo (clinical) study with celecoxib treatment of patients with severe knee osteoarthritis (OA) and subsequent evaluation of cartilage tissue ex vivo. METHODS: Patients with knee OA were treated 4 weeks prior to total knee replacement surgery with either celecoxib 200mg b.d., indomethacin 50mg b.d., or received no treatment. During surgery cartilage and synovium were collected and analyzed in detail ex vivo. RESULTS: When compared to non-treated patients, patients treated with celecoxib showed significant beneficial effects on proteoglycan synthesis, -release, and -content, confirming the in vitro data. In the indomethacin group, no significant differences were found compared to the control group. On the contrary, a tendency towards a lower content and lower synthesis rate was found. In the treated groups prostaglandin-E(2) levels were lower than in the control group, indicating COX-2 inhibition. Ex vivo release of interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha by synovial tissue was decreased by treatment with celecoxib, whereas in the indomethacin group only IL-1 beta release was decreased. CONCLUSION: Using this novel approach we were able to demonstrate an in vivo generated chondrobeneficial effect of celecoxib in patients with end stage knee OA.