No abstract

Dietary cholesterol and accordingly increased plasma levels play a role in the development of OA. The correlation found between OA, cholesterol and ATH demonstrates that these variables are connected, but indicates the contribution of other ongoing processes in the development of OA. The suppressive effect on OA development of atorvastatin but not of ezetimibe, which had similar cholesterol exposure levels, corroborates these findings.

Objective. The infrapatellar fat pad (IPFP) in the knee joint is hypothesized to contribute to osteoarthritis (OA) development by the IFPF possibly by influencing inflammatory processes. Oxylipins are essential mediators in the inflammatory process. We undertook this study to investigate secretion by the IFPF of fatty acids and oxylipins derived from those fatty acids.Methods. IPFP explants from 13 OA donors undergoing joint replacement surgery and from 10 normal donors postmortem were cultured for 24 hours, and supernatants (fat-conditioned medium [FCM]) were collected. Liquid chromatography tandem mass spectrometry detected fatty acids and oxylipins in FCM samples. Univariate and multivariate (partial leastsquares discriminant analysis [PLS-DA]) analyses were performed, followed by pathway analysis. To validate these outcomes, a second set of OA FCM samples was measured (n ‫؍‬ 23).Results. Twenty-nine oxylipins and fatty acids could be detected in FCM. Univariate analysis showed no differences between normal donor and OA donor FCM; however, PLS-DA revealed an oxylipin/fatty acid profile consisting of 14 mediators associated with OA (accuracy rate 72%). The most important contributors to the model were lipoxin A 4 (decreased), thromboxane B 2 (increased), and arachidonic acid (increased). The statistical model predicted 64% of the second set of OA FCM samples correctly. Pathway analysis indicated differences in individual mediators rather than in complete pathways. Conclusion. The IPFP secretes multiple and different oxylipins, and a subset of these oxylipins provides a distinctive profile for OA donors. It is likely that the observed changes are regulated by the OA process rather than being a consequence of basal metabolism changes, as an increase in fatty acid levels was not necessarily associated with an increase in oxylipins derived from that fatty acid.

Objective. To determine possible patterns of synovitis on contrast-enhanced magnetic resonance imaging (CE-MRI) and its relation to pain and severity in patients with radiographic knee osteoarthritis (OA).Methods. In total, 86 patients (mean age 62 years, 66% women, median body mass index 29 kg/m 2 ) with symptomatic knee OA (Kellgren/Lawrence radiographic score 3) were included. T1-weighted, gadoliniumchelate-enhanced MRI with fat suppression was used to semiquantitatively score the extent of synovitis at 11 knee sites (total score range 0-22). Self-reported pain was assessed with 3 standardized questionnaires. Principal components analysis (PCA) was used to investigate patterns (the location and severity) of synovitis. Subsequently, these patterns were assessed for associations with pain measures and radiographic severity in adjusted logistic regression models.Results. Synovitis was observed in 86 patients and was found to be generally mild on CE-MRI (median total synovitis Conclusion. Different patterns of synovitis in knee OA were observed. The pattern that included several patellar sites was associated with pain, whereas other patterns showed no association, suggesting that pain perception in patients with knee OA is a localized response.

Purpose: Osteoarthritis (OA) is associated with obesity in which altered fatty acid levels have been observed. We investigated whether the most common fatty acids in synovial fluid influence cartilage deterioration in OA. Design: Cartilage was obtained from OA patients undergoing total knee arthroplasty. Chondrocytes or cartilage explants were cultured with linoleic (n-6 polyunsaturated), oleic (monounsaturated), or palmitic (saturated) acid. After preculture, media were renewed and inflammation was simulated in half of the samples by addition of 10 ng/mL tumor necrosis factor-α (TNFα) with or without the fatty acids. Effects on lipid uptake (Oil-Red-O), cell toxicity (lactate dehydrogenase), prostaglandin-E2 (PGE2) release and gene expression for prostaglandin-endoperoxide synthase-2 (PTGS2), matrix metalloproteinase-1 (MMP1), and MMP13, and a disintegrin and metalloproteinase with thrombospondin motifs 4 were determined on chondrocytes in monolayer. Effects on glycosaminoglycan (GAG) release were evaluated on cartilage explants. Results: None of the fatty acids were cytotoxic and all were taken up by the cells, resulting in a higher amount of intracellular lipid in chondrocytes. Linoleic acid increased PGE2 production in the presence of TNFα. Oleic acid and palmitic acid inhibited MMP1 gene expression in chondrocytes stimulated with TNFα. In cartilage explants, GAG release was also inhibited by oleic acid and palmitic acid, and oleic acid decreased PTGS2 gene expression in stimulated chondrocytes. Conclusions: Linoleic acid has a pro-inflammatory effect on cartilage whereas oleic acid and palmitic acid seem to inhibit cartilage destruction. These results indicate that altered fatty acid levels may influence loss of cartilage structure in OA.