It is well known that estrogens are implicated in the pathogenesis of osteoarthritis. Raloxifene is a selective estrogen receptor modulator used in the treatment of osteoporosis, though little is known about the possible effects of raloxifene on cartilage metabolism. The aim of our study was to evaluate the possible in vitro effects of raloxifene in human osteoarthritis chondrocytes cultivated in the presence or absence of Interleukin-1 beta (IL-1β) (5 ng/ml). The effects of 0.1 μM and 1 μM of raloxifene in the culture medium were assessed using an immuno-enzymatic method for proteoglycans and metalloproteinase-3 (MMP-3), and the Griess method for nitrite. Gene expression of inducible Nitric Oxide Synthase (iNOS) was detected by real-time PCR. A morphological analysis was performed by transmission electron microscopy (TEM). Cell viability was significantly (P<0.01) reduced by the IL-1β, and restored to basal levels by raloxifene at both of the concentrations used. The presence of IL-1 β led to a significant decrease (P<0.01) in proteoglycan levels as well as a significant increase of MMP-3 and NO (P<0.01). When the cells were co-incubated with IL-1β and raloxifene, a significant and dose-dependent increase in proteoglycans and a reduction of MMP-3 and nitric oxide (NO) were detected. iNOS was noticeably expressed in IL-1β stimulated chondrocytes, while raloxifene decreased in a very significant manner the gene expression of iNOS at both of the concentrations used. The results of the biochemical evaluation were confirmed by TEM. Our data suggest that raloxifene may have a potential chondroprotective role in osteoarthritis.
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