Purpose: Clinical and in vitro studies suggest that subchondral bone sclerosis due to abnormal osteoblasts (Ob) is involved in the progression and/or onset of osteoarthritis (OA). Human Ob isolated from sclerotic subchondral OA bone tissue show an altered phenotype, a decreased canonical Wnt/s-catenin signaling pathway (cWnt), and a reduced mineralization in vitro, alterations linked with an abnormal response to BMP-2. Recent studies have shown an association between dietary polyphenols and the prevention of OA. Resveratrol (RSV) is a polyphenolic phytoestrogen that activates Sirtuin 1, which we previously showed to be reduced in OA Ob. RSV also stimulates Ob differentiation and may have a positive effect on cartilage protection. RSV regulates the cWnt pathway in different cell systems and stimulates BMP-2 expression in human Ob, however, the role of RSV and its effect in OA Ob remains unknown. Here we investigated the role of RSV in OA Ob and if it is responsible for their altered response to BMP-2. Methods: We prepared primary human subchondral Ob using the sclerotic medial portion of the tibial plateaus of OA patients undergoing total knee arthroplasty, or from tibial plateaus of normal individuals at autopsy. The expression of genes was evaluated by qRT-PCR and the protein production by Western blot analysis. Alkaline phosphatase activity (ALPase) and osteocalcin release (OC) were measured by substrate hydrolysis and EIA respectively. The cWnt pathway was evaluated using two approaches: 1) target gene expression was measured using the TOPflash TCF/lef luciferase reporter assay, and 2) intracellular signaling partners beta-catenin and phospho beta-catenin levels were evaluated by Western blot analysis. Mineralization in response to RSV was evaluated by Alizarin red staining. Results: OA Ob showed an increased alkaline phosphatase activity and osteocalcin release that were partly corrected in presence of increasing doses of RSV. RSV had little effect on cell proliferation and only slightly affected the Bax/Bcl2 ratio, an indicator of cell survival. The expression of Runx2/Cbfa1 and PPARgamma were not affected by increasing doses of RSV. However, although it did not affect Sirtuin1 expression, RSV reduced the expression of leptin. Moreover, Wnt3a alone increased beta-catenin levels and cWnt signaling activity, and both parameters were further increased by RSV treatment. The BMP-2-dependent mineralization of OA Ob, which is also reduced compared to normal, was partially restored by RSV treatment as detected by alizarin red staining. Conclusions: These data indicate that RSV can promote the Wnt/bcatenin signaling pathway which is altered OA Ob. This last situation could explain the role of RSV on alkaline phosphatase activity, osteocalcin release, and in vitro mineralization which are all altered in these cells.
Abed, É., Delalandre, A., Pelletier, J.-P., Martel-Pelletier, J., & Lajeunesse, D. (2014). Resveratrol Regulates the Wnt/ß-catenin pathway in human osteoarthritis osteoblasts. Osteoarthritis and Cartilage, 22, S158–S159. https://doi.org/10.1016/j.joca.2014.02.294