Indomethacin Promotes Adipogenesis of Mesenchymal Stem Cells Through a Cyclooxygenase Independent Mechanism

Regulation of mesenchymal stem cell (MSC) lineage selection is important for the generation of bone mass. Inhibition of cyclooxygenase-2 (COX2) may increase adipogenesis at the cost of decreasing osteoprogenitor output. Here we investigated the role of COX2 and its products during MSC differentiation. Indomethacin stimulated adipogenesis (increased aP2, adiponectin and lipid droplets) of CH310T1/2 stem cells as well as marrow-derived MSCs to a degree similar to the PPAR gamma 2 ligand, rosiglitazone. Unlike rosiglitazone, indomethacin significantly upregulated PPAR gamma 2 expression. Indomethacin and the COX2 specific inhibitor celecoxib suppressed PGE2 production, but celecoxib did not induce adipogenesis. As well, addition of PGE2 failed to reverse indomethacin induced adipogenesis, indicating that indomethacin's effects were prostaglandin independent. In MSCs over-expressing PPAR gamma 2 and RXR alpha, indomethacin did not increase PPAR-induced transcription, while rosiglitazone and 15d-PGJ2 did (1.7- and 1.3-fold, respectively, P < 0.001). We considered whether indomethacin might directly affect C/EBP beta proximally to PPAR gamma 2 induction. Indomethacin significantly increased C/EBP beta expression and protein within 24 h of addition. These results indicate that indomethacin promotes adipogenesis by increasing C/EBP beta and PPAR gamma 2 expression in a prostaglandin-independent fashion. This effect of indomethacin is pertinent to potential deleterious effects of this commonly used anti-inflammatory drug on bone remodeling and tissue healing. J. Cell. Biochem. 111: 1042-1050, 2010. (C) 2010 Wiley-Liss, Inc.