The effects of COX-2 inhibitor during osteogenic differentiation of bone marrow-derived human mesenchymal stem cells.

Cyclooxygenase-2 (COX-2) inhibitors suppress bone repair and bone formation by suppressing angiogenesis as well as potentially interfering with osteoblast and osteoclast functions. In spite of these reports, there is a controversy over the exact effects of COX-2 inhibitors on bone formation processes itself. This work was designed to investigate the effect of COX-2 inhibitor on osteogenesis of human bone marrow-derived mesenchymal stem cells (MSC). MSCs in osteogenesis were treated with COX-2 inhibitor (celecoxib and naproxen) in the absence or presence of interleukin-1β (IL-1β), which was used to induce inflammation. Following differentiation, alkaline phosphatase (ALP) and calcium contents of IL-1β-treated MSC were significantly reduced by high doses of COX-2 inhibitors compared with the low-dose group. However, in non-inflammatory-conditioned MSCs, ALP and calcium contents were not reduced by COX-2 inhibitors. The mRNA expression of Runx2/Cbf alpha 1, Dlx5, and osteocalcin was also decreased by COX-2 inhibitors in inflammatory-conditioned MSCs and showed a significant decrease for the high dose while they remained constant in the non-inflammatory-conditioned MSCs. These data indicate that the osteogenic potential of MSC is inhibited/delayed by the treatment of high-dose NSAIDs under inflammatory conditions.