Combination of Platelet-rich Plasma and Cyclooxygenase-2 Inhibitor Potently Stimulates Bone Marrow Stromal Cell Proliferation in Vitro

Abstract Objectives : To assess the effects of platelet-rich plasma on the proliferation of cultured mouse bone marrow stromal cells and on the production of cyclooxygenase-2 and prostaglandin E 2 by these cells, and to determine whether the mitogenic activity of platelet-rich plasma is enhanced by combination with a selective cyclooxygenase-2 inhibitor Materials and Methods : A dish with 2 chambers, separated by a porous membrane, and platelet-rich plasma gel were used to assess the effects of platelet-rich plasma on cultured mouse bone marrow stromal cells in the absence of serum. The cells were cultured for 7 days with low (0.05 mL), medium (0.25 mL), or high (0.5 mL) volumes of platelet-rich plasma gel, and the effects on bone marrow stromal cell proliferation were examined. Concentrations of cyclooxygenase-2 and prostaglandin E 2 in the culture media were assayed. The effect of celecoxib, a cyclooxygenase-2 inhibitor, on the mitogenic activity of platelet-rich plasma was examined. The mitogenic activity of platelet-rich plasma was compared between bone marrow stromal cells from cyclooxygenase-2-deficient mice and bone marrow stromal cells from wild-type littermates. Results : Platelet-rich plasma stimulated bone marrow stromal cell proliferation over a 7-day period. Platelet-rich plasma potently increased the cyclooxygenase-2 mRNA level and prostaglandin E 2 production, and endogenous prostaglandin E 2 treatment inhibited the proliferation of bone marrow stromal cells. The cyclooxygenase-2 inhibitor celecoxib stimulated the mitogenic activity of platelet-rich plasma. The mitogenic activity of platelet-rich plasma that was added to the culture medium of bone marrow stromal cells derived from cyclooxygenase-2-deficient mice was approximately twice that of platelet-rich plasma added to the culture medium of bone marrow stromal cells derived from wild-type mice. Conclusions : Platelet-rich plasma may directly induce bone formation by stimulating the proliferation of bone marrow stromal cells. Because cyclooxygenase-2 induction by platelet-rich plasma blunts its mitogenic activity, combination with a cyclooxygenase-2 inhibitor may enhance the osteogenic activity of platelet-rich plasma.