Effects of Platelet-rich Plasma and Washed Platelets on Macrophage Functions

Objective: Platelet-rich plasma (PRP) is an autologous source of platelet-derived growth factors, and has been used successfully in oral surgery repair and the placement of osseointegrated implants. However, little is known about the mechanism(s) of factor release and the manner in which activation is controlled. The present study investigated the efficacy of PRP as a stimulator of interferon-g (IFN-g)-induced nitric oxide (NO) production in mouse macrophages. Methods: The mouse macrophage-like cell-line RAW264.7, was used in this study. NO production in conditioned medium was assessed by measuring the stable NO metabolite nitrite, as assessed by the Greiss reaction. Results: IFN-g-induced expression of iNOS mRNA and production of NO were additively stimulated by treatment with PRP. Washed platelet treatment was more effective for NO production of the cells. Interestingly, the formation of osteoclasts in RAW264.7 cells induced by receptor activator of nuclear factor kappa B ligand (RANKL) was inhibited by PRP treatment. Conclusions: These results suggest that PRP is a potent stimulator of IFN-g-induced mouse macrophage activation and is an inhibitor of osteoclast formation.