Dose-dependent effects of platelet gel releasate on activities of human osteoblasts

Platelet-rich plasma is used in oral and maxillofacial surgery; however, its real efficacy is debated. Also, the in vitro effects on bone-specific functions are contradictory. Understanding the mechanisms of action of platelet-derived factors could be the basis for their proper use in clinical applications.

The functional parameters of osteoblasts (proliferation, alkaline phosphatase, collagen synthesis, and calcium deposition) were analyzed in vitro for 14 days in the presence of different concentrations (100%, 33%, and 11%) of platelet gel releasate (PGR).

Concentrations of 100% PGR and 33% PGR stimulated cells to proliferate more than 10% fetal calf serum. The effect on cell proliferation was dose dependent, and the addition of dexamethasone (dex) and beta-glycerophosphate (beta-GP) reduced the proliferative effects. Alkaline phosphatase activity was stimulated by 33% PGR and 11% PGR after 7 days and was induced further by dex and beta-GP. Also, collagen synthesis, measured on day 11, was stimulated by 33% PGR and 11% PGR. Calcium deposition, evaluated after 7 and 14 days, was greatest in cells treated with PGR supplemented with dex and GP. The mineralization process increased with time; on day 14, calcium aggregates were observed in all cultures treated with PGR (100%, 33%, and 11%).

PGR stimulated osteoblast proliferation in a dose dependent manner and, when used at 33% and 11%, induced maximum levels of alkaline phosphatase and collagen synthesis. Moreover, in the presence of dex and beta-GP, PGR stimulated the end maturative status of cells as expressed by the deposition of calcium nodules.