Plasma rich in growth factors(PRGF)can be rapidly obtained from patient blood. PRGF has been used in regenerative therapy for soft tissue and bone formation, and represents a new and potentially useful adjunct in oral and maxillofacial bone reconstructive surgery. However, few studies have investigated the biological functions of PRGF in bone regeneration. Human mesenchymal stem cells(hMSC)isolated from human bone marrow have the capacity to commit to multiple cell types such as the osteoblastic lineage, and have been widely applied in tissue engineering studies in recent years. The aim of this study is to evaluate the effects of PRGF for osteogenic differentiation in hMSC. PRGF was prepared from whole blood centrifuged at 460 × g for 8 min. PRGF F2 was incubated with 10% calcium chloride solution at 37℃ for 1 h to trigger platelet activation and growth factor release. Activated PRGF Fraction 2 was centrifuged at 3, 000 × g for 15 min, and the supernatant was then isolated. We examined the effects of soluble factors in PRGF on proliferation and mineralization in hMSC culture supplemented with PRGF. The proliferation of hMSC was increased in osteogenic induction medium(OIM)supplemented with PRGF. Alkaline phosphatase activity increased in hMSC by PRGF. Staining for alizarin red S and von Kossa was strong in hMSC supplemented with PRGF. These results suggest that PRGF is able to promote bone generation.

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Stem/progenitor cells isolated from human dental follicles differentiate into osteogenic cells. To investigate factors associated with osteogenic differentiation/mineralization in human dental follicle cells (hDFCs), we performed gene expression profiling of hDFCs during osteogenic differentiation. Cyclooxygenase(COX)-1 and -2 were up-regulated in hDFCs cultured in osteogenic induction medium(OIM)compared to growth medium(GM). Prostaglandin E 2 (PGE 2 ), which is the most studied prostanoid derived from arachidonic acid through the actions of COXs, may regulate bone metabolism. All PGE 2 E-type prostanoid receptors(EP), EP1-EP4, were expressed in hDFCs. Real-time PCR showed that the expression of EP2 and EP4 was increased in hDFCs cultured in OIM and GM at days 10 and 17 compared to day 0. We investigated the action of PGE 2 in osteogenic differentiation using hDFCs. PGE 2 decreased gene expression levels of osterix and alkaline phosphatase, which are factors associated with osteogenic differentiation. PGE 2 elicited inhibitory action on matrix mineralization of hDFCs as seen with alizarin red S staining. These findings suggest that PGE 2 may inhibit osteogenic differentiation/mineralization of stem/progenitor cells.