Platelet-poor plasma stimulates the proliferation but inhibits the differentiation of rat osteoblastic cells in vitro.

INTRODUCTION: Recent studies have shown that the use of platelet preparations in bone and implant surgery might stimulate bone formation. However, the biological mechanisms are not well understood. Moreover, few studies have attempted to evaluate the effect of platelet-poor plasma (PPP), which is a product of the platelet-rich plasma preparation process. OBJECTIVE: Thus, this study investigated the behavior of osteoblasts isolated from fetal rat calvaria cultivated in the presence of homologous PPP. MATERIAL AND METHODS: PPP was obtained by centrifugation of the rat mother's blood and used in replacement of fetal calf serum, which is classically used in primary culture procedures. Proliferation was measured by an MTT assay at 24, 48, and 72 h. Real-time PCR was performed to study the expression of Runx2, Dlx5, and osteocalcin (OC) on days 0 (4 h), 1, 3, 7, and 12. RESULTS: Alkaline phosphatase (ALP) biochemical activity was evaluated on days 0 (4 h), 1, 3, 7, and 12. Observations by phase-contrast microscopy showed that osteoblasts were able to differentiate until the mineralization of the matrix in the presence of PPP. PPP enhanced the proliferation significantly compared with the control group (P< or =0.001). PCR results showed that Runx2, Dlx5, and OC were expressed by cells in the experimental group at lower levels compared with the control group. Biochemical assay of ALP showed a lower activity in the experimental group compared with the control group (P<0.001). CONCLUSION: These results suggest that, in the presence of homologous PPP, rat osteoblastic cells are able to maintain their phenotype, with a higher rate of proliferation. However, PPP seems to inhibit osteoblastic differentiation.