Sequential induction of marrow stromal cells by FGF2 and BMP2 improves their growth and differentiation potential in vivo.

BACKGROUND: repairing bone loss by autologous grafting requires that a patient's marrow stromal cells (MSCs) be collected and cultured until the number of cells is adequate for implantation. Currently used techniques allow a slow proliferation rate and produce a culture that contains only small amounts of pluripotent stem cells that will become osteoblasts in culture.
OBJECTIVE: to develop culture conditions that permit a rapid increase in the number of MSCs while retaining or improving their potential for complete differentiation in vivo.
RESULTS: sequential applications of low doses of basic fibroblast growth factor 2 (FGF2) and bone morphogenetic protein 2 (BMP2) improved the growth and differentiation potential of MSCs. FGF2 also elevated sensitivity of the cells to BMP2. BMP2 increased the syntheses of alkaline phosphatase (ALP), collagen type I and bone sialoprotein, while FGF2 increased the expression of osteocalcin (OC). Full induction as determined by the formation of mineralised nodules in vitro was observed within 7 days. Seeding the induced cells onto scaffolds and then implanting them into nude mice resulted in newly formed bone 4 weeks later. The results of real-time polymerase chain reaction (PCR) and Western blotting suggested that FGF2 increased the pool of committed osteoblasts by up-regulating the Cbfa1/Runx2 gene. The later stages of bone formation seemed to be induced by Cbfa1/Runx2-downstream factors such as BMP2, ALP, collagen type I, bone sialoprotein and OC.
CONCLUSION: the culture system that was developed increased both the proliferation of MSC and the proportion that developed into pre-osteoblasts. 2010 Elsevier Ltd. All rights reserved.