Enhanced osseointegration by the chemotactic activity of plasma fibronectin for cellular fibronectin positive cells

Plasma fibronectin (pFN) is known to regulate cell growth, differentiation or survival of osteoblasts in vitro. It is also speculated to be important for the early phase of osseointegration, however, its actual in vivo behavior is unknown. The objective of this study is to clarify the role of pFN during osseointegration. We developed a titanium ion-plated acrylic implant (Ti-acryl) for thin sectioning without removal of the implant. Either Ti-acryl or pFN-coated Ti-acryl (FN-Ti-acryl) was implanted in the mouse femur. Samples were taken on days 1–7 and on day 14 after the operation, and were decalcified and paraffin embedded. The bone healing process and immunofluorescence localization of pFN and cellular fibronectin (cFN), a marker for fibroblastic cells were examined. Simultaneously, the effect of pFN on chemotaxis, proliferation and differentiation of bone marrow stromal cells (BMSCs) was analyzed in vitro. The in vivo results showed that faster direct bone formation was seen for the FN-Ti-acryl group compared to the Ti-acryl group. The in vitro results showed that pFN significantly promoted BMSCs chemotaxis, however, had no effect on proliferation or differentiation. The results indicate that pFN regulated chemotaxis of osteogenic cells and coating the implant with pFN enhanced earlier osseointegration.