Gene expression of bone-related adhesive proteins in bone-implant integration

There are two types of healing processes in the bone-implant interface: contact osteogenesis and distance osteogenesis. The adhesion of osteoblasts is the prerequisite for contact osteogenesis. Cell membrane receptors that mediated adhesion of osteoblasts include integrin receptors and heparan sulfate receptors. Objective: To evaluate the gene expression of four bone-related adhesive proteins during the early stage of bone defect healing and bone-implant integration in animals. Methods: T-shaped hollow implants fabricated of commercially pure titanium with dual acid-etched surfaces were placed into the femurs of 8-week-old male Sprague-Dawley rats, and bone defects with the same size were made in the same position in other Sprague-Dawley rats. Newly formed bone was harvested at 5 days, 8 days and 16 days after the operation respectively. The gene expression of collagen I, bone sialoprotein II(BSP II), fibronectin(FN) and osteopontin(OPN) in healing of non-implant bone defect and bone-implant integration were examined using semiquantity reverse transcriptase-polymerase chain reaction. Results: The gene expression of OPN in the bone defect healing was slightly higher than that of bone-implant integration, both of them peaked at 8 days. An up-regulated expression of BSP II for the bone-implant integration over the bone defect at an early healing stage at 8 days was found, while the gene expression of collagen I and FN in the bone-implant integration was significantly higher than that of the bone defect at the same time. Conclusions: The results indicate that the gene expression of the four bone-related adhesive proteins are different between bone defect healing and bone-implant integration, collagen I and FN may show more positive effect for the early adhesion of osteoblasts to endosseous implant surface. *Supported by the National Natural Science Foundation of China. No.30300392