THE EFFECT OF INSULIN-LIKE GROWTH-FACTOR-1 ON CRANIOFACIAL BONE HEALING

Human insulin-like growth factor 1, a known regulator of bone formatio n, was investigated for its possible effect on membranous bone formati on in a rat model. Full-thickness bone defects (10 x 10 x 1 mm) were c reated in the rat calvarium, and insulin-like growth factor 1 was admi nistered by an osmotic minipump directly into the defect enclosed by t he periosteum and dura mater. The dose of insulin-like growth factor 1 was 100 mu g every 2 weeks. The defects were studied radiographically , macroscopically, and microscopically at 3, 6, 9, and 12 weeks. The g roup treated with insulin-like growth factor 1 showed qualitative and quantitative differences when compared with the control group. The amo unt of new bone formation in the group treated with insulin-like growt h factor 1 was significantly larger than that of the control group. In the insulin-like growth factor 1 group, the location of new bone form ation occurred in the center and at the margin of the bone defect. In the control group, bone was formed only around the margin of the bone defect. This study suggests that insulin-like growth factor 1 improved membranous bone healing in vivo and that insulin-like growth factor 1 makes mesenchymal precursor cells of bone differentiate directly into bone-forming cells.