Osteogenic Effect Of Tensile Force To The Cranial Sagittal Suture Of Rats In Vitro

Objective: To develop an in vitro model for crania] suture of neonatal SD rat, and explore the osteogenic effect of exogenous tensile force. Method: The parietal bones with the sagittal suture were removed from SD rats (19-days old) for organ culture. In the experimental group, tensile force (0.4 g)were applied by helical springs, whereas no tension (0g) were set in control group. These explants were observed by inverted microscope. At the end of each incubation period(0.5 hours,3 hours,6 hours),we dissected sagittal suture under anatomical microscope for RT-PCR. The changes of IGF-1 mRNA and collagen-I mRNA were investigated. Then the explants cultured for 24 hours were removed for histological observation and immunohistochemistry examination (PCNA,IGF-1,IGF-1R and co]lagen-Ⅰ) .Result: Under inverted microscope, sutures had no obvious changes in control group, whereas sutures were enlarged gradually in experimental group. Under histological observation, sutures developed normally in control group. But in experimental group, osteoblasts and capillary vessels proliferated actively in the suture. The transcripts by RT-PCR were 398bp for IGF-1,lllbp for collagen-Ⅰand 276bp forβ-actin. IGF-1 mRNA were increased significantly in experimental group compared with control group, whereas collagen-ⅠmRNA changed insignificantly. After immunohistochemistry staining, IGF-1, IGF-1R and PCNA were positive in osteoblasts and fibroblasts, and the results in experimental group were stronger than controls; Col]agen-Ⅰwere positive in connective tissue, dura mater and periosteum, and there were no obvious differences between experimental and control group. Conclusion" In vitro model of cranial suture can be cultured successively. Exogenous tensile force has osteogenic effect in cranial suture, which companied by significant increase of IGF-1 level.