The effect of silk fibroin and rhBMP-2 on bone regeneration in rat calvarial defect model

ABSTRACT

INTRODUCTION: This study evaluated the capability of silk fibroin (SF) and recombinant human bone morphogenetic protein-2 loaded SF (SF-BMP) as a bone defect replacement matrix when grafted in a calvarial bone defect of rats in vivo. MATERIALS AND METHODS: A total 70 calvarial critical size defects (5.0 mm in diameter) made on 35 adult female Sprague-Dawley rats were used in this study. The defects were transplanted with (1) rhBMP-2 loaded silk fibroin graft (SF-BMP 0.8+10 microg), (2) Silk fibroin (SF 10 microg), and (3) no graft material (Raw). The samples were evaluated with soft x-rays, alkaline phosphatase activity, calcium/phosphate quantification, histological and histomorphometric analysis at postoperative 4 and 8 weeks. RESULTS: The SF-BMP group (48.86+/-14.92%) had a significantly higher mean percentage bone area than the SF group (24.96+/-11.01%) at postoperative 4 weeks.(P<0.05) In addition, the SF-BMP group (40.01+/-12.43%) had a higher % bone area at postoperative 8 weeks than the SF group (33.26+/-5.15%). The mean ratio of gray scale levels to the host bone showed that the SF-BMP group (0.67+/-0.08) had a higher mean ratio level than the SF group (0.61+/-0.09) at postoperative 8 weeks. These differences were not statistically significant.(P=0.168 and P=0.243, respectively) CONCLUSION: The rhBMP-2 loaded silk fibroin graft revealed fewer immunoreactions and inflammation as well as more new bone formation than the pure silk fibroin graft. Therefore, silk fibroin may be a candidate scaffold for tissue engineered bone regeneration.