Repair of rabbit radial bone defects using bone morphogenetic protein-2 combined with 3D porous silk fibroin/-tricalcium phosphate hybrid scaffolds

Our study aimed to investigate the effect of bone morphogenetic protein-2 (BMP-2) bound to silk fibroin and -tricalcium phosphate (SF/-TCP) hybrid on the healing of critical-size radial defects in rabbits. A 15-mm critical-size defect was induced at mid-diaphysis in the left radius of 20 New Zealand white rabbits (average age, 3.5months; weight, 2.5-3.0kg). The animals were randomized into Group 1 (SF/-TCP combined with BMP-2), Group 2 (SF/-TCP alone), and Group 3 (nothing implanted). Radiographs were obtained every 2weeks and euthanasia was performed after 8weeks for visual, radiological, micro-computed tomography (micro-CT), and histological studies. Eight weeks after implantation (SF/-TCP combined with BMP-2), radiographs showed that new bone formed on the surface of the implant and had bridged the defect in Group 1. Micro-CT imaging also confirmed the formation of new bone around the implant, and the newly formed bone was quantified. Histological examination revealed newly formed bone in the implanted area. Meanwhile, there was no formation of new bone in Group 3. Among the groups, most active formation of new bones was found in Group 1, while there was no difference between Group 2 and Group 3. Based on these results, we concluded that BMP-2-SF/-TCP showed significant improvement in healing of critical-size defects. Therefore, the combination of BMP-2 and SF/-TCP would be useful in the field of bone tissue engineering.