Comparative study between coral-mesenchymal stem cells-rhBMP-2 composite and auto-bone-graft in rabbit critical-sized cranial defect model

Tissue engineered bone has become a bone substitute for the treatment of bone defects in animal research. This study investigated the osteogenesis capacity of coral-MSCs-rhBMP-2 composite with the auto-bone-graft as control. Coral-MSCs-rhBMP-2 composite were fabricated by coral (as main scaffold), rhBMP-2 (as growth factor), and MSCs (cultured from iliac marrow as seed cells). Critical-sized defects (d = 15 mm) were made on forty rabbits crania and treated by different composite scaffolds: iliac autograft (n = 8), coral (n = 8), rhBMP-2/coral (n = 8), and MSCs/rhBMP-2/coral (n = 8). The defects were evaluated by gross observation, radiographic examination, histological examination, and histological fluorescence examinations after 8 and 16 weeks. The results showed that repair of bone defect was the least in coral group, and significant ingrowth of new bone formation and incorporation could be seen with 77.45% +/- 0.52% in radiopacity in MSCs/rhBMP-2/coral group, which was similar to that in iliac autograft group (84.61% +/- 0.56% in radiopacity). New bone formation in MSCs/rhBMP-2/coral group was more than that in rhBMP-2/coral group. And osteogenesis rate in MSCs/rhBMP-2/coral group (10.23 +/- 1.45 microm) was much faster than that in rhBMP-2/coral group (5.85 +/- 2.19 microm) according to histological fluorescence examination. Newly formed bone partly came from induced MSCs in composite scaffold according to bromodeoxyuridine immunohistochemical examination. These data implicated that MSCs could produce synergic effect with coral-rhBMP-2, and the tissue engineered bone of coral-MSCs-rhBMP-2 is comparable to auto-bone-graft for the repair of critical-sized bone defect.