[Experimental study on repair of critical-sized cranial defect by tissue engineered bone]

To evaluate repair of critical-sized cranial defect with tissue engineered bone fabricated by coral, bone mesenchymal stem cells (MSCs) and sustainedly released recombinant human bone morphogenetic protein 2 (rhBMP-2) by collagen.

Three scaffolds of rhBMP-2 + coral, collagen + rhBMP-2 + coral and MSCs+collagen+rhBMP-2+coral were fabricated. Forty New Zealand rabbits were made the models of critical-sized defects and divided into 5 groups according to different implants: group I, auto-ilium; group II, coral; group III, rhBMP-2+coral; group IV, collagen+rhBMP-2+coral; and group V , MSCs+collagen+rhBMP-2+coral. Repair of bone defect was evaluated after 8 and 16 weeks of implantation by gross observation, X-ray, HE staining and Masson's trichrome staining.

Repair of bone defect in group V was similar to that in group I, and was better than that in group IV; and group III was worse. The gross appearance showed that defect region filled with bony tissue which had similar strength to adjacent bone and formed bone union with surrounding bone. The X-ray result displayed high radiopacity (80.45% +/- 2.52% in the 16th week). Histological observation showed new lamellar bone tissue and with few pore blank area. However, only transparent fibrous tissue filled the defect in group II.

Collagen may be a suitable sustained release system for rhBMP-2. And MSCs may have important effect on enhancing repair of bone defect. Tissue engineered bone fabricated by MSCs+collagen+rhBMP-2+coral may be a useful material for bone defect repair.