Abstract:

BACKGROUND: Bone morphogenetic protein 2 (BMP-2) is the unique growth factor that independently induces osteogenesis, but its promoting angiogenesis is weak, and cannot produce sufficient capillaries in the newly-born bones, thereafter, other auxilliary factors are necessary. Hypoxia-inducible factor 1α (HIF-1 α) plays an important role in promoting angiogenesis.
OBJECTIVE: To study the repair capacity of the adenovirus mediated BMP-2 combined with mutant HIF1α (Ad-BMP-2-IRES-HIF-1αmu) transfecting bone marrow mesenchymal stem cells (BMSCs) in steroid-induced avascular necrosis of the femoral head.
METHODS: Ad-BMP-2-IRES-HIF-1αmu was transfected to BMSCs, the alkaline phosphatase activity and calcium nodules alizarin red staining were conducted to detect the osteogenic ability. The rabbit model of steroid-induced avascular necrosis of the femoral head was established, and then divided into three groups: The cells were divided into three groups: Ad-BMP-2-IRES-HIF-1αmu transfected BMSCs were transplanted into group A, and untransfected BMSCs were transplanted into group B, and only the cell culture medium was added in the group C. At 8 weeks after transplantation, the expression levels of BMP-2 and HIF-1α were detected by western blot assay; the repair of avascular necrosis of the femoral head was observed by hematoxylin-eosin staining; the angiogenesis of the necrotic region was observed by toner perfusion transplantation vascular morphology. 
RESULTS AND CONCLUSION: The alkaline phosphatase activity in the transfected BMSCs and number of calcium nodules were higher than those in the untransfected BMSCs, indicating that Ad-BMP-2-IRES-HIF-1αmu could promote the osteogenic differentiation of BMSCs. The expression levels of BMP-2 and HIF-1α in the group A were significantly higher than those in the groups B and C (P < 0.05). Compared with groups B and C, obvious osteogenesis was observed in group A, the percentage of empty lacunae was significantly decreased, and trabecular bone volume fraction was significantly increased (P < 0.05). Ink perfusion results showed that compared with the groups B and C, there was a vascularization in the group A, and there was a structure of bone lacuna, an increase in blood vessel diameter, a clear connection between blood vessels, and rich and effective blood vessels in the defect area (P < 0.05). The blood vessel area in the three groups was 114.22 ± 3.78, 63.78 ± 2.61 and 21.39 ± 3.52, respectively (P < 0.05). In conclusion, BMP-2 combined with mutant HIF1α can promote the repair of steroid-induced avascular necrosis of the femoral head.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: Femur Head Necrosis, Bone Morphogenetic Proteins, Hypoxia-Inducible Factor 1, alpha Subunit, Stem Cell Transplantation, Tissue Engineering