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[Effects of BMP-2 gene therapy on vascularization in repairing bone defects].

OBJECTIVE
To study the effects of BMP-2 gene therapy on vascularization in repairing bone defects.


METHODS
The isolated rabbit mesenchymal stem cells (rBMSC), after being transfected by adenovirus carrying BMP-2 gene (Ad-BMP-2) and seeded on xenogeneic bone scaffolds, were used to repair 1.5 cm-long radius bone defects. Five methods were in use in the experiments: Ad-BMP-2 infected rBMSC plus antigen-free bovine cancellous bone (BCB, Group A), rBMSC-BCB plus reconstructed hBMP-2 (Group B1), Ad-LacZ infected rBMSC-BCB (Group C), rBMSC-BCB (Group D) and only BCB scaffolds (Group E). After 4, 8, and 12 weeks of the operations, capillary vessel ink infusion, vascular endothelial growth factor ( VEGF) immunohistochemical staining and histological examination were conducted.


RESULTS
After 4 weeks of the operations, usually in Group A one newly formed artery was found in every pore between the trabeculae of the BCB. The density of these intraosseous vessels was high in the periphery and decreasing towards the center of the grafts; by transmission electron microscopy, osteoblasts were always next to vascular endothelial cells and gradually developed into osteocytes with the increase of capillary vessel; VEGF expression were apparently enhanced in mesenchymocytes.


CONCLUSIONS
BMP-2 gene therapy, by up-regulating VEGF expression, indirectly induces vascularization of grafts and is of great value to the treatment of bone in union and bone defects.