Objective       To investigate the effects of (bone morphogenetic protein-9

BMP-9)-transfected marrow stromal cells (MSCs) on healing of goat femur defect.      Methods       Twelve goats (12-18 months) were equally randomized into a control group and an experimental group. In both groups

a critical-sized bone defect model was built by resecting the femur middle segments of the goats

and the defect regions were filled with gelatin sponge. MSCs were treated by adenovirus-mediated BMP-9 transfection and then cell suspension was added to the gelatin sponge in the experimental group

while green fluorescence protein (GFP)-transfected MSC suspension was added to the gelatin sponge in the control group. X-ray examination was conducted 1 d and 2

4

8

12

and 20 weeks after operation. Gross examination

CT examination

histological staining

and biomechanical testing were performed 20 weeks after operation.      Results       X-ray examination showed that the experimental group generated bone callus earlier and more than the control group. Gross examination and histological staining showed that the new bone of the experimental group was maturer than that of the control group. CT examination and biomechanical testing proved that the new bone of the experimental group had better remodeling and higher mechanical strength than that of the control group.      Conclusion       BMP-9-transfected MSCs can effectively promote the healing of goat femur defect.