Objective: The investigate the effect of transplantation of bone marrow mesenchymal stem cells (MSCs) transfected with TGF-β1 on survival of prefabricated flap and the mechanism. 
Methods: The rat MSCs were isolated and cultured, and then transfected with pcDNA3.1 (+)/TGF-β1 eukaryotic expression vectors through liposome delivery system. The phenotype and tube formation ability in vitro of the MSCs after transfection were determined. Twelve SD rats were used, and random flaps with 5 cm in length and 1 cm in width were established on the symmetric parts of the back of the rats, and then the bottom of the flap on both sides was injected with MSCs after transfection (experimental side) or vehicle (control side), respectively. The survival rate of flap was calculated and the vessel density in the flap was determined by HE and immunohistochemical staining.
Results: Flow cytometry analysis showed that bone marrow stem cells transfected with TGF-β1 exhibited the characteristics of the naïve MSCs, and had better tube formation ability in vitro. In the flaps on experimental side injected with MSCs transfected with TGF-β1, the survival rate was significantly higher than that in the flaps on control sides (82.83% vs. 61.33%, P<0.05), and meanwhile, the capillary density was significantly greater than that in the flaps on control sides (19.69 vs. 8.19, P<0.05).
Conclusion: Transplantation of MSCs transfected with TGF-β1 can promote angiogenesis in skin flaps and thereby improve the survival of the flaps.