Intramuscular Transplantation Of Bone Marrow-derived Mesenchymal Stem Cells Promotes Wound Healing Of Diabetic Foot Ulcers In Rats

Objective:To evaluate if transplantation of allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) could enhance the wound healing in rat diabetic foot ulcers (DFUs) and the therapeutic effect between intramuscular transplantation and subcutaneous transplantation and to investigate the possible underlying biological mechanisms involved in this process.Methods:An animal model of rat DFUs was established by injecting intraperitoneally with streptozotocin (STZ) and making a rectangular wound (3mmx7mm) on both sides of the hind feet of diabetic rats. BM-MSCs from male Wistar rats were cultured by the whole bone marrow adherence method until the third generation and were labeled with4,6-diamino-2-phenylindole (DAPI) in vitro. Forty-eight male Wistar rats were randomly divided into four groups:group A, non-diabetic rats with PBS treatment; group B, DFUs rats with PBS treatment; group C, DFUs rats with subcutaneous transplantation of BM-MSCs; and group D, DFUs with intramuscular transplantation of BM-MSCs. On days2,5,8and11post-transplantation, trace of DAPI labeled-BM-MSCs in wound tissues were detected on frozen sections and the effect of wound healing was evaluated by the rate of wound contraction, granulation tissue formation and the expression of CD31, Ki-67as well as vascular endothelial growth factor (VEGF) in wound tissues.Results:Compared to rats in group B (DFUs controls), which were treated with PBS, transplantation of BM-MSCs significantly promoted the wound healing in groups C and D. While the group D demonstrated better efficacy than group C, in which a higher rate of wound contraction (on day11, P<0.05), stronger and broader area of fluorescence on days2and5, thicker granulation tissue on day5, more CD31-positive small blood vessels (on day5and day8, P<0.05and P<0.05respectively), and a significantly higher expression of VEGF (on day8and day11, P<0.05and P<0.001respectively) were detected. While there were no differences on cellular proliferation at every time point between group C and group D. But there are significant differences when the two groups compared with group B respectively at every time point (P<0.01).Conclusions:Both the subcutaneous transplantation and intramuscular transplantation of BM-MSCs promoted the wound healing of DFUs in rats. But the intramuscular transplantation of BM-MSCs significantly enhanced the wound healing of DFUs in rats. This effect is associated with better granulation tissue formation, increased angiogenesis, and higher lever of cellular proliferation and VEGF expressions in wound tissues.