Effect of osteopontin in regulating bone marrow mesenchymal stem cell treatment of skin wounds in diabetic mice

Background We aimed to investigate the role of osteopontin in regulating mesenchymal stem cells transplanted to promote wound healing in diabetic mice. Methods The mesenchymal stem cells of osteopontin knock-out (KO) and wild-type (WT) mice were isolated separately for in vitro culture and characterization. A skin wound on the back of mice was established by skin punching. In 27 osteopontin KO male mice, induced diabetes mellitus was via intraperitoneal injection of streptozotocin. 9 normal mice were used as controls. The mice were divided into four groups and injected with Dulbecco's modified Eagle's medium (DMEM) or mesenchymal stem cells via the tail vein: A (diabetic mice injected with DMEM), B (diabetic mice injected with osteopontin KO mesenchymal stem cells), C (diabetic mice injected with WT mesenchymal stem cells), D (normal mice injected with DMEM). The healing times and closure rates of skin wounds were recorded. The microvessel density of healing wounds was measured, and the localized expression of osteopontin was identified by western blotting and immunohistochemistry. The migration of mesenchymal stem cells was observed on normal mice with skin wound injected with mesenchymal stem cells of C57BL6~GFP transgenic mice, which show green fluorescent under UV light. Results Compared with normal mice, the healing time of wounds in the mice with diabetes and osteopontin KO was significantly prolonged (p < 0.01). After transplanting osteopontin KO mesenchymal stem cells, the healing time was slightly shorter. Meanwhile, the healing time was significantly shorter after transplanted with WT mesenchymal stem cells and more significant neovascularization at healing wounds (p < 0.05). The expression of osteopontin in local healing wounds after transplantation of WT mesenchymal stem cells was demonstrated with western blotting and immunohistochemistry. After 4 days, the green fluoresces were noted on the wounds of mice injected with mesenchymal stem cells of fluorescent mice. Conclusions Mesenchymal stem cells can migrate to wound sites, and osteopontin plays a regulatory role in mesenchymal stem cells promoting the healing of diabetic skin wounds. Copyright © 2014 John Wiley & Sons, Ltd.