Engrafted bone marrow-derived Flk-1+ mesenchymal stem cells regenerate skin tissue

Stem cell plasticity has created great interest because of its potential therapeutic application in degenerative or inherited diseases. Transplantation of bone marrow-derived stem cells was shown to give rise to cells of muscle, liver, nerve, endothelium, epithelium, and so on. But there are still disputes about stem cell plasticity, especially concerning the contribution of bone marrow-derived cells to skin cells. In this study, CM-DiI fluorescence-labeled Flk-1(+) bone marrow mesenchymal stem cells (bMSCs) of BALB/c mice (H-2K(d), white) were transplanted into lethally irradiated C57BL/6 mice ( H-2K(b), black). By fluorescence tracing, we found that donor cells could migrate and take residency at the skin, which was confirmed by Y chromosome-specific PCR and Southern blot. The recipient mice grew white hairs about 40 days later and white hairs could spread over the body. Immunochemistry staining and RT-PCR demonstrated that skin tissue within the white hair regions was largely composed of donor-derived H-2K(d) cells, including stem cells and committed cells. Furthermore, most skin cells cultured from white hair skin originated from the donor. Thus, our findings provide direct evidence that bone marrow-derived cells can give rise to functional skin cells and regenerate skin tissue. These may have important scientific implications in stem cell biology and transplantation therapy for skin tissue injury.