| When skin is severely damaged, the immune system is activated promptly with the action of endogenous and exogenous pathogenic agents (oxygen free radical, virus, bacterium, Dust, etc.) and produces an inflammatory reaction. Slow-healing wounds and hypertrophic or keloid scarring afer the severe skin trauma is still one of the unsolved problem in clinic. Although there are many different treatment options available for promoting wound healing and inhibiting scar formation, several contradictions exist between them. For example, enhanced growth factor activity increases the rate of wound healing but may also increases the risk of scarring formation。 Currently, scar treatments in clinic have their limitations, and some have side effects like delaying wound healing. Thus, it is very important to seek a new skin scar treatment that would promote wound healing, at same time, prevent scar formation.With the thorough studies and the development of related technologies on stem cells, the use of stem cells in the treatment of various refractory diseases has shown attractive prospects. In all of cell types attainable for cell therapy, mesenchymal stem cells (MSCs) appear to be especially interesting due to some of its features, such as sources conveniently, low immunogenicity, autologous transplantation. Studies have recently confirmed that BM-MSCs appeared to contribute to tissue repair by multiple regulatory mechanisms. And the beneficial effects of MSCs administration can be ascribed in part to their paracrine activity. In preclinical and clinical studies, intravenous MSCs improved myocardial infarction, and reduced the area of myocardial scar, and MSCs implantation has positive effects on the treatment for lung fibrosis. However, for skin scar, there is not yet related evidence and it is not known whether the efficacy may involve decrease of proliferation and collagen expression of skin fibroblasts mediated by MSC paracrine factors.For this purpose, scarring formation microenvironment simulated in vitro and in vivo is established. The present study is divided into two parts: 1. The study on the effect of human bone marrow derived-mesenchymal stem cells (HBM-MSCs) in the hypertrophic scar fibroblasts(1) HBM-MSCs were isolated, cultured, identified and amplified by the whole bone marrow adherence on plastic.(2) The hypertrophic scar fibroblasts were cultured, identified and amplified.(3) With HBM-MSCs conditioned medium acting on the hypertrophic scar fibroblasts, the proliferation and collagen expression of fibroblasts were analyzed.(4) Some key proteins secreted by HBM-MSCs were screened, which functioned for the proliferation and collagen expression of the hypertrophic scar fibroblasts. And the mechanism was explored in the progress.2. To observe the effect of bone marrow derived mesenchymal stem cell on attenuating skin fibrosis development(1) The skin progressive scar animal model was induced by bleomycin.(2) GFP transgenic mice BM-MSCs were isolated, cultured, identified and amplified. GFP+BM-MSCs were traced to estimate the apparent engraftment and biological action of the cells based on skin progressive scar model, and explore the role of MSCs in the progress of skin scar formation.(3) The mechanism of BM-MSCs attenuating fibrosis in the mouse model of dermal fibrosis was initially explored, and we evaluated the possibility of BM-MSCs as a new cell therapy in inhibiting skin scar formation.The main results and conclusions of the study are as followed:1. HBM-MSCs conditioned medium significantly reduced the proliferation and differentiation of the hypertrophic scar fibroblasts, and down-regulated the expression of collagen.2. With anti-fibrotic bioactive factors secretedby HBM-MSCs screening processes, transforming growth factor-β (TGF-P) family closely related to tissue fibrosis appeared to be highly expressed, and the levels of TGF-β1and TGF-β3were significantly greater under inflammatory environment compared to without intervention group.3. When anti-fibrotic bioactive factors secretedby HBM-MSCs were blocked with the corresponding body, the inhibitory efficacy of HBM-MSCs conditioned medium for the hypertrophic scar fibroblasts was weakened.4. The fluorescent tracer technique and tunel staining assaywere used to detect the apparent engraftment and biological action of GFP+BM-MSCs in fibrotic skin lesions after implantation, and we found the number of survival BM-MSCs was dependent on the time of engraftment and exhibited a gradual decrease trend.5. BM-MSCs had the potential that significantly inhibited the scar formation by secreting anti-fibrotic bioactive factors in skin progressive scar model.The present findings in this study demonstrated that BM-MSCs transplantation by secreting anti-fibrotic bioactive factors have significant effects upon alleviation of skin fibrosis induced by bleomycin. Furthermore, our study provide the information to indicate BM-MSCs CM could mediate a sequence of events including inflammatory factor, myofibroblasts proliferation and differentiation as well as collagen deposition and ECM homeostasis in the fibrotic changes. BM-MSCs may modulate the development of skin fibrosis in virtue of TGF-β3effects, at least in part. Of note, although TGF-β3secreted by BM-MSCs indeed may account for most of the anti-fibrotic effect, it seems unlikely that it could be only relevant efficient ingredient in term of reducing skin fibrosis and improving dermal wound healing. The beneficial effects from the paracrine factors of BM-MSCs remain partly unidentified and multiple factors might function synergistically. More importantly, our study demonstrated that the intervention therapy for skin fibrosis mice was effective, but it’s not clear whether this effect exist universality and stability, and its specific mechanism still needs to be further explored. The deep research of its basic mechanisms will help the novel therapeutic approach for fibrosis reduction promotion and will provide a new treatment strategy for anti-scar repair of skin wound.In conclusion, the findings have shown that antifibrotic paracrine effects of BM-MSCs may modulate fibroblasts proliferation and prevent collagen accumulation. These studies open new perspectives for regarding the mechanisms of action of MSCs in promoting wound healing and alleviating skin fibrosis, and provide new theoretical supports for cell therapy to reduce cutaneous scarring. |
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