减体积肝移植的供肝体积过小有可能导致严重的移植肝损伤甚至肝功能衰竭，而现有的防治措施尚存在诸多局限。缺氧预处理的骨髓间充质干细胞（BM-MSC）是目前的研究热点。我们前期研究也证实缺氧预处理的BM-MSC移植可通过旁分泌VEGF减轻大鼠肝大部切除后的肝损伤、促进肝再生，且可改善小体积肝移植术后大鼠生存率，然其对小体积肝移植供肝损伤的保护作用及相关分子机制尚不清楚。研究显示microRNAs参与缺氧环境下BM-MSC的功能调节，我们也发现缺氧预处理的BM-MSC胞内miR-199a的水平显著下降，伴随HIF-1a及VEGF水平的升高，为探索缺氧预处理BM-MSC治疗小体积肝损伤的机制提供了新的契机。本研究拟以缺氧预处理为切入点，以miR-199a为研究靶点，在大鼠小体积肝移植的基础上探讨BM-MSC移植改善小体积肝损伤的作用及机制。研究成果将为小体积肝移植的相关基础研究和临床治疗提供新的思路

Reduced-size and living-donor liver transplantation are introduced to counter the graft shortage in the context of more and more end-stage liver disease patients waiting for a liver transplantation. However, severe graft injury or even graft failure may arise if the graft volume doesn't meet the body's demands. The efficacy of current treatments is not satisfying. Hypoxia preconditioned BM-MSC is drawing much attention now as it can treat many type of tissue injury by its prominent paracrinal function. We confirmed in our pilot study that hypoxia preconditioned BM-MSC reduced liver injury and promoted liver regeneration in rat massive hepatectomy by producing VEGF. It also improved the survival of small-for-size liver transplantation rats when infused into the remnant liver graft. The mechanism underlying is still unclear. It's reported that microRNAs are involved in change of function of BM-MSC under hypoxia environment. We found the level of miR-199a in BM-MSC significantly decreased accompanied with increased expression of HIF-1a and VEGF when hypoxia applied, highlighting the potential role of miR-199a in paracrinal function of hypoxia preconditioned BM-MSC and its therapeutic potential in treating small-for-size liver graft injury. In this study, we will test the treatment efficacy of hypoxia preconditioned BM-MSC in rat small-for-size liver transplantation and explore the mechanism underlying, especially the role of miR-199a in paracrinal VEGF production of hypoxia preconditioned BM-MSC. The results of this study will facilitate the progress of basic studies and development of novel treatment strategies for small-for-size liver graft injury.