间充质干细胞源性外泌体诱导肺泡巨噬细胞极化防治肝移植急性肺损伤的作用研究

Acute lung injury (ALI) is a major cause of early death after liver transplantation. The mechanisms of ALI still remain to be elucidated and there’s a lack of effective prevention and treatment. In our previous studies we discovered that alveolar macrophages (AM) mainly existed as M1 phenotype exerting pro-inflammatory activity in lungs suffering severe ALI. The proportion of M1 over M2 is in accordance with the severity of ALI. Meanwhile, in vitro studies have demonstrated that exosomes secreted from Mesenchymal Stem Cells (MSC) can shift stimulated macrophages from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. Based on these facts we postulate that AM polarization regulated by MSC exosomes may be therapeutic to perioperative ALI associated with liver transplantation. The current study aims to explore whether the regulation of AM phenotype by MSC exosomes will be effective in ameliorating ALI following liver transplantation, by applying MSC exosomes treatment on allogenic liver transplantation model of rats, autologous liver transplantation model of CD11c-DRT transgenic mice excluding M1 macrophages and ex vivo isolated lung perfusion model. Moreover, mRNA profile analysis of MSC-secreted exosomes induced by various conditions will be conducted to screen and verify the differences among their mRNA profiles, followed by functional analysis to elucidate the underlying mechanisms in which MSC exosomes regulate AM polarization. This study will help provide further theoretical insight for the prevention and treatment of perioperative ALI associated with liver transplantation.

急性肺损伤(ALI)是肝移植术后早期死亡的主要原因，目前暂无有效防治手段。前期研究证实ALI显著的肺组织中肺泡巨噬细胞(AM)主要以促炎活性的M1表型存在，M1/M2比例与ALI严重程度一致，且MIF/CD74通路参与AM极化的调控；预实验发现活化间充质干细胞（MSC）外泌体能促进巨噬细胞由M1向有抗炎活性的M2表型转化，且通过生物信息学分析PCR检测验证发现miR-21是MIF的可能调控基因。据此，我们提出“活化MSC外泌体通过miR-21负调控MIF/CD74信号通路诱导AM向M2转化是防治肝移植ALI的新途径”的假设。本课题拟用大鼠肝移植模型、CD11c-DRT转基因小鼠剔除巨噬细胞后离体肺灌注模型，结合体外细胞学研究，明确MSC外泌体能否通过诱导AM极化减轻肝移植围术期ALI，并从miR-21与MIF/CD74通路关系入手，探讨其机制，为肝移植围术期ALI防治提供理论及实验依据。

间充质干细胞（MSC）外泌体在急性肺损伤（ALI）防治中的机制尚未阐明。我们发现ALI显著的肺组织中肺泡巨噬细胞(AM)主要以促炎活性的M1表型存在，且通过预实验证明活化间充质干细胞外泌体能促进巨噬细胞由M1向有抗炎活性的M2表型转化，且通过生物信息学分析PCR检测验证发现miR-21是MIF的可能调控基因。本项目通过体外细胞学实验验证了活化的间充质干细胞外泌体可抑制肺泡巨噬细胞M1的极化；采用大鼠肝移植模型验证了活化的间充质干细胞来源的外泌体可减轻肺组织巨噬细胞的浸润，且多为M2表型；利用CD11c-DRT转基因小鼠剔除巨噬细胞后离体肺灌注模型证明miR-21通过负调控MIF/CD74信号通路诱导肺泡巨噬细胞向M2表型转化，为寻找肝移植后急性肺损伤的保护治疗靶点提供科学依据。