背景：间充质干细胞（MSC）来源的外泌体先前已被证明在各种动物疾病模型中促进组织再生。这项研究调查了外泌体治疗对四氯化碳（CCl4）诱导的急性肝损伤的保护作用，并描述了可能的潜在机制。
方法：将从先前表征的人脐带来源的MSC的条件培养基中收集的外泌体腹膜内给予患有CCl4诱导的急性肝损伤的雄性CD-1小鼠。生物化学,组织学和分子参数用于评估肝损伤的严重程度。大鼠肝细胞细胞系,克隆-9用于验证通过外泌体处理的分子变化。
结果：外泌体治疗显著抑制血浆AST水平，ALT,和促炎细胞因子，包括IL-6和TNF-α，在CCl4诱导的急性肝损伤小鼠中。组织学形态测定显示，外泌体治疗后，受伤肝脏的坏死面积显着减少。始终如一，westernblot分析显示PCNA肝表达显著升高，c-Met,外泌体处理后的Ets-1和HO-1蛋白。此外,信号介质JNK的磷酸化水平显著增加，p38通过外泌体治疗恢复。免疫组织化学双重染色证实了c-Met和HO-1蛋白的核Ets-1表达和胞质定位。体外研究表明，外泌体处理增加了克隆9肝细胞的增殖，并保护它们免受CCl4诱导的细胞毒性。激酶抑制实验表明，外泌体驱动的肝保护可能是通过JNK途径介导的。
结论：外泌体治疗激活了JNK信号通路，并上调了Ets-1和HO-1的表达，从而保护肝细胞免受肝毒素诱导的细胞死亡。
BACKGROUND: Mesenchymal stem cells (MSCs)-derived exosomes have been previously demonstrated to promote tissue regeneration in various animal disease models. This study investigated the protective effect of exosome treatment in carbon tetrachloride (CCl4)-induced acute liver injury and delineated possible underlying mechanism.
METHODS: Exosomes collected from conditioned media of previously characterized human umbilical cord-derived MSCs were intravenously administered into male CD-1 mice with CCl4-induced acute liver injury. Biochemical, histological and molecular parameters were used to evaluate the severity of liver injury. A rat hepatocyte cell line, Clone-9, was used to validate the molecular changes by exosome treatment.
RESULTS: Exosome treatment significantly suppressed plasma levels of AST, ALT, and pro-inflammatory cytokines, including IL-6 and TNF-α, in the mice with CCl4-induced acute liver injury. Histological morphometry revealed a significant reduction in the necropoptic area in the injured livers following exosome therapy. Consistently, western blot analysis indicated marked elevations in hepatic expression of PCNA, c-Met, Ets-1, and HO-1 proteins after exosome treatment. Besides, the phosphorylation level of signaling mediator JNK was significantly increased, and that of p38 was restored by exosome therapy. Immunohistochemistry double staining confirmed nuclear Ets-1 expression and cytoplasmic localization of c-Met and HO-1 proteins. In vitro studies demonstrated that exosome treatment increased the proliferation of Clone-9 hepatocytes and protected them from CCl4-induced cytotoxicity. Kinase inhibition experiment indicated that the exosome-driven hepatoprotection might be mediated through the JNK pathway.
CONCLUSIONS: Exosome therapy activates the JNK signaling activation pathway as well as up-regulates Ets-1 and HO-1 expression, thereby protecting hepatocytes against hepatotoxin-induced cell death.
