肠道菌群干预新策略：结肠靶向递送miRNA及其在改善雌激素缺乏心脏功能受损中的应用

Recent studies have revealed that the healthy gut microbiota is essential for the maintenance of the healthy condition, while aberrant gut microbiota is associated with different diseases, such cardiovascular dysfunction. Therapeutic intervention of the gut microbiota is considered as novel strategy for the management of associated diseases, while there remains no feasible strategies to increase or decrease specific bacteria. Our preliminary study has found that the intestine epithelial cells express and secrete more miR155 in the ovariectomized (OVX) mice. Moreover, the secreted miR155 could be phagocytosed by the gut microbe and results in decreased abundance of Lactobacillus, a well-known probiotics. Additionally, our data suggest that the miR155 caused decrease of Lactobacillus play an essential role in the cardiomyopathy of OVX mice. Together, we hypothesize that therapeutic intervention of gut miR155 would remodel the microbiota and thus improve the cardiac function in the context of estrogen deficiency. In the current program, we would first confirm the mechanism how fecal miR155 changes the abundance of Lactobacillus by combinatorial use of bacterium culture, gene intervention and gene expression analysis. Then, we would try to reduce the fecal miR155 expression via construction of Eudragit S based colon specific delivery strategy. The control release effects and the effects on the Lactobacillus abundance would be explored. Finally, the effects of colon specific delivery miR155 inhibitor on the cardiac function would be also explored. We would possibly develop a novel strategy to remodel the gut microbe and thus improve cardiac function in the estrogen deficiency context, independent of fecal transplantation. The novel strategy would also shed light on the treatment of other gut microbiota related diseases.

肠道菌群参与心血管功能调节，纠正菌群紊乱有望降低心血管疾病风险。截至目前，临床依然缺乏有效纠正特定菌群紊乱的可行策略。课题组前期发现，卵巢去势模型（OVX）小鼠肠道上皮miR155分泌增加，后者被肠道菌群摄入后导致益生菌乳酸杆菌等的含量降低，是OVX小鼠低炎症状态和心脏功能受损的重要机制（Nature Commu修回），提示肠道靶向递送miRNA可能特异性纠正肠道菌群紊乱，改善雌激素缺乏条件下心脏功能。本项目拟首先联合利用基因干预、细菌生长和基因表达检测等方法，明确miR155调控乳酸杆菌增殖的分子机制；然后通过Eudragit S衣壳包裹技术构建结肠特异的miR155抑制剂递送策略，明确其降低OVX小鼠肠道miR155表达的效率，确立该策略改变肠道菌群的效能；最后探讨该策略通过改善机体炎症状态实现心脏保护的作用。本项目有望建立一种不依赖于菌群移植的菌群干预策略，为相关疾病防治提供新思路。

肠道菌群参与心血管功能调节，纠正菌群紊乱有望降低心血管疾病风险。截至目前，临床依然缺乏有效纠正特定菌群紊乱的可行策略。课题组前期发现，卵巢去势模型（OVX）小鼠肠道上皮miR155分泌增加，后者被肠道菌群摄入后导致益生菌乳酸杆菌等的含量降低，可能是OVX小鼠炎症状态和心脏功能受损的重要机制，提示肠道靶向递送miRNA可能特异性纠正肠道菌群紊乱，改善雌激素缺乏条件下心脏功能。本项目通过将细菌和候选miRNA在体外共培养，共聚焦荧光显微镜证实microRNA能够被细菌胞吞，进入细菌并调节细菌增殖能力，再利用OD值确立不同miRNA对细菌生长的调控以及细菌吞噬不同miRNA的能力，其中miR155进入乳酸杆菌后显著抑制乳酸杆菌的增殖能力；为保证菌群干预的有效性，构建了结肠靶向递送系统并对miRNA进行封装，证实结肠靶向递送miRNA系统可使miRNA富集于结肠组织，递送效率高，微球大小适合包裹miRNA，该微球包裹成功率较高，也不易进入其它组织中；在此基础上，对OVX小鼠进行miR155拮抗剂结肠靶向递送，发现可以相对特异的增加乳酸杆菌含量，部分纠正OVX小鼠的菌群紊乱，改善OVX小鼠心脏功能，降低心脏及脂肪组织的炎性反应，而结肠靶向递送miR155拮抗剂的基础上给予抗生素几乎削弱了结肠特异性递送miR155拮抗剂对OVX小鼠心脏的保护作用。本研究阐明了纠正miR155的高表达状态在保护雌激素缺乏状态下肠道菌群紊乱和相关心脏损害中的作用，在代谢综合征的条件下，结肠特异性的治疗性miRNA递送可能会使微生物群恢复到保护性表型。