Therapeutically intervening the function of RNA in vivo remains a big challenge. We here developed an exosome-based strategy to deliver engineered RNA-binding protein for the purpose of recruiting specific RNA to the lysosomes for degradation. As a proof-of-principle study, RNA-binding protein HuR was fused to the C-terminus of Lamp2b, a membrane protein localized in both exosome and lysosome. The fusion protein was able to be incorporated into the exosomes. Moreover, exosomes engineered with Lamp2b-HuR successfully decreased the abundance of RNA targets possibly via lysosome-mediated degradation, especially when the exosomes were acidified. The system was specifically effective in macrophages, which are lysosome enriched and resistant to routine transfection mediated RNAi strategy. In the CCl4-induced liver injury mouse model, we found that delivery of acidified exosomes engineered with Lamp2b-HuR significantly reduced liver fibrosis, together with decreased miR-155 and other inflammatory genes. In summary, the established exosome-based RNA-binding protein delivery strategy, namely “exosome-mediated lysosomal clearance”, takes the advantage of exosome in targeted delivery and holds great promise in regulating a set of genes in vivo.

治疗性地干预体内RNA的功能仍然是一个巨大的挑战。我们在这里开发了一种基于外泌体的策略来递送工程化的RNA结合蛋白，目的是将特异性RNA募集到溶酶体进行降解。作为原理验证研究，RNA结合蛋白HuR与Lamp2b的C末端融合，Lamp2b是一种位于外来体和溶酶体中的膜蛋白。融合蛋白能够掺入外泌体。此外，用Lamp2b-HuR改造的外泌体可能通过溶酶体介导的降解成功降低了RNA靶标的丰度，尤其是当外泌体被酸化时。该系统在富含溶酶体并且对常规转染介导的RNAi策略具有抗性的巨噬细胞中特别有效。在CCl4诱导的肝损伤小鼠模型中，我们发现，用Lamp2b-HuR设计的酸化外泌体的递送可显着减少肝纤维化，同时减少miR-155和其他炎症基因。总之，已建立的基于外泌体的RNA结合蛋白递送策略，即“外泌体介导的溶酶体清除”，利用了外泌体的靶向递送优势，并有望在体内调节一组基因。