外泌体来源的 CircWhsc1 通过激活 TRIM59/STAT3/Cyclin B2 通路促进心肌细胞增殖和心脏修复。

INTRODUCTION: Extracellular vesicles (EVs)-mediated cell-to-cell communication is crucial for hypoxia-induced cell proliferation and tissue repair, but its function in endogenous cardiac regeneration is still unknown. OBJECTIVES: Herein, we aimed to determine whether hypoxia-inducible circWhsc1 in endothelial EVs promoted cardiomyocyte (CM) proliferation and cardiac regeneration. METHODS: RNA-sequence data was used to identify EV circRNAs that were involved into endogenous cardiac regeneration. Quantitative polymerase chain reactions were conducted to determine circRNA expression in tissue, cells and EVs. Gain- and loss-of-function assays were performed to explore the function of EV-derived circWhsc1 during cardiac regeneration. Western blotting and RNA pulldown assays were used to investigate its underlying mechanism. RESULTS: We found that circWhsc1 was enriched in neonatal mouse hearts, particularly in cardiac ECs, and was further upregulated both in ECs and EC-derived EVs under hypoxic conditions. When cocultured with hypoxia-preconditioned neonatal ECs or their secreted EVs, both neonatal and adult CMs exhibited an increased proliferation rate and G2/M ratio, which could be attenuated by knockdown of circWhsc1 in ECs. In vivo, EC-restricted overexpression of circWhsc1 and EV-mediated delivery of circWhsc1 induced CM proliferation, alleviated cardiac fibrosis and restored cardiac function following myocardial infarction in adult mice. Mechanistic studies revealed that EV-derived circWhsc1 activated TRIM59 by enhancing its phosphorylation, thereby reinforcing the binding of TRIM59 to STAT3, phosphorylating STAT3 and inducing CM proliferation. CONCLUSION: The current study demonstrated that hypoxia-inducible circWhsc1 in EC-derived EVs induces CM proliferation and heart regeneration. EC-CM communication mediated by EV-derived circWhsc1 might represent a prospective therapeutic target for inducing cardiac repair post-myocardial infarction.

简介：细胞外囊泡（EV）介导的细胞间通讯对于缺氧诱导的细胞增殖和组织修复至关重要，但它在内源性心脏再生中的作用尚不清楚。

目的：本研究旨在确定内皮细胞 EV 中的缺氧诱导circWhsc1 是否促进心肌细胞（CM）增殖和心脏再生。

方法：利用 RNA 测序数据鉴定参与内源性心脏再生的 EV circRNAs。通过定量聚合酶链反应（qPCR）检测组织、细胞和 EV 中的 circRNA 表达。进行增益和缺失功能实验，以探讨 EV 衍生的 circWhsc1 在心脏再生过程中的功能。通过 Western blot 和 RNA 下拉实验研究其潜在机制。

结果：我们发现，circWhsc1 在新生鼠心脏中丰富，特别是在心脏 EC 中，在缺氧条件下，EC 和 EC 衍生的 EV 中进一步上调。当与缺氧预处理的新生 EC 或其分泌的 EV 共培养时，新生和成年 CM 的增殖率和 G2/M 比值均增加，而 EC 中的 circWhsc1 敲低可减弱该作用。在体内，EC 特异性过表达 circWhsc1 和 EV 介导的 circWhsc1 传递可诱导 CM 增殖，减轻心肌梗死后的心脏纤维化并恢复心脏功能。机制研究表明，EV 衍生的 circWhsc1 通过增强其磷酸化来激活 TRIM59，从而加强 TRIM59 与 STAT3 的结合，磷酸化 STAT3 并诱导 CM 增殖。

结论：本研究表明，EC 衍生 EV 中的缺氧诱导 circWhsc1 诱导 CM 增殖和心脏再生。EV 衍生的 circWhsc1 介导的 EC-CM 通讯可能代表心肌梗死后诱导心脏修复的有前途的治疗靶点。