Background and Aims Cardiac fibrosis in response to injury leads to myocardial stiffness and heart failure. At the cellular level, fibrosis is triggered by the conversion of cardiac fibroblasts (CF) into extracellular matrix–producing myofibroblasts. miR-24-3p regulates this process in animal models. Here, we investigated whether miR-24-3p plays similar roles in human models. Methods and Results Gain– and loss–of–function experiments were performed using human induced pluripotent stem cell–derived cardiomyocytes (hCM) and primary hCF under normoxic or ischaemia–simulating conditions. hCM–derived extracellular vesicles (EVs) were added to hCF. Similar experiments were performed using three-dimensional human cardiac microtissues and ex vivo–cultured human cardiac slices. hCF transfection with miR-24-3p mimic prevented TGFβ1–mediated induction of FURIN, CCND1 and SMAD4—miR-24-3p target genes participating in TGFβ1–dependent fibrinogenesis —, regulating hCF–to–myofibroblast conversion. hCM secreted miR-24-3p as EV cargo. hCM–derived EVs modulated hCF activation. Ischaemia–simulating conditions induced miR-24-3p depletion in hCM-EVs and microtissues. Similarly, hypoxia downregulated miR-24-3p in cardiac slices. Analyses of clinical samples revealed decreased miR-24-3p levels in circulating EVs in acute myocardial infarction (AMI) patients, compared with healthy subjects. Post-mortem RNAScope analysis showed miR-24-3p downregulation in myocardium from AMI patients, compared with patients who died from noncardiac diseases. Berberin, a plant–derived agent with miR-24-3p–stimulatory activity, increased miR-24-3p contents in hCM-EVs, downregulated FURIN, CCND1 and SMAD4, and inhibited fibrosis in cardiac microtissues. Conclusions These findings suggest that hCM may control hCF activation through miR-24-3p secreted as EV cargo. Ischaemia impairs this mechanism, favouring fibrosis.

中文翻译：

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心肌细胞作为细胞外囊泡货物分泌的 miR-24-3p 抑制人心脏微组织的纤维化


背景和目标 对损伤的反应性心肌纤维化会导致心肌僵硬和心力衰竭。在细胞水平上，心脏成纤维细胞 （CF） 转化为产生细胞外基质的肌成纤维细胞会触发纤维化。miR-24-3p 在动物模型中调节这一过程。在这里，我们研究了 miR-24-3p 在人类模型中是否发挥相似的作用。方法和结果 在常氧或缺血模拟条件下，使用人诱导多能干细胞来源的心肌细胞 （hCM） 和原代 hCF 进行功能获得和丧失实验。将 hCM 衍生的细胞外囊泡 （EV） 添加到 hCF 中。使用三维人类心脏微组织和体外培养的人类心脏切片进行了类似的实验。用 miR-24-3p 模拟物转染 hCF 阻止了 TGFβ1 介导的 FURIN、CCND1 和 SMAD4 的诱导——参与 TGFβ1 依赖性纤维蛋白生成的 miR-24-3p 靶基因——调节 hCF 向肌成纤维细胞的转化。hCM 分泌 miR-24-3p 作为 EV 货物。hCM 衍生的 EV 调节 hCF 激活。缺血模拟条件诱导 hCM-EVs 和微组织中 miR-24-3p 耗竭。同样，缺氧下调心脏切片中的 miR-24-3p。临床样本分析显示，与健康受试者相比，急性心肌梗死 （AMI） 患者循环 EVs 中 miR-24-3p 水平降低。尸检 RNAScope 分析显示，与死于非心脏疾病的患者相比，AMI 患者心肌中 miR-24-3p 下调。小檗素是一种具有 miR-24-3p 刺激活性的植物衍生剂，可增加 hCM-EV 中的 miR-24-3p 含量，下调 FURIN、CCND1 和 SMAD4，并抑制心脏微组织中的纤维化。 结论 这些发现表明，hCM 可能通过以 EV 货物形式分泌的 miR-24-3p 控制 hCF 的激活。缺血会损害这种机制，有利于纤维化。