microRNA-378a (miR-378a) is one of the most highly expressed microRNAs in the heart. However, its role in the human cardiac tissue has not been fully understood. It was observed that miR-378a protects cardiomyocytes from hypertrophic growth by regulation of IGF1R and the expression of downstream kinases. Increased levels of miR-378a were reported in the serum of Duchenne muscular dystrophy (DMD) patients and female carriers of DMD gene-associated mutations with developed cardiomyopathy. In order to shed more light on the role of miR-378a in human cardiomyocytes and its potential involvement in DMD-related cardiomyopathy, we generated two human induced pluripotent stem cell (hiPSC) models; one with deletion of miR-378a and the second one with deletion of DMD exon 50 leading to the DMD phenotype. Our results indicate that lack of miR-378a does not influence the pluripotency of hiPSC and their ability to differentiate into cardiomyocytes (hiPSC-CM). miR-378a-deficient hiPSC-CM exhibited, however, significantly bigger size compared to the isogenic control cells, indicating the role of this miRNA in the hypertrophic growth of human cardiomyocytes. In accordance, the level of NFATc3, phosphoAKT, phosphoERK and ERK was higher in these cells compared to the control counterparts. A similar effect was achieved by silencing miR-378a with antagomirs. Of note, the percentage of cells with nuclear localization of NFATc3 was higher in miR-378a-deficient hiPSC-CM. Analysis of electrophysiological properties and Ca²⁺ oscillations revealed the decrease in the spike slope velocity and lower frequency of calcium spikes in miR-378a-deficient hiPSC-CM. Interestingly, the level of miR-378a increased gradually during cardiac differentiation of hiPSC. Of note, it was low until day 15 in differentiating DMD-deficient hiPSC-CM and then rose to a similar level as in the isogenic control counterparts. In summary, our findings confirmed the utility of hiPSC-based models for deciphering the role of miR-378a in the control and diseased human cardiomyocytes.

microRNA-378a (miR-378a) 是心脏中表达最高的 microRNA 之一。然而，它在人体心脏组织中的作用尚未完全清楚。据观察，miR-378a 通过调节 IGF1R 和下游激酶的表达来保护心肌细胞免受肥大性生长。据报道，杜氏肌营养不良症 (DMD) 患者和患有发展为心肌病的DMD基因相关突变的女性携带者的血清中 miR-378a 水平升高。为了更多地阐明 miR-378a 在人类心肌细胞中的作用及其在 DMD 相关心肌病中的潜在作用，我们生成了两个人类诱导多能干细胞 (hiPSC) 模型。一种缺失 miR-378a，另一种缺失DMD外显子 50 导致 DMD 表型。我们的结果表明，缺乏 miR-378a 不会影响 hiPSC 的多能性及其分化为心肌细胞 (hiPSC-CM) 的能力。然而，与同基因对照细胞相比，缺乏 miR-378a 的 hiPSC-CM 表现出明显更大的尺寸，表明该 miRNA 在人心肌细胞肥大生长中的作用。因此，与对照对应物相比，这些细胞中 NFATc3、磷酸化AKT、磷酸化 ERK 和 ERK 的水平更高。用 antagomir 使 miR-378a 沉默也可以达到类似的效果。值得注意的是，在 miR-378a 缺陷型 hiPSC-CM 中，具有 NFATc3 核定位的细胞百分比较高。电生理特性和Ca ^2+分析振荡揭示了 miR-378a 缺陷型 hiPSC-CM 中尖峰斜率速度的降低和钙尖峰的频率降低。有趣的是，在 hiPSC 的心脏分化过程中，miR-378a 的水平逐渐升高。值得注意的是，直到第 15 天，它在区分DMD缺陷型 hiPSC-CM 时一直很低，然后上升到与等基因对照对应物相似的水平。总之，我们的研究结果证实了基于 hiPSC 的模型在破译 miR-378a 在对照和患病人类心肌细胞中的作用方面的效用。