Geometry-dependent functional changes in iPSC-derived cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) are a promising platform for cardiac studies in vitro, and possibly for tissue repair in humans. However, hiPSC-CM cells tend to retain morphology, metabolism, patterns of gene expression, and electrophysiology similar to that of embryonic cardiomyocytes. We grew hiPSC-CM in patterned islands of different sizes and shapes, and measured the effect of island geometry on action potential waveform and calcium dynamics using optical recordings of voltage and calcium from 970 islands of different sizes. hiPSC-CM in larger islands showed electrical and calcium dynamics indicative of greater functional maturity. We then compared transcriptional signatures of the small and large islands against a developmental time course of cardiac differentiation. Although island size had little effect on expression of most genes whose levels differed between hiPSC-CM and adult primary CM, we identified a subset of genes for which island size drove the majority (58%) of the changes associated with functional maturation. Finally, we patterned hiPSC-CM on islands with a variety of shapes to probe the relative contributions of soluble factors, electrical coupling, and direct cell-cell contacts to the functional maturation. Collectively, our data show that optical electrophysiology is a powerful tool for assaying hiPSC-CM maturation, and that island size powerfully drives activation of a subset of genes involved in cardiac maturation.

人诱导多能干细胞衍生心肌细胞（human induced pluripotent stem cell-derived cardiomyocytes, hiPSC-CM）是极具前景的体外心脏研究平台，亦有望应用于人类组织修复领域。然而，hiPSC-CM往往会保留与胚胎心肌细胞相似的形态、代谢、基因表达谱及电生理特性。我们将hiPSC-CM培养于不同尺寸与形状的图案化岛状结构中，并通过对970个不同尺寸的岛状结构开展电压与钙信号的光学记录，分析了岛状几何结构对动作电位波形及钙动力学的影响。相较于尺寸较小的岛状结构，培养于更大岛状结构中的hiPSC-CM所呈现的电活动与钙动力学特征，提示其功能成熟度更高。随后，我们对比了大小两种岛状结构的转录特征，并结合心脏分化的发育时间进程进行分析。尽管对于多数在hiPSC-CM与成人原代心肌细胞之间表达存在差异的基因而言，岛状尺寸对其表达水平影响甚微，但我们仍鉴定出一组基因，其表达变化的大部分（58%）由岛状尺寸驱动，且这些变化与功能成熟相关。最后，我们将hiPSC-CM培养于多种形状的岛状结构中，以探究可溶性因子、电耦合以及直接细胞-细胞接触对功能成熟的相对贡献。综上，本研究数据表明，光学电生理技术是检测hiPSC-CM成熟状态的高效工具，而岛状尺寸可显著激活一组参与心脏成熟过程的基因的表达，从而有力驱动功能成熟进程。