Abstract
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.
Highlights
Human Induced pluripotent stem cell (iPSC)-derived cardiomyocytes are morphologically [1], genetically [2], and functionally closer to embryonic than adult primary myocytes [3]
High-throughput optical electrophysiology and gene expression profiling revealed that functional maturity of hiPSC-CM grown in confluent islands increased as a function of island size
For a subset of genes associated with functional maturation, changes in island size accounted for approximately 58% of the change in gene expression that occurs during cardiac maturation in human development
Summary
Human iPSC-derived cardiomyocytes (hiPSC-CM) are morphologically [1], genetically [2], and functionally closer to embryonic than adult primary myocytes [3]. Mature primary cardiomyocytes dissociated and maintained in culture rapidly lose their characteristic morphology and take a more immature appearance [6]. The cell culture environment favors an immature phenotype, as measured by morphology, gene expression, and electrophysiology. Soluble factors [10,11,12], substrate mechanical stiffness [13], and electrical and mechanical pacing [14,15] all play an important role. Cell patterning is a powerful tool for dissecting the role of different factors in maturation and development [16,17]. By tuning the geometry of cellular islands, one can probe the nature of intercellular interactions that influence development
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