Miniaturized iPS-Cell-Derived Cardiac Muscles for Physiologically Relevant Drug Response Analyses

TLDR

Tissue engineering can increase the physiological relevance of human iPS‑derived cardiomyocytes, but current engineered heart muscle requires >1 million cells and complex miniaturization limits mass production; micro‑scale cardiospheres are easy to produce but lack elongated muscle assembly and force measurement capability. The study introduces Micro‑Heart Muscle (μHM) arrays that combine engineered heart muscle and cardiosphere features, enabling elongated muscle fibers with as few as 2,000 iPS‑CM per tissue. These μHM arrays are fabricated in a simple template that supports elongated muscle fibers from only 2,000 iPS‑CM per tissue. μHM tissues display uniaxial contractility, aligned sarcomeres, reduced variability and hypersensitivity to drugs compared to monolayers, exhibit a robust Frank‑Starling response to stretch, and a dose‑dependent inotropic response to isoproterenol, making them a powerful tool for cardiomyocyte maturation, disease modeling, and cardiotoxicity studies.

Abstract

Abstract Tissue engineering approaches have the potential to increase the physiologic relevance of human iPS-derived cells, such as cardiomyocytes (iPS-CM). However, forming Engineered Heart Muscle (EHM) typically requires >1 million cells per tissue. Existing miniaturization strategies involve complex approaches not amenable to mass production, limiting the ability to use EHM for iPS-based disease modeling and drug screening. Micro-scale cardiospheres are easily produced, but do not facilitate assembly of elongated muscle or direct force measurements. Here we describe an approach that combines features of EHM and cardiospheres: Micro-Heart Muscle (μHM) arrays, in which elongated muscle fibers are formed in an easily fabricated template, with as few as 2,000 iPS-CM per individual tissue. Within μHM, iPS-CM exhibit uniaxial contractility and alignment, robust sarcomere assembly and reduced variability and hypersensitivity in drug responsiveness, compared to monolayers with the same cellular composition. μHM mounted onto standard force measurement apparatus exhibited a robust Frank-Starling response to external stretch and a dose-dependent inotropic response to the β-adrenergic agonist isoproterenol. Based on the ease of fabrication, the potential for mass production and the small number of cells required to form μHM, this system provides a potentially powerful tool to study cardiomyocyte maturation, disease and cardiotoxicology in vitro .