RESEARCH ARTICLE Screening identifies small molecules that enhance the maturation of human pluripotent stem cell-derived myotubes Sridhar Selvaraj1†, Ricardo Mondragon-Gonzalez1,2†, Bin Xu3, Alessandro Magli1,4, Hyunkee Kim1, Jeanne Laine´ 5, James Kiley1, Holly Mckee1, Fabrizio Rinaldi6, Joy Aho6, Nacira Tabti5, Wei Shen1,3,4, Rita CR Perlingeiro1,4* 1Lillehei Heart Institute, Department of Medicine, University of Minnesota, Minneapolis, United States; 2Departamento de Gene´tica y Biologı´a Molecular, Centro de Investigacio´n y de Estudios Avanzados del IPN (CINVESTAV-IPN), Ciudad de Me´xico, Mexico; 3Department of Biomedical Engineering, University of Minnesota, Minneapolis, United States; 4Stem Cell Institute, University of Minnesota, Minneapolis, United States; 5De´partement de Physiologie, Sorbonne Universite´s, Faculte´ de Me´decine site Pitie´-Salpeˆtrie`re, Paris, France; 6Stem Cell Department, Bio-Techne, Minneapolis, United States Abstract Targeted differentiation of pluripotent stem (PS) cells into myotubes enables in vitro disease modeling of skeletal muscle diseases. Although various protocols achieve myogenic differentiation in vitro, resulting myotubes typically display an embryonic identity. This is a major hurdle for accurately recapitulating disease phenotypes in vitro, as disease commonly manifests at later stages of development. To address this problem, we identified four factors from a small molecule screen whose combinatorial treatment resulted in myotubes with enhanced maturation, as shown by the expression profile of myosin heavy chain isoforms, as well as the upregulation of genes related with muscle contractile function. These molecular changes were confirmed by global chromatin accessibility and transcriptome studies. Importantly, we also observed this maturation in *For correspondence: three-dimensional muscle constructs, which displayed improved in vitro contractile force generation
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