Inspired by utero-like biochemical conditions, Kareen Coulombe and PhD student Cassady Rupert investigated the potential of insulin-like growth factor 1 (IGF1) and neuregulin-1B (NRG1), two growth factors crucial to cardiac development in vivo , to promote the maturation of human embryonic stem cell- (hESC-) derived cardiomyocytes ex vivo.  These growth factors elicited functional responses in 3D engineered cardiac tissues (ECTs) including increased cardiomyocyte proliferation by IGF1 and metabolic maturation by NRG1. Underscoring the importance of 3D in vitro models, they observed responses from cells in 2D (cell growth increased) and at the gene expression level did not predict 3D engineered tissue functional behavior (force generation decreased). Their study "IGF1 and NRG1 Enhance Proliferation, Metabolic Maturity, and the Force-Frequency Response in hESC-Derived Engineered Cardiac Tissues" was recently published in Stem Cell International.