The use of induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CM) has great potential for developing novel therapies to treat cardiovascular disease (CVD). Unfortunately, CM derived from pluripotent stem cells (PSC) are immature, displaying characteristics of fetal CM. Immature PSC-derived CM show automaticity (spontaneous beating), which can lead to potential arrhythmic events and thus these cells would not be safe for use in transplantation. They also lack mature cell ion channels and so drug screening using these cells would also be ineffective. Consequently, it is imperative to create strategies to generate mature PSC-derived CM, and we have focused our studies on the cardiac microenvironment’s role in this process.

There is evidence that components within the cardiac microenvironment contribute to CM development in vivo, and our studies investigated the impact of cardiac extracellular matrix (ECM) and endothelial cells (EC) on human iPSC-derived CM development and maturation. Specifically, we generated native decellularized cardiac ECM from bovine heart tissue and compared the mechanical properties and ECM fiber distribution in ECM from fetal and adult tissue. Normally, CM differentiation is performed on Matrigel, ECM derived from a mouse tumor. When compared to Matrigel, the iPSC-derived CM differentiated on cardiac ECM showed enhanced expression of CM development and functional genes. Maturation was further enhanced by culture in 3D versus 2D matrix as evidenced by increases in CM maturation markers, calcium signaling, and responsiveness to drugs. We also discovered that EC promote iPSC-derived CM maturation during EC/CM co-culture and that the maturation is mediated, in part, by notch signaling and endothelin-1. Taken together, these data identify a critical role for the cardiac microenvironment components: 3D culture, cardiac ECM, and EC in regulating iPSC-derived CM development and maturation, and provide a novel strategy to generate mature iPSC-derived CMs to be used in treatments for CVD.