Title: Engineering Adult-like Human Myocardium for Predictive Models of Cardiotoxicity and Disease
Description: Preclinical screening during the development of new drugs is poorly predictive and costly, creating a significant interest from pharmaceutical companies, government agencies, and the public in the development of better preclinical tests. To create more predictive organ models, human derived stem cells can be coupled with biomimetic tissue engineering approaches to create physiologically relevant functional subunits of each tissue/organ within the body. However, existing methods of generating cardiomyocytes (CMs) and cardiac tissues from human induced pluripotent stem cells (hiPSC) derived CMs (hiPS-CMs) are relatively immature and produce tissues that resemble that of a fetal heart at best. This limits their use in therapeutic development and thus, methods to overcome their immature phenotype are of high importance. In pursuit of this goal, this dissertation focuses on the role of biophysical stimuli in driving the functional maturation of hiPSC-CMs to engineer cardiac muscle of high biological fidelity.

In an effort to recapitulate the hierarchical structure and functionality of native heart tissue, methods to pattern cells at the nano- and microscale levels were developed and optimized towards the functional assembly of cardiac tissues at the macroscale. To address the challenges currently associated with hiPS-CM immaturity, the decoupled effects of electrical and electromechanical stimulation in driving cardiac maturation were investigated. Subsequently, optimal electromechanical stimulation regimens were established. Daily intervals of high intensity electromechanical training were shown to upregulate cardiac functionality and energetics, and thus, enhance maturation. Combining these methods enabled the development of a custom bioreactor capable of generating larger, more functionally mature hiPS-CM tissues. Mimicking the developmental increases in cardiac beating frequency, exposure of the resulting tissues to a dynamic electromechanical intensity training regimen matured hiPS-CMs beyond levels currently demonstrated within the field.

Specifically, the engineered tissues recapitulated many of the molecular, structural, and functional properties of adult human heart muscle, including well developed registers of sarcomeres, networks of T-tubules, calcium homeostasis, and a positive force-frequency relationship. The enhanced functionality of the resulting bio-engineered adult-like myocardium enabled its utility in predicting drug cardiotoxicity and modeling human cardiac disease.