Mechanical regulation of maturation and pathology of engineered human heart tissues

摘要

ABSTRACT The advent of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offers exciting opportunities to study human cardiac disease and development in vitro. However, hiPSC-CMs are structurally and functionally immature and more closely resemble fetal than adult CMs as evident from their reliance on glycolytic instead of oxidative metabolism, weak contractions and excitability, and expression of immature isoforms of structural proteins including myosin and troponin. This makes hiPSC-CMs inadequate for studies of adult-acquired cardiac diseases, such as heart failure (HF), which remains the leading cause of death in the United States and worldwide. The mechanical environment of CMs is widely recognized as a key regulator of cardiac tissue development, physiology, and disease. In particular, dynamic changes in mechanical load experienced by CMs during postnatal development may play a key role in their acquisition of a mature adult phenotype. I hypothesize that presentation of dynamic, time-varying stretch (preload) and resistance to contraction (afterload) to human engineered heart tissues (hEHTs) made of hiPSC-CMs will increase their structural and functional maturity. Furthermore, I predict that mechanical overload of hEHTs will induce pathological features characteristic of HF progression. To test these hypotheses, I have developed a novel bioreactor where mechanical preload and afterload imposed on hEHTs can be independently varied with time of culture via application of stretch and electrical stimulation. Using this platform, I will systematically study how different regimes of progressively increased preload and afterload affect structure, contractile force generation, propagation of action potentials, and transcriptomic and metabolic properties of hEHTs. Additionally, I will employ real-time imaging to identify and characterize the mechanotransduction mechanisms underlying the observed functional changes in the hEHTs. For mechanical overload regimes that induce molecular and functional signatures of an HF phenotype, I will study if different adjuvant therapies combined with applied mechanical unloading akin to use of left ventricular assist devices (LVADs) can reverse-remodel structural and functional deficits in hEHTs. When completed, these studies will identify new mechanobiological drivers of in vitro CM maturation and further the molecular understanding of HF disease and therapy.