Effects of Nanotopography on Structural Maturation and Differentiation of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Abstract

Heart diseases remain the leading cause of morbidity and mortality worldwide. As damages done to the heart are irreversible, heart transplant is the ultimate therapy, but it is greatly limited by the shortage of heart donors. Thus, scientists are attracted by induced pluripotent stem cells (iPSCs) as a solution because of their ability to be reprogrammed from a somatic cell source, potentially unlimited proliferative properties, and ability to be differentiated into many different cell types. However, hiPSC-derived cardiomyocytes display immature phenotypes in contractile properties, electrophysiology, metabolism, structure, and protein isoform expression, thus greatly limiting their application in regenerative medicine, disease modeling, and drug screening. Therefore, there is a great need for a technique to drive the maturation of stem cell-derived cardiomyocytes to better recapitulate the properties of their adult counterpart. Our approach was to recreate a developmentally-inspired microenvironment for maturing hiPSC-derived cardiomyocytes (hPSC-CMs). The native myocardium is characterized by aligned extracellular matrix (ECM) fibers and cells have been shown to sense and respond to cues in the ECM. In addition, thyroid hormone is a major regulator of heart development in promoting cell hypertrophy and elongation. Thus, we tested the effects of biomimetic, nanotopographical cues – using an anisotropic nanofabricated substrata (ANFS) composed of nanogrooves and nanoridges in the nanopattern (NP) – combined with thyroid hormone T3 on the structural maturation of cardiomyocytes. We found that cells exposed to nanotopography exhibited structural organization and maturation. However, the effect of T3 was not clear and appeared to have a detrimental effect at prolonged exposure at high concentration. ANFS was also used to differentiate cardiomyocytes from the cardiac progenitor stage and suggested nanotopography could have a positive effect on cardiomyocyte differentiation yield. However, experiments suggested that the differentiating cell population was highly dynamic and responded differently to the replating procedure at different time points. Therefore, a photothermal-responsive polymer was developed to introduce nanotopography with an external light stimulus, and cells were confirmed to stay attached to the polymer substrate with the topographical switch. This resulted in the development of an effective platform with vast potential, allowing the introduction of topographical cues to a cell culture with an easily manipulated external stimulus.