Muhamad Mergaye, Ohio State University
Conference: 14th Annual Conference on Stem Cell and Biomaterials, Paris, France
Abstract Title: Functional assessment of low oxygen preconditioned human iPSC-derived cardiomyocytes subjected to anoxia challenge
Abstract: Cardiovascular disease accounts for 1 in every 4 deaths in the United States (US), making it the leading cause of death. Myocardial infarction (MI; aka, heart attack) accounts for an alarming amount of hospitalizations in US. An MI occurs when an artery is blocked due to the formation of a blood clot, restricting the flow of oxygen-rich blood to the cells in the heart. The supply of oxygen is critical for cardiomyocyte (CM) survival; if it is not restored within 4-6 hours it leads to irreversible necrosis of the heart cells. It is estimated that 1 billion CMs die following an episode of MI, thus it is crucial for patients to be treated quickly after the onset of symptoms to restore blood flow to the infarct area. Currently, transplantation of differentiated stem cells is being explored as a potential therapeutic option for directly replacing lost CMs. However, a major impediment for this approach is the poor survival of transplanted cells in the austere environment of the ischemic post-MI heart. To overcome this obstacle we explored whether preconditioning of human iPSC-derived CMs under low oxygen concentrations would better withstand an anoxia challenge. We hypothesized that preconditioned CMs will preserve their functionality better than those cultured at 21% O2, as evidenced by electrophysiological function and decreased apoptosis. The cells were preconditioned for two weeks in a low oxygen microenvironment (5% O2 and 1% O2) as opposed to standard laboratory conditions of 21% O2. Phase contrast microscopy and fluorescent F-Actin staining showed no compelling morphological changes in the CMs during preconditioning. Additionally, MitoTracker staining revealed no overt changes to mitochondrial localization. Axion Microelectrode (MEA) array plates were used to analyze conduction velocity, field potential duration, and beat period of the cells during preconditioning and following anoxia challenge. Results demonstrated that preconditioning under 1% O2 best maintained CM functionality after 12 hours of anoxia. Furthermore, analysis of apoptosis via TUNEL staining indicated lowest percentage of cell death in the CMs preconditioned under 1% O2. Overall, our studies demonstrate that hypoxic preconditioning of CMs allows for their maintained health and function under extreme hypoxic stress. Therefore, preconditioning at 1% O2 could enhance survival of transplanted cells in the harsh ischemic environment of the post-MI heart.