Abstract 467: p53 Stabilized iPS Derived Cardiomyocytes Promote Myocardial Repair

Abstract

Rapid and continuous culturing of cells leads to accumulation of oxidative stress and DNA damage. These heterogeneous mixtures of healthy and damaged functionally incompetent cells (FIC) are not suitable for transplantation. We hypothesized that selecting only the healthy cells and use for cell would improve engraftment rate and cardiac function. Utilizing the discriminating nature of p53, inducing apoptosis in damaged cells while retaining cell cycle in healthy cells, we tested whether stabilizing p53 can retain only the healthy cells in the culture. p53 in iPS cultures were stabilized using small-molecule nutlin-3a. Cells that didn’t die due to p53 stabilization were collected and differentiated into cardiomyocytes. The markers for cell stress such as the ROS, superoxide and DNA damage were significantly reduced in p53S cells. Following differentiation p53S-CMs were characterized by high expression of CM markers Nkx2.5, Gata4, TnI, MYL2, MLYK, KCNH2 and CAMK2B. Efficiency of p53S-CM to engraft and remuscularize the injured myocardium were tested in small animal MI model. After one week of cell transplantion cardiac function, infarct size and engraftment rate of cells were comparable between p53S-CM and control-CM recieved groups. At week four significant improvement in cardiac function and reduction in infarct size were observed in both groups. However, improvement in these parameters were more prominent in p53S-CM groups. Macrophage analysis revealed enhanced recruitment of anti-infalmatory M2 macrophages in p53S-CM groups and inflammatory M1 macropaheges in control-CM groups at the injection site. Moreover, p53S-CM exosomes induced predominant M2 polarization while control-CM exosomes favored M1 polarization of RAW264.7 macrophages. Our data clearly shows functionally competent cells can be isolated from a population of heterogeneous cells by stabilizing p53. The p53S-CMs showed superior performance in in vitro and in vivo. Therefore, selecting healthy cells by stabilizing p53 would better repopulate the deteriorating myocardium and improve cardiac performance.