RRM2 and myocardial infarction: Although there are structural differences between neonatal and adultcardiomyocytes, it is important to note that Rrm1+Rrm2 over-expressionincreased contractility to a similar extent in both cell types (Supplemental Figure 2).Interestingly, as neonatal cardiomyocytes have been used to study the effects ofcellular engraftment following myocardial infarction[13], improved contractility in these cellsmay be another mechanism to improve cardiac function following an infarct.