The role of stem cells in the response to myocardial and vascular wall injury

Myocardium has long been considered a terminally differentiated tissue, with injury invariably leading to replacement with fibrosis. However, new reports suggest potential roles for circulating or endogenous stem cells in repopulating myocardium after irreversible injury. Unfortunately, these benefits may represent a double-edged sword. While offering exciting possibilities for therapy following myocardial infarction (MI), stem cells are also increasingly implicated in contributing to a number of vascular pathologies, including the formation of graft arterial disease (GAD) after cardiac transplantation. In this review, the function of stem cells in repopulating infarcted myocardium and their role in the pathogenesis of intimal hyperplastic lesions such as GAD will be discussed.