Smooth muscle cells: to be or not to be? Response to Nguyen et Al.

Our laboratory has identified a new adult stem cell type, multipotent vascular stem cells, that contributes to the formation of atherosclerosis and restenosis. These findings were challenged by investigators who adhere to the previous model that these vascular diseases arise purely by de-differentiation of vascular smooth muscle cells. In this perspective piece, we review the evidence for the two models and conclude with the question, "Is vascular disease a stem cell disease, a smooth muscle disease, or both?"