Endothelial progenitor cells, angioblasts, and angiogenesis--old terms reconsidered from a current perspective

When the term 'angioblast' was initially used, almost a century ago, the cells bearing this name were thought to give rise to plasma, red blood cells and endothelium, with new blood vessels arising from 'within the (cell) bodies of these angioblasts'. More recently, putative circulating 'progenitor endothelial cells', often also referred to as angioblasts, were first described in the adult human a mere decade ago. Therefore, while our understanding of progenitor cell biology and other relevant vascular developmental programs has progressed enormously, key terms such as 'angioblast' and 'angiogenesis' have remained constant. With the recent intense interest in angioblasts and endothelial progenitor cells, and their potential with respect to cardiovascular regenerative medicine, our knowledge of how these and other nonprogenitor cells might contribute to new vessel formation has taken a further leap in understanding. In this review, we focus on the controversial use and definition of these terms based upon our current understanding of vascular biology and progenitor cells.