Stem/Progenitor Cells in Vascular Regeneration
Stem cell therapy could be a promising option for the treatment of vascular diseases. The finding of stem/progenitor cells in circulating blood and the vessel wall indicates that endogenous (adult) stem cells have the ability to repair endothelial cells, thereby restoring the integrity of the vessel and most importantly its function.1 However, embryonic stem cells, which are a population of undifferentiated cells that can develop into any type of cells in the body including endothelial and smooth muscle cells, occur as an another source for stem cell therapy.2 Finally, recent progress in somatic cell reprogramming (ie, induced pluripotent stem [iPS] cells), propelled the research field toward more attractive and promising heights.3 Overall, significant progress in stem cell research has been made recently, especially the mechanisms of stem cell activation, homing, and differentiation in vascular repair and remodeling.4 In this regard, many recent publications in ATVB have provided further insight into the functional role of stem/progenitor cells in (1) rescuing ischemic tissues,5–10 (2) the stem cell–derived smooth muscle accumulation in neointima, and (3) the stem cell differentiation into vascular lineages.11–14 In the present article, we will highlight these recent publications within a brief context of the literature on vascular stem/progenitor cells.
Circulating Proangiogenic Cells
Since the first report on endothelial progenitor cells in blood in 1997,15 a large number of articles in the field have been published, in which a large proportion was describing early endothelial progenitor cells and colony-forming cells.16–18 Most of these cells were identified to be monocytes/macrophages.16–18 It is now conceivable that a small population of outgrowth cells cultivated for several passages from human blood could be late endothelial progenitor cells.17 Although the nature and functions of endothelial progenitors are controversial, it is …