Cell therapies for therapeutic angiogenesis: back to the bench.

The discovery, over a decade ago, of endothelial progenitor cells that are able to participate in neovascularization of adult tissue has been greeted enthusiastically because of the potential for new cell-based therapies for therapeutic angiogenesis. Since that time, an ever-growing list of candidate cells has been proposed for cardiovascular regeneration. However, to date, pre-clinical and clinical studies evaluating the therapeutic potential of various cell therapies have reported conflicting results, generating controversy. Key issues within the field of cell therapy research include a lack of uniform cellular definitions, as well as inadequate functional characterization of the role of putative stem/progenitor cells in angiogenesis. Given the mixed results of initial clinical studies, there is now a scientific imperative to understand better the vascular biology of candidate cells in order to better translate cell therapy to the bedside. This review will provide a translationally relevant overview of the biology of candidate stem/progenitor cells for therapeutic angiogenesis.