Clonogenic assay of endothelial progenitor cells.

In stem cell biology, CD34+ or CD133+ hematopoietic stem cells (HSCs) give rise to two types of endothelial progenitor cell (EPC) colonies: primitive and definitive EPC-colony forming units (primitive EPC-CFU and definitive EPC-CFU), which can be morphologically defined. Based on their morphology, an evaluation of the number or the ratio of each EPC colony constitutes the Endothelial Progenitor Cell Clonogenic Forming Assay (EPC-CFA), a novel assay to quantify the differentiation of colony forming EPCs. This assay system allows us to practically evaluate the vasculogenic potential of primary or cultured stem cell populations, i.e., mononuclear cells or fractionated stem cells (CD34+ or CD133+ cells) in peripheral blood, bone marrow, or umbilical cord blood. EPC-CFA can be used not only for basic research in vascular biology but also for evaluating the vascular reparative activity of patients with cardiovascular diseases. This review summarizes the underlying concepts and significance of the EPC-CFA in vascular biology.