Differentiation of endothelial progenitor cells from human umbilical cord blood CD 34⁺ cells in vitro

To study the time course of the expression of stem cell marker and endothelial cell markers on human cord blood CD34⁺ cells during in vitro differentiation process of endothelial progenitor cells (EPC). METHODS: CD34⁺ cells were selected and enriched from human cord blood by magnetically activated cell sorting (MACS), and cultured in dishes coated with or without fibronectin (Fn). Endothelial cells were identified by staining the cells with anti Flk-1 and vWF antibodies. The percentage of AC133⁺ cells in adherent CD34⁺ cell population was analyzed by fluorescence-activated cell sorting (FACS). RESULTS: The expression of Flk-1 and vWF on adherent CD34⁺ cells increased during the culture time, with 27.0 % positive for Flk-1 and negative for vWF at d 3, and 100 % positive for both Flk-1 and vWF at d 7. When cells were cultured in Fn-treated dishes, the percentages of Flk-1 and vWF positive cells increased to 34 % and 47 %, respectively at d 3, and 100 % at d 7. In contrast, the percentages of AC133⁺ cells among the adherent cell population decreased rapidly, and similar changes occurred in cells cultured in the presence of Fn. CONCLUSION: The gradual appearance of endothelial cell markers and the disappearance of stem cell marker characterized the in vitro differentiation of endothelial progenitor cells. Fibronectin accelerated the differentiation process of EPC.