Abstract: Objective To establish a culture system of endothelial progenitor cells from umbilical cord blood. Methods Using density gradient centrifugation to obtain Mononuclear cells,and then cultured them with our labs'culture system.In this study, immunocytochemistry and flow cytometric analysis of CD144,CD146,vWF,CD34 and CD133 were performed. Results The first five days were latent period, cells became adherent, but the number of cells did not increase obviously. At the 6th day, the number of cells came up to 287+45(the average number under 10X10 visual field),and the 9th day up to 282+46（P>0.05）.After cultured for 12 days, the cells came into logarithmic phase ,and the number of cells was 805.33+66.61（P<0.05）,and continued to incease at day 19, the number of cells was up to 1115+182（P<0.05）.Apoptosis took place at day 23, the number of cells decreased to 265+615（P<0.05）. Immunocytochemistric analysis indicated that the cells were weakly positive for vWF,CD144 and CD146, and the percentage of CD34 in cobblestone-shaped cells was 88.98%+5.15%(P<0.05), and that of CD133 was 1.20%+1.44%(P<0.05) with flow cytometric analysis. Conclusions The method established in our lab for EPCs culture is effective. The first five days is a latent period, cells become adherent,but do not increase in number; and from day 12 ,the cells come into logarithmic phase. The number of EPCs is increasing at day 19,and then the cells undergo apoptosis at day 23.

Key words: Endothelialprogenitor cells, Culture in viro, Cell typing