Isolated colony-forming ECs produce tens of millions of endothelial daughter cells in vitro.

<p>(A) Growth kinetics of five separate EC monolayer cultures originating from individual lin−CD31+CD105+ CFCs that were picked up from colony assays and propagated in 2-D cultures. The cultures were split when 90% confluent and no cells were discarded during the experiment. A summary growth curve (mean ± SD) of the five cultures is also shown. Cell number is in log scale. (B) The long term 2-D EC cultures were analyzed at passage 24 by immunofluorescence microscopy. The cells express the endothelial markers CD105, VEGFR-2, and the stem/progenitor cell marker CD117. The nuclei are stained with DAPI (blue) to recognize individual cells. Scale bars, 50 µm; 5 µm (insert).