Quantitation of clonogenic and proliferative potential of single cell-derived colonies from VVEC, aortic endothelial cells (AOEC), and main pulmonary artery endothelial cells (MPAEC). Data represent the percentage of single cell-derived colonies from VVEC-Co (n = 3), VVEC-Hx (n = 3), AOEC-Hx (n = 3), and MPAEC-Hx (n = 3) on day 14 after single cell sorting. Colonies of each cell population were analyzed from 4–5 96-well plates (384–480 wells in total). HPP-CFC, high proliferative potential colony-forming cells; LPP-CFC, low proliferative potential colony-forming cells; EC, endothelial clusters. **P = 0.008 and *** P = 0.0001 (Student's t-test, followed by a Mann-Whitney posttest).