Figure 1.

Placental Endothelial Progenitor Cells Are Enriched in the CD45⁻CD34⁺ Population

(A) To enrich the endothelial colony-forming cell (ECFC) population, we enriched placental cells for CD45⁻CD34⁺ cells.

(B) Number of HPP-ECFCs forming cobblestone-like endothelial colonies in this population was superior to the CD45⁻ and the CD45⁻CD34⁻ populations (data presented as mean ± SD).

(C) Flow cytometry on placental unsorted cells showing frequency of CD34⁺ or CD34⁺CD45⁻ cells. To further purify EPC we devised a sorting strategy.

(D and E) Four different populations were observed based on CD31 levels in CD45⁻CD34⁺ population. Fluorescence minus one analysis (D) demonstrated that (E) one population is CD31 negative, while the three other populations express low, intermediate, and high levels of CD31.

(F) Percentage of each population (data presented as mean ± SD).

(G–K) CD31Neg cells resulted in pure mesenchymal stem cell (MSC) colonies. Pure endothelial cells were derived from CD31Int and CD31Hi populations; upon culture, CD31Int and CD31Hi cells never formed mesenchymal colonies. EPCs were to be almost exclusively in the CD31Int population. For CD31Low population the number of bipotential colonies is presented (data presented as median with interquartile range). Scale bar, 100 μm.

^∗p < 0.05 and ^∗∗∗p < 0.005.