Presence of high proliferative potential resident endothelial progenitor cells within the lung microcirculation

Endothelial progenitor cells (EPCs) isolated from peripheral blood display a hierarchy determined by their proliferative potential and self‐renewal capacity. However, it is not known whether EPCs exhibiting similar behaviors reside within the lung’s microcirculation. Thus, we hypothesize that the adult lung microcirculation is enriched with resident EPCs with high proliferative potential and self‐renewal capacity. Rat endothelial cells isolated from the pulmonary artery (PAEC) and the microcirculation (PMVECs) express the “endothelial” markers, von Willebrand factor, CD31, and CD144, and interact with the lectin Helix pomatia (PAEC) and Griffonia simplicifolia (PMVEC). In the single‐cell clonogenic assay, 70% of PMVECs exhibit a high proliferative potential (i.e. single cells grow to more than 10 4 cells in 2 weeks) while only 18% of PAECs exhibit such behavior. When high proliferative PMVECs are re‐seeded in the clonogenic assay, they retain their high proliferative potential, which indicates their progenitor capacity. Resident EPCs express the circulating endothelial progenitor markers, VEGFR2 and CD34, and possess telomeres that are 10% and 35% longer, when compared to the mixed population of PMVECs and PAECs, respectively. These data indicate the lung’s microcirculation is enriched with resident EPCs that possess a high proliferative potential, and the capacity for self‐renewal. HL66299.