IntroductionAmong subtypes of endothelial progenitor cells, endothelial colony-forming cells (ECFC) display high proliferative and angiogenic capacity in vitro and are considered biomarkers of angiogenic/regenerative capacity. Cord blood ECFC from preterm born (PT) infants have impaired bioactivity, especially in those who develop prematurity-related complications such as bronchopulmonary dysplasia. Whether ECFC dysfunction persists in PT beyond the neonatal period is not known.ObjectiveOur aim was to assess ECFC bioactivity (in vitro growth, angiogenic capacity) in extremely PT vs. term (T) born young adults.MethodsECFC were obtained from peripheral blood from 19 young adults (21-28 years old) born extremely PT (<29 weeks gestation) and 19 T (≥37 weeks, paired by gender, age and socioeconomic status). Mononuclear cells (PBMC) were separated by density gradient and plated (5x10(6) cells/flask) to allow ECFC colony formation. ECFC were cultured to assess cell phenotype (CD45-/CD34+/CD31+/KDR+), in vitro proliferation rate by modified thymidine analogue EdU incorporation, and tubular formation in Matrigel.ResultsECFC colonies were obtained from 9 PT (48%) and 12 T (63%). The frequency distribution of the number of days to first colony formation was significantly different in PT vs. T, with higher frequency of late (> 15 days) and absence of any colony formation in PT (p=0.033). In PT, days to form 1st ECFC colony inversely correlated with ECFC proliferation rate (r=-0.85, p<0.001), and angiogenic capacity shown as number of tubes (r=-0.72, p=0.037) and branches (r=-0.68, p=0.043) formed in Matrigel, whereas in T these correlations were not significant with similar ECFC function at any time of colony formation. In PT, tubular formation negatively correlated with neonatal length of hospital stay (r=-0.72, p=0.03), a proxy of prematurity-related complications.ConclusionsTime to first ECFC colony formation, proliferation rate and in vitro tubular formation are significantly altered in PT vs. T young adults. Overall data suggests that extremely PT born young adults display impaired ECFC bioactivity, which may contribute to the development of cardiovascular diseases associated with impaired angiogenesis in this population.