Rationale: Pulmonary hypertension (PH) is associated with poor outcomes among preterm infants with bronchopulmonary dysplasia (BPD), but whether early signs of pulmonary vascular disease are associated with the subsequent development of BPD or PH at 36 weeks post-menstrual age (PMA) is unknown.Objectives: To prospectively evaluate the relationship of early echocardiogram signs of pulmonary vascular disease in preterm infants to the subsequent development of BPD and late PH (at 36 wk PMA).Methods: Prospectively enrolled preterm infants with birthweights 500-1,250 g underwent echocardiogram evaluations at 7 days of age (early) and 36 weeks PMA (late). Clinical and echocardiographic data were analyzed to identify early risk factors for BPD and late PH. Measurements and Main Results:A total of 277 preterm infants completed echocardiogram and BPD assessments at 36 weeks PMA. The median gestational age at birth and birthweight of the infants were 27 weeks and 909 g, respectively. Early PH was identified in 42% of infants, and 14% were diagnosed with late PH. Early PH was a risk factor for increased BPD severity (relative risk, 1.12; 95% confidence interval, 1.03-1.23) and late PH (relative risk, 2.85; 95% confidence interval, 1.28-6.33). Infants with late PH had greater duration of oxygen therapy and increased mortality in the first year of life (P , 0.05).Conclusions: Early pulmonary vascular disease is associated with the development of BPD and with late PH in preterm infants. Echocardiograms at 7 days of age may be a useful tool to identify infants at high risk for BPD and PH.Keywords: bronchopulmonary dysplasia; pulmonary vascular disease; pulmonary hypertension; echocardiography; prematurity At a Glance CommentaryScientific Knowledge on the Subject: Preterm infants remain at high risk for late respiratory morbidity and mortality caused by the development of bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). Early injury to the developing lung can impair angiogenesis and alveolarization and result in simplification of distal lung airspace and the clinical manifestations of BPD and PH. However, whether early signs of pulmonary vascular disease are indicative of the subsequent development of BPD or PH at 36 weeks postmenstrual age (PMA) has not been well established.What This Study Adds to the Field: This paper presents a longitudinal study identifying echocardiogram-derived risk factors at 7 days of age for the subsequent development of both BPD and PH. We also describe the incidence of PH at 36 weeks PMA and its relationship to BPD severity.

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Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is associated with impaired vascular and alveolar growth. Antenatal factors contribute to the risk for developing BPD by unclear mechanisms. Endothelial progenitor cells, such as angiogenic circulating progenitor cells (CPCs) and late-outgrowth endothelial colony-forming cells (ECFCs), may contribute to angiogenesis in the developing lung. We hypothesise that cord blood angiogenic CPCs and ECFCs are decreased in preterm infants with moderate and severe BPD. We quantified ECFCs and the CPC/nonangiogenic-CPC ratio (CPC/non-CPC) in cord blood samples from 62 preterm infants and assessed their relationships to maternal and perinatal risk factors as well as BPD severity. The CPC/non-CPC ratio and ECFC number were compared between preterm infants with mild or no BPD and those with moderate or severe BPD. ECFC number (p<0.001) and CPC/non-CPC ratio (p<0.05) were significantly decreased in cord blood samples of preterm infants who subsequently developed moderate or severe BPD. Gestational age and birth weight were not associated with either angiogenic marker. Circulating vascular progenitor cells are decreased in the cord blood of preterm infants who develop moderate and severe BPD. These findings suggest that prenatal factors contribute to late respiratory outcomes in preterm infants.

Rationale: Preterm birth and hyperoxic exposure increase the risk for bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by impaired vascular and alveolar growth. Endothelial progenitor cells, such as self-renewing highly proliferative endothelial colony-forming cells (ECFCs), may participate in vascular repair. The effect of hyperoxia on ECFC growth is unknown. Objectives: We hypothesize that umbilical cord blood (CB) from premature infants contains more ECFCs with greater growth potential than term CB. However, preterm ECFCs may be more susceptible to hyperoxia. Methods: ECFC colonies were quantified by established methods and characterized by immunohistochemistry and flow cytometry. Growth kinetics were assessed in room air and hyperoxia (FI O 2 5 0.4). Measurements and Main Results: Preterm CB (28-35 wk gestation) yielded significantly more ECFC colonies than term CB. Importantly, we found that CD45 2 /CD34 1 /CD133 1 /VEGFR-2 1 cell number did not correlate with ECFC colony count. Preterm ECFCs demonstrated increased growth compared with term ECFCs. Hyperoxia impaired growth of preterm but not term ECFCs. Treatment with superoxide dismutase and catalase enhanced preterm ECFC growth during hyperoxia. Conclusions: Preterm ECFCs appear in increased numbers and proliferate more rapidly but have an increased susceptibility to hyperoxia compared with term ECFCs. Antioxidants protect preterm ECFCs from hyperoxia.