Retinopathy of prematurity (ROP) is a result of increased pathological neoangiogenesis of the retina in preterm infants. Cells responsible for the pathogenesis of ROP are unclear, but some evidence indicates that bone marrow derived cells are involved in this disorder. Endothelial progenitor cells (EPCs), play a role in angiogenesis in response to tissue ischemia or endothelial damage. In this study, the number of cEPCs in preterm infants with ROP was determined to identify whether the circulation mobilization of EPCs is associated with ROP. We evaluated 99 participants in this study: 22 preterm infants with ROP, 35 preterm infants without ROP, and 42 full-term infants. The release of EPCs in the circulation was first quantified. Thereafter, cEPCs were harvested and cultivated, then the biological features of these cells including migratory, proliferative, and tubulogenic activities were analyzed. The mRNA levels of some proangiogenic factors were also measured in preterm infants. Our results showed greater numbers of cEPCs in infants with ROP, which was associated with increased serum concentrations of angiogenic factors and with augmented proliferative, migratory, and tubulogenic activity of these cells. Western blotting showed increased protein levels of VEGF and HIF-α in cEPCs harvested from ROP infants. This study showed that ROP in preterm infants is associated with increased mobilization of EPCs into the circulation. Therefore, increased cEPCs along with elevated levels of angiogenic factors and tubulogenesis suggest that these cells may play a role in the development and progression of ROP.

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Many infants who develop bronchopulmonary dysplasia (BPD) are born with serious respiratory distress syndrome (RDS), which is associated with impaired vascular and alveolar growth. RDS is a breathing disorder that mostly affects preterm infants and occurs in infants whose lungs have not yet been fully developed. The use of surfactant in RDS treatment does not necessarily prevent BPD. Endothelial progenitor cells (EPCs) may contribute to lung angiogenesis for the prevention and treatment of BPD. The aim of this study was to evaluate the therapeutic efficacy of phototherapy for EPC release in preterm infants born with RDS. Seventy-five RDS preterm infants were divided into two groups: RDS with phototherapy and RDS without phototherapy. Respiratory indices were recorded for each patient. Circulating EPCs were isolated before and after phototherapy and colony forming efficiency, chemotactic, tubulogenic, proliferative, and functional properties of these cells were analyzed. Our results showed that phototherapy increased the release of EPCs into the circulation in RDS preterm infants, with augmentation of cell proliferation, tubulogenic, chemotactic, and proliferative properties of EPCs. Phototherapy-induced EPC release was associated with improved lung function as was recorded by significantly decrease in continuous positive airway pressure (CPAP) days, CPAP plus ventilator days, and PCO along with a significant increase in PO and PaO /FiO , resulting in markedly decreased rate of BPD occurrence in preterm infants with RDS. Overall, phototherapy is touted as a promising modality for the amelioration of respiratory performance and prohibition of BPD occurrence in RDS preterm infants. J. Cell. Biochem. 118: 594-604, 2017. © 2016 Wiley Periodicals, Inc.