Increased circulation mobilization of endothelial progenitor cells in preterm infants with retinopathy of prematurity

Abstract

To the Editor, We would like to thank you for the opportunity to respond to a letter written by some authors regarding our recently published article entitled “Increased circulation mobilization of endothelial progenitor cells in preterm infants with retinopathy of prematurity.” First, we thank the authors for their inputs on our manuscript. Actually, the information requested by the authors is provided in our paper. In line with the journal policy, we hereby prepared a response letter to answer the authors’ comments. In our study, we showed that retinopathy of prematurity (ROP) in preterm infants is associated with increased mobilization of endothelial progenitor cells (EPCs) into 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. These specimens were taken at birth. The age of the infants is shown in Table 1. There was no significant difference between premature infants with and without ROP. In this study based on our previous works, we considered CD133+, CD34+, and VEGFR‐2+ cell population as EPCs, which is not the same as that of CD133+, CD34+, and CD144+ population in the works of Safranow et al. and Machalińska et al. Also, Machalińska et al (2009) reported that the increased number of early endothelial progenitor cells along with elevated levels of vascular endothelial growth factor (VEGF) and hepatocyte growth factor in preterm infants with ROP suggest that circulating vasculogenic factors may play a role in the development and progression of ROP. There is some evidence that VEGF concentration is increased after 10 weeks of delivery in the peripheral blood of preterm babies with ROP compared with preterm babies without retinopathy as well as with full‐term control infants, which can provide a chemotactic axis for the circulation mobilization of EPCs. The P values in Table 1 are related to comparisons between preterm infants with and without ROP (P > 0.05). However, the reported statistically significant differences in the text are between preterm infants with or without ROP and control full‐term infants. By flow cytometry, we showed a significantly greater population of CD34 positive cells in the peripheral blood of preterm infants with ROP than in preterm infants without ROP or full‐term controls.