Vascular endothelial processes are greatly affected by endothelial progenitor cells (EPC) circulating in peripheral blood. This unique progeny has been shown to play an important role in vascular endothelial maintenance and healing processes as well as in pathological formation of new blood vessels (neovascularisation) specifically in diseases such as diabetic retinopathy and retinopathy of prematurity.
To address the role of EPC in premature infants we measured gene expression of endothelial-specific and progenitor-associated genes (AC133, TIE-2, FLK-1 (VEGFR2), SCL/TAL1 and VEGF) by quantitative reverse transcription PCR in the peripheral blood of preterm infants, born between 24 and 34 weeks gestational age. Transcript levels were assessed in three consecutive time points—on day 3–5 of life, on day 10–15 and at one month of age.
The mRNA expression level of EPC markers did not significantly change between different gestational age groups or birth weights. Elevated levels of TIE-2 correlated with increased brain echogenicity on sonography (p = 0.0001) implying a possible association with prematurity cerebrovascular morbidity.
To our surprise a significant reduction of TIE-2 levels was found in preterm infants who were treated with erythropoietin compared with infants who were not treated (p = 0.001). We found a similar yet not statistically significant tendency for the other progenitor markers (AC133, SCL/TAL1 and VEGF).
These preliminary findings may further suggest a potential role for progenitor cells in the pathophysiology of preterm morbidity, as well as pointing out the need for further investigation of the role of erythropoietin and its effect in preterm infants.