Neutrophil Extracellular Trap Formation in Newborn Infants at Risk for Inflammatory Syndromes

Overview

The purpose of this study is to characterize the time to maturation of neutrophil extracellular trap(NET) formation capability in polymorphonuclear leukocytes(PMNs) isolated from newborn premature and term infants. Preterm infants who are enrolled into the study who then go on to require surgery \<1 year due to surgical NEC, will have the NET formation reassessed. This study will also determine whether NETs contribute to the pathogenesis of necrotizing enterocolitis (NEC). We hypothesize that NET formation contributes to the pathogenesis of NEC by inappropriately releasing degradative proteins and tissue destructive enzymes into the inflammatory milieu of the premature infant gastrointestinal tract following bacterial translocation. We also hypothesize that the delay in NEC development in premature infants (3rd - 4th week of life) as compared to at-risk term infants (1st week of life) results from a developmental delay in PMN ability to form NETs.

Prematurely born infants are at risk for necrotizing enterocolitis (NEC), the most common gastrointestinal emergency encountered in the newborn intensive care unit. This disease occurs in between 5 - 10% of infants born at less than 30 weeks gestation or less than 1500 grams birth weight. In these patients, NEC routinely develops during the 3rd or 4th week of life. NEC rarely occurs in infants born closer to term; for these patients NEC usually develops during the 1st week of life. So far, no one has explained the inverse relationship between gestational age at birth and the delay in NEC development. Recently, our laboratory described for the first time an inherent deficiency of innate immunity in newborn infants - failure of neutrophil extracellular trap formation. Neutrophil extracellular traps or NETs are complex lattices of extracellular chromatin and DNA decorated with anti-microbial proteins and degradative enzymes which trap and kill microbes. When the neutrophils of newborn infants develop the ability to form NETs and whether the maturation of NET formation correlates with development of NEC in at risk infants remains unknown. We have therefore undertaken the following study best described as a prospective, in vitro longitudinal cellular biology study of LPS/PAF-stimulated PMNs isolated from the cord and peripheral blood of premature infants at risk for NEC and from term infants not considered at risk for NEC. We will also assay for NET formation in gastrointestinal tissue samples obtained at the time of surgery for severe NEC in enrolled prematurely born infants. These studies are the first of their kind and aim to answer these important questions.