The goal of this application is to investigate the association between surfactant protein-A (SP-A) in premature infants with the subsequent diagnosis of necrotizing enterocolitis (NEC), a serious gastrointestinal complication in ~10% of hospitalized preterm infants (<32 wk). NEC is an insidious complication of premature birth due to its sudden onset in the first weeks of life, devastating health consequences (death and long-term complications) and limited treatment options. NEC is responsible for 7% of all NICU admissions with up to 25% mortality and healthcare costs of ~$1 billion annually. Since no single risk factor is known to trigger NEC, there is an unmet need for novel biomarkers that can identify premature infants most at risk for developing NEC who will require enhanced monitoring. Prematurity results in undeveloped intestines that are highly susceptible to intestinal bacteria which leads to progressive inflammation due to activation of intestinal toll-like receptor 4 (TLR4), a central player in the progression of NEC. Ultimately, rampant intestinal inflammation leads to destruction of the intestine. Gavaged SP-A, a key component of the innate immune system, significantly reduces TLR4 levels, inflammation and intestinal damage in animal models of experimental NEC. Intestines of juvenile SP-A -/- mice have significantly higher inflammatory cytokine and TLR4 levels compared to wildtype mice. Additionally, SP-A gavage of neonatal SP-A -/- mice reduces intestinal TLR4 levels and inflammation. In the fetus, robust expression of SP-A occurs in fetal lungs after 7 months of gestation. SP-A is secreted and concentrates in amniotic fluid, which the fetus continuously swallows, bathing the intestine with SP-A. Our data suggests this SP-A reduces intestinal TLR4 levels and reduced SP-A due to prematurity can lead to increased intestinal TLR4 activity. Adverse extra-uterine environmental insults (i.e., infant formula, bacteria, hypoxia) in conjunction with enhanced TLR4 activity could result in excessive intestinal inflammation, leading to NEC. We hypothesize that evaluation of SP-A concentration in amniotic and gastric fluid collected during premature birth can be utilized as a biomarker to predict the development and severity of NEC. We propose a prospective observational trial where amniotic fluid will be non-invasively collected during birth of premature infants (24 to 34 wk) and SP-A concentration measured by ELISA and quantitative western analysis. Infant demographics and clinical parameters associated with diagnosis, staging and treatment of NEC will be recorded from birth to postmenstrual age 40 wk. The data will be combined and analyzed and stratified to identify statistically significant correlations between levels of SPA birth with infant health and demographic data. We will correlate SP-A concentration in fluids at birth with the subsequent diagnosis and severity of NEC in premature infants. The impact of this work is high as it will constitute the first step towards using SP-A as a biomarker for NEC, establish a novel role for SP-A in protection of immature intestine in neonates against excessive and damaging inflammation and lay the foundation for the development of NEC therapeutics.
The immature intestine of premature babies is exquisitely sensitive to extra-uterine environmental insults that can lead to excessive inflammation and destruction of the intestine in a devastating disorder called necrotizing enterocolitis (NEC) that has no clear predictive symptoms or biomarkers. We have found that surfactant protein-A (SP-A) can reduce expression and activity of intestinal toll-like receptor 4 (TLR4), which is key to this exaggerated inflammation in neonatal intestine. This prospective observational study will determine whether levels of SP-A associated with premature birth can predict the incidence and severity of NEC in premature infants, leading to the use of SP-A as a novel biomarker that can indicate the newborn?s susceptibility to NEC.
