Alain Cuna

Alterations in Gene Expression and DNA Methylation during Murine and Human Lung Alveolar Septation

DNA methylation, a major epigenetic mechanism, may regulate coordinated expression of multiple genes at specific time points during alveolar septation in lung development. The objective of this study was to identify genes regulated by methylation during normal septation in mice and during disordered septation in bronchopulmonary dysplasia. In mice, newborn lungs (preseptation) and adult lungs (postseptation) were evaluated by microarray analysis of gene expression and immunoprecipitation of methylated DNA followed by sequencing (MeDIP-Seq). In humans, microarray gene expression data were integrated with genome-wide DNA methylation data from bronchopulmonary dysplasia versus preterm and term lung. Genes with reciprocal changes in expression and methylation, suggesting regulation by DNA methylation, were identified. In mice, 95 genes with inverse correlation between expression and methylation during normal septation were identified. In addition to genes known to be important in lung development (Wnt signaling, Angpt2, Sox9, etc.) and its extracellular matrix (Tnc, Eln, etc.), genes involved with immune and antioxidant defense (Stat4, Sod3, Prdx6, etc.) were also observed. In humans, 23 genes were differentially methylated with reciprocal changes in expression in bronchopulmonary dysplasia compared with preterm or term lung. Genes of interest included those involved with detoxifying enzymes (Gstm3) and transforming growth factor-β signaling (bone morphogenetic protein 7 [Bmp7]). In terms of overlap, 20 genes and three pathways methylated during mouse lung development also demonstrated changes in methylation between preterm and term human lung. Changes in methylation correspond to altered expression of a number of genes associated with lung development, suggesting that DNA methylation of these genes may regulate normal and abnormal alveolar septation.

A randomised trial of re-feeding gastric residuals in preterm infants

Objective To determine whether re-feeding of gastric residual volumes reduces the time needed to achieve full enteral feeding in preterm infants. Design Parallel-group randomised controlled trial with a 1:1 allocation ratio. Setting Regional referral neonatal intensive care unit. Patients 72 infants of gestational age 230/7 to 286/7 weeks receiving minimal enteral nutrition (<24 mL/kg/day) during the first week after birth. Interventions Infants were randomised to either be re-fed with gastric residual volumes (Re-feeding group) or receive fresh formula/human milk (Fresh-feeding group) whenever large gastric residual volumes were noted. Main outcome measure The primary efficacy end point was time to achieve full enteral feeding (≥120 mL/kg/day) after randomisation. Results The mean time to full enteral feeding was 10.0 days in the Re-feeding group and 11.3 days in the Fresh-feeding group (mean difference favouring re-feeding: −1.3 days; 95% CI −2.9 to 0.3; p=0.11). The composite safety end point of spontaneous intestinal perforation, surgical necrotising enterocolitis, or death occurred in 6 of 36 infants (17%) in the Re-feeding group versus 10 of 36 infants (28%) in the Fresh-feeding group (p=0.26). Conclusions Re-feeding gastric residual volumes in extremely preterm infants does not reduce time to achieve full enteral feeding. This trial suggests that re-feeding might be as safe as fresh feeding, but further research is needed, due to lack of sufficient statistical power in this study for safety analysis. Trial registration number NCT01420263NCT01420263.

Genetic alterations in necrotizing enterocolitis

An underlying genetic predisposition to necrotizing enterocolitis (NEC) is increasingly being recognized. Candidate gene or pathway approaches as well as genome-wide approaches are beginning to identify potential pathogenic variants for NEC in premature infants. However, a majority of these studies have not yielded definitive results because of limited sample size and lack of validation. Despite these challenges, understanding the contribution of genetic variation to NEC is important for providing new insights into the pathogenesis of NEC as well as allowing for targeted care of infants with inherent susceptibility. In this review we provide a summary of published genetic association studies in NEC along with defining the challenges and possible future approaches.

Single-Immunoglobulin Interleukin-1-Related Receptor regulates vulnerability to TLR4-mediated necrotizing enterocolitis in a mouse model

BackgroundThe mechanisms underlying aberrant activation of intestinal Toll-like receptor 4 (TLR4) signaling in necrotizing enterocolitis (NEC) remain unclear. In this study, we examined the role of single-immunoglobulin interleukin-1 receptor-related molecule (SIGIRR), an inhibitor of TLR signaling, in modulating experimental NEC vulnerability in mice.MethodsExperimental NEC was induced in neonatal wild-type and SIGIRR−/− mice using hypoxia, formula-feeding, and lipopolysaccharide administration. Intestinal TLR canonical signaling, inflammation, apoptosis, and severity of experimental NEC were examined at baseline and after NEC induction in mice.ResultsSIGIRR is developmentally regulated in the neonatal intestine with a restricted expression after birth and a gradual increase by day 8. At baseline, breast-fed SIGIRR−/− mouse pups exhibited low-grade inflammation and TLR pathway activation compared with SIGIRR+/+ pups. With experimental NEC, SIGIRR−/− mice had significantly more intestinal interleukin (IL)-1β, KC (mouse homolog to IL-8), intercellular adhesion molecule-1 (ICAM-1), and interferon-beta (IFN-β) expression in association with the amplified TLR pathway activation. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining, cleaved caspase 3, and severity of intestinal injury with NEC were worse in SIGIRR−/− mice in comparison with SIGIRR+/+ mice.ConclusionSIGIRR is a negative regulator of TLR4 signaling in the developing intestine, and its insufficiency results in native intestinal TLR hyper-responsiveness conducive to the development of severe experimental NEC in mice.

Outcomes of Infants Who Failed to Extubate despite Systemic Corticosteroids

Objective The objective of this study was to assess the outcomes of preterm infants who failed to extubate following initial treatment with steroids. Materials and Methods This is a retrospective cohort study of ventilator‐dependent preterm infants treated with first course of systemic steroids to facilitate extubation. Outcomes of infants who successfully extubated were compared with infants who failed to extubate. Results In this study, 74 infants (mean gestation 25.4 ± 1.4 weeks and mean birth weight 764 ± 163 g) met inclusion criteria. Of these, 41 (55%) were successfully extubated and 33 (45%) were not. Baseline demographics were similar between the two groups. The primary outcome of severe bronchopulmonary dysplasia (BPD) or death at 36 weeks was higher among infants who failed to extubate (94 vs. 63%, p = 0.002). Severe BPD remained significantly higher even after adjustment for potential confounders (odds ratio: 12.2, 95% confidence interval: 2.1‐70.5, p = 0.005). Extubation failure was also associated with substantially higher rate of tracheostomy (32 vs. 5%, p = 0.003) and gastrostomy tube placement (61 vs. 22%, p = 0.001), as well as longer days of hospitalization (179 ± 72 vs. 129 ± 44 days, p = 0.001) and mechanical ventilation (112 ± 89 vs. 52 ± 42 days, p < 0.001). Conclusion Failure to extubate after first course of systemic steroids for BPD is associated with poor prognostic implications.

Usefulness of an Online Risk Estimator for Bronchopulmonary Dysplasia in Predicting Corticosteroid Treatment in Infants Born Preterm

Objective To assess the usefulness of a bronchopulmonary dysplasia (BPD) outcome estimator developed by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) in identifying high‐risk preterm infants treated with steroids. Study design This was a single‐center retrospective study of infants born ≤30 weeks of gestational age. The NICHD BPD outcome estimator was used to retrospectively calculate BPD risk at various postnatal ages. The best combination of risk estimates for identifying steroid treatment was identified using stepwise model selection. A cut‐off value with the best combination of sensitivity and specificity was identified using receiver operating characteristic analysis. Results A total of 165 infants born preterm (mean gestational age 26 ± 1.6 weeks, mean birth weight 837 ± 171 g) were included. Of these, 61 were treated with steroids for BPD and 104 were not. Risk estimates for BPD or death were significantly greater in infants treated with steroids compared with controls. Both combined risk for severe BPD or death and single risk of no BPD were identified as factors with the best predictive power for identifying treatment with steroids, with accurate prediction possible as early as the second week of life. A greater than 37% risk for severe BPD or death or a less than 3% risk of no BPD on day of life 14 had 84%‐92% sensitivity and 77%‐80% specificity for predicting steroid treatment. Conclusion The NICHD BPD outcome estimator can be a useful objective tool for identifying infants at high risk for BPD who may benefit from postnatal steroids.