Aquaporine-5 and epithelial sodium channel β-subunit gene expression in gastric aspirates in human term newborns

Both transient tachypnea of the newborn and neonatal respiratory distress syndrome have been associated with changes in gene expression of aquaporine-5 (AQP5) and the β subunit of the epithelial sodium channel (β-ENaC) in the respiratory epithelium. Gastric aspirate (GA) obtained immediately after birth could represent a new source for gene expression analysis for these respiratory diseases. The aims of this study were to determine the feasibility of estimating AQP5 and β-ENaC gene expression in exfoliated respiratory epithelial cells from the GA of term neonates, and to compare the values with those found in scraped nasal epithelial cells, previously validated as a surrogate for distal lung epithelium in terms of ionic channel activity. The study had a cross-sectional, proof-of-concept design. Immediately after birth, we obtained GA and nasal mucous membrane scrapings from term newborns, in which total RNA and RT-qPCR assays for AQP5 and β-ENaC genes were performed. AQP5 gene expression was greater in GA than in nasal scrapings, and β-ENaC gene expression was at least as great in GA as that obtained in nasal scrapings. Amplification of samples from the two sites was comparable. AQP5 gene expression was greater in babies delivered by cesarean section; β-ENaC gene expression was greater in babies delivered vaginally, but only in the nasal samples. Quantitation of the expression of AQP5 and of β-ENaC genes in GA, obtained shortly after birth from term newborns is feasible. If confirmed in preterm neonates, this approach could aid in the differential diagnosis of neonatal respiratory diseases.