HIF1α Is Essential for Normal Intrauterine Differentiation of Alveolar Epithelium and Surfactant Production in the Newborn Lung of Mice

Neonatal respiratory distress syndrome (RDS) is mainly the result of perturbation in surfactant production and is a common complication seen in premature infants. Normal fetal lung development and alveolar cell differentiation is regulated by a network of transcription factors. Functional loss of any of these factors will alter the developmental program and impact surfactant production and normal gas exchange. During development, the fetus is exposed to varying oxygen concentrations and must be able to quickly adapt to these changes in order to survive. Hypoxia-inducible factor 1 alpha(HIF1 alpha) is the primary transcription factor that is responsible for regulating the cellular response to changes in oxygen tension and is essential for normal development. Its role in lung maturation is not well defined and to address this knowledge gap, a lung-specific HIF1 alpha knock-out model has been developed. Loss of HIF1 alpha early in lung development leads to pups that die within hours of parturition, exhibiting symptoms similar to RDS. Lungs from these pups display impaired alveolar epithelial differentiation and an almost complete loss of surfactant protein expression. Ultrastructural analysis of lungs from HIF1 alpha deletion pups had high levels of glycogen, aberrant septal development, and decreased expression of several factors necessary for proper lung development, including HIF2 alpha, beta-catenin, and vascular endothelial growth factor. These results suggest that HIF1 alpha is essential for proper lung maturation and alteration in its normal signaling during premature delivery might explain the pathophysiology of neonatal RDS.