Antenatal vitamin A administration attenuates lung hypoplasia by interfering with early instead of late determinants of lung underdevelopment in congenital diaphragmatic hernia

Abstract

Background/Purpose Early and late lung underdevelopment in congenital diaphragmatic hernia (CDH) is likely caused by nonmechanical (directly mediated by nitrofen) and mechanical (mediated by thoracic herniation) factors, respectively. The authors investigated if vitamin A enhances lung growth because of effects on both early and late determinants of lung hypoplasia. Methods Twenty-seven pregnant Wistar rats were exposed on embryonic day (E)9.5 to 100 mg of nitrofen or just olive oil. From nitrofen-exposed pregnant rats, 12 were treated at day 9.5 or 18.5 with 15,000 IU of vitamin A. Lungs were harvested at E18, E20, and E22, weighed, and analyzed for DNA and protein contents. Left and/or right lung hypoplasia was estimated by assessment of the ratios of lung to body weight and left to right lung weight. Fetuses were assigned to 5 experimental groups: baseline (exposed neither to nitrofen nor vitamin A), nitrofen (exposed to nitrofen without CDH), CDH (exposed to nitrofen with CDH), nitr+vitA (exposed to nitrofen without CDH and treated with vitamin A), and CDH+vitA (exposed to nitrofen with CDH and treated with vitamin A). Results Incidence of hernia was significantly reduced in fetuses treated with vitamin A. When vitamin A was administered at E9.5, the authors observed similar effect on lung hypoplasia measured through ratio of lung to body weight at E18 in the nitrofen and CDH groups (nitrofen 1.92% ± 0.05%, CDH 1.92% ± 0.04%), whereas lung hypoplasia was attenuated relative to baseline (2.45% ± 0.05%) in 5% and 4% in nitrofen (nitr+vitA 2.05% ± 0.03%) and CDH (CDH+vitA 2.08% ± 0.04%) groups, respectively. At E20, lung hypoplasia was increased in CDH compared with nitrofen groups (nitrofen 2.52% ± 0.1%, CDH 2.39% ± 0.05%), whereas vitamin A attenuated lung hypoplasia, in relation to baseline (3.20% ± 0.07%), 14% in both nitrofen-exposed groups (nitr+vitA 2.96% ± 0.03%, CDH+vitA 2.83% ± 0.03%). At E22, lung hypoplasia was significantly higher in CDH group than nitrofen group (nitrofen 2.13% ± 0.06%, CDH 1.48% ± 0.03%), whereas lung hypoplasia was attenuated in 9% of both nitrofen-exposed groups (nitr+vitA 2.35% ± 0.06%, CDH+vitA 1.69% ± 0.05%) in relation to baseline group (2.38% ± 0.04%). Administration of vitamin A at E18.5 produced no significant effects on lung growth. Conclusions The authors conclude from these results that antenatal administration of vitamin A attenuates lung hypoplasia in CDH by interfering with early determinants of lung underdevelopment. This finding may have clinical implications because prenatal diagnosis of human CDH commonly occurs after 16 weeks' gestation when late determinants of lung hypoplasia likely predominate.