Prenatal administration of all-trans retinoic acid upregulates leptin signaling in hypoplastic rat lungs with experimental congenital diaphragmatic hernia.

[congenital diaphragmatic hernia]

Pulmonary hypoplasia (PH ), characterized by alveolar immaturity , is one of the leading causes of respiratory insufficiency in newborns with congenital diaphragmatic hernia (CDH ). Leptin (Lep ) and its receptor (Lep-R ) play an important role in fetal lung growth by stimulating alveolar differentiation and maturation . Lep and Lep-R are strongly expressed by alveolar cells during the saccular stage of fetal lung development . Lep-deficient mice exhibit decreased alveolarization with reduced pulmonary surfactant phospholipid synthesis , similar to human and nitrofen-induced PH . Prenatal administration of all-trans retinoic acid (ATRA ) has been shown to stimulate alveolarization in nitrofen-induced PH . Recent studies have demonstrated that Lep and Lep-R expression in developing lungs is regulated by ATRA . We hypothesized that prenatal treatment with ATRA increases pulmonary Lep and Lep-R expression in the nitrofen model of CDH -associated PH .T ime-mated rats received either 100 mg nitrofen or vehicle via oral -gastric lavage on embryonic day 9 .5 (E 9 .5 ). Control and nitrofen-exposed dams were randomly assigned to either intraperitoneal ATRA (5 mg /kg /d ) or placebo administration on E 18 .5 , E 19 .5 and E 20 .5 . Fetal lungs were harvested on E 21 .5 , and divided into Control +Placebo , Control +ATRA , Nitrofen +Placebo and Nitrofen +ATRA . Alveolarization was assessed using stereo- and morphometric analysis techniques . Surfactant phospholipid synthesis was analyzed by labeling for surfactant protein B (SP-B ). Pulmonary gene expression levels of Lep and Lep-R were determined using quantitative real-time polymerase chain reaction . Immunohistochemical staining for Lep and Lep-R was performed to evaluate alveolar protein expression and localization .In vivo administration of ATRA resulted in significantly increased lung -to -body weight ratio with enhanced radial alveolar count and decreased mean linear intercept compared to placebo treatment . Immunofluorescence analysis demonstrated markedly increased pulmonary SP-B expression in Nitrofen +ATRA compared to Nitrofen +Placebo . Relative mRNA expression of Lep and Lep-R was significantly increased in Nitrofen +ATRA compared to Nitrofen +Placebo . Lep and Lep-R immunoreactivity was markedly increased in interstitial and alveolar epithelial cells of Nitrofen +ATRA compared to Nitrofen +Placebo .Increased Lep and Lep-R expression after prenatal administration of ATRA in nitrofen-induced PH suggests that ATRA may have therapeutic potential in attenuating CDH -associated PH by stimulating alveolarization and de novo surfactant production .