Prenatal treatment with retinoic acid promotes pulmonary alveologenesis in the nitrofen model of congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Severe pulmonary hypoplasia remains the main cause of the high mortality in newborn infants with congenital diaphragmatic hernia (CDH). Retinoids are a family of molecules derived from vitamin A, which play an important role in lung development. We hypothesized that retinoids promote alveologenesis at the end of gestation and therefore designed this study to investigate the effects of retinoid acid on nitrofen-induced hypoplastic lungs in CDH. METHODS: Pregnant rats were exposed to either olive oil or 100 mg nitrofen on day 9 of gestation. Retinoic acid 5 mg/kg was given intraperitoneally on days 18, 19, and 20 of gestation and fetuses were recovered on day 21. We had 4 study groups: control (n = 24), control + retinoic acid (n = 22), CDH (n = 24), and CDH + retinoic acid (n = 19). Lungs from the 4 study groups were fixed, and the following stereological measurements were performed on vertical random sections: total lung volume, volume density of airspaces, volume density of air walls, gas exchange surface area, alveolar volume, and total number of alveoli per lung. Total DNA content of each lung was measured using a spectrophotometer. RESULTS: Total lung volume increased in CDH lungs after the addition of retinoic acid but remained the same in the control group. Gas exchange surface area was larger in CDH lungs after the addition of retinoic acid but remained unchanged in the control group. The total number of alveoli per lung was higher after the addition of retinoic acid. Total DNA content as well as total DNA content-lung weight ratio of the left lung increased significantly in the CDH group after the addition of retinoic acid compared with CDH without retinoic acid. CONCLUSIONS: Our results demonstrate that prenatal treatment with retinoic acid stimulates alveologenesis in hypoplastic lungs in CDH.

Prenatal treatment with retinoic acid accelerates type 1 alveolar cell proliferation of the hypoplastic lung in the nitrofen model of congenital diaphragmatic hernia.

PURPOSE: Retinoids play an important role in lung development. A recent study has demonstrated that prenatal treatment with retinoic acid (RA) stimulates alveologenesis in hypoplastic lungs in the nitrofen model of congenital diaphragmatic hernia (CDH). Furthermore, it has also been demonstrated that the differentiation from alveolar epithelial cells type II (AECs-II) into alveolar epithelial cells type I (AECs-I), which is the key process in lung development, is disturbed in this model. We hypothesized that retinoids promote alveologenesis by stimulating differentiation of AECs-II to AECs-I at the end of gestation; and therefore, we investigated the effect of RA on the pulmonary expression of intercellular adhesion molecule 1 (ICAM-1), a marker for AECs-I, and thyroid transcription factor 1 (Ttf-1), a marker for AECs-II, in nitrofen-induced hypoplastic lungs. MATERIALS AND METHODS: Pregnant rats were exposed to either olive oil or 100 mg nitrofen on day of gestation (D) 9. Five milligrams per kilogram of RA was given intraperitoneally on D18, D19, and D20; and fetuses were recovered on D21. We had 4 study groups: control (n = 7), control + RA (n = 7), CDH (n = 6), and CDH + RA (n = 6). The expression of ICAM-1 and Ttf-1 was analysed in each lung by real-time reverse transcription polymerase chain reaction and immunohistochemistry. One-way analysis of variance test was used for statistical analysis. RESULTS: Expression levels of ICAM-1 were significantly reduced in CDH lungs compared with normal controls, whereas levels increased significantly in CDH group after the addition of RA (P < .05). Expression levels of Ttf-1 were significantly decreased in lungs from RA-treated CDH animals compared with CDH without RA (P < .05). The ICAM-1 and Ttf-1 immunoreactivity demonstrated similar pattern of expression in various groups. CONCLUSIONS: Our results demonstrate that prenatal treatment with RA accelerates AEC-I proliferation in the hypoplastic lung in CDH.

Lung growth induced by prenatal instillation of perfluorocarbon into the fetal rabbit lung.

The study's aim was to evaluate whether prenatal instillation of perfluorooctylbromide (PFOB, a perfluorocarbon) into the lungs of fetal rabbits leads to increased lung growth. Hysteroamniotomy was performed in eight pregnant New Zealand white rabbits on gestational day 27. In each mother, four fetuses were randomized to undergo either 1) endotracheal intubation and intrapulmonary instillation of 1 ml PFOB, 2) intrapulmonary instillation of 1 ml 0.9% NaCl solution (saline), 3) no fetal manipulation (control), or 4) tracheal occlusion (TO). The distribution of PFOB was documented radiographically. The fetuses were born by cesarean section after 48 h, sacrificed, weighed, and their lungs excised. Fetal lung to body weight ratios (FLBW) were determined, and the lungs were snap frozen for histomorphologic analysis and lung tissue distillation. On macroscopic inspection, PFOB-filled and tracheally-occluded lungs were markedly larger than saline-filled and control lungs. Mean FLBW was higher in fetuses treated with intrapulmonary instillation of PFOB (0.037+/-0.009), compared with fetuses receiving saline (0.027+/-0.008) or the unmanipulated controls (0.028+/-0.008). FLBW was highest after TO (0.049+/-0.008). After 48 h, in-vivo radiographs did not demonstrate any residual PFOB. Average dry fetal left lung weight (in g) was much higher in the TO (0.064+/-0.029) and PFOB (0.062+/-0.016) fetuses compared with the saline (0.054+/-0.017) and control (0.043+/-0.012) groups. Alveolar architecture on microscopy was similar between all groups, although the alveolar septae appeared thicker and more cellular after PFOB treatment and TO. We concluded that prenatal intrapulmonary PFOB instillation leads to increased lung growth in the late gestation rabbit model. Although PFOB instillation resulted in lower wet FLBW than TO, the increase in dry lung weight is comparable. This novel technique may be a less invasive and less noxious treatment strategy for pulmonary hypoplasia associated with diaphragmatic hernia.

Prenatal vitamin E improves lung and heart hypoplasia in experimental diaphragmatic [correction of diaphragamatic] hernia.

Nitrofen induces in rats diaphragmatic hernia (CDH) with heart and lung hypoplasia by a mechanism involving oxidation. The aim of this study was to examine if prenatal administration of the anti-oxidant agent vitamin E (VitE) prevents to some extent heart and lung hypoplasia. Pregnant rats received on E9.5 either 100 mg of nitrofen alone or followed by 150 IU of VitE on E16.5-E20.5. Control animals received either vehicle or VitE alone. The fetuses were recovered on E21. The hearts and lungs were weighed and DNA and proteins were measured. Sections of the heart and lung were immunohistochemically stained for ki-67, Tunel and TTF-1, and the proportions of proliferating, apoptotic and TTF-1-expressing cells were determined. Cultured human pneumocytes were exposed to the same agents and similarly processed. TTF-1 expression and the proportion of proliferating cells were quantitated. The ANOVA or Kruskall-Wallis tests were used for comparison with p<0.05 as threshold of significance. Nitrofen-exposed rats had decreased lung and heart weight/body weight ratios, lung and heart DNA and protein, lung TTF-1 expression and proportion of proliferating cells in lung and heart. Additional treatment with VitE ameliorated these decreases except for lung TTF-1 and heart weight. In cultured pneumocytes, TTF-1 expression was decreased by nitrofen and rescued by VitE. Cell proliferation followed the same pattern. Antioxidant VitE partially reverses the effects of nitrofen on the heart and lungs of exposed rats. The same effects are observed in cultured human pneumocytes. These results further substantiate the oxidative nature of the effects of nitrofen and suggest that anti-oxidant agents could have a potential clinical application.

Increased expression of ICAM-1 and VCAM-1 in the lung of nitrofen-induced congenital diaphragmatic hernia in rats.

Recently, increased expression of inflammatory cytokine, tumor necrosis factor (TNF)-alpha, has been reported in both humans and animal models with CDH and the decreased TNF-alpha expression in CDH lung after antenatal dexamethasone (Dex) treatment. Intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 are induced by several inflammatory cytokines such as TNF-alpha. The aim of this study was to investigate pulmonary ICAM-1 and VCAM-1 expression in CDH lung in rats and to determine the effect of antenatal glucocorticoid. CDH model was induced in pregnant rats following administration of nitrofen on day 9.5 of gestation. In control animals, the same dose of olive oil was given without nitrofen. Dex (0.25 mg/kg) was given on day 18.5 and 19.5 of gestation. RT-PCR was performed to evaluate the relative amount of ICAM-1 and VCAM-1 mRNA expression. Fluorescein immunohistochemistry using anti-ICAM-1 and anti-VCAM-1 antibody was performed using light and confocal microscopy. ICAM-1 and VCAM-1 mRNA expression and ICAM-1 and VCAM-1 immunoreactivity were markedly increased in CDH lung compared to controls. Dex downregulated the expression of both adhesion molecules in the hypoplastic lung. Increased ICAM-1 and VCAM-1 mRNA expression in hypoplastic lungs would suggest that the increased local synthesis of pulmonary adhesion molecules may induce respiratory distress in CDH. Decreased expression of adhesion molecules in CDH lungs after Dex treatment suggests that antenatal glucocorticoids therapy may improve pulmonary immaturity and associated respiratory distress in nitrofen-induced CDH lung.

Abdominal wall hernia: an uncommon complication of in utero vesicoamniotic shunt placement.

Three cases are reported in which placement of a vesicoamniotic shunt in utero for the treatment of obstructive uropathy led to the rare complication of abdominal wall hernia. All 3 patients underwent vesicoamniotic shunt placement for severe oligohydramnios and a markedly dilated bladder in an effort to preserve renal function and to prevent pulmonary hypoplasia. All three shunts were initially placed at or above the umbilicus. The abdominal wall hernias were closed postnatally at the time of temporary vesicostomy for urethral obstruction. All 3 patients had sufficient pulmonary development, but 2 of 3 had renal failure, requiring dialysis. Management and potential etiology of this rare complication are discussed.