Retinoic acid and tracheal occlusion for diaphragmatic hernia treatment in rabbit fetuses

Introduction: Lung hypoplasia and pulmonary arterial hypertension in congenital diaphragmatic hernia lead to a high perinatal mortality. Although sustained fetoscopic tracheal occlusion (TO) improves lung development, a major side effect is abnormal pneumocyte differentiation. This study evaluated the potential ability of intratracheal retinoic acid (RA) administration to reduce adverse effects of sustained TO in a rabbit model of diaphragmatic hernia. Methods: A left diaphragmatic defect was created on day 23 in time-dated pregnant rabbits. On day 28, the same rabbits underwent sham surgery or TO, with an injection of empty or RA-loaded liposomes. On day 30, the fetuses were harvested, and the lungs were processed for histology, immunohistochemistry, and gene expression quantification. Results: A tracheal RA injection at the time of TO had no effect on the lung-to-body-weight ratio, radial alveolar count or lung connective tissue composition. Retinoic acid plus TO had synergic effects on vascular measurements, proportional medial thickness, and endothelin-1 receptor type-A gene expression. The most noticeable effect was recovery of normal pneumocyte differentiation. Conclusion: Retinoic acid plus TO prevented abnormal pneumocyte differentiation and seemed to have a beneficial effect on pulmonary vascularization.