Complementary Effect of Maternal Sildenafil and Fetal Tracheal Occlusion Improves Lung Development in the Rabbit Model of Congenital Diaphragmatic Hernia

Abstract

Objective: To evaluate the effect of combining antenatal sildenafil with fetal tracheal occlusion (TO) in fetal rabbits with surgically induced congenital diaphragmatic hernia (CDH). Background: Although antenatal sildenafil administration rescues vascular abnormalities in lungs of fetal rabbits with CDH, it only partially improves airway morphometry. We hypothesized that we could additionally stimulate lung growth by combining this medical treatment with fetal TO. Methods: CDH was created on gestational day (GD)23 (n¼54). Does were randomized to receive either sildenafil 10 mg/kg/d or placebo by subcutaneous injection from GD24 to GD30. On GD28, fetuses were randomly assigned to TO or sham neck dissection. At term (GD30) fetuses were delivered, ventilated, and finally harvested for histological and molecular analyses. Unoperated littermates served as controls.Results: The lung-to-body-weight ratio was significantly reduced in sham-CDH fetuses either (1.2 AE 0.3% vs 2.3 AE 0.3% in controls, P¼0.0003). Sildenafil had no effect on this parameter, while CDH fetuses undergoing TO had a lung-to-bodyweight ratio comparable to that of controls (2.5 AE 0.8%, P<0.0001). Sildenafil alone induced an improvement in the mean terminal bronchiolar density (2.5 AE 0.8 br/mm 2 vs 3.5 AE 0.9 br/mm 2 , P¼0.043) and lung mechanics (static elastance 61 AE 36 cmH 2 O /mL vs 113 AE 40 cmH 2 O/mL, P¼0.008), but both effects were more pronounced in fetuses undergoing additional TO (2.1 AE 0.8 br/mm 2 , P¼0.001 and 31 AE 9 cmH 2 O/mL, P<0.0001 respectively). Both CDH-sham and CDH-TO fetuses treated with placebo had an increased medial wall thickness of peripheral pulmonary vessels (41.9 AE 2.9% and 41.8 AE 3.2%, vs 24.0 AE 2.9% in controls, P<0.0001). CDH fetuses treated with sildenafil, either with or without TO, had a medial thickness in the normal range (29.4% AE 2.6%). Finally, TO reduced gene expression of vascular endothelial growth factor and surfactant protein A and B, but this effect was counteracted by sildenafil. Conclusion:In the rabbit model for CDH, the combination of maternal sildenafil and TO has a complementary effect on vascular and parenchymal lung development.

Identification of protein biomarkers associated with congenital diaphragmatic hernia in human amniotic fluid

“…Another study which concluded that there was no difference in amniotic fluid levels of surfactant also did not measure SP-B 25 . In a surgical rabbit model of CDH, SP-B gene expression was reduced compared to the sham controls, as was the SP-B staining intensity determined by immunohistochemistry 26 . Boucherat et al compared surfactant levels in fetuses with CDH with unaffected fetuses at different time points during pregnancy and observed that affected lungs were significantly smaller and histologically immature, but no delay in surfactant development or content (including SP-B) in CDH fetal lungs was observed by western blotting 27 .…”

Neonatal and fetal therapy of congenital diaphragmatic hernia-related pulmonary hypertension

“…Many rat studies as well as a rabbit study demonstrated attenuated vascular remodelling, reduced arteriolar muscularisation and increased vessel density in hernia pups exposed to prenatal sildenafil. In rabbits, the effects of sildenafil and tracheal occlusion were synergistic 56. In addition, in fetal lambs with CDH, maternal administration also improved neonatal pulmonary haemodynamics and gas exchange 57.…”

Sildenafil during the 2nd and 3rd Trimester of Pregnancy: Trials and Tribulations

“…In a surgical rabbit model with CDH, sildenafil reduced the proportional wall thickness of peripheral lung vessels to the normal range, increased vascular branching, improved airway morphometry, and postnatal lung mechanics [ 111 ]. Combined with tracheal occlusion, sildenafil’s beneficial effect on airway development and lung function was augmented in pups with CDH [ 112 ]. Similarly to the findings in the rat studies, sildenafil reduced pulmonary vascular branching in non-hypoplastic littermates [ 111 ].…”