Abnormal Fetal Lung of Hoxa1-/- Piglets Is Rescued by Maternal Feeding with All-Trans Retinoic Acid

Abstract

Neonatal Hoxa1^-/- piglets were characterized by dyspnea owing to the Hoxa1 mutation, and maternal administration with ATRA alleviated the dyspnea of neonatal Hoxa1^-/- piglets. The purpose of this experiment was to explore how maternal ATRA administration rescued the abnormal fetal lungs of Hoxa1^-/- piglets. Samples of the lungs were collected from neonatal Hoxa1^-/- and non-Hoxa1^-/- piglets delivered by sows in the control group, and from neonatal Hoxa1^-/- piglets born by sows administered with ATRA at 4 mg/kg body weight on dpc 12, 13, or 14, respectively. These were used for the analysis of ELISA, histological morphology, immunofluorescence staining, immunohistochemistry staining, and quantitative real-time PCR. The results indicate that the Hoxa1 mutation had adverse impacts on the development of the alveoli and pulmonary microvessels of Hoxa1^-/- piglets. Maternal administration with ATRA at 4 mg/kg body weight on dpc 14 rescued the abnormal lung development of Hoxa1^-/- piglets by increasing the IFN-γ concentration (p < 0.05), airspace area (p < 0.01) and pulmonary microvessel density (p < 0.01); increasing the expression of VEGFD (p < 0.01), PDGFD (p < 0.01), KDR (p < 0.01), ID1 (p < 0.01), and NEDD4 (p < 0.01); and decreasing the septal wall thickness (p < 0.01) and the expression of SFTPC (p < 0.01) and FOXO3 (p < 0.01). Maternal administration with ATRA plays a vital role in rescuing the abnormal development of lung of Hoxa1^-/- fetal piglets.

Keywords: ATRA; Hoxa1 mutation; alveoli; fetal piglets; maternal administration; pulmonary blood vessel.

Figure 1

Effects of Hoxa1 mutation and maternal ATRA administration on the outward appearance of the ears and lungs of Hoxa1^−/− piglets.

Figure 2

Results of HE staining. (A) Representative photomicrographs (×200). (B) Average thickness of the septal wall. (C) Average area of airspace. All data are expressed as mean ± SEM. ** p < 0.01; n.s., not significant.

Figure 3

Results of immunofluorescence staining. (A): results of AQP5 staining; (B): results of SFTPC staining; Magnification: 200×. Scale bar: 30 μm.

Figure 4

Results of immunohistochemical staining. (A) representative photomicrographs (magnification, 400×; scale bar, 15 μm). (B) mean microvessel density in the lung tissues. (C) microvascular-development-related genes. VEGFD: vascular endothelial growth factor D. PDGFD: platelet-derived growth factor-D. KDR: kinase insert domain receptor. ID1: inhibitor of differentiation 1. NEDD4: neuronal precursor cell-expressed developmentally downregulated 4. FoxO3: forkhead box O3. All data are expressed as mean ± SEM. ** p < 0.01, n.s., not significant.