Mechanisms of in utero cortisol effects on the newborn heart revealed by transcriptomic modeling

Abstract

We have identified effects of elevated maternal cortisol (induced by maternal infusion 1 mg·kg^-1·day^-1) on fetal cardiac maturation and function using an ovine model. Whereas short-term exposure (115-130-day gestation) increased myocyte proliferation and Purkinje fiber apoptosis, infusions until birth caused bradycardia with increased incidence of arrhythmias at birth and increased perinatal death, despite normal fetal cortisol concentrations from 130 days to birth. Statistical modeling of the transcriptomic changes in hearts at 130 and 140 days suggested that maternal cortisol excess disrupts cardiac metabolism. In the current study, we modeled pathways in the left ventricle (LV) and interventricular septum (IVS) of newborn lambs after maternal cortisol infusion from 115 days to birth. In both LV and IVS the transcriptomic model indicated over-representation of cell cycle genes and suggested disruption of cell cycle progression. Pathways in the LV involved in cardiac architecture, including SMAD and bone morphogenetic protein ( BMP) were altered, and collagen deposition was increased. Pathways in IVS related to metabolism, calcium signaling, and the actin cytoskeleton were altered. Comparison of the effects of maternal cortisol excess to the effects of normal maturation from day 140 to birth revealed that only 20% of the genes changed in the LV were consistent with normal maturation, indicating that chronic elevation of maternal cortisol alters normal maturation of the fetal myocardium. These effects of maternal cortisol on the cardiac transcriptome, which may be secondary to metabolic effects, are consistent with cardiac remodeling and likely contribute to the adverse impact of maternal stress on perinatal cardiac function.

Keywords: cardiac; fetus; maturation; microarray; pregnancy.

Fig. 1.

Enriched ClueGO gene networks from the left ventricle (A) and the septum (B) in newborn lambs. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with the differentially expressed genes involved in the network (genes named in red). Green lines with arrows represent gene activation interactions; red lines with bars represent interactions involved in gene repression.

Fig. 2.

Representative images of left ventricle stained with picrosirius red (depicted as bright areas) and imaged using circular polarized light from control (A) and cortisol (CORT) (B) newborn lambs. Quantification of stained area relative to tissue area (C) is shown. *Statistical difference (P ≤ 0.05) between control and CORT fetuses.

Fig. 3.

Representative images of septum from control (A) and cortisol (CORT) (B) newborn lambs stained with anti-COX4 antibody (red). Nuclei are stained in blue (DAPI) and myocytes in green (wheat germ agglutinin). Quantification of stained area relative to tissue area (C) is shown. *Statistical difference (P ≤ 0.05) between control and CORT fetuses. COX, cytochrome c oxidase.

Fig. 4.

Venn diagram showing overlap of differentially regulated (DR) genes in left ventricle (LV) up (yellow) and down (green) regulated in cortisol (CORT) newborns and DR genes up (purple) and down (pink) regulated in the control newborns compared with control 142-day fetuses, as a reflection of normal maturation. There were 32 genes upregulated in both sets of LV data, and 45 genes downregulated in both sets of LV data. There were 13 genes downregulated in CORT newborn LV but downregulated from 142 days to newborn in the LV, and 12 genes upregulated in CORT newborn LV but upregulated in newborn LV compared with the 142-day fetus LV. There were 122 upregulated and 162 downregulated genes in the CORT newborns LV that were not significantly changed in LV with the transition between 142 days of fetal life and the first day of life.

Fig. 5.

Summary of the effects of increased maternal cortisol, produced by infusion of 1 mg·kg⁻¹·day⁻¹ from 115 days to birth, on fetal cardiac phenotype, and the changes in pathways modeled using transcriptomics. Data from hearts at 130 days and 140 days have been previously reported (59, 60). LV, left ventricle; IVS, septum; RV, right ventricle; TGF, transforming growth factor.