Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Betamethasone and fetal sex alter glucocorticoid and angiogenic signalling pathways in the sheep placenta (#227)

Ashley S Meakin 1 , Mitchell C Lock 1 , Stacey L Holman 1 , Joshua L Robinson 2 , Claire T Roberts 3 , Vicki L Clifton 4 , Michael D Wiese 5 , Kathryn L Gatford 2 , Janna L Morrison 1
  1. Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
  2. Robinson Research Institute, The University of Adelaide, Adelaide, South Australia, Australia
  3. Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, South Australia, Australia
  4. Mater Medical Research Institute - University of Queensland, Woolloongabba, QLD, Australia
  5. Centre for Pharmaceutical Innovation, UniSA: Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia

Antenatal corticosteroids (ACS, e.g., betamethasone) are standard clinical care for pregnancies at risk of preterm delivery to reduce the incidence of neonatal lung disease and death. In some studies, ACS decrease placental vascular resistance, increase umbilical artery diameter and blood flow, and accelerate placental villus maturation, particularly in females. However, ACS impaired placental development and led to fetal growth restriction in others. Differences in placental responses to ACS may reflect differing expression profiles of glucocorticoid receptor (GR) isoforms. Therefore, we examined placental molecular responses to betamethasone in a clinically relevant sheep model of human pregnancy.
Pregnant Merino ewes at ~138d gestation (term=150d) received intramuscular injections of either saline or 11.6 mg betamethasone 48 and 24 hours prior to Caesarean section. Major fetal organs, including placentae (saline: female n=6, male n=8; betamethasone: female n=7, male n=5) were collected and snap frozen. Placental glucocorticoid concentrations were measured using mass spectrometry. Cytosolic and nuclear GR isoform expression profiles were measured using Western blot, and expression of genes involved in glucocorticoid signalling, angiogenesis, growth, and proliferation was measured using qRT-PCR.
Betamethasone reduced placental cortisol concentrations in males only (P=0.0001). Betamethasone reduced HSD11B1 (P=0.0491) and increased NR3C1 (encoding GR, P=0.0401) expression, irrespective of fetal sex. Female betamethasone-exposed placentae had higher cytoplasmic GRαC (P=0.0112), GR-P (P=0.0018), and GRαD (P=0.0079) expression than their male counterparts. Neither betamethasone nor fetal sex altered expression of nuclear localised GR isoforms. Expression of ANGPT2 (P=0.0018), IGF2 (P=0.0126), PGF (P=0.0007), VEGFR1 (P<0.0001), and VEGFR2 (P=0.0006) were higher, whereas KI67 (P=0.0007) and PCNA (P=0.0010) were lower in betamethasone-exposed placentae, irrespective of fetal sex.
Despite sex-specific impacts of betamethasone on GR isoform expression, betamethasone induced pro-angiogenic and anti-proliferative gene expression responses in placentae from both sexes. Further investigation is needed to understand the effect of betamethasone and sex on placental function.