Oral Presentation ESA-SRB-AOTA 2019

Altered placental androgen signalling contributes to growth restricted outcomes (#32)

Ashley Meakin 1 , Zarqa Saif 1 , Ratana Lim 2 , Martha Lappas 2 , Vicki Clifton 1
  1. Mater Medical Research Institute - University of Queensland, Woolloongabba, QLD, Australia
  2. University of Melbourne, Melbourne

Background

Current epidemiological data shows male fetuses have greater birthweight outcomes, but are at a greater risk of being born small for gestational age (SGA), when compared to female fetuses. The mechanisms contributing to these male-specific outcomes remain unclear but may be mediated, in part, by altered placental androgen signalling. Our group recently identified sex-specific expression of multiple androgen receptor (AR) variants in the human placenta that may modulate placental androgen signalling. Specifically, expression of a 45kDa variant, AR-45, was associated with growth outcomes in males only. We have questioned whether altered AR-45 expression and localisation contributes to growth perturbations. Therefore, this study has investigated AR-45 function in vitro, and characterised its expression and localisation in SGA placentae.

Methodology

AR-45 cellular localisation was measured in response to 0.1nM dihydrotestosterone (DHT), as was the expression of androgen-mediated downstream targets. AR-45-overexpressing trophoblast cell proliferation was also measured in response to DHT. AR variant protein levels were measured in appropriate for gestation age (AGA) (n=28) and SGA (n=84) placentae.

Results

AR-45-overexpressing trophoblast cells had reduced proliferation, reduced gene expression of targets involved in the IGF-axis, but significantly increased VEGF mRNA expression. Cytoplasmic AR-45 expression was significantly increased in male placentae from severe SGA neonates (<5th birthweight centile (BWC)), when compared to moderate SGA (5th–10th BWC) and AGA (>10th BWC). Cytoplasmic-localised placental AR-45 trended towards a negative association with BWC in males only (r2=-0.294, p=0.059).

Conclusion

Our data shows AR-45 inhibits growth signalling, but enhances the expression of angiogenic factors. It is postulated that cytoplasmic sequestering of AR-45 alters androgen signalling, thereby contributing to growth restriction via perturbed placental vasculature. Evidently, further studies are needed to understand mechanisms contributing to AR-45 localisation and downstream target gene transcriptional regulation within the placenta, and the implications these may have for fetal growth outcomes.