Oral Presentation ESA-SRB-NZSE-CaSR 2026 in conjunction with ENSA

Do phthalates interact with activin A in fetal life to influence testis development (142835)

Junlan (Iris) Ma 1 2 , Sarah C Moody 2 3 , Penny AF Whiley 1 2 , Dagmar Wilhelm 4 , Kate L Loveland 1 2
  1. Department of Molecular and Translational Sciences, School of Clinical Sciences, Monash University, Clayton, VIC, Australia
  2. Centre for Endocrinology and Reproductive Health , Hudson Institute of Medical Research, Clayton, VIC, Australia
  3. Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland
  4. Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia

This study examines two factors that affect mammalian testis development, di-2ethylhexyl phthalate (DEHP), and the TGFβ superfamily ligand, activin A, investigating their individual and combined contributions to male reproductive pathologies. Elevated activin A features in human pregnancy conditions including preeclampsia. Fetal mice exposed to either elevated activin A bioactivity (Inha-/- KO, lacking inhibin) or phthalates have similar testis phenotypes. We hypothesized that simultaneous exposure to both exacerbates testis development disruption. Inha-/- HET pregnant females received either vehicle or 500mg/kg/day DEHP from embryonic day (E)12.5 to E14.5 or E16.5. Testes collected at E15.5 and E17.5 (WT, HET, KO, n=4-7/genotype/treatment) were examined using immunohistology and RNAseq. At E15.5, DEHP-exposed litters exhibited higher embryo resorption rates than vehicle controls (78% vs 40%). E15.5 Inha-/- KO testes with unopposed activin featured smaller cord area (0.8-fold), fewer germ cells (0.66-fold), and more gonocytes outside of cords (37-fold) compared to WT testes. Notably, these phenotypes were significantly and exclusively exacerbated in KO testes following DEHP exposure. KO testes also exhibited greater immune cell infiltration (CD45+ cells:1.57-fold; F4/80+ cells: 2.5-fold) compared to WT testes, but DEHP exposure reduced this to WT levels. At E17.5, DEHP exposure increased the proportion of multinucleated gonocytes in HET (3.16-fold) and KO (2.85-fold) testes, but not in WT testes. Whole-testis transcriptomic analyses on E17.5 samples identified distinct and overlapping targets of activin A and DEHP (activin A: 49 Differentially Expressed Genes [DEGs]; DEHP: 6 DEGs), with combined exposure resulting in 309 DEGs. By providing evidence of functional outcomes linking activin A and phthalates that affect germline and somatic cells, these results demonstrate for the first time that activin A bioactivity can determine fetal testis susceptibility to environmental exposures. This evidence may be important for pregnant women with common pregnancy complications and contribute to the regulation of environmental chemical exposures.