Oral Presentation ESA-SRB-APEG-NZSE 2022

Beta-defensin 22 in seminal fluid promotes female fecundability through effects on maternal receptivity to implantation in mice (#59)

Hon Y Chan 1 , Ricky A Matias 1 , John E Schjenken 1 2 3 , Peck Yin Chin 1 , David J Sharkey 1 , Lachlan M Moldenhauer 1 , Sarah A Robertson 1
  1. Robinson Research Institute & Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
  2. Priority Research Centre for Reproductive Science, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, Australia
  3. Infertility and Reproduction Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia

In many mammalian species, components of seminal plasma and sperm interact with the female reproductive tract after mating to elicit an immune response that promotes reproductive success. Beta-defensins are a diverse group of antimicrobial and immune-modulatory peptides carried by sperm, which interact with female reproductive tract cells after mating, potentially via TLR4 binding. In men, the major beta-defensin moiety is DEFB126, and reduced expression of DEFB126 is associated with impaired fertility. To investigate the physiological significance of DEFB126 in fertility, we utilised CRISPR technology to generate C57Bl/6 mice with null mutation in Defb22 (Defb22-/-), the murine ortholog of human DEFB126.  Defb22-/- males sired pregnancies with poorer outcomes than Defb22+/+ males when mated to wild-type Balb/c females, with reduced implantation rates, increased post-implantation fetal loss, and fetal growth restriction in late gestation (n=24-30 dams/group,P<0.05). However, this was not attributable to reduced fertilisation, as there was no detectable difference in blastocyst numbers or development in females mated to Defb22+/+ or Defb22-/- males on day 3.5 post-coitum (d3.5pc) (n=10-12), implicating an embryo implantation defect. qPCR analysis of the uterine endometrium collected 8h after mating showed that unlike Defb22+/+ males, mating with Defb22-/- males failed to induce expression of endometrial cytokine genes Il6 and Tnf, and microRNAs miR155 and miR223 (n=10-12,P<0.05), likely impacting the uterine immune environment. RNAseq analysis of the uterine endometrium on d3.5pc (n=4/group) showed altered expression of genes associated with implantation-related immune-regulatory and tissue remodelling pathways, with downregulation of Mmp7, Wnt7b, Il11, Fosl1, Lifr, Ptgs2, Cebpb, Cd55, Csf1, and Atp6v0d2, when females were mated with Defb22-/- males. These data demonstrate that DEFB22 is required for optimal fertility in males, through a role in enabling seminal fluid to interact with the uterine endometrium to stimulate a permissive female immune response promoting endometrial receptivity to support healthy embryo implantation and optimal reproductive outcomes.