Molecular agents in seminal plasma and on sperm have the capacity to interact with the uterine epithelium to prepare the female reproductive tract for pregnancy in mice. Recent findings suggest that sperm-associated molecules ligate TLR4 on uterine epithelial cells to assist in this process. Human DEFB126 is a ligand of TLR4 that is present on the sperm glycocalyx, and males homozygous for a DEFB126 frameshift mutation have reduced fertility. The aim of this study was to identify and explore how the murine orthologue of DEFB126, Defb22 contributes to this interaction to affect pregnancy success.
Defb22-/- mice were generated using CRISPR-CAS9 technology at the University of Adelaide SAGE Facility. Defb22+/+and Defb22-/-mice were bred from a Defb22+/-breeding colony. Males were housed as studs from 8 weeks of age. Fertility of males was assessed by mating Defb22+/+or Defb22-/- males with Balb/c females. On d17.5pc, viable and resorbing fetuses were counted then fetal and placental tissues were weighed (n=8 dams/group). At 20-22 weeks of age, a full post-mortem analysis of organ and reproductive parameters was conducted on the males (n=16/group).
Paternal Defb22 deficiency resulted in reduced pregnancy rates, fewer total viable pups per litter, and reduced fetal weights and fetal:placental weight ratios. At post-mortem, Defb22-/- males had reduced epididymal sperm (p<0.01), a reduced proportion of progressive motile sperm (p<0.001), and increased proportions of immotile sperm (p<0.01) compared to wildtype males. There was no difference in the weight of male reproductive organs between groups.
This study provides evidence that Defb22 deficiency affects male reproductive potential by reducing the number and motility of sperm, which impacts fertility. Current studies aim to identify how sperm-associated Defb22 affects immune reprogramming in the female reproductive tract, and its role in driving female TLR4 activation to contribute to the female response to seminal fluid.