Oral Presentation The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2017

Advanced parental age is associated with decreased gamete quality and altered early embryonic development. (#94)

Macarena Gonzalez 1 , Rebecca Robker 1
  1. Robinson Research Institute, University of Adelaide, Adelaide, SA, Australia

Increasing ART use to treat age-related infertility necessitates a better understanding of how advanced parental age impacts gamete quality and IVF outcomes. This study aimed to measure gamete and embryonic quality markers in naturally-aged mice. Female and male C57BL6 mice were either 6 weeks old/“young” or 12 months old/”old”. Females were treated with PMSG/hCG gonadotropins to stimulate ovulation, while males were time-mated 4-7 days prior to sperm collection. Statistical analyses used was Student’s T-test. P-values of <0.05 were considered statistically significant. To study the effects of aging on oocyte quality, cytoplasmic autophagy levels and mitochondrial ROS production were measured using fluorescent live-cell assays.  “Old” oocytes exhibited higher autophagy levels than “young” ones at both GV (P=0.006, N=11-13/group) and MII stages (P=0.01, N=11/group). Embryo morphokinetics analyses showed that embryos from “old” oocytes had delayed 4 to 5-cell stage (P=0.01; N=25-26/group). Further, although zygotes from old females had lower 2-cell rate, they presented higher hatching rate at blastocyst stage (P=0.04; N=10-17/group). To analyse the effect of aging on sperm quality, semen analyses were conducted as per WHO guidelines. Old males presented lower sperm density, zona-binding capacity, and motility (P=0.02; N=7-9/group) than younger males. Mitochondrial membrane potential (MMP), detected by JC-1 stain and flow cytometry, was reduced in “old” vs “young” sperm (P=0.04; N>10K/group). Embryo morphokinetic analysis of embryos showed that embryos from old males had delayed time to 2-cells (P=0.01; N=21-27/group), decreased percentage of 2-cell embryos ‘on-time’ (P=0.02; N=10-11 per group), and produced fewer blastocysts (P=0.007; N=10-11/group). While “old” oocytes have increased autophagy levels, “old” spermatozoa present lower motility and MMP. Following IVF, cleavage rates were lower for all zygotes, however only those from old fathers produced lower blastocyst rates. These findings show that both maternal and paternal age negatively impact gamete quality and embryo development.