(184) A Non-Human Primate Model of Programmed Frozen Embryo Transfer

Lisa A. Vrooman¹, Kiersey R. Nielsen¹, Gracelyn M. Fine¹, Fangzhou Luo¹, Sacha A. Krieg², Jon D. Hennebold^1,2, Ov D. Slayden¹

< !1. Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR

< !2. Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR

 

Abstract Text:

Programmed frozen embryo transfers (p-FET) require exogenous estradiol and progesterone treatments. They are the predominant type of frozen embryo transfer used for assisted reproductive technology cycles in the United States. Besides logistical advantages, p-FET is necessary for patients with anovulatory or irregular menstrual cycles. Unfortunately, p-FET is associated with increased risk for pregnancy complications when compared to natural cycle-FET. Given the rise in ART use, it is important to mitigate the incidence of p-FET associated pregnancy complications. Accordingly, we established a p-FET rhesus macaque model. Exogenous estradiol and progesterone were delivered to a naturally cycling rhesus macaque (n=1) by Silastic implants. Day 1 (D1) was defined as the day of first estradiol implant. We targeted estradiol levels 1-2-fold higher than endogenous rhesus macaque levels to mimic relative levels observed in humans. Serum estradiol levels ranged between ~60-400 pg/mL during the programmed follicular phase. Progesterone levels ranged between ~4-12 ng/mL during the programmed luteal phase. Two good quality non-autologous cryopreserved blastocysts were transferred on D20. Ovaries were visually confirmed to be anovulatory at transfer. A dizygotic twin pregnancy was confirmed by ultrasound on D45/gestational day (GD)32. By D55/GD42, serum estradiol and progesterone levels were 192 pg/mL and 19 ng/mL, respectively. Late first trimester concepti were collected on D63/GD50. The same monkey had undergone a previous p-FET attempt that resulted in implantation of two non-viable embryos detected by ultrasound. Overall, 4/5 (80%) transferred embryos implanted, 2/5 (40%) embryos developed into a fetus, and 1/2 (50%) p-FET cycles resulted in a viable pregnancy. This is the first, to our knowledge, successful p-FET NHP pregnancy. Establishing this model enables further studies to experimentally determine the iatrogenic effects of programmed cycles. It can also be applied to the production of transgenic NHPs for human health studies and to wildlife conservation efforts.