Effect of FGF2, LIF, IGF1 supplementation on pregnancy success following embryo transfer of in vitro derived embryos

Culture modifications are a logical approach for improving in vitro-derived embryo competence. Previously, the addition of the growth factors FGF2, LIF, and IGF1, termed FLI, to the culture medium improved bovine embryo development and survival following freezing. At Day 15, embryos treated with or without FLI appeared phenotypically similar, but transcriptomic analysis revealed differences in functions related to conceptus and placental development as well as maternal-embryo crosstalk. The objective of this study was to investigate how FLI influences the ability of a bovine embryo to establish pregnancy following slow-rate freezing. Embryos were produced in vitro and cultured to the blastocyst stage with or without FLI. Embryos with a quality grade of 1 (6–1 or 5–1) were cryopreserved by slow-rate freezing. A single frozen-thawed embryo was transferred to synchronized recipient females (n = 192). Blood samples were collected on Days 7, 19, 20, and 24 and pregnancy diagnosis was performed using transrectal ultrasonography after Day 28. This experiment was carried out across three locations and pregnancies per ET were similar between both groups at all locations (P = 0.3). Progesterone on days 7, 19, and 24, and day 19 and 20 interferon-stimulated genes (ISG15, MX2, OAS1) expression were similar among both treatments (P > 0.05). There were increased (P = 0.0061) circulating concentrations of PAGs in recipients receiving FLI embryos suggesting advanced placental development and possible improvements in viability beyond day 30. No adverse effects of FLI supplementation on early embryo development were detected in these studies, thus, this is a promising addition to bovine in vitro embryo production systems.