Abstract
In vitro embryo production systems are limited by their inability to consistently produce embryos with the competency to develop to the blastocyst stage, survive cryopreservation, and establish a pregnancy. Previous work identified a combination of three cytokines [fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1)], called FLI, that we hypothesize improve preimplantation development of bovine embryos in vitro. To test this hypothesis, FLI was supplemented into oocyte maturation or embryo culture medium. Embryos were produced in vitro using abattoir-derived oocytes and fertilized with sperm from a single bull known to have high fertility. After an 18–20 h fertilization period, putative zygotes were cultured in synthetic oviductal fluid (SOF) for 8 days. The addition of FLI to the oocyte maturation medium increased (P < 0.05) the dissociation of transzonal projections at 12, 18, and 24 h of maturation, as well as, the proportion of oocytes that reached the metaphase II stage of meiosis. Additionally, lipid content was decreased (P < 0.05) in the blastocyst stage embryo. The addition of FLI during the culture period increased development to the blastocyst stage, cytoskeleton integrity, and survival following slow freezing, as well as, decreased post thaw cell apoptosis (P < 0.05). In conclusion, the supplementation of these cytokines in vitro has the potential to alleviate some of the challenges associated with the cryo-survival of in vitro produced bovine embryos through improving embryo development and embryo quality.
Highlights
In vitro embryo production is an assisted reproductive technique used in livestock production to maximize the use of valuable genetics [1]
There was a significant treatment by time interaction as FLI-treated cumulus oocyte complexes (COCs) had fewer (P < 0.05) transzonal projections at 12 h, 18 h, and 24 h compared to the controls (Fig 5A)
Supplementation of the cytokine combination FGF2, leukemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1) (FLI) has been shown to increase the efficiency of in vitro porcine embryo production in [37]. These cytokines have been used individually in in vitro bovine embryo production systems and yielded positive results [27, 35, 51,52,53], so it is possible that combining these cytokines has the potential to increase bovine embryo development in vitro
Summary
In vitro embryo production is an assisted reproductive technique used in livestock production to maximize the use of valuable genetics [1]. Bos taurus heavily rely on these technologies compared to others. In 2018, a total of 1,499,367 transferrable embryos were produced worldwide, from which 68.7% were in vitro produced (IVP) [2]. FLI improves bovine embryo development, quality, and cryopreservation
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