Actions of CSF2 and DKK1 on bovine embryo development and pregnancy outcomes are affected by composition of embryo culture medium

Abstract

Procedures for in vitro embryo production in cattle have not been optimized. In the current experiment, we utilized a 3 × 3 factorial design to test whether the proportion of embryos becoming blastocysts in culture and the pregnancy rate after embryo transfer are affected by type of serum in the medium [no serum; 3% (v/v) KnockOut Serum Replacement (SR); 3% (v/v) fetal bovine serum (FBS)] and addition of specific embryokines [vehicle; 10 ng/mL colony stimulating factor 2 (CSF2); 100 ng/mL dickkopf related protein 1 (DKK1)] at day 5 of culture. Embryos were produced using abattoir-derived ovaries and Y-sorted semen from two Angus sires. The percent of putative zygotes and cleaved embryos becoming blastocysts was improved by SR and FBS. Pregnancy rate at day 30 was determined for 1426 Nelore recipients and calving rate for 266 recipients. In the absence of CSF2 or DKK1, pregnancy rates were lower for embryos cultured with SR or FBS. CSF2 and DKK1 reduced pregnancy rate for embryos cultured without serum but had no detrimental effect in the SR or FBS groups. Indeed, CSF2 blocked the negative effect of FBS on pregnancy rate. Data on birth weights were available for 67 bull calves. There were no effects of treatment. The sire used to produce embryos had significant and large effects on development to the blastocyst stage, pregnancy rate at day 30, calving rate and pregnancy loss between day 30 and calving. Results indicate that (1) SR and FBS can improve embryonic development in vitro while also compromising competence of embryos to survive after transfer, (2) actions of CSF2 and DKK1 depend upon other characteristics of the embryo production system, and (3) sire can have a large effect on embryonic development before and after transfer.

Maternal contributions to pregnancy success: from gamete quality to uterine environment

“…Because determinants of pregnancy success are multifactorial, some studies have not observed benefits of treating embryos during culture or, in some cases, the embryo culture system and media composition affected pregnancy outcomes. For example, Amaral et al (2022) observed a positive effect on development to the blastocyst stage in embryos exposed to serum or serum replacer during culture, but a lower pregnancy rate after the transfer of these embryos into recipients. Moreover, if CSF2 or DKK1 were added to culture medium, actions of theses embryokines were dependent on the presence of serum in the medium.…”

Review: Some challenges and unrealized opportunities toward widespread use of the in vitro-produced embryo in cattle production

“…Efforts to enhance blastocyst yield by modifying embryo culture media have been less successful. Addition of serum to culture medium can have a large positive effect on development to the blastocyst stage but may also reduce competence of the resultant embryos to establish pregnancy ( Amaral et al, 2022 ). The percent of embryos becoming blastocysts can also be increased by addition to embryo culture medium of oviductal fluid ( Lopera-Vasquez et al, 2017 ) and specific embryokines produced by the reproductive tract ( Wooldridge et al, 2022 ) but the magnitude of effects is small.…”

“…Initial experiments with two embryokines, colony-stimulating factor 2 ( CSF2 ) and dickkopf WNT signaling inhibitor 1, indicated that the addition of either molecule to embryo culture medium increased pregnancy rate after embryo transfer ( Loureiro et al, 2009 ; Denicol et al, 2014 ). More recently, however, the beneficial effects of these molecules were not observed ( Estrada-Cortés et al, 2021b ; Amaral et al, 2022 ). Actions of these or other embryokines may depend on the specific characteristics of the embryo or recipient, as some results indicate ( Dobbs et al, 2014 ; Amaral et al, 2022 ).…”

Disruption of CSF2RA in the bovine preimplantation embryo reduces development and affects embryonic gene expression in utero

“…Treatment with CSF2 decreased embryo length and accumulation of interferon tau in the uterus in female embryos but increased both measurements in male embryos (Dobbs et al 2014). There have also been reports that blastocysts derived in the presence of CSF2 have increased competence to establish pregnancy after transfer to females, as reported in mouse (Sjöblom et al 2005), human (Ziebe et al 2013;Okabe-Kinoshita et al 2022) and cattle (Loureiro et al, 2009;Denicol et al, 2014), although contradicting reports exist on this effect of CSF2 (Zhou et al, 2016;Tribulo et al 2017;Estrada-Cortes et al 2021;Amaral et al 2022). There are reports that CSF2 influences fetal and postnatal programming when introduced during the preimplantation period in the mouse (Sjöblom et al 2005) and bovine (Kannampuzha-Francis et al 2015;Siqueira et al 2017;Estrada-Cortés et al 2021).…”