Actions of DKK1 on the preimplantation bovine embryo to affect pregnancy establishment, placental function, and postnatal phenotype

Abstract

One mechanism by which the maternal environment regulates the early embryo is by secretion of cell-signaling molecules. One of these is dickkopf WNT signaling pathway inhibitor 1 (DKK1). Objectives were to A) resolve discrepancies in the literature regarding effects of DKK1 in the bovine embryo on development of trophectoderm (TE) and competence to establish pregnancy after embryo transfer and B) determine whether there are long-term consequences of DKK1 on placental function and postnatal phenotype. Embryos produced in vitro were cultured with vehicle or 100 ng/mL recombinant human DKK1 from day 5 to 7.5 of development (i.e. the morula and blastocyst stages of development). DKK1 increased the number of cells positive for the TE marker CDX2 at day 7.5 of development while having no effect on numbers of cells positive for the inner cell mass marker SOX2. There was no effect of DKK1 on pregnancy or calving rate after transfer of blastocysts produced with Y-sorted semen to either lactating dairy cows or suckling beef cows. Treatment with DKK1 at the morula-to-blastocyst stages programmed placental function, as measured by an effect of DKK1 on plasma concentrations of pregnancy associated glycoproteins and placental lactogen at day 160 of gestation (although not on other days examined). DKK1 treatment also resulted in calves that were heavier at birth as compared to calves derived from control embryos. After birth, DKK1 calves grew slower than controls. Results confirm that DKK1 alters the developmental program of the bovine embryo to affect both prenatal and postnatal phenotype.

Presence of KREMEN receptors for DKK1 in the preimplantation bovine embryo

“…Thus, the final concentration of DKK1 was 100 ng/mL. This concentration was effective at altering embryo function in other experiments ( Denicol et al 2013 , Tríbulo et al 2017 b , 2019 a , Amaral et al 2022 ). At day 7.5, blastocysts were harvested for immunolabeling of total CTNNB1 by either immunofluorescent localization or by western blotting.…”

“…DKK1 blocked the deleterious effect of chemical WNT activators on development to the blastocyst stage ( Denicol et al 2013 , Tríbulo et al 2017 b ). In addition, treatment of embryos with DKK1 beginning at day 5 of development promoted the development of the trophectoderm in the resulting blastocysts ( Denicol et al 2013 , Amaral et al 2022 ). Recent evidence indicates that actions of DKK1 from day 5 to 7 of development can program subsequent placental function so that trophoblast elongation at day 15 is enhanced ( Tríbulo et al 2019 a ) and circulating concentrations of pregnancy-associated glycoproteins are elevated at day 160 of gestation ( Amaral et al 2022 ).…”

“…In addition, treatment of embryos with DKK1 beginning at day 5 of development promoted the development of the trophectoderm in the resulting blastocysts ( Denicol et al 2013 , Amaral et al 2022 ). Recent evidence indicates that actions of DKK1 from day 5 to 7 of development can program subsequent placental function so that trophoblast elongation at day 15 is enhanced ( Tríbulo et al 2019 a ) and circulating concentrations of pregnancy-associated glycoproteins are elevated at day 160 of gestation ( Amaral et al 2022 ). Consequences of DKK1 actions on the preimplantation embryo can persist into the postnatal period because calves derived from DKK1-treated embryos were reported to have either lower ( Tríbulo et al 2017 c ) or higher birth weights ( Amaral et al 2022 ) and lower growth rates after birth than those of calves from control embryos ( Amaral et al 2022 ).…”

Effects of Regulating Hippo and Wnt on the Development and Fate Differentiation of Bovine Embryo

“…Furthermore, inhibition of the Wnt signaling pathway contributes to an increase in TE cell numbers and the total cell numbers of the blastocyst [51]. The likelihood is that DKK1 increases the expression of transcription factors that promote cell differentiation in the TE lineage [52]. Treatment of embryos with DKK1 from day 5 of development encourages the proliferation of the TE cell lineage in porcine [53], bovine [14,52,54,55] and other mammalian blastocysts.…”

Developmental competence of IVF and SCNT goat embryos is improved by inhibition of canonical WNT signaling

“…Canonical WNT/ß-Catenin is a maternally-derived pathway that seems to be essential for the preimplantation development of embryos [ 34 ]. Studies in the mouse indicate that this pathway is active as early as the two-cell stage around embryonic genome activation (EGA) [ 35 ].…”