Actions of putative embryokines on development of the preimplantation bovine embryo to the blastocyst stage

Abstract

Once it enters the uterus at d 4 to 5 after ovulation, the preimplantation bovine embryo is controlled in its development by regulatory signaling molecules from the mother called embryokines. Here, several cell-signaling molecules whose genes are expressed in the endometrium during d 5 to 7 after estrus were tested for the ability to affect the competence of the embryo for further development and the characteristics of the resultant blastocysts. Molecules tested were Cnatriuretic peptide (CNP), IL-8, bovine morphogenetic protein 4 (BMP-4), IL-6, and leukemia inhibitory factor (LIF). None of the cell-signaling molecules tested improved the competence of the embryo to become a blastocyst; in fact, BMP-4 decreased development. All molecules modified attributes of the blastocyst formed in culture. In particular, CNP increased the number of cells in the ICM, whereas IL-8 decreased inner cell mass cell numbers and tended to increase the proportion of blastocysts that were hatching or hatched. In addition, BMP-4 decreased the proportion of blastocysts that were hatching. Interleukin-6 and, to a lesser extent, LIF activated the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in the inner cell mass, and LIF increased the percent of cells in the blastocyst that were positive for both NANOG and phosphorylated (activated) STAT3. In conclusion, our results indicate that CNP, IL-8, IL-6, LIF, and BMP-4 can modify embryonic development of the cow in a manner that affects characteristics of the resultant blastocyst. Further research is required to understand how these changes in characteristics of the blastocyst would affect competence of the embryo to establish and maintain pregnancy.

Atlas of receptor genes expressed by the bovine morula and corresponding ligand‐related genes expressed by uterine endometrium

“…This gene was expressed by the morula (average TPM = 2.4) but at a lower level than for many other receptor genes. Nonetheless, treatment of bovine embryos with the prototypical ligand for NPR2, C-natriuretic peptide, caused an increase in number of cells in the inner cell mass of the blastocyst (Sang et al, 2020). Furthermore, some endometrial genes could be expressed in compartments of the endometrium (stromal cells or F I G U R E 5 Transcript abundance in the bovine morula for receptor genes using small molecules as ligands.…”

“…In the cow, the focus of the current investigation, these molecules include IGF1 (Bonilla et al, 2011;Sirisathien et al, 2003), CSF2 (Loureiro et al, 2009), the WNT inhibitor DKK1 (Denicol et al, 2014), activin A (Kannampuzha-Francis et al, 2017) and IL6 (Wooldridge et al, 2019). Among the embryo functions regulated by embryokines are promotion of development to the blastocyst stage (Bonilla et al, 2011;Kannampuzha-Francis et al, 2017), protection from cell stress (Jousan & Hansen, 2007), and control of lineage commitment towards inner cell mass and trophectoderm (Denicol et al, 2014;Sang et al, 2020;Wooldridge et al, 2019). Some embryokines, such as CSF2 (Kannampuzha-Francis et al, 2015) and DKK1 (Tríbulo et al, 2017), have been reported to program development in a way that affects postnatal phenotype.…”

Cytokines That Serve as Embryokines in Cattle

“…Less impressive improvements in ICM cell numbers could be seen when providing 1 and 10 ng/mL IL6 [ 49 ]. Sang et al did not detect a positive effect of IL6 on ICM numbers in bovine embryos [ 51 ]. They used an IL6 concentration of 50 ng/mL.…”

“…Our previous research detected increases in EPI cell numbers when counting NANOG + nuclei, a marker for EPI cells [ 56 ]. However, another research group failed to detect changes in the number of NANOG + cells after treatment with 50 ng/mL IL6 [ 51 ].…”

“…The only other cytokines we are aware of that have been explored as embryokines in bovine IVP embryos are interleukin-1α (IL1A), interleukin-1ß (IL1B), IL8, and stem cell factor (SCF, Kit ligand). Each of these ligands is expressed either by the endometrium or the embryo itself [ 48 , 106 , 107 ], and receptors, co-receptors, and receptor inhibitors for these cytokines have been detected in bovine embryos [ 46 , 50 , 51 , 108 ] (see Table 1 ). No definitive role for SCF as an embryokine has been found thus far.…”