Abstract
Colony-stimulating factor 2 (CSF2), also known as granulocyte macrophage colony-stimulating factor, facilitates mammalian embryonic development and implantation. However, biological functions and regulatory mechanisms of action of porcine endometrial CSF2 in peri-implantation events have not been elucidated. The aim of present study was to determine changes in cellular activities induced by CSFs and to access CSF2-induced intracellular signaling in porcine primary trophectoderm (pTr) cells. Differences in expression of CSF2 mRNA in endometrium from cyclic and pregnant gilts were evaluated. Endometrial CSF2 mRNA expression increases during the peri-implantation period, Days 10 to 14 of pregnancy, as compared to the estrous cycle. pTr cells obtained in Day 12 of pregnancy were cultured in the presence or absence of CSF2 (20 ng/ml) and LY294002 (20 µM), U0126 (20 µM), rapamycin (20 nM), and SB203580 (20 µM). CSF2 in pTr cell culture medium at 20 ng/ml significantly induced phosphorylation of AKT1, ERK1/2, MTOR, p70RSK and RPS6 protein, but not STAT3 protein. Also, the PI3K specific inhibitor (LY294002) abolished CSF2-induced increases in p-ERK1/2 and p-MTOR proteins, as well as CSF2-induced phosphorylation of AKT1. Changes in proliferation and migration of pTr cells in response to CSF2 were examined in dose- and time-response experiments. CSF2 significantly stimulated pTr cell proliferation and, U0126, rapamycin and LY294002 blocked this CSF2-induced proliferation of pTr cells. Collectively, during the peri-implantation phase of pregnancy in pigs, endometrial CSF2 stimulates proliferation of trophectoderm cells by activation of the PI3K-and ERK1/2 MAPK-dependent MTOR signal transduction cascades.
Highlights
In pregnant gilts, porcine zygotes undergo cleavage to reach the 4-cell stage when they migrate into the uterine horns and develop to the blastocyst stage and hatch from the zona pellucida by Day 7 of pregnancy
No significant differences were found in Colony-stimulating factor 2 (CSF2) transcripts due to day of the estrous cycle, but expression of CSF2 mRNA increased between Days 10 and 14 of pregnancy (P,0.001) and declined to Day 20 of pregnancy
To examine involvement of other intracellular messengers, we used a pharmacological inhibitor of P38 MAPK (SB203580) to find that it did not inhibit proliferation of primary trophectoderm (pTr) cells in response to CSF2 (P.0.05). These results suggest that activation of PI3K-AKT1-MTOR and ERK1/ 2 MAPK signaling pathways play a central role in stimulation of pTr cell proliferation in response to uterine-derived CSF2 during the peri-implantation period of pregnancy
Summary
Porcine zygotes undergo cleavage to reach the 4-cell stage when they migrate into the uterine horns and develop to the blastocyst stage and hatch from the zona pellucida by Day 7 of pregnancy. The porcine filamentous conceptuse remains free-floating until Days to 14 of pregnancy, and make initial attachment to the uterine luminal epithelium (LE), and implantation is complete resulting in the interdigitation of uterine LE and trophectoderm in preparation for establishment of a a true epitheliochorial type of placenta by Day 24 of pregnancy [2,5,6,7,8,9,10] For this process, the conceptus is dependent upon an astonishing amount of secretions from uterine LE and glandular epithelium (GE), that is known collectively as histotroph, which includes hormones, enzymes, nutrients, growth factors, cytokines and other factors [11,12,13,14,15,16,17]. Deficiencies in histotroph-mediated local communication at the maternal-conceptus interface leads to a majority of conceptus mortality and poor outcomes of pregnancy [18,19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
