Involvement of VCAM1 in the bovine conceptus adhesion to the uterine endometrium

Abstract

Following bidirectional communication, the conceptus and the uterine epithelium must establish a proper cell-cell interaction, resulting in the progression of implantation processes. To clarify the mechanism of conceptus attachment to the uterine endometrium, we studied whether vascular cell adhesion molecule (VCAM1) was expressed in bovine conceptuses or endometrium during the peri-attachment period. Uterine VCAM1 expression was minimal in day 17 (day 0Zday of estrus) cyclic and pregnant animals, but increased between days 20 and 22 of pregnancy. In the intercaruncular regions, VCAM1 protein was localized to the luminal and glandular epithelia, whereas in the caruncular regions, VCAM1 protein was detected in the stroma and endothelia of the uterine endometrium. In cultured endometrial epithelial cells (EECs), VCAM1 expression was up-regulated when treated with uterine flushings or growth factor and further increased when EECs were cocultured with bovine trophoblast CT1 cells. VCAM1 expression in CT1 cells was also up-regulated with the use of uterine flushings, and further increased when these cells were cocultured with EECs. Expression of VCAM1 receptor, integrin a 4 (ITGA4) mRNA, increased significantly in day 22 conceptuses. In day 22 pregnant uteri, VCAM1 protein was found in both EECs and conceptuses, but ITGA4 was localized only to trophoblasts. These observations indicate that cell-cell interactions between conceptuses and uterine epithelial cells are required for sufficient VCAM1 and ITGA4 expression in the bovine species and suggest that uterine VCAM1 and conceptus ITGA4 play a role in the establishment of conceptus adhesion to the uterine endometrium.

Continuous model of conceptus implantation to the maternal endometrium

“…It was also identified that homozygous ITGA4 null knockout mice fail to complete fusion of the allantois with the chorionic membrane during placentation period (Yang et al 1995), the cellular event similar to that of VCAM-1 gene ablation. In our previous investigations, EECs' VCAM-1 expression was enhanced with the addition of IFNT (Bai et al 2014) and elevated ITGA4 mRNA in bovine conceptuses was found on day 22, 2-3 days after the initiation of trophoblast attachment to the endometrial epithelium (Yamakoshi et al 2012, Bai et al 2014. We also found that changes in TE cells' gene expression including ITGs were seen when bovine CT-1 cells were cocultured with EECs, which was further enhanced with the addition of uterine flushings from pregnant animals , Bai et al 2014.…”

“…In our previous investigations, EECs' VCAM-1 expression was enhanced with the addition of IFNT (Bai et al 2014) and elevated ITGA4 mRNA in bovine conceptuses was found on day 22, 2-3 days after the initiation of trophoblast attachment to the endometrial epithelium (Yamakoshi et al 2012, Bai et al 2014. We also found that changes in TE cells' gene expression including ITGs were seen when bovine CT-1 cells were cocultured with EECs, which was further enhanced with the addition of uterine flushings from pregnant animals , Bai et al 2014. These results suggest that TEs-EECs interactions as well as constituents of uterine flushings/ histotroph including ECMs and/or various cytokines are important in the progression of conceptus attachment to the uterine epithelium in the bovine and other mammalian species.…”

“…It should be noted that this decline of IFNT after conceptus attachment to the uterine epithelium was originally observed nearly three decades ago (Guillomot et al 1990), but the significance of IFNT's downregulation has still not been well characterized (Sakurai et al 2013b). Data continue to accumulate that when IFNT is further downregulated on day 22 (Kusama et al 2016a), expression of cell adhesion molecules and EMT-related factors is upregulated (Yamakoshi et al 2012, Bai et al 2014.…”

DNA methylation changes in endometrium and correlation with gene expression during the transition from pre-receptive to receptive phase

“…Genes related to extracellular matrix organization and immune response with positive correlation between methylation and expression levels included those that have previously been associated with endometrial receptivity, decidualization and embryo implantation either in humans or animal models, such as TGFB3 26 , ADAMTS1 27 , VCAM1 28 , IL1RL1 (also known as ST2 ) 29 , CXCL13 30 and BCL3 31 . Interestingly, a direct link between BCL3 methylation and expression has also been shown in mouse endometrial cells 31 .…”

Conceptus implantation and placentation: molecules related to epithelial–mesenchymal transition, lymphocyte homing, endogenous retroviruses, and exosomes

“…In our previous investigation on bovine conceptuses, ITGA4 mRNA was found at elevated expression levels on day 22, 2-3 days after the initiation of trophoblast attachment to the endometrial epithelium [41,52]. We also found that changes in TE cells' gene expression including ITGs were seen when bovine TE (CT-1) cells were cocultured with endometrial epithelial cells (EECs), which was further enhanced with the addition of uterine flushings from pregnant animals [52,53]. These results suggest that components of uterine flushings/histotroph including ECMs and/or various cytokines, as well as cell-cell interactions are important in the progression of conceptus attachment to the uterine epithelium in the bovine and other mammalian species.…”