To characterize molecular mechanism underlying the regulation of sialylated glycan expression and its roles for endometrial receptivity and embryo implantation. Here, we characterized the role of a truncated form of sialylated O-glycan, sialyl-Tn, for endometrial receptivity.
The transcriptomes of human endometrium at mid-secretory phase were analyzed by Bioinformatics. Changes in gene expression, protein, and signal pathway were measured using RT-PCR and Western blot. The cell adhesion assay was visualized using a fluorescent microscope. In peri-implantation phase of mice, the expression of leukemia inhibitory factor (LIF) and sialyl-Tn were confirmed using immunohistochemistry and immnofluorescence analysis. The effect of sialy-Tn expression on embryo implantation was estimated by in vitro fertilization and embryo transfer using mice.
In in silico analysis, expression of O-glycosylation genes, especially ST6GalNAc1, was significantly increased in the human uterus of mid-secretory phase. Overexpression of the ST6GalNAc1 gene in non-receptive human endometrial AN3CA cells enhances the attachment of trophoblastic JAr cells. In an animal study, the results clearly indicated that sialyl-Tn was expressed on the surface of the mid-secretory uterus. In addition, blockade of the receptor using free sialyl-Tn epitope diminished the implantation rates of intrauterine transferred murine embryos.
From these results, here we suggest that sialyl-Tn expression might be a novel factor regulating the endometrial receptivity for successful embryo implantation.