Lewis x-carrying O-glycans are candidate modulators for conceptus attachment in pigs†.

Successful attachment of conceptus to the uterine luminal epithelium (LE) is crucial for establishing a functional placenta in pigs. However, the underlying mechanisms are yet to be elucidated. The uterine LE-conceptus interface is enriched in various glycoconjugates essential to implantation. Using MALDI-MS profiling, we identified for the first time the O-glycan repertoire of pig endometrium during the conceptus attachment stage. The expression pattern of blood group A, O(H), Lewis x, y, a, b (Lex, Ley, Lea, and Leb), the sialylated and sulfated Lex antigens in the uterine LE-conceptus interface was assessed using immunofluorescence assays. Notably, the Lex-carrying O-glycans exhibited a temporal-spatial expression pattern. They were absent in the endometrium on estrous cycle days but strongly and spatially presented in the conceptus and uterine LE to which the conceptus apposes during the early conceptus attachment stage. In addition, Lex-carrying O-glycans were co-localized with secreted phosphoprotein 1 (SPP1), a well-characterized factor that plays a role in promoting conceptus attachment through interacting with integrin αVß3 and integrin αVß6. Meanwhile, the immunoprecipitation assays revealed an interaction between the Lex-carrying O-glycans and SPP1, integrin αV, and integrin ß6. Furthermore, we provided evidence that the ß1,4-galactosyltransferase 1 (B4GALT1) gene is a potential regulator for Lex antigen expression in the uterine LE-conceptus interface during the early conceptus attachment stage. In conclusion, our findings show that Lex-carrying O-glycans, presumably dependent on B4GALT1 gene expression, might modulate conceptus attachment by interacting with the SPP1-integrin receptor complex in pigs.

Glycomics reveal that ST6GAL1-mediated sialylation regulates uterine lumen closure during implantation.

OBJECTIVES: Implantation failure is a major cause of prenatal mortality. The uterine lumen closure contributes to embryo adhesion to the uterus, but its underlying mechanisms are largely unknown. Our previous study has reported that endometrial fold extension can lead to uterine lumen closure in pigs. The objective of this study was to reveal molecular mechanisms of the uterine lumen closure by characterizing the molecular basis of the endometrial fold extension during implantation in pigs. MATERIALS AND METHODS: Uterine and endometrium tissues during implantation were collected in pigs. MALDI-TOF MS was used to characterize the N-glycomic profiles. Histochemistry, siRNA transfection, Western blotting, lectin immumoprecipitation, mass spectrometry and assays of wounding healing and cell aggregation were performed to investigate the molecular basis. RESULTS: We observed that uterine luminal epithelium (LE) migrated collectively during endometrial fold extension. For the first time, we identified a large number of N-glycan compositions from endometrium during implantation using MALDI-TOF MS. Notably, the α2,6-linked sialic acid and ST6GAL1 were highly expressed in uterine LE when the endometrial folds extended greatly. Subsequently, the role of ST6GAL1-mediated 2,6-sialylation in collective epithelial migration was demonstrated. Finally, we found that ST6GAL1-mediated α2,6-sialylation of E-cadherin may participate in collective migration of uterine LE. CONCLUSIONS: The study reveals a mechanism of uterine lumen closure by identifying that ST6GAL1-mediated α2,6-sialylation of cell adhesion molecules contributes to endometrial fold extension through regulating collective migration of uterine LE.