The regulatory role of N-linked glycosylation in shaping the characteristics of trophoblasts

Abstract

Dysregulation in placental N-glycosylation has been linked to placental complications during pregnancy, highlighting the need to understand how N-glycosylation shapes trophoblast phenotypes. To explore this, N-glycomic profiling was used to study N-glycan structures and populations in human first-trimester placentae, and the impacts of interfering with specific steps in N-glycan biosynthesis on trophoblast phenotype were demonstrated using the choriocarcinoma cell line JEG-3. Placental tissues from pregnant women with normal or high resistance indexes in the first trimester were examined to assess the correlation between placental N-glycomic profile and the risk of developing early onset pre-eclampsia. The analysis revealed lower levels of bisected and tri-antennary N-glycan in the group with higher risk. Additionally, in vitro studies on JEG-3 demonstrated that the inhibition of specific steps in the N-glycosylation pathway relevant to observations in placental tissues altered JEG-3 N-glycomic profile and its trophoblast phenotypes including the expression pattern of human leukocyte antigen G (HLA-G), secretion of human chorionic gonadotropin, and abundance of transcription factor GATA3. Pregnancies at increased risk of pre-eclampsia exhibit abnormal crosstalk between trophoblasts and decidual natural killer (NK) cells. To investigate the potential involvement of N-glycosylation in immunoregulatory effects of trophoblast, responses of JEG-3 with altered N-glycomic profiles to co-culture with CD56+ CD16– cell line NK-92 were examined, and JEG-3 being more susceptible to NK-92 was observed when subjected to either desialylation or swainsonine-induced inhibition of demannosylation. As a known reference target for NK-mediated cytolysis, HLA class I-negative cell line K562 exhibited a higher resistance to cytolysis mediated by NK-92 when possessing a JEG-3-like N-glycomic profile but expressing HLA-G on cell surface could not achieve the same level of resistance. Collectively, these findings suggested that N-glycosylation is involved in the shaping of trophoblast phenotypes, and dysregulation of this process may contribute to placental complications during pregnancy.