Lectin histochemistry reveals two cytotrophoblast differentiation pathways during placental development in the feline (Feliscatus)

Abstract

IntroductionPlacental glycosylation has been examined on eight feline placentae ranging from approximately 15 to 60 days post-conception as little is known about changes in glycan distribution in this species. MethodsSpecimens were resin embedded and lectin histochemistry was applied to semi-thin sections using a panel of 24 lectins and an avidin-biotin revealing system. ResultsAbundant tri-tetraantennary complex N-glycan and α-galactosyl residues found in the syncytium in early pregnancy were greatly reduced in mid-pregnancy, though retained at the invasion front in the syncytium (N-glycan) or cytotrophoblast layer (αGal). Some other glycans were also uniquely present in invading cells. Abundant polylactosamine was found in the infolding basal lamina of syncytiotrophoblast and the apical villous cytotrophoblast membrane. Syncytial secretory granules often clustered near the apical membrane abutting maternal vessels. Decidual cells selectively expressed β-galactosyl residues throughout pregnancy and highly branched N-glycan levels increased over time. DiscussionGlycan distribution changes significantly over pregnancy, probably relating to the development of transport and invasive properties of trophoblast which in the endotheliochorial placenta reaches the level of the maternal vessels. Highly branched complex N-glycans, often associated with invasive cells, N-Acetylgalactosamine and terminal α-galactosyl residues are present at the invasion front abutting the junctional zone of the endometrium. Abundant polylactosamine on the syncytiotrophoblast basal lamina may reflect the presence of specialised adhesive interactions, while clustering of glycosylated granules apically is probably associated with secretion and absorption of material via maternal vasculature. It is suggested that lamellar and invasive cytotrophoblast represent distinct differentiation pathways. 246 words.