Equine placental cup cells show glycan expression distinct from that of both chorionic girdle progenitor cells and early allantochorionic trophoblast of the placenta.

This study examines the different glycan expression patterns in various types of placental cells in horses during various stages of gestation, contributing to a better understanding of equine pregnancy and placental development.

Research Methodology

• The researchers used a technique called lectin histochemistry on plastic-embedded material. This method involves staining tissues with lectins, proteins that can identify and bind to specific types of carbohydrates.
• They focused on three types of placental cells – girdle cells, cup cells, and allantochorionic trophoblast cells in horses, during gestation from 37 to 67 days.
• The lectins were used to detect glycans – complex carbohydrates that can have various roles in biological processes, and their presence and patterns were investigated.

Findings

• Results revealed distinct sugar molecule (glycan) patterns in the different types of cells. Crucially, cup cells, which secrete a hormone known as equine chorionic gonadotropin (eCG), displayed a unique glycosylation (the process where glycans attach to proteins) pattern.
• This pattern was markedly different from that of the cells which precede them (the girdle cells) and the cells from the allantochorionic trophoblast (which forms part of the established placenta).
• Specifically, the cup cells had high levels of certain types of glycans (alpha2,6 and alpha2,3-linked sialic acid, N-acetyllactosamine and bi/tri antennary non-bisected and bisected complex N-glycan). This correlates with what is known about the carbohydrate content of the hormone eCG.

Glycan Variations in Different Placental Cells

• In contrast, the allantochorionic trophoblast cells at 50 days gestation had barely detectable amounts of sialic acid but high amounts of another type of glycans (tri/tetra-antennary non-bisected complex N-glycan and N-acetyl galactosamine). The latter was not found in the cup cells.
• Interestingly, there was also a change in the endometrial glands (glands in the uterus) during girdle cell migration into maternal tissues. These glands enlarged and dilated at the base, indicating increased amounts of glycosylated secretory products. These products were often seen leaking out into surrounding cellular spaces through ruptures in the gland wall.

Implications

• The findings shed light on the various placental developmental stages and cellular differentiation in equine gestation, which is crucial for understanding reproductive biology and potentially enhancing veterinary practices.
• Understanding different glycan patterns may also offer insights into the roles these complex sugars play in pregnancy, including their influence on hormone secretion and immune responses.