Simultaneous exocrine and endocrine secretion: trophoblast and glands of the endometrial cups.

This research investigates the interactions between two types of cells in the equine endometrium during gestation. The study focuses on the invasion of trophoblast cells from the chorionic girdle into the endometrium to become endometrial cup cells, and how these cells affect endometrial gland cells, which undergo significant changes throughout gestation.

Study Methodology

• The research involved the examination of endometrial cups from day 36 to day 83 of equine gestation. The methods used included light and electron microscopy, immunohistochemical analysis, and lectin analysis, all of which enabled the researchers to identify and track changes in the cells.

Cellular Interaction and Transformation

• When trophoblast cells invade the endometrium, they migrate along the basal lamina of glands. This process helps preserve the integrity of the glands.
• These migrating cells, now known as cup cells, undergo hypertrophy, experiencing growth and an increase in size. They develop a large network of cytokeratin-positive filaments and Golgi zones, the latter of which stains positively with equine chorionic gonadotrophin antibodies and specific lectins.

Changes in Endometrial Glands

• Gland cells within and adjacent to the endometrial cups also undergo hypertrophy.
• The gland cells within the cup possess specific staining properties when exposed to alcian blue and some lectins, differing from gland cells in unmodified endometrium which stain positively with antibodies to transforming growth factor a.
• Secretory material within the glands stains heterogeneously with alcian blue, periodic acid Schiff, and lectins.
• As gestation progresses, the glands within the cup become progressively disorganized. Glands may rupture, releasing their contents into the stroma of the cup.

Later Gestation Observations & Conclusion

• By day 83 of gestation, areas of lipid accumulation and apparent degeneration of cup cells were observed. This suggests that the cup cells significantly modify the integrity and secretion of adjacent endometrial glands.
• Further, the progressive disruption of gland integrity and isolation of endometrial vessels by extracellular matrix appear to precede the deterioration of the cup cells. Necrosis and disintegration, rather than programmed cell death, are likely to limit the lifespan of the endometrial cup cells.