Expression of major histocompatibility complex antigen and timing of invasion by equine chorionic girdle cells cultured on Matrigel.

The research study examines the behavior, timing of invasion, and major histocompatibility complex (MHC) expression by equine chorionic girdle cells in a lab setting (Matrigel) compared to their behaviors in their natural environment (in vivo). The research found that neither the timing of the cell invasion nor the MHCI expression in Matrigel replicated what happens inside a horse’s body (in vivo), suggesting the in utero environment may regulate these characteristics.

About Chorionic Girdle Cells and Major Histocompatibility Complex

• Chorionic girdle cells are a unique subgroup of cells called trophoblast cells, found in the horse conceptus (embryo and its associated membranes).
• These cells are known to adhere to the uterus lining (uterine epithelium) and start invading the endometrium (the inner lining of the uterus), particularly on Days 34-36 of the horse’s conception. The timeline starts at Day 0, which is the day of ovulation.
• The Major Histocompatibility Complex (MHC) is a group of genes that code for proteins found on the surfaces of cells that help the immune system identify if a cell is self or non-self. MHC I is one of the categories of MHC.
• Chorionic girdle cells express high levels of MHC I just before and during the invasion period, but the expression of this antigen reduces by Days 40-45 and vanishes by Day 55.

Objective of the Study

• The overarching goal of the study was to gain a deeper understanding of how the chorionic girdle cells invade the endometrium and why the MHCI expression changes over time.
• For this, the researchers cultured chorionic girdle cells on a matrix called Matrigel to see if the behavior of these cells in this environment would mimic their behavior when inside the horse’s body (in vivo).

Methodology and Findings

• The researchers collected chorionic girdles from several conceptuses and placed them in Matrigel invasion chambers at different stages (Days 30, 31, and 32).
• Using NIH image software, they determined the area of the filter covered by the invasive cells after 48 hours and over longer time periods equivalent to the number of days from the day of collection to Day 36.
• The study found that the Day 31 and Day 32 girdle cells had invaded Matrigel after 48 hours, but only one Day 30 cell preparation had done so.
• All the chorionic girdles had invaded Matrigel by the time equivalent to Day 36.
• Further, the researchers also analyzed the expression of MHC I, MHC II, and a trophoblast-specific antigen by the invasive Day 34 girdle cells over a span of Days 36 to 60.
• They observed that these invasive cells expressed MHCI and the trophoblast-specific antigen, but not MHCII, at each time examined.

Conclusion

• Given the discrepancy observed in the invasion timing and MHCI expression by the chorionic girdle cells in Matrigel as compared to in vivo conditions, the study suggests that the in utero environment likely plays a role in managing these two factors of equine chorionic girdle cells.