Steroid secretion by different cell types of the horse conceptus.

This research paper delves into the different steroid secretions produced by various cell types found in the horse conceptus during early stages of pregnancy. The study concludes that the differentiation of secretion based on cell type might play an integral role in maintaining pregnancy in horses.

Research Methodology

• To carry out this study, horse conceptuses were retrieved non-surgically from Day 12 to Day 15 of pregnancy. Post extraction, these conceptuses were dissociated using collagenase, an enzyme that aids in breaking cellular bonds.
• The dissociated cells were then separated on a 31.8% Percoll gradient. This led to the formation of two differentiated groups or bands of cells. The lower density cells, referred to as LDC, were hypothesized to be endoderm cells, while the higher density cells, or HDC, were speculated to be trophectoderm cells.

Incubation and Analysis

• Each group of cells was incubated separately for a period of 24 hours in a Minimum Essential Medium, a common culture medium used in cellular research.
• Following incubation, the concentrations of two vital hormones, oestradiol and progesterone, present in the medium were measured using a method called radioimmunoassay (RIA).
• The results showed distinct hormonal secretion patterns. The LDC predominantly secreted progesterone, while the HDC majorly produced oestradiol.
• On incubating the cells for an additional 24 hours in fresh medium, it was observed that the production of oestradiol decreased by approximately 84% to 85%, while progesterone production dropped by 50% to 57% for both LDC and HDC.

Further Evaluation

• For further analysis, cells from each band were incubated for another 24 hours with [3H]pregnenolone – a radioactively labelled steroid hormone.
• The resulting radiolabelled metabolites were separated and analysed by reversed-phase high-pressure liquid chromatography, revealing a distinct steroid secretion profile for each cell type.

Conclusion

• The study indicates that within an intact horse embryo, the interaction between various cell types, specifically the LDC and HDC, may be crucial for oestrogen synthesis. This could possibly play a major role in maintaining pregnancy.