Tissue-specific localization of cytochrome P450 aromatase in the equine embryo by in situ hybridization and immunocytochemistry.

This study is aiming to identify the location and potential developmental patterns of the enzyme cytochrome P450 aromatase in horse embryos. The researchers found that the enzyme was abundant in certain tissues of the embryo and less so in others, suggesting there may be intrinsic regulatory mechanisms at work.

Objective of the Research

This research aimed to identify exactly where in the horse embryo the enzyme cytochrome P450 aromatase (P450arom) is located and examine potential patterns of expression. This enzyme is responsible for the conversion of C19 androgens into C18 estrogens, a process thought to be crucial in the communication between the preimplantation horse embryo and the mother (mare).

Methodology

• The researchers collected blastocyst-stage horse embryos on days 12 to 15 of pregnancy using a non-surgical procedure.
• These embryos were then fixed in 4% paraformaldehyde and embedded in paraffin.
• P450arom localization was identified using rabbit anti-human placental aromatase antiserum coupled with a detection system that uses peroxidase and 3-amino-9-ethylcarbazole.
• For identifying the location of the enzyme at the gene level, researchers used in situ hybridization. This method involved incubating tissue sections with sense or antisense [(35)S]UTP-labeled cRNA probes prepared from horse aromatase cDNA in cells.

Results and Findings

• The researchers found that both the aromatase protein and its corresponding mRNA transcript were abundant in a part of the embryo called the extraembryonic trophectoderm. However, they were noticeably absent from the embryonic ectoderm.
• Additionally, no P450arom expression was detected in the abembryonic endoderm or mesoderm, regions of the embryo that will eventually develop into the animal’s organs and tissues.
• Interestingly, the P450arom enzyme was present in the endoderm that lies beneath the disc (also known as the hypoblast).
• The pattern identified in the horse embryo closely resembles a pattern seen in pig embryos, suggesting that the regulation of this enzyme’s expression – the mechanisms that control where, when and how much of the enzyme is produced – may be preserved across species.