Expression of steroidogenic enzymes during equine testicular development.

This research investigates the role of key steroid-producing enzymes in the development of horse testes across various stages: prepuberty, postpuberty, and adulthood. The study concludes that Leydig cells, which increase their activity after puberty, are the primary cells responsible for the production of sex hormones in the equine testis.

Key Steroidogenic Enzymes

• The research focuses on two essential enzymes — 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4)-isomerase (3βHSD) and 17α-hydroxylase/17,20-lyase (P450c17) — which regulate the synthesis of testosterone, a crucial hormone for sexual development and maturity. These enzymes are most active in Leydig cells, the primary cells associated with steroid production.
• The study also discusses another enzyme, P450arom, which creates substrates for estrogen synthesis using androgens produced by P450c17. Estrogen, albeit primarily a female sex hormone, also plays various roles in the male body.

Methods of Investigation

• The researchers tracked the location and change in expression of these enzymes in the equine testes at different developmental stages using two biological techniques: immunohistochemistry (IHC) and real-time quantitative PCR.
• IHC is used to visually represent the presence and location of specific proteins in tissue samples, while real-time quantitative PCR is a tool used to measure the amount of specific RNA (indicative of gene expression levels).

Findings of the Study

• The study found that the activity of the examined enzymes and subsequent hormone production changes according to the developmental stage of the horse.
• 3βHSD, for example, was active within the seminiferous tubules (site of sperm production) of prepubertal testes. Its activity later decreased after puberty within these tubules, but increased in the Leydig cells.
• P450c17 and P450arom, in contrast, showed very weak activity in immature Leydig cells of prepubertal testes but increased their activity significantly after puberty.
• The expression of genes (HSD3B1, CYP17, and CYP19) corresponding to these enzymes was found to be higher in adult testes compared to prepubertal and postpubertal testes.

Conclusion

• The study concludes that Leydig cells are the primary cell type in equine testes for producing androgens and estrogens. The activity of these cells and the expression of key steroidogenic enzymes increase after puberty, suggesting a significant role in equine testicular development and sexual maturity.