Cellular localization of androgen synthesis in equine granulosa-theca cell tumors: immunohistochemical expression of 17alpha-hydroxylase/17,20-lyase cytochrome P450.

The research article is about a study that used immunohistochemistry to locate the cellular expression of an enzyme in granulosa-theca cell tumors (GTCTs) in horses. This enzyme is responsible for the synthesis of androgens in these tumors.

Background

• The study focuses on granulosa-theca cell tumors (GTCTs) often found in female horses. One of the common symptoms in these horses is an increase in blood testosterone levels, which usually leads to male-like behavior.
• Despite the symptoms, there was a lack of solid information about how the GTCTs and androgen secretion were linked. This investigation aimed to solve that gap by looking at the expression of a particular enzyme,17alpha-hydroxylase/17,20-lyase cytochrome P450 (P450c17), known for its potent role in androgen production.

Methodology

• The researchers explored P450c17 expression in 30 GTCTs and control tissues from reproductive organs and adrenal glands, employing a method called immunohistochemistry (IHC). This technique involves staining specific proteins (in this case, P450c17) in a tissue section to observe precisely where the protein is produced.

Findings

• The investigation revealed the presence of P450c17 was significantly accessible in sample tissues. It was more consistently observed in the interstitial cells located around existing or forming cysts. Immuno-reactivity was less intense within the cysts themselves in the smaller proportion of specimens.
• In control tissues, P450c17 expression was found mostly in theca interna cells within normal ovarian follicles, in theca-lutein cells in some corpora lutea, but not in granulosa-lutein cells. The expression was also noticeable in testicular interstitial cells and clusters of adrenal cortical cells in the adrenal medulla, supporting the specificity of the applied antisera.
• The results presented the first strong evidence that some particular cells (polyhedral cells) previously identified in GTCTs by histopathology do indeed have the potential to generate and secrete androgens, much like theca interna and theca lutein cells in normal horse ovaries.

Implications

• This study’s results provide significant insights into why mares with GTCTs exhibit increased blood testosterone levels and male-typical behaviours. They also contribute crucial knowledge to the field of equine reproductive pathology and can be used in coming up with more effective diagnostic tools and treatments for GTCTs.