Expression of anti‐ M üllerian hormone, CDKN1B , connexin 43, androgen receptor and steroidogenic enzymes in the equine cryptorchid testis

Summary Reasons for performing study Cryptorchidism affects 2–8% of male horses and the affected testis undergoes a disruption of normal spermatogenesis. The underlying molecular changes are poorly understood in the cryptorchid equine testis. Objectives Compare the expression of anti‐ M üllerian hormone ( AMH ), anti‐ M üllerian hormone receptor ( AMHR 2), androgen receptor ( AR ), cyclin kinase inhibitor ( CDKN1B ), connexin 43 ( C x43), 3β hydroxysteroid dehydrogenase/Δ 5 ‐Δ 4 ‐ isomerase (3β HSD ), P 450c17 hydroxylase/lyase ( P 450c17) and cytochrome P 450 aromatase ( P 450arom) in the undescended testis of cryptorchid stallions with that of normal stallions. Methods Undescended, abdominal testes from four cryptorchid stallions between 2 and 3 years of age were collected during routine castrations along with normally descended testes from normal stallions between 2 and 3 years of age (n = 7). Samples were analysed by immunohistochemistry and quantitative real‐time PCR . Results Cryptorchid testes had increased AMH and AMHR 2 immunolabelling when compared with normal testes, which indicates failure of maturation of S ertoli cells and/or lack of testosterone suppression. Failure of S ertoli cell maturation in the cryptorchid testis may also be attributed to AR abnormalities and/or a consequence of lack of testosterone suppression due to decreased 3β HSD . Cyclin‐dependent kinase ( CDKN1B ) was not expressed in S ertoli cells of cryptorchid testes suggesting that S ertoli cells are still proliferating, which is also a characteristic of the immature testis. In addition, C x43 expression is decreased in the cryptorchid testis, indicating a disruption in intercellular communication. Conclusions Undescended testes of cryptorchid horses present characteristics of immaturity suggesting that the failure of S ertoli cell maturation may be a consequence of cryptorchidism. Potential relevance This study provides a better understanding of the effect of cryptorchidism on testicular function in stallions.