Expression of anti-Müllerian hormone, CDKN1B, connexin 43, androgen receptor and steroidogenic enzymes in the equine cryptorchid testis.
Authors: Almeida J, Conley A J, Ball B A
Journal: Equine veterinary journal
Summary
# Editorial Summary Cryptorchidism affects 2–8% of stallions and causes marked disruption to spermatogenesis, yet the cellular mechanisms underlying testicular dysfunction in undescended testes remain incompletely characterised in equine medicine. Almeida and colleagues used immunohistochemistry and quantitative PCR to compare expression of eight key regulatory molecules—including anti-Müllerian hormone (AMH), androgen receptor, steroidogenic enzymes, and gap junction protein connexin 43—in abdominal testes from four cryptorchid stallions aged 2–3 years against normally descended testes from seven age-matched controls. The cryptorchid testes demonstrated elevated AMH and AMH receptor expression alongside reduced 3β-HSD enzyme activity, patterns consistent with failed Sertoli cell maturation and inadequate testosterone production; additionally, the absence of the cell-cycle inhibitor CDKN1B in Sertoli cells and decreased connexin 43 expression indicated continued cellular proliferation and disrupted intercellular communication typical of immature tissue. These molecular signatures suggest that the architectural and functional abnormalities observed clinically in cryptorchid stallions stem fundamentally from arrested Sertoli cell development, which has practical implications for predicting fertility outcomes post-castration and understanding why fertility recovery is unlikely if cryptorchid tissue is retained.
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Practical Takeaways
- •Cryptorchid testes in stallions demonstrate molecular characteristics of immaturity rather than degeneration, helping explain poor fertility outcomes
- •Early castration of cryptorchid stallions prevents prolonged testicular dysfunction; the undescended testis cannot recover normal function
- •Knowledge of these molecular changes supports clinical decision-making regarding breeding soundness examinations and castration timing in horses with cryptorchidism
Key Findings
- •Cryptorchid testes showed increased AMH and AMHR2 immunolabelling indicating failure of Sertoli cell maturation
- •CDKN1B was not expressed in cryptorchid Sertoli cells, suggesting continued proliferation characteristic of immature testis
- •Connexin 43 expression was significantly decreased in cryptorchid testes, disrupting intercellular communication
- •Decreased 3β-HSD expression in cryptorchid testes may result in lack of testosterone suppression contributing to Sertoli cell immaturity