This study investigates how cryptorchidism – a condition where one or both testes fail to descend at birth – impacts the expression of heat shock proteins (HSPs) 60, 70, and 90 in horses. The results highlighted that this condition increased the presence of these proteins in the retained gonad.

Introduction

• Heat shock proteins (HSPs) are a group of proteins usually produced by cells in response to stressful conditions such as increased temperature.
• Cryptorchidism, a disorder prevalent in nearly nine percent of newborn horses, heightens testicular temperatures and challenges the animal’s reproductive potential.
• However, few studies have delved into the molecular intricacies of the undescended testis in horses, making this study an explorative effort in this terrain.

Methods

• The researchers engaged in examining the variation in the expression of HSP60, 70, and 90 in different testicular locations: the descended testes, the retained abdominal and inguinal counterparts, and in the testes of normal horses.
• They used Western blot analysis and immunohistochemistry (a lab procedure used to visually localize and determine the presence of specific antigens in cells of a tissue section) to investigate this.
• They also evaluated the histopathology of scrotal and retained testes.

Findings

• The investigation revealed disrupted spermatogenesis and a vacuolated appearance in the seminiferous epithelium of the retained testes.
• These features were contrastingly absent in the contralateral scrotal testes that showed all stages of the spermatogenic cycle, aligning perfectly with the normal testes.
• Leydig cells, responsible for producing testosterone in the male body, were discovered to be unaffected morphologically by the cryptorchid state.
• The expressions of HSP60, 70, and 90 were confirmed in both scrotal and retained testes with HSP70 emerging as the most expressed chaperone—especially in combination with HSP90—in the retained gonad.
• Retained testes showed the least HSP60 but the highest HSP90 expression in spermatogonia (the male germ cells from which spermatozoa develop).
• HSP60 was absent in spermatocytes, spermatids of scrotal testes, and retained and scrotal Sertoli cells (cells involved in the process of spermatogenesis).
• However, these cells collectively expressed HSP 70 and 90. These heat-shock proteins were located in the premeiotic cell nucleus.
• HSP70 and 90 had particularly higher immunostaining in the cryptorchid testes’ Leydig cells.

Conclusion

• The researchers determined a definite correlation between the heat stress condition induced by cryptorchidism and the expression of HSPs in equine testes.
• This increased HSP expression could signify the cellular attempts to combat the stressful conditions that pervade undescended testes in cryptorchid horses.