Testicular and Epididymal Gene Expression Changes in Response to Scrotal Heating in Stallions

Scrotal heating - overview of the study in an imageHeat stress is a well-recognized cause of testicular and epididymal dysfunction, yet the underlying molecular events driving these changes remain poorly understood. This study used transcriptomic analysis to characterize early gene expression responses in testicular and epididymal tissues following acute scrotal insulation in stallions.

Study Design:

  • 10 normospermic adult light-breed stallions: control (n=5) and scrotal insulation (n=5)
  • Scrotal insulation applied for 24 hours via insulation bag; stallions castrated immediately upon removal
  • Tissue biopsies collected from testes, epididymal head, body, and tail
  • RNA sequencing and differential gene expression analysis performed; differentially expressed genes identified at p<0.05 with log2 fold change ≥1

Key Results:

  • Differentially expressed gene counts: testes (507), epididymal head (1,198), epididymal body (3,420), epididymal tail (1,245)
  • Testes: Spermatogenesis pathways downregulated; upregulated pathways associated with oxidant-antioxidant balance, immune activation (innate and adaptive), lipid and amino acid metabolism, and amyloid deposition
  • Epididymal head: Dysregulation of spermatogenesis, energy metabolism, antigen presentation, and immune cell signaling
  • Epididymal body: Differentially expressed genes associated with microtubule formation, sperm flagellum components, and cell motility
  • Epididymal tail: Differentially expressed genes linked to energy metabolism and cell respiration

Conclusions:

  • Acute scrotal heating rapidly dysregulates oxidant-antioxidant balance, energy metabolism, and immune homeostasis across testicular and epididymal tissues
  • Region-specific gene expression patterns reflect distinct functional vulnerabilities within the reproductive tract
  • Findings establish a molecular framework for understanding heat-induced reproductive dysfunction in stallions

(Ferrer M, Barletta M, Williams J, Moran K, Bilbao G, Bartolome J. 2025. Changes in equine testicular and epididymal homeostasis in response to scrotal heating. JEVS 145:105284 – https://doi.org/10.1016/j.jevs.2024.105284 – Presented in Association with and by Permission of the International Society for Equine Reproduction)