Beneficial effects of pentoxifylline on spermatogenesis and germ cell apoptosis in stallions subjected to scrotal heat stress.

Overview

• This study investigated whether oral pentoxifylline could protect stallion testes from damage caused by scrotal heat stress, focusing on testicular structure, cellular health, and gene activity related to cell death and protection.

Background and Objective

• Scrotal heat stress in stallions can cause testicular degeneration, negatively impacting spermatogenesis (the production of sperm) and leading to germ cell apoptosis (programmed cell death).
• Pentoxifylline is a drug known for its anti-inflammatory and blood flow-improving effects, but its role in protecting testicular tissue under heat stress was unclear.
• The objective was to assess the effects of orally administered pentoxifylline on testicular biometry (size and volume), histological structure, and expression of key genes involved in apoptosis and cellular protection in heat-stressed stallions.

Methodology

• Fourteen stallions were assigned to three groups:
  • Control (CRL, n=4): no heat stress, no treatment.
  • Testicular Degeneration (DEG, n=5): subjected to scrotal heat stress without treatment.
  • Testicular Degeneration Treated with Pentoxifylline (DEG+PTX, n=5): subjected to heat stress and treated with pentoxifylline.
• Heat stress was induced by scrotal insulation twice daily over two days (Day -1 and Day 0).
• Pentoxifylline was administered orally at 17 mg/kg every 12 hours, starting on Day 1, for 30 consecutive days.
• Testicular biometry was regularly measured with a caliper from 5 days before treatment (Day -5) to 60 days after treatment (Day 60).
• Testicular biopsies were obtained on Days 30 and 60 for:
  • Histopathological examination (microscopic tissue structure analysis).
  • Gene expression analysis using RT-qPCR for apoptosis and protective genes: BAX, CASP8, CASP9, FAS, HSF1, and PTGS2.

Key Findings

• Pentoxifylline treatment partially protected testes from heat-induced damage:
  • Histology showed reduced basal lamina undulation and less seminiferous tubule atrophy in the treated group compared to the untreated degeneration group.
  • Despite histological improvements, pentoxifylline did not completely prevent lesions such as germ cell vacuolization.
• Functionally, both heat-stressed groups displayed decreased testicular volume, indicating some residual structural damage despite treatment.
• At the molecular level:
  • Pentoxifylline lowered the expression of BAX, a gene promoting apoptosis.
  • It prevented activation of CASP8 and CASP9, key enzymes that drive apoptosis.
  • It increased HSF1 gene expression, which is related to cellular protective responses against stress.

Interpretation and Implications

• Oral pentoxifylline shows beneficial effects in reducing cellular and structural damage caused by scrotal heat stress in stallions, mainly by modulating apoptotic pathways and enhancing cellular protection.
• This suggests pentoxifylline as a promising therapeutic candidate for managing equine testicular damage due to environmental or pathological heat stress.
• However, since some damage was not fully prevented, further investigations are needed to:
  • Optimize the dosage and duration of treatment for maximum protective effects.
  • Explore the mechanisms underlying incomplete protection, especially regarding germ cell vacuolization.
  • Assess the longer-term impact on fertility and sperm quality post-treatment.

Conclusion

• Pentoxifylline can mitigate testicular damage caused by scrotal heat stress by reducing apoptotic gene activation and promoting cellular defense mechanisms.
• The study encourages further research to fine-tune treatment protocols to improve reproductive outcomes in stallions affected by heat stress.