Effect of stallion age on the expression of LH and FSH receptors and aromatase P450 in equine male reproductive tissues
Authors: Herrera-Luna Carlos Vladimir, Scarlet Dragos, Walter Ingrid, Aurich Christine
Journal: Reproduction, Fertility and Development
Summary
# Editorial Summary Reproductive hormonal responsiveness in stallions undergoes substantial maturation throughout development, with critical implications for breeding soundness assessment and fertility management. Herrera-Luna and colleagues characterised expression patterns of luteinising hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), and aromatase—the enzyme responsible for oestrogen synthesis—across testicular and epididymal tissues in stallions ranging from prepubertal colts to aged animals, using quantitative PCR, immunohistochemistry and immunofluorescence techniques. Whilst LHR expression remained stable across age groups, both FSHR and aromatase expression increased significantly with maturity in all epididymal regions and testicular parenchyma (P < 0.001), with protein localisation shifting from seminiferous tubules in prepubertal colts to Sertoli cells and Leydig cells respectively in mature stallions. These findings underscore that oestrogen production and FSH-mediated signalling are essential not merely for pubertal development, but for maintaining testicular function and spermatogenic competence throughout a stallion's breeding career—suggesting that age-related changes in hormonal receptor expression warrant consideration when evaluating fertility decline or investigating subfertility in older animals.
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Practical Takeaways
- •Reproductive maturation in stallions involves age-dependent upregulation of FSH and estrogen signaling; fertility issues in young stallions may relate to incomplete development of these pathways
- •Estrogen production appears critical for maintaining testicular function throughout a stallion's life, suggesting that conditions affecting aromatase activity could impact fertility and longevity
- •Understanding the regional distribution of hormone receptors in reproductive tissues provides insight into stage-specific vulnerabilities during development and aging
Key Findings
- •FSHR and aromatase (CYP19A1) expression in epididymis and testicular parenchyma increased significantly with age (P<0.001), while LHR mRNA expression remained unchanged
- •LHR and aromatase immunolabelling was localized to Leydig cells in postpubertal stallions but diffusely distributed in seminiferous tubules of prepubertal colts
- •FSHR protein expression was present in Sertoli cells and primary spermatocytes, suggesting direct FSH effects on spermatogenesis in horses
- •Aromatase was detected in cauda epididymis only, regardless of age, indicating localized estrogen production in the distal epididymis