The sperm defects and expression of androgen receptor in reproductive tissues of dogs from post-puberty to advanced age

Introduction

The canine reproductive functions and semen quality gradually decline with aging, but when the risk develops is poorly defined. Androgen receptors (AR) are target sites of androgen essential to initiate and maintain spermatogenesis⁽¹⁾ and epidydimal secretory function⁽²⁾ . In rodents and men, AR declines with aging^{(3, 4)} . This study aimed to determine when senescence results in changes in sperm morphology and AR in reproductive tissues.

Materials and Methods

48 healthy medium-sized dogs⁽⁵⁾ were divided into 4 groups; young (1-3 y/o), adult (>3-6 y/o), old (>6-9 y/o) and senile (>9 y/o). After routine castration, caudal epidydimal sperm, testes, epididymides (head, body, tail) and vas deferens, were collected. Sperm morphology was evaluated (Table 1). AR expression was investigated by immunohistochemistry; H-score was evaluated using NuclearQuant (3DHISTECH), image analysis software.

Results

In Figure 1, the primary, secondary, major and minor sperm defects (%) were significantly higher in senile dogs compared to young dogs. Pearson’s correlation revealed significant positive correlations (p < 0.05) between age and sperm defects: primary; r = .42, secondary; r = .57, major; r = .42 and minor defect; r = .48. Testicular AR localization was observed in the nucleus of sertoli, leydig’s and peritubular myeloid cell but not in germ cells. It was observed in all epithelium, lamina propria and smooth muscle cell of epididymis and vas deferens. Although the AR H-score in reproductive tissues did not differ among age groups, a positive correlation was found between age and AR expression in testicular tissue; r = .32 (Figure 2). There was no correlation between AR expression and sperm defects in this study.

Conclusions

Senescence is associated with sperm quality and AR expression in testis. Sperm defects increased with age and, in this study, significant differences were found at age >9 y/o.