Influence of age and sexual maturation on the expression of LH and FSH receptors and aromatase P450 in equine male reproductive tissues

Abstract

Testicular function and maturation in male domestic animals is regulated by a complex interplay of endocrine, paracrine and autocrine factors. The objective of the present study was to characterize gene expression of the receptors for LH (LHR) and FSH (FSHR) as well as aromatase in equine epididymal and testicular tissue with regard to sexual maturity of stallions. We hypothesized tissueand age-related differences in the expression and localization of these genes. Tissue from testis and epididymis (corpus and cauda) was collected at routine castration of 21 sexually healthy stallions. They belonged to 4 different age groups: prepubertal ( 9 years, n 1⁄4 4). Changes in mRNA expression and protein localisation of LHR, FSHR and aromatase were analysed using quantitative real-time PCR (qRT-PCR) with GAPDH as reference gene, immunohistochemistry (IHC), and multiple immunofluorescence labelling. Statistical analysis was performed with the SPSS/PC statistics package (version 17.0 for windows, SPSS Inc., Chicago, IL, USA) Comparisons between age groups were done by KruskalWallis test with a subsequent Wilcoxon test. In testicular and corpus and cauda epididymal tissue collected from older stallions, the relative gene expression of aromatase in testicular parenchyma was significantly higher (p<0.05) than in animals of all other age groups. No differences in LHR and FSHR mRNA expression in testes were seen with respect to age. However, quantitative total expression of FSHR-mRNA in corpus and cauda epididymidis was significantly elevated (p<0.05) in older horses compared