Follicle-stimulating hormone regulates Notch signalling in the seminiferous epithelium of continuously and seasonally breeding rodents.

Juxtacrine (contact-dependent) communication between the cells of seminiferous epithelium mediated by Notch signalling is of importance for the proper course of spermatogenesis in mammals. The present study was designed to evaluate the role of follicle-stimulating hormone (FSH) in the regulation of Notch signalling in rodent seminiferous epithelium. We explored the effects (1) of pharmacological inhibition of the hypothalamus-pituitary-gonadal (HPG) axis and FSH replacement in pubertal rats, and (2) of photoinhibition of HPG axis followed by FSH substitution in seasonally breeding rodents, bank voles, on Notch pathway activity. Experiments on isolated rat Sertoli cells exposed to FSH were also performed. Gene and protein expressions of Notch pathway components were analysed using RT-qPCR, western blot and immunohistochemistry/immunofluorescence. Distribution patterns of Notch pathway proteins in bank vole and rat seminiferous epithelium were comparable; however, levels of activated Notch1 and Notch3, hairy/enhancer of split 1 (HES1) and hairy/enhancer of split-related with YRPW motif 1 (HEY1) in bank voles were dependent on the length of the photoperiod. In response to FSH similar changes in these proteins were found in both species, indicating that FSH is a negative regulator of Notch pathway activity in seminiferous epithelium. Our results support a common mechanism of FSH action on Notch pathway during onset and recrudescence of spermatogenesis in rodents. Interaction between FSH signalling and Notch pathway in Sertoli cells may be involved in spermatogenic activity changes of the testes occurring during puberty or photoperiod shift in continuously and seasonally breeding rodents, respectively.