Aromatase gene expression in immature rat Sertoli cells: age-related changes in the FSH signalling pathway.

Aromatase, the enzyme responsible for the transformation of androgens into oestrogens, is encoded by the cyp19 gene expressed in the testis. The aim of the present study was to analyse the evolution of aromatase gene expression under FSH control in rat Sertoli cells between 10 and 30 days post partum, corresponding to the end of the proliferative period of Sertoli cells, establishment of the blood-testis barrier and acquisition of the mature phenotype. The maximum stimulatory effect of FSH on aromatase gene expression was obtained in 20-day-old rat Sertoli cells, compared with cells from 10- and 30-day-old rats, in parallel with the differentiation of Sertoli cells. Using two effectors of the protein kinase A pathway (i.e. forskolin and dibutyryl-cAMP) revealed differential effects between cells from rats aged 20 and 30 days, implying the involvement of another signalling pathway. Experiments using the specific phosphatidylinositol 3-kinase (PI3-K) inhibitor LY294002 revealed that PI3-K is strongly involved in FSH-induced aromatase expression in Sertoli cells from both 20- and 30-day-old rats. In vivo, this decrease could be explained by a negative effect exerted by germ cells because, in coculture, aromatase gene expression in 20-day-old Sertoli cells is greatly diminished.