Rôle des récepteurs stéroïdiens dans les fonctions testiculaires endocrine et exocrine au cours du développement chez l'homme

Dans ce travail, nous nous sommes intéressés aux rôles de l œstrogène (E) et de la testostérone (T) dans le testicule humain. Nous démontrons que le testicule fœtal est une source et une cible des E surtout entre 13 et 22 semaines de gestation. Nos résultats suggèrent que les E sont importants dans le développement testiculaire et agissent via le récepteur des œstrogènes par des mécanismes autocrine et paracrine.En parallèle, nous avons étudié certains effets de la T dans le testicule relayés par la cellule de Sertoli (CS). Chez le fœtus et le nouveau-né, nous démontrons que, l absence de l expression du récepteur aux androgènes (AR) dans la CS coïncide avec l absence de la spermatogenèse et une forte expression de l hormone anti-Müllérienne (AMH). Chez l adulte, la spermatogenèse s accompagne d une expression sertolienne d AR et d une baisse de l expression d AMH. Les études, in vitro (CS) et in vivo (homme), démontre que l expression d un AR fonctionnel sertolien est indispensable pour la répression de l AMH par la T.Enfin, l établissement d un nouveau modèle de CS ST38C exprimant l AR a permis de déterminer les mécanismes de la signalisation androgénique.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Human fetal testis: source of estrogen and target of estrogen action.: Estrogen production in human foetal testis

BACKGROUND Estrogens are involved in masculine fertility and spermatogenesis. However, little is known about estrogen involvement in human testicular organogenesis. Therefore the aim of this study was to investigate the cellular sources and targets of estrogens and their variations in the human testis during fetal development. Expression profiles of aromatase (CYP19) and estrogen receptors alpha and beta were analysed in human fetal testes at various gestational stages by immunohistochemistry and quantitative RT-PCR. METHODS Fifty-four archival paraffin-embedded and four frozen fetal testes were studied by immunohistochemistry and real-time PCR. Tissue quality was confirmed by histology and expression of specific functional markers: androgenic enzymes for Leydig cells, anti-M?rian hormone for Sertoli cells and Steel factor receptor for germ cells. RESULTS We demonstrate that the human fetal testes express aromatase and ERbeta simultaneously in Sertoli, Leydig and germ cells but are devoid of ERalpha. Quantification of positive cells indicates a window of protein expression, especially between 13 and 22-24 weeks. Quantitative RT-PCR confirmed that the human fetal testis expresses CYP19 and ERbeta but not ERalpha mRNA. CONCLUSIONS Our findings suggest that locally produced estrogens influence human testicular development through autocrine and paracrine mechanisms, most notably during the period of maximal testicular susceptibility to endocrine disruptors

: AR stabilization in a novel murine Sertoli cell line

Mature Sertoli cells (SC) are critical mediators of androgen regulation of spermatogenesis, via the androgen receptor (AR) signaling. Available immortalized SC lines loose AR expression or androgen responsiveness, hampering the study of endogenous AR regulation in SC. We have established and characterized a novel clonal mouse immortalized SC line, ST38c. These cells express some SC specific genes (sox9, wt1, tjp1, clu, abp, inhbb), but not fshr, yet more importantly, maintain substantial expression of endogenous AR as determined by PCR, immunocytochemistry, testosterone binding assays and Western blots. Microarrays allowed identification of some (146) but not all (rhox5, spinlw1), androgen-dependent, SC expressed target genes. Quantitative Real-Time PCR validated regulation of five up-regulated and two down-regulated genes. We show that AR undergoes androgen-dependent transcriptional activation as well as agonist-dependent posttranslational stabilization in ST38c cells. This cell line constitutes a useful experimental tool for future investigations on the molecular and cellular mechanisms of androgen receptor signaling in SC function

Lack of androgen receptor expression in Sertoli cells accounts for the absence of anti-Mullerian hormone repression during early human testis development.: Lack of AR in Sertoli cells in early human development

International audienceCONTEXT: Puberty is associated with increased testicular testosterone (TT) synthesis, which is required to trigger spermatogenesis and to repress anti-Mullerian hormone (AMH) production. However, testicular gonadotropin stimulation during fetal and newborn life neither initiates spermatogenesis nor represses AMH. OBJECTIVE: We postulated that a lack of androgen receptor (AR) expression in Sertoli cells (SC) might explain why these processes do not occur during early human development. METHODS AND PATIENTS: Using immunohistochemistry and quantitative PCR, we examined the relationship between AR, AMH, and FSH receptor expression in fetal, newborn, and adult human testis. The ability of testosterone to repress AMH secretion was evaluated in male newborns, neonates, and two adults with androgen insensitivity syndrome and also in vitro using SMAT1 SC. RESULTS: FSH receptor was present in SC at all developmental stages. In fetal and newborn testis, AR was expressed in peritubular and Leydig cells but not in SC. This coincided with the absence of spermatogenesis and with strong SC AMH expression. In adult testis, spermatogenesis was associated with AR expression and with a decrease in SC AMH content. Accordingly, AR mRNA expression was lower and AMH mRNA expression higher in fetal testes than in adult testes. In androgen insensitivity syndrome patients, combined gonadotropin stimulation induced an increase in circulating testosterone and AMH, a finding consistent with a failure of TT to repress AMH in the absence of AR signalling. Finally, direct androgen repression of AMH only occurred in AR-expressing SMAT1 cells. CONCLUSION: Functional ARs are essential for TT-mediated AMH repression in SC