Ligand-dependent stabilization of androgen receptor in a novel mouse ST38c 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.

Expression and characterization of androgen receptor coregulators, SRC-2 and HBO1, during human testis ontogenesis and in androgen signaling deficient patients

Androgen receptor (AR) is essential for testicular physiology and spermatogenesis. SRC-2 and HBO1 are two AR coregulators yet their expression and roles in human testis are unknown. For the first time, we studied by immunohistochemistry and RT-PCR, the expression and distribution of these two coregulators during human testicular ontogenesis, in patients with altered AR signaling (Androgen insensitivity syndrome, AIS) and evaluated the functional impact of SRC-2 and HBO1 on AR signaling in a Sertoli cell context. SRC-2 was present in Sertoli cells at all developmental stages. HBO1 was barely or focally detected in the fetal testis yet its expression, in Sertoli and germ cells, drastically increased postnatally from early infancy to adulthood. In transient co-transfection studies we showed that SRC-2 induced, while HBO1 inhibited AR-mediated transactivation of reporter constructs in murine Sertoli SMAT1 cells. HBO1, but not SRC-2, expression was reduced in testes of patients with AIS compared to normal testes.

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

CONTEXT

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.

Human fetal testis: source of estrogen and target of estrogen action

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 (ER) 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-Müllerian 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.