The future of testis research is turning 6! Six years of international network for young researchers in male fertility.

The 'International Network for Young Researchers in Male Fertility' has now turned 6 years old and offers a platform that stimulates scientific exchange as well as the development of international cooperation for young researchers. We report on our scope and the exciting achievements, amongst others, the continually increasing number of participants and the growing success of our annual meetings.

Direct action through the sertoli cells is essential for androgen stimulation of spermatogenesis.

Androgens act to stimulate spermatogenesis through androgen receptors (ARs) on the Sertoli cells and peritubular myoid cells. Specific ablation of the AR in either cell type will cause a severe disruption of spermatogenesis. To determine whether androgens can stimulate spermatogenesis through direct action on the peritubular myoid cells alone or whether action on the Sertoli cells is essential, we crossed hypogonadal (hpg) mice that lack gonadotrophins and intratesticular androgen with mice lacking ARs either ubiquitously (ARKO) or specifically on the Sertoli cells (SCARKO). These hpg.ARKO and hpg.SCARKO mice were treated with testosterone (T) or dihydrotestosterone (DHT) for 7 d and testicular morphology and cell numbers assessed. Androgen treatment did not affect Sertoli cell numbers in any animal group. Both T and DHT increased numbers of spermatogonia and spermatocytes in hpg mice, but DHT has no effect on germ cell numbers in hpg.SCARKO and hpg.ARKO mice. T increased germ cell numbers in hpg.SCARKO and hpg.ARKO mice, but this was associated with stimulation of FSH release. Results show that androgen stimulation of spermatogenesis requires direct androgen action on the Sertoli cells.

Effect of FSH on testicular morphology and spermatogenesis in gonadotrophin-deficient hypogonadal mice lacking androgen receptors.

FSH and androgen act to stimulate and maintain spermatogenesis. FSH acts directly on the Sertoli cells to stimulate germ cell number and acts indirectly to increase androgen production by the Leydig cells. In order to differentiate between the direct effects of FSH on spermatogenesis and those mediated indirectly through androgen action, we have crossed hypogonadal (hpg) mice, which lack gonadotrophins, with mice lacking androgen receptors (AR) either ubiquitously (ARKO) or specifically on the Sertoli cells (SCARKO). These hpg.ARKO and hpg.SCARKO mice were treated with recombinant FSH for 7 days and testicular morphology and cell numbers were assessed. In untreated hpg and hpg.SCARKO mice, germ cell development was limited and did not progress beyond the pachytene stage. In hpg.ARKO mice, testes were smaller with fewer Sertoli cells and germ cells compared to hpg mice. Treatment with FSH had no effect on Sertoli cell number but significantly increased germ cell numbers in all groups. In hpg mice, FSH increased the numbers of spermatogonia and spermatocytes, and induced round spermatid formation. In hpg.SCARKO and hpg.ARKO mice, in contrast, only spermatogonial and spermatocyte numbers were increased with no formation of spermatids. Leydig cell numbers were increased by FSH in hpg and hpg.SCARKO mice but not in hpg.ARKO mice. Results show that in rodents 1) FSH acts to stimulate spermatogenesis through an increase in spermatogonial number and subsequent entry of these cells into meiosis, 2) FSH has no direct effect on the completion of meiosis and 3) FSH effects on Leydig cell number are mediated through interstitial ARs.

Early effects of Sertoli cell-selective androgen receptor ablation on testicular gene expression.

Evidence from several models of hormone depletion and/or replacement and from knockout animals points to a key role of androgens in the control of spermatogenesis. In testes of mice with a Sertoli cell-selective ablation of the androgen receptor (SCARKO), transcriptional profiling, using microarray technology, revealed that, already on postnatal day 10,692 genes are differentially expressed compared with testes of control mice. Further evaluation of a subset of these genes by quantitative RT-PCR suggested that differences in expression may already be evident on day 8 or earlier. As the androgen receptor in mouse Sertoli cells becomes immunologically detectable around day 5, we tried to identify the earliest responses to androgens by a new transcriptional profiling study on testes from 6-day-old SCARKO and control mice. No obvious and novel early androgen response genes, potentially acting as mediators of subsequent indirect androgen actions, could be identified. However, several genes differentially expressed on day 10 already displayed a response to androgen receptor ablation on day 6. Quantitative RT-PCR studies for 12 of these genes on 10 paired SCARKO and control testes from 4-, 6-, 8-, 10-, 20- and 50-day-old mice revealed significant differences in expression level from day 4 onwards for three genes (Eppin, PCI, Cldn11) and from day 6 onwards for one more gene (Rhox5). For at least two of these genes (Rhox5 and Eppin), there is evidence for direct regulation via the androgen receptor. For three additional genes (Gpd1, Tubb3 and Tpd52l1) significantly lower expression in the SCARKO was noted from day 8 onwards. For all the studied genes, an impressive increase in transcript levels was observed between day 4-50 and differential expression was maintained in adulthood. It is concluded that the SCARKO model indicates incipient androgen action in mouse Sertoli cells from day 4 onwards.

Spermatogenesis and sertoli cell activity in mice lacking sertoli cell receptors for follicle-stimulating hormone and androgen.

Spermatogenesis in the adult male depends on the action of FSH and androgen. Ablation of either hormone has deleterious effects on Sertoli cell function and the progression of germ cells through spermatogenesis. In this study we generated mice lacking both FSH receptors (FSHRKO) and androgen receptors on the Sertoli cell (SCARKO) to examine how FSH and androgen combine to regulate Sertoli cell function and spermatogenesis. Sertoli cell number in FSHRKO-SCARKO mice was reduced by about 50% but was not significantly different from FSHRKO mice. In contrast, total germ cell number in FSHRKO-SCARKO mice was reduced to 2% of control mice (and 20% of SCARKO mice) due to a failure to progress beyond early meiosis. Measurement of Sertoli cell-specific transcript levels showed that about a third were independent of hormonal action on the Sertoli cell, whereas others were predominantly androgen dependent or showed redundant control by FSH and androgen. Results show that FSH and androgen act through redundant, additive, and synergistic regulation of spermatogenesis and Sertoli cell activity. In addition, the Sertoli cell retains a significant capacity for activity, which is independent of direct hormonal regulation.

Androgen regulation of stage-dependent cyclin D2 expression in Sertoli cells suggests a role in modulating androgen action on spermatogenesis.

Regulation of spermatogenesis involves stage-dependent androgen action on Sertoli cells, but the pathways involved are unclear. We assessed if cyclin D2 could play a role. In rats, Sertoli cell nuclear, stage-dependent immunoexpression of cyclin D2 switched on after Day 10 and persisted through Day 35, but disappeared by adulthood. However, ethane dimethane sulfonate (EDS)-induced testosterone withdrawal in adult rats for 6 days induced stage-dependent cyclin D2 immunoexpression in Sertoli cells, with highest expression at stages IX-XII and nondetectable at stages VI-VIII (opposite that for androgen receptor [AR] immunoexpression). In EDS-treated rats, a single injection of testosterone but not of estrogen reversed this change in 4 h, and testosterone administration from the time of EDS treatment prevented expression of cyclin D2 in Sertoli cells. The EDS-induced changes in cyclin D2 immunoexpression were matched by changes in expression of Ccnd2 (cyclin D2) mRNA in isolated stage-dissected tubules. Treatment of adult rats with flutamide induced stage-dependent cyclin D2 immunoexpression in Sertoli cells within 18 h, and confocal microscopy revealed that immunoexpression of AR and cyclin D2 were mutually exclusive within individual seminiferous tubules in these animals. Sertoli cell-selective ablation of the AR in mice using Cre/loxP technology also resulted in stage-dependent Sertoli cell cyclin D2 immunoexpression. Downstream from cyclin D2 action is retinoblastoma 1 (RB1), a tumor suppressor protein, immunoexpression of which paralleled stage-dependent AR expression in Sertoli cells; RB1 stage specificity disappeared after EDS treatment. These results point to a non-cell cycle role for cyclin D2 and RB1 in mature Sertoli cells in the stage-dependent mechanisms regulated by AR expression and androgen action.

Hepatitis B surface antigenaemia following vaccination with a combined vaccine against hepatitis A and B.

We report a case of transient hepatitis B surface antigenaemia (HBsAg) following vaccination with a combined vaccine against hepatitis A and B in healthy adults. This phenomenon has been observed following administration of recombinant hepatitis B (monovalent) vaccine, mainly in newborns or dialysis patients. Reports on healthy adults are much less frequent and mostly concern blood donors. The frequency of its occurrence is largely unknown but its duration does not exceed 28 days. It is not detected by all available assays. It is caused by a passive transfer of antigen by vaccination, and not by viral replication; hence there is no risk for vaccination-induced infection. An important implication resulting from our findings is that the results of HBsAg assays should be interpreted according to the time elapsed since the last administration of a recombinant monovalent vaccine against hepatitis B or a combined vaccine against hepatitis A and B.

Effects and characterization of paracrine factors produced by human prostate stromal cells in bioassays using rat Sertoli cells, LNCaP tumor cells, and cultured prostate epithelial cells.

BACKGROUND: Prostatic stroma affects both proliferation and differentiation of epithelial cells but the factors involved remain poorly understood. In order to identify and characterize potential paracrine mediators, we studied the effects of human prostate fibroblast-conditioned media (PFCM) in three bioassay systems. METHODS: The first bioassay uses transferrin secretion by cultured rat Sertoli cells as an endpoint for differentiating activity. Factors active in this (heterologous) assay were compared to PModS, a mediator of mesenchymal-epithelial interactions in the testis, also produced by rat prostate stromal cells. The two other (homologous) bioassays use LNCaP tumor cells or subcultured human prostate epithelial cells (PEC) as targets. Differentiation is evaluated by prostate-specific antigen (PSA) secretion and reverse transcriptase-polymerase chain reaction (RT-PCR) for a number of markers of epithelial function. Proliferation is assayed by measurements of DNA and thymidine incorporation. RESULTS: PFCM markedly stimulates transferrin production by Sertoli cells. The main factor(s) involved are acid stable and bind to heparin. However, both their size (approximately 37 kDa) and their behavior on reversed-phase chromatography differ from that of PModS. Although PFCM increases total RNA content of LNCaP, it does not increase or restore differentiated function of LNCaP or PEC. Proliferative effects are observed in LNCaP and these effects cannot be neutralized by an antiserum directed against basic fibroblast growth factor (bFGF). Antiproliferative effects are observed in PEC and these effects are largely due to transforming growth factor-beta (TGF-beta). CONCLUSIONS: PFCM provokes differentiating effects in a Sertoli cell bioassay, but unlike with rat stromal cells, the factor(s) involved differ from PModS. In the two homologous systems studied, differentiating effects could not be demonstrated and discordant effects were noted on proliferation. Various bioassay systems will be required to identify the spectrum of mediators present in PFCM.

Peritubular cell-Sertoli cell interactions: factors involved in PmodS activity.

The widespread occurrence of peritubular myoid cells in mammalian and other species suggests that they form an integral and functional component of the testis. Peritubular cells contribute to the contractile activity of testicular tubules and maintain mesenchymal-epithelial interactions with Sertoli cells both by cooperation in the deposition of extracellular matrix elements and by secretion of paracrine agonists. One of the most intriguing of these paracrine agonists is known as PModS (Peritubular factor that Modulates Sertoli cell function). The demonstration that, at least under some conditions, PModS production may be stimulated by androgens has led to the hypothesis that PModS may mediate part or all of the effects of androgens on Sertoli cells. The identity of PModS, however, remains elusive. Here we summarize data showing: (1) that production of PModS (-like factors) may not be limited to peritubular cells; (2) that the role of androgens in the control of PModS production remains controversial; (3) that other known mediators including IGF-I, bFGF, cytokines and heregulins mimic some or all of the effects of PModS; (4) that combinations of such growth factors have potent effects. It is concluded that, until PModS has been identified unambiguously, the hypothesis that it acts as an essential andromedin in the testis should be regarded with caution.