FSH receptor mRNA is expressed stage-dependently during rat spermatogenesis

Decoding the Spermatogenesis Program: New Insights from Transcriptomic Analyses

Spermatogenesis is a complex differentiation process coordinated spatiotemporally across and along seminiferous tubules. Cellular heterogeneity has made it challenging to obtain stage-specific molecular profiles of germ and somatic cells using bulk transcriptomic analyses. This has limited our ability to understand regulation of spermatogenesis and to integrate knowledge from model organisms to humans. The recent advancement of single-cell RNA-sequencing (scRNA-seq) technologies provides insights into the cell type diversity and molecular signatures in the testis. Fine-grained cell atlases of the testis contain both known and novel cell types and define the functional states along the germ cell developmental trajectory in many species. These atlases provide a reference system for integrated interspecies comparisons to discover mechanistic parallels and to enable future studies. Despite recent advances, we currently lack high-resolution data to probe germ cell-somatic cell interactions in the tissue environment, but the use of highly multiplexed spatial analysis technologies has begun to resolve this problem. Taken together, recent single-cell studies provide an improvedunderstanding of gametogenesis to examine underlying causes of infertility and enable the development of new therapeutic interventions.

FSH-R Human Early Male Genital Tract, Testicular Tumors and Sperm: Its Involvement in Testicular Disorders

The follicle-stimulating hormone receptor (FSH-R) expression was always considered human gonad-specific. The receptor has also been newly detected in extragonadal tissues. In this finding, we evaluated FSH-R expression in the human male early genital tract, in testicular tumors, and in sperm from healthy and varicocele patients. In sperm, we also studied the mechanism of FSH-R action. Immunohystochemistry and Western blot analysis showed FSH-R presence in the first pathways of the human genital tract, in embryonal carcinoma, and in sperm, but it was absent in seminoma and in lower varicocele. In sperm, FSH/FSH-R activity is mediated by G proteins activating the PKA pathway, as we observed by using the H89. It emerged that increasing FSH treatments induced motility, survival, capacitation, and acrosome reaction in both sperm samples. The different FSH-R expression in tumor testicular tissues may be discriminate by tumor histological type. In spermatozoa, FSH-R indicates a direct action of FSH in these cells, which could be beneficial during semen preparation for in vitro fertilization procedures. For instance, FSH positive effects could be relevant in idiopathic infertility and in the clinic surgery of varicocele. In conclusion, FSH-R expression may be considered a molecular marker of testicular disorders.

Gene expression analysis of ovine prepubertal testicular tissue vitrified with a novel cryodevice (E.Vit)

PURPOSE

Testicular tissue cryopreservation prior to gonadotoxic therapies is a method to preserve fertility in children. However, the technique still requires development, especially when the tissue is immature and rather susceptible to stress derived from in vitro manipulation. This study aimed to investigate the effects of vitrification with a new cryodevice (E.Vit) on cell membrane integrity and gene expression of prepubertal testicular tissue in the ovine model.

METHODS

Pieces of immature testicular tissue (1 mm³) were inserted into "E.Vit" devices and vitrified with a two-step protocol. After warming, tissues were cultured in vitro and cell membrane integrity was assessed after 0, 2, and 24 h by trypan blue exclusion test. Controls consisted of non-vitrified tissue analyzed after 0, 2, and 24 h in vitro culture (IVC). Expression of genes involved in transcriptional stress response (BAX, SOD1, CIRBP, HSP90AB1), cell proliferation (KIF11), and germ- (ZBDB16, TERT, POU5F1, KIT) and somatic- (AR, FSHR, STAR) cell specific markers was evaluated 2 and 24 h after warming.

RESULTS

Post-warming trypan blue staining showed the survival of most cells, although membrane integrity immediately after warming (66.00% ± 4.73) or after 2 h IVC (59.67% ± 4.18) was significantly lower than controls (C0h 89.67% ± 1.45). Extended post-warming IVC (24 h) caused an additional decrease to 31% ± 3.46 (P < 0.05). Germ- and somatic-cell specific markers showed the survival of both cell types after cryopreservation and IVC. All genes were affected by cryopreservation and/or IVC, and moderate stress conditions were indicated by transcriptional stress response.

CONCLUSIONS

Vitrification with the cryodevice E.Vit is a promising strategy to cryopreserve prepubertal testicular tissue.

A Comprehensive Roadmap of Murine Spermatogenesis Defined by Single-Cell RNA-Seq

Spermatogenesis requires intricate interactions between the germline and somatic cells. Within a given cross section of a seminiferous tubule, multiple germ and somatic cell types co-occur. This cellular heterogeneity has made it difficult to profile distinct cell types at different stages of development. To address this challenge, we collected single-cell RNA sequencing data from ∼35,000 cells from the adult mouse testis and identified all known germ and somatic cells, as well as two unexpected somatic cell types. Our analysis revealed a continuous developmental trajectory of germ cells from spermatogonia to spermatids and identified candidate transcriptional regulators at several transition points during differentiation. Focused analyses delineated four subtypes of spermatogonia and nine subtypes of Sertoli cells; the latter linked to histologically defined developmental stages over the seminiferous epithelial cycle. Overall, this high-resolution cellular atlas represents a community resource and foundation of knowledge to study germ cell development and in vivo gametogenesis.

The Role of GATA in Mammalian Reproduction

GATA transcription factors are emerging as critical players in mammalian reproductive development and function. GATA-4 contributes to fetal male gonadal development by regulating genes mediating Müllerian duct regression and the onset of testosterone production. GATA-2 expression appears to be sexually dimorphic being transiently expressed in the germ cell lineage of the fetal ovary but not the fetal testis. In the reproductive system, GATA-1 is exclusively expressed in Sertoli cells at specific seminiferous tubule stages. In addition, GATA-4 and GATA-6 are localized primary to ovarian and testicular somatic cells. The majority of cell transfection studies demonstrate that GATA-1 and GATA-4 can stimulate inhibin subunit gene promoter constructs. Other studies provide strong evidence that GATA-4 and GATA-6 can activate genes mediating gonadal cell steroidogenesis. GATA-2 and GATA-3 are found in pituitary and placental cells and can regulate alpha-glycoprotein subunit gene expression. Gonadal expression and activation of GATAs appear to be regulated in part by gonadotropin signaling via the cyclic AMP-protein kinase A pathway. This review will cover the current knowledge regarding GATA expression and function at all levels of the reproductive axis.

Timing in the Testis

The testis provides not just one but several models of temporal organization. The complexity of its rhythmic function arises in part from its compartmentalization and diversity of cell types: not only does the testis produce gametes, but it also serves as the major source of circulating androgens. Within the seminiferous tubules, the germ cells divide and differentiate while in intimate contact with Sertoli cells. The tubule is highly periodic: a spermatogenic wave travels along its length to determine the timing of the commitment of spermatogonia to differentiate, the phases of meiotic division, and the rate of differentiation of the postmeiotic germ cells. Recent evidence indicates that oscillations of retinoic acid play a major role in determining periodicity of the seminiferous epithelium. In the interstitial space, Leydig cells produce the steroid hormones required both for the completion of spermatogenesis and the development and maintenance of male sexual characteristics throughout the body. This endocrine output also oscillates; although the pulse generator lies outside the gonad, the steroidogenic function of Leydig cells is tuned to a regular episodic input. While the oscillations of the intratubular and interstitial cells have multihour (ultradian) and multiday (infradian) periodicities, respectively, the functions of both compartments also display dramatic seasonal rhythms. Furthermore, circadian rhythms are evident in some of the cell types, although their amplitude and pervasiveness are not as great as in many other tissues of the same organism, and their detection may require methods that recognize the heterogeneity of the testis. This review examines the periodicity of testicular function along multiple time scales.

Peritubular myoid cells have a role in postnatal testicular growth

FSH stimulates testicular growth by increasing Sertoli cell proliferation and elongation of seminiferous cords. Little is known about the peritubular myoid cells in testicular development. In order to investigate the role of peritubular myoid cells in early testicular growth in rodents, two traditional models to induce testicular growth were used: FSH treatment and hemicastration. In order to affect proliferation of peritubular myoid cells, both treatments were combined with imatinib, a tyrosine kinase inhibitor. In addition, effects of imatinib on human testicular peritubular cell proliferation were investigated. Testicular weight, diameter and length of seminiferous cords, numbers of germ, Sertoli and BrdU-positive cells and FSH-levels were measured. FSH treatment and hemicastration increased length of the seminiferous cords and testicular weight by increasing first the early proliferation of peritubular myoid cells and later also the proliferation of the Sertoli cells. Imatinib blocked the FSH and hemicastration -induced testicular hypertrophy and decreased the proliferation of PDGF-stimulated human testicular peritubular cells in vitro. Present results provide new evidence that peritubular myoid cells have an important role in postnatal testicular growth.

Endocrine regulation of spermatogonial stem cells in the seminiferous epithelium of adult mice

A balance between self-renewal and differentiation of spermatogonial stem cells (SSCs) is required to maintain sperm production throughout male life. The seminiferous epithelium is organized into stages of spermatogenesis based on the complement of germ cell types within a tubular section of the testis. The stages exist in close physical proximity and foster diverse phases of germ cell development despite exposure to a similar endocrine milieu that supports coordinated spermatogenesis. The objective of the current study was to identify the population dynamics of SSCs in vivo. We hypothesized that SSC populations and their niches are specifically distributed across the mature seminiferous epithelium in the mouse testis. To test this hypothesis, we conducted stem cell transplantation of germ cells obtained from stage-specific clusters of seminiferous tubules representing areas of high responsiveness to follicle-stimulating hormone (IX–I), androgen (II–IV), and retinoid (V–VIII) signaling. Similarly, we analyzed the expression of genes linked with SSC activity in these groups of stages. No stage-specific differences in the colonization efficiency or the colony number were detected after SSC transplantation, indicating that SSCs are equally distributed across all stages of the seminiferous tubule. In contrast, SSCs obtained from donor stages IX–IV established larger donor-derived colonies due to increased colony expansion. SSCs originating from different stages have varying degrees of stem cell activity in vivo, a notion consistent with Gdnf, Ret, and Bcl6b expression data. These results support the conclusion of a stage-specific, microenvironment-regulating SSC self-renewal and suggest the presence of a transit-amplifying population of undifferentiated spermatogonia in vivo.

Exploring the cyclooxygenase 2 (COX2)/15d-Δ(12,14)PGJ(2) system in hamster Sertoli cells: regulation by FSH/testosterone and relevance to glucose uptake

We have previously described a stimulatory effect of testosterone on cyclooxygenase 2 (COX2) expression and prostaglandin (PG) synthesis, and the involvement of PGs in the modulation of testosterone production in Leydig cells of the seasonal breeder Syrian hamster. In this study, we investigated the existence of a COX2/PGs system in hamster Sertoli cells, its regulation by testosterone and FSH, and its effect on glucose uptake. COX2 expression was observed in Sertoli cells of both reproductively active and inactive adult hamsters. Testosterone and the plasma membrane-impermeable testosterone-BSA significantly induced COX2 expression, mitogen activated protein kinases 1/2 (MAPK1/2) phosphorylation and 15d-Δ(12,14)PGJ(2) production in Sertoli cells purified from photoperiodically regressed hamsters. These actions were abolished by the antiandrogen bicalutamide and by the inhibitor of MAPK kinase (MEK1/2) U0126, suggesting that testosterone exerts its stimulatory effect on COX2/PGs through a non-classical mechanism that involves the presence of androgen receptors and MAPK1/2 activation. FSH also stimulated COX2/PGs via MAPK1/2 phosphorylation. FSH and testosterone stimulate, whereas 15d-Δ(12,14)PGJ(2) via PPARγ inhibits, [2,6-(3)H]-2-deoxy-d-glucose ([(3)H]-2-DOG) uptake. Meloxicam, a selective COX2 inhibitor, further increases [(3)H]-2-DOG uptake in the presence of FSH or testosterone. Thus, in addition to their positive effect, FSH and testosterone may also exert an indirect negative regulation on glucose uptake which involves the COX2/15d-Δ(12,14)PGJ(2)/PPARγ system. Overall, these results demonstrate the presence of a COX2/PG system in hamster Sertoli cells which might act as a local modulator of FSH and testosterone actions.

Current concepts of follicle-stimulating hormone receptor gene regulation

Follicle-stimulating hormone (FSH), a pituitary glycoprotein hormone, is an integral component of the endocrine axis that regulates gonadal function and fertility. To transmit its signal, FSH must bind to its receptor (FSHR) located on Sertoli cells of the testis and granulosa cells of the ovary. Thus, both the magnitude and the target of hormone response are controlled by mechanisms that determine FSHR levels and cell-specific expression, which are supported by transcription of its gene. The present review examines the status of FSHR/Fshr gene regulation, emphasizing the importance of distal sequences in FSHR/Fshr transcription, new insights gained from the influx of genomics data and bioinformatics, and emerging trends that offer direction in deciphering the FSHR/Fshr regulatory landscape.

FSH in therapy: physiological basis, new preparations and clinical use

Follicle stimulating hormone (FSH) is a glycoprotein hormone secreted by the pituitary gland that, together with luteinizing hormone (LH), controls development, maturation and function of the gonad. Like the related hormones, LH, thyroid stimulating hormone (TSH) and human chorionic gonadotropin (hCG), FSH consists of two polypeptide chains, α and β, bearing carbohydrate moietiesN-linked to asparagine (Asn) residues. The α subunit is common to all members of the glycoprotein hormone family, whereas the β subunit, although structurally very similar, differs in each hormone and confers specificity of action.

Nuclear regulator Pygo2 controls spermiogenesis and histone H3 acetylation

Mammalian spermiogenesis, a process where haploid male germ cells differentiate to become mature spermatozoa, entails dramatic morphological and biochemical changes including remodeling of the germ cell chromatin. Proteins that contain one or more plant homeodomain (PHD) fingers have been implicated in the regulation of chromatin structure and function. Pygopus 2 (Pygo2) belongs to a family of evolutionarily conserved PHD finger proteins thought to act as co-activators of Wnt signaling effector complexes composed of beta-catenin and LEF/TCF transcription factor. Here we analyze mice containing hypomorphic alleles of pygopus 2 (Pygo2 or mpygo2) and uncover a beta-catenin-independent involvement of the Pygo2 protein in spermiogenesis. Pygo2 is expressed in elongating spermatids at stages when chromatin remodeling occurs, and block of Pygo2 function leads to spermiogenesis arrest and consequent infertility. Analysis of spermiogenesis in Pygo2 mutants reveals reduced expression of select post-meiotic genes including protamines, transition protein 2, and H1fnt, all of which are required for germ cell chromatin condensation, and drastically altered pattern of histone H3 hyperacetylation. These findings suggest that Pygo2 is involved in the chromatin remodeling events that lead to nuclear compaction of male germ cells.

Effect of germ cell depletion on levels of specific mRNA transcripts in mouse Sertoli cells and Leydig cells

It has been shown that testicular germ cell development is critically dependent upon somatic cell activity but, conversely, the extent to which germ cells normally regulate somatic cell function is less clear. This study was designed, therefore, to examine the effect of germ cell depletion on Sertoli cell and Leydig cell transcript levels. Mice were treated with busulphan to deplete the germ cell population and levels of mRNA transcripts encoding 26 Sertoli cell-specific proteins and 6 Leydig cell proteins were measured by real-time PCR up to 50 days after treatment. Spermatogonia were lost from the testis between 5 and 10 days after treatment, while spermatocytes were depleted after 10 days and spermatids after 20 days. By 30 days after treatment, most tubules were devoid of germ cells. Circulating FSH and intratesticular testosterone were not significantly affected by treatment. Of the 26 Sertoli cell markers tested, 13 showed no change in transcript levels after busulphan treatment, 2 showed decreased levels, 9 showed increased levels and 2 showed a biphasic response. In 60% of cases, changes in transcript levels occurred after the loss of the spermatids. Levels of mRNA transcripts encoding Leydig cell-specific products related to steroidogenesis were unaffected by treatment. Results indicate (1) that germ cells play a major and widespread role in the regulation of Sertoli cell activity, (2) most changes in transcript levels are associated with the loss of spermatids and (3) Leydig cell steroidogenesis is largely unaffected by germ cell ablation.

Transcriptional regulation of the FSH receptor: new perspectives

The cell-surface receptor for the gonadotropin follicle-stimulating hormone (FSH) is expressed exclusively on Sertoli cells of the testis and granulosa cells of the ovary. FSH signal transduction through its receptor (Fshr) is critical for the timing and maintenance of normal gametogenesis in the mammalian gonad. In the 13 years since the gene encoding Fshr was first cloned, the mechanisms controlling its transcription have been extensively examined, but a clear understanding of what drives its unique cell-specificity remains elusive. Current knowledge of basal Fshr transcription highlights the role of an E-box in the proximal promoter which is bound by the basic helix-loop-helix transcription factors upstream stimulatory factor 1 (Usf1) and Usf2. Recent studies utilizing knockout mice and chromatin immunoprecipitation validated the importance of Usf to Fshr transcription and demonstrated a sexually dimorphic requirement for the Usf proteins to maintain normal Fshr expression. Studies have also shown that the promoter region itself is insufficient for appropriate Fshr expression in transgenic mice, indicating Fshr transcription depends on regulatory elements that lie outside of the promoter. Identification of such elements has been propelled by recent availability of genome sequence data, which facilitated studies using comparative genomics, DNase I hypersensitivity mapping, and transgenic analysis with large fragments of DNA. This review will focus on the current understanding of transcriptional regulatory processes that control expression of rat Fshr, including recent advances from our laboratory.

The radiation-induced block in spermatogonial differentiation is due to damage to the somatic environment, not the germ cells

Radiation and chemotherapeutic drugs cause permanent sterility in male rats, not by killing most of the spermatogonial stem cells, but by blocking their differentiation in a testosterone-dependent manner. However, it is not known whether radiation induces this block by altering the germ or the somatic cells. To address this question, we transplanted populations of rat testicular cells containing stem spermatogonia and expressing the green fluorescent protein (GFP) transgene into various hosts. Transplantation of the stem spermatogonia from irradiated adult rats into the testes of irradiated nude mice, which do not show the differentiation block of their own spermatogonia, permitted differentiation of the rat spermatogonia into spermatozoa. Conversely transplantation of spermatogonial stem cells from untreated prepubertal rats into irradiated rat testes showed that the donor spermatogonia were able to colonize along the basement membrane of the seminiferous tubules but could not differentiate. Finally, suppression of testosterone in the recipient irradiated rats allowed the differentiation of the transplanted spermatogonia. These results conclusively show that the defect caused by radiation in the rat testes that results in the block of spermatogonial differentiation is due to injury to the somatic compartment. We also observed colonization of tubules by transplanted Sertoli cells from immature rats. The present results suggest that transplantation of spermatogonia, harvested from prepubertal testes to adult testes that have been exposed to cytotoxic therapy might be limited by the somatic damage and may require hormonal treatments or transplantation of somatic elements to restore the ability of the tissue to support spermatogenesis.

Effects of FSH receptor deletion on epididymal tubules and sperm morphology, numbers, and motility

Follicle stimulating hormone (FSH) interacts with its cognate receptor (R) on Sertoli cells within the testis and plays an important role in the maintenance of spermatogenesis. Male FSH-R knockout (FORKO) mice show fewer Sertoli cells and many that are structurally abnormal and as a consequence fewer germ cells. Lower levels of serum testosterone (T) and androgen binding protein (ABP) also occur, along with reduced fertility. To assess the effects of FSH-R depletion as an outcome of testicular abnormalities, sperm from the cauda epididymidis were counted and examined ultrastructurally. As reduced fertility may also reflect changes to the epididymis, the secondary responses of the epididymis to lower T and ABP levels were also examined by comparing differences in sizes of epididymal tubules in various regions of FORKO and wild type (WT) mice. Sperm motility was evaluated in FORKO mice and compared to that of WT mice by computer assisted sperm analysis (CASA). Quantitatively, the data revealed that epithelial areas of the caput and corpus epididymidis were significantly smaller in FORKO mice compared to WT mice. Cauda epididymal sperm counts in FORKO mice were also much lower than in WT mice. This resulted in changes to 9 out of 14 sperm motility parameters, related mostly to velocity measures, which were significantly lower in the FORKO mice. The greatest change was observed relative to the percent static sperm, which was elevated by 20% in FORKO mice compared to controls. EM analyses revealed major changes to the structure of the heads and tails of cauda luminal sperm in FORKO mice. Taken together these data suggest a key role for the FSH receptor in maintaining Sertoli cells to sustain normal sperm numbers and proper shapes of their heads and tails. In addition, the shrinkage in epididymal epithelial areas observed in FORKO mice likely reflect direct and/or indirect changes in the functions of these cells and their role in promoting sperm motility, which is noticeably altered in FORKO mice.

Effects of follicle-stimulating hormone and androgen on proliferation of cultured testicular germ cells of embryonic chickens

A germ-Sertoli cell coculture model was established to study effects of follicle-stimulating hormone (FSH) and testosterone (T) on testicular germ cell proliferation of the embryonic chickens. Germ and somatic cells were dispersed from 18-day-old embryonic testes and cultured in 96-well plates. Germ cells were characterized by expression of stem cell factor receptor c-kit. Germ cell proliferation was assessed by an increase in cell number and expression of proliferating cell nuclear antigen (PCNA). Results showed that the germ and Sertoli cells kept alive in serum-free McCoy's 5A medium supplemented with insulin, transferrin, and selenite (ITS medium). Germ cells adhered to the free surface of Sertoli cells that spread the filopodia and formed a monolayer in ITS medium. In the serum-containing medium, Sertoli cells displayed an increment with a flat squamous form and only a few very large germ cell masses were found in the free surface of Sertoli cells. Many germ cells showed apoptosis in the McCoy's 5A medium without ITS or serum. Only germ cells showed positive staining for c-kit in the coculture. Ovine FSH (0.25-1.0 IU/ml) significantly increased the number of germ cells, and PCNA-labeling index (P < 0.05). FSH also induced stronger c-kit expression compared with the control. In the FSH-treated groups, germ cells were manifested distinct knob-like form. Similar stimulating effect was found in the germ cell number by T treatments (10(-7)-10(-6)M). Furthermore, FSH (0.5 IU/ml) combined with T significantly promoted higher testicular germ cell proliferation (P < 0.05) compared with either FSH or T alone, which indicated that interaction of FSH and T might be additive. The above results showed that the serum-free germ-Sertoli cell coculture model allowed evaluating hormonal regulation of testicular germ cell proliferation. FSH and T promoted testicular germ cell proliferation probably through indirect effects on Sertoli cells.

Regulation of Sertoli cell number and activity by follicle-stimulating hormone and androgen during postnatal development in the mouse

The roles of FSH and androgen in the postnatal development of Sertoli cell number and function have been investigated using mice that lack FSH (FSHbetaKO), FSH-receptors (FSHRKO), or androgen receptors (Tfm). At birth and d 5, Sertoli cell number was normal in FSHRKO and FSHbetaKO mice, but was significantly reduced on d 20 and in adulthood. In contrast, Sertoli cell number was reduced at birth in Tfm mice and remained significantly less than normal up to adulthood. Sertoli cell activity was determined through measurement of 11 different mRNA transcript levels. From birth to adulthood, the expression of most transcripts increased, with a significant rise occurring between d 5 and 10. In animals lacking FSH stimulation, mRNA expression (measured per Sertoli cell) was largely normal on d 5, but was reduced in seven transcripts on d 20 and in five transcripts at adulthood. In Tfm mice two transcripts showed reduced expression on d 5, and four were reduced on d 20, although expression in adult Tfm mice did not differ from that in normal cryptorchid controls. The results show that 1) testosterone, but not FSH, is required for Sertoli cell proliferation during fetal and early neonatal life; 2) FSH and testosterone both regulate the late stages of Sertoli cell proliferation; 3) FSH has a general trophic effect on Sertoli cell activity in the pubertal and adult mouse; and 4) androgens are required for specific transcript expression during prepubertal development. Specific effects of androgens were not seen in the adult, although these may be masked by the effects of cryptorchidism.

beta-estradiol 3-benzoate affects spermatogenesis in the adult mouse

beta-estradiol 3-benzoate (E(2)B) (10, 16, 20, 40, 80 and 160 microg/kg body weight) was administered daily to experimental groups of adult mice for the following periods; 2, 3 days, 1, 2, 4, and 8 weeks. Morphological changes in the testes were observed by both light and electron microscopy. Exfoliation of the germ cells was observed in the lumen of the seminiferous tubule. The spermatogenic cycle, especially stage XII, was disordered. Spermatids older than step 6 were severely affected. Detected abnormalities in the spermatids were deformation of the nucleus and acrosome. Partial deletion in the Sertoli-spermatid ectoplasmic specialization was also observed. Germ cells younger than step 7 spermatids were not affected morphologically. These abnormalities were not detected in the mice treated with the chemical at less than 16 microg/kg body weight. It is concluded that the chemical seems to affect round spermatids metabolically, but the morphological effect can be detected only from the spermatids older than step 6. The effects of the chemical on adult mice were reversible.

Localization of human follicle-stimulating hormone in the testis

Localization of the follicle-stimulating hormone (FSH) molecule and its receptor (FSHR), as well as the role of FSH in Sertoli cell mitosis and maturation, has been demonstrated by several investigators in human and murine testis by detecting the localization of anti-FSH antibodies or [(131)I]-labeled FSH and by detecting FSH receptor (FSHR) mRNA by in situ hybridization, or FSHR by anti-FSHR antibodies. The presence of FSH in germinal cells is controversial or, in humans, excluded. We have investigated the distribution of the human FSH molecule and its receptor in human and mouse testicular cells under different experimental conditions, at the submicroscopical level, by using a better antigenicity conservative procedure. Thus, the distribution of FSH and of the messenger RNA for its receptor in Sertoli cells has now been clarified. In germinal cells, our observations demonstrate the presence of FSH and the FSHR mRNA: the first on the plasma membrane and in endocytotic vesicles, and the second scattered in the cytoplasm. The cells presenting the higher amount of positivity ranged from spermatogonia to spermatocytes, including round spermatids. Penetration was by the endocytosis via membrane vesicles in which the FSHR is present, whereas its messenger is largely present in the cytoplasm and is responsible for the binding and subsequent internalization of the FSH molecule. As a control, human FSH was administered in vitro to the Y1 mouse cell line, which was stably transfected with cDNA for FSHR and devoid of endogenous FSH. The FSH molecule has been localized by monoclonal antibodies on plasma membranes and vesicles, and the FSHR mRNA was found scattered in the cytoplasm after in situ hybridization. We can now conclude that FSH is present in Sertoli cells and in round germinal cells, both expressing the FSHR. FSH penetrates in a similar way in both kinds of cells via endocytosis, and is therefore subsequently localized in the same membranous organelles.

Tamoxifen-induced light and electron microscopic changes in the rat testicular morphology and serum hormonal profile of reproductive hormones

The effects of oral administration of tamoxifen at doses of 40 and 200 micrograms/kg/day on testicular histology, testicular ultrastructure and serum hormonal profile were studied. The drug was administered to adult male rats over a period of 90 days and the effect was assessed at 10-day intervals. The morphometry, microscopic structures of the testis, including ultrastructure and daily sperm production rate, were evaluated. The hormone profiles of luteinizing hormone (LH), follice-stimulating hormone (FSH), testosterone, and estradiol were studied. The testes from treated animals showed disorganization of tubular elements with increased intercellular space. At day 50, the changes were extensive including presence of phagosomes. Morphometric studies showed a reduction in the spermatid and spermatozoan population (69.3%) with no changes in tubular diameter. The mean Leydig cell area was significantly lowered at day 50, at both doses. The daily sperm production rate was reduced as compared with controls. An array of degenerative changes were revealed by ultrastructural studies. The changes were extensive at day 50 at both doses. The characteristic features were lost in most of the cells with phagolysosomes becoming abundant. The cytoplasm of the cells was dense with poorly defined cytoplasmic organelles. Circulating LH levels were not modified at the 40 micrograms/kg/day dose but at 200 micrograms/kg/day, LH levels were significantly decreased. Initial transitory rise in FSH was seen with both doses. Both doses of tamoxifen decreased testosterone levels. Changes in the circulating estradiol levels were inconsistent, and no apparent relationship between dose and days of treatment was observed. Thus, this study supports our thesis of tamoxifen as a potential male contraceptive agent.

Endocrine control of germ cell proliferation in the primate testis. What do we really know?

The present chapter reviews current knowledge concerning hormonal regulation of gametogenesis in the primate testis. LH/testosterone and FSH are the prime regulators of primate spermatogenesis. Although either hormone is capable of stimulating all phases of the spermatogenic process including the formation of sperm, the combination of both hormones is necessary in most instances to achieve quantitatively normal germ cell numbers. Sertoli cell proliferation can also be induced by either hormone in juvenile monkeys. Evidence for differential effects of testosterone and FSH on gametogenesis, however, is lacking and a synergistic effect is observed when they are combined. Receptors for androgens and FSH occur exclusively on testicular somatic cells and, hence, the trophic effects of these hormones on germ cell numbers are indirect ones. Interestingly, both hormones seem to have a common target, the spermatogonial population but it is unknown how such an indirect albeit highly specific effect is mediated. Whether the trophic hormone action influences germ cell numbers via increased proliferation or decreased cell death or both remains to be seen. There is evidence to suggest that the local androgen requirements for primate spermatogenesis might be comparatively high.

Expression of the preoptic regulatory factor-1 and -2 genes in rat testis. Developmental and hormonal regulation

Hormone-responsive peptides play a vital role in development and regulation of testicular function. The preoptic regulatory factors, porf-1 and porf-2, were originally discovered in the rat brain, but are also expressed in the rat and human testis. In the brain expression is age-related, hormone-responsive, region- specific, and gender-related, suggesting that porf-1 and porf-2 are involved in gender-specific brain development and function. Tissue-specific porf-1 and porf-2 mRNAs are also found in the testis and hypophysectomy may alter testicular porf-2 expression. It was thus of interest to further examine porf-1 and porf-2 expression in the testis to evaluate their potential as hormone-responsive peptides that regulate testicular development and function. Testicular expression of both porf-1 and -2 was analyzed as a function of maturational stage, aging and hypophysectomy by the solution hybridization/nuclease protection assay, and cellular location determined by in situ hybridization histochemistry. Expression was quantitatively compared in normal male rats at 15, 30 and 60 d (n = 4) and at 2, 6, 12, and 24 mo of age (n = 5). During development porf-1 is expressed at a constant level at 15, 30 and 60 d, then declines significantly with advancing age; levels at 24 mo are only 20% of those seen at 2 mo (p < 0.05). In contrast, porf-2 expression is highest at 15 d of age and steadily declines at 30 and 60 d, plateaus in the mature adult (6 and 12 mo), then exhibits an additional significant decline in the aged 24 mo animals (6 vs 24 mo, p < 0.05). Hypophysectomy of young adult rats at day 42 results in increased testicular expression 12 d later of both porf-1 (p < 0.05) and porf-2(p < 0.005) compared to intact 54-d-old rats (n = 5). In situ hybridization histochemistry confirms that both porf-1 and porf-2 are expressed in the mature testis at 60 d of age. Porf-2 mRNA is localized to immature germ cells including spermatogonia and primary spermatocytes. Porf-1 mRNA is associated with mature sperm and at low levels in the Sertoli cell cytoplasm surrounding spermatocytes. These data suggest that porf-2 is a pituitary hormone-responsive factor in the developing testis and that both porf-1 and porf-2 have cell-type specific functions in the germ cell compartment of the mature testis

Effects of pure human follicle-stimulating hormone (pFSH) on sperm quality correlate with the hypophyseal response to gonadotrophin-releasing hormone (GnRH)

In 41 men with idiopathic infertility, the effect of pure follicle-stimulating hormone (pFSH) therapy on semen parameters was evaluated in relation to the results of the gonadotrophin-releasing hormone (GnRH) stimulation test in an open study. The patients showed a mean (+/-standard error) sperm concentration of 15.84 (+/-2.87) Mill. ml-1, 41.02 (+/-4.19)% of the spermatozoa were motile and 46.16 (+/-2.36)% normomorph before treatment. All patients were administered 150 IU pFSH subcutaneously three times weekly for 10 weeks. After therapy with pFSH, no significant differences compared with the pre-treatment sperm characteristics were observed (P > 0.05) except for the velocity average path, VAP (P = 0.029). However, the stimulation factors of FSH in the GnRH test showed a significantly negative correlation with the pFSH mediated improvement of sperm concentration (r = -0.662, P = 0.000002), of percentage of normomorph spermatozoa (r = -0.480, P = 0.0015) and total count of motile spermatozoa per ejaculate (r = -0.567, P = 0.00014). In consequence, the patients were divided into two groups depending on the stimulation factor of hypophyseal FSH secretion, FSH-SF. The cut-off point of the FSH-SF was set at 1.7 because the correlation analyses detected a 1.5-fold improvement of sperm parameters at this hypophyseal response on average. Pure FSH treatment increased the concentration of spermatozoa (P = 0.0007), the total count of motile spermatozoa in the ejaculate (P = 0.015) as well as the computer-aided sperm motion parameters VAP (P = 0.029) and velocity curve linear, VCL (P = 0.049) in patients with FSH-SF < 1.7, whereas in the patient group with FSH-SF > 1.7 no improvement of semen parameters was found. Insufficient stimulation of hypophyseal FSH secretion may be a prerequisite but not a guarantee for responsiveness to pFSH treatment. The results of the present investigation suggest that FSH stimulation in the GnRH test should be taken into account in idiopathic infertile men before pFSH therapy.

Expression of follicle stimulating hormone-receptor mRNA during gonadal development

Receptors for follicle-stimulating hormone (FSH) are found only in the gonads and have been localised to the Sertoli cells of the testis and the granulosa cells of the ovary. During gonadal development, functional signal transduction systems are present before gonadotrophin receptors appear indicating the expression of the receptors is the crucial step in development of gonadal responsiveness to gonadotrophins. The FSH receptor gene contains a single large exon which encodes the transmembrane and intracellular domains and nine smaller exons which encode most of the extracellular domain. In all species studied so far the FSH-receptor primary transcript has been shown to undergo alternate splicing. The function of these alternate transcripts is unclear but changes in alternate splicing appear to be associated with development of receptor mRNA expression. In the rat transcripts encoding only the extracellular domain of the receptor are detectable 2 days before transcripts encoding the full length receptor. In the mouse ovary FSH-receptor mRNA levels and alternate splicing has been measured during development. Results show that FSH-receptor mRNA is detectable in day 1 ovaries which contain only primordial follicles. At this stage mRNA levels are low but a significant increase in FSH-receptor mRNA is seen around day 5 when primary follicles first appear. This correlates with in situ hybridisation studies which first detect FSH-receptor transcripts in primary follicles. At all stages of development the level of transcripts encoding the extracellular domain was significantly greater than that encoding for the transmembrane and intracellular regions suggesting that significant levels of shortened transcripts are produced. In the hypogonadal (hpg) mouse which lacks circulating gonadotrophins levels of FSH-receptor mRNA appeared normal up to 15 days. This shows that gonadotrophins ar not require for development of FSH-receptor mRNA levels. Studies on FSH-receptor mRNA levels during granulosa cell luteinization show that there is complete loss of full-length transcripts soon after luteinization. Transcripts encoding the extracellular domain remain present, however, up to at least mid-cycle. Thus, changes in receptor transcript splicing during loss of FSH-receptors appear to mimic, in reverse, changes occurring during development. It may be that the FSH-receptor gene is constitutively expressed in follicular (pre-granulosa) cells, granulosa cells and granulosa-luteal cells but that control of RNA splicing regulates levels of full-length FSH-receptor transcript.

Quantification of androgen receptor and follicle-stimulating hormone receptor mRNA levels in human and monkey testes by a ribonuclease-protection assay

A sensitive, solution-hybridization ribonuclease-protection assay (RPA) was established to quantify the expression of mRNA for the androgen receptor (AR) and follicle-stimulating hormone receptor (FSHR) in total RNA samples isolated from tissues of the cynomolgous monkey, human testes obtained from elderly patients undergoing orchidectomy because of prostatic carcinoma or from transsexual men undergoing gender reassignment as well as human cell lines DU 145, REP and RVP. Sensitivity experiments revealed that, in the human and monkey, 1-2 micrograms of total RNA were sufficient to achieve quantifiable signals of the different receptor mRNA species. Quantification of AR and FSHR mRNA levels showed a 1.7-fold higher expression of AR mRNA and a 2.4-fold higher expression of FSHR mRNA in the monkey testes compared to human testes from patients with prostatic carcinoma. Normal spermatogenesis in both human and monkey testes indicated no relationship between spermatogenic status and receptor expression. The significantly lower expression of AR and FSHR mRNA in humans than in monkeys might therefore be either age- or species-related. Quantification of mRNA for AR and FSHR in the testis of the transsexual patients undergoing oestrogen and antiandrogen treatment displayed a drastic increase (4.5-fold) in mRNA for the AR, whereas mRNA for the FSHR was barely detectable. Due to its high sensitivity, reproducibility and its ability to quantify mRNA transcripts, the RPA is a useful tool for investigating expression of low abundant receptor genes and their regulation when only very small amounts of tissue are available. Furthermore, it is suitable for use in clinical and experimental studies in which accurate quantification of transcripts is necessary.

Hormonal control of spermatogenesis

FSH and testosterone (T) secretion are essential for the successful completion of spermatogenesis. Because there are no receptors for FSH or testosterone on germ cells, there are intermediate steps in this action, the nature of which are unknown. However, as the Sertoli cell contains receptors for both FSH and T, it is likely that these hormones exert their influence on germ cells by modulating Sertoli cell function. Both FSH and T exert synergistic actions on germ cells, but T has a specific action on the later stages of spermatid maturation. FSH, by its ability to stimulate Sertoli cell mitosis during testicular development, can influence the spermatogenic capacity of the adult testis.

Ontogeny of follicle-stimulating hormone receptor gene expression in the rat testis and ovary

The ontogeny of the follicle-stimulating hormone (FSH) receptor (R) gene expression was studied in the rat testis and ovary between day 12.5 or 14.5 of fetal life (f), respectively, and adulthood. In Northern blots hydbridized with a cRNA probe corresponding to a part of the extracellular domain of the FSHR, specific hybridization to testicular RNA was detected from day f18.5, and to ovarian RNA from postnatal day 7 onwards. The main transcripts in the testis were at all ages 7.0 kb and 2.5 kb in size. In the ovary, the main transcript was always 2.5 kb in size. In order to increase the sensitivity of mRNA detection, the FSHR gene expression was also analyzed using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique with primer pairs corresponding to the near full-length FSHR mRNA or to its extracellular domain. The specificity of the PCR products was verified by Southern hybridization using a nested 32P-labeled cDNA probe. The results indicated that the expression of the extracellular domain of the FSHR was first detected on day f14.5 in the testis and on day f20.5 in the ovary. The full-length mRNA appeared in both sexes 2 days later, which is in agreement with earlier measurements of appearance of FSHR binding in the rat testis (day f17.5) and ovary (day 3 post partum). In situ hybridization using an antisense cRNA probe for FSHR demonstrated that, as early in development as specific hybridization was detected, it was confined to the Sertoli cells in the testis and to granulosa cells in the ovary. When compared with the developmental onset of the LHR gene expression (our earlier data), a major difference was observed in the ovary; the message encoding the extracellular LHR domain appeared > 10 days earlier than that corresponding to the full-length LHR message. In the case of mRNAs for the testicular LHR, and for FSHR of both sexes, the difference between the developmental appearance of the truncated and full-length RNA forms was only 2 days.

Gonadotrophin control of testicular germ cell development

Successful and complete male germ cell development is dependent on the balanced, endocrine interplay of the hypothalamus, the pituitary and the testis. The hypothalamus secretes gonadotrophin-releasing hormone in a pulsatile manner which, in turn, elicits the pulsatile release of the gonadotrophins LH and FSH from the pituitary. Luteinizing hormone stimulates spermatogenesis indirectly via testosterone, whereas FSH acts directly on the seminiferous tubules. The synthesis and release of gonadotrophic hormones is under the feedback control of testosterone. Whether other testicular peptides such as inhibin and activin are also involved is not yet clear. Luteinizing hormone/testosterone and FSH are the prime regulators of germ cell development. On their own, these hormones are capable of exerting clear-cut stimulatory effects on the spermatogenic process. However, the quantitative production of spermatozoa generally requires the presence of both LH/testosterone and FSH. Since receptors for androgens and FSH are confined to the somatic cells of the testis, the trophic effects of these hormones on germ cells must be indirect. However, it is not known as yet precisely which genes/factors mediate the beneficial effects of androgens and FSH on spermatogenesis. The gonadotrophic hormones have been found in a number of isoforms and multiple transcripts of the LH and FSH receptor have been detected. Therefore, the possibility must be considered that certain forms of male infertility could be due to dysfunctional hormones and/or mutated receptors.

Localization of follicle-stimulating hormone (FSH) immunoreactivity and hormone receptor mRNA in testicular tissue of infertile men

Testicular biopsies from 82 oligo- or azoo-spermic male patients were subjected to immunostaining using anti-human FSH antibodies. Histological evaluation showed normal spermatogenesis (nspg) in 7 (FSH: (2.7 +/- 0.7), mixed atrophy (ma) in 63 (FSH:L 5.3 +/- 0.5), and bilateral or unilateral Sertoli Cell Only syndrome (SCO) in 12 (FSH: 21.7 +/- 3.5) patients. For the relationship between FSH values and testicular histology, see Bergmann et al. (1994). FSH immunoreactivity was found exclusively in Sertoli cells and in some interstitial cells. Seminiferous epithelium showing normal or impaired spermatogenesis displayed only weak immunoreactivity compared to intense immunoreaction, i.e. large and numerous vesicles in Sertoli cells of SCO tubules in biopsies showing mixed atrophy or SCO. In addition, h-FSH receptor mRNA was demonstrated by in situ hybridization using biotinylated cDNA antisense oligonucleotides. Hybridization signals were found within the seminiferous epithelium exclusively in Sertoli cell cytoplasm associated with normal spermatogenesis and in epithelia showing different signs of impairment, including SCO. It is concluded that: (1) Sertoli cells are the only cells within the seminiferous epithelium expressing FSH receptors; (2) the accumulation of FSH immunoreactivity in Sertoli cells of SCO tubules appears to be a sign of impaired Sertoli cell function.

Characterization of the 5' flanking region of the human follicle-stimulating hormone receptor gene

A genomic clone containing 2.3 kilobases (kb) of the 5' flanking region of the human follicle-stimulating hormone receptor (FSHR) plus the translated region of exon 1 and subsequent sequences of intron A has been isolated and characterized. This portion of the 5' flanking region has neither a TATA nor a CCAAT box and shows features of promoters seen in "housekeeping" genes. Using RNAse protection multiple transcriptional start sites could be identified, the major ones clustered between -114 and -79 bp. Chimeras containing 1486 bp of the 5' flanking region, or deletions thereof, expressed significant chloramphenicol acetyltransferase (CAT) activity when transiently transfected into Chinese hamster ovary (CHO), primary rat Sertoli and human granulosa-lutein cells. Deletion analyses indicated that a proximal promoter can be allocated to the region from -225 to -1 bp.

Regulation of gonadotropin receptor gene expression

The receptors for the gonadotropins differ from the other G protein-coupled receptors by having a large extracellular hormone-binding domain, encoded by nine or ten exons. Alternative splicing of the large pre-mRNA of approximately 100 kb can result in mRNA species that encode truncated receptor proteins. In this review we discuss the regulation of gonadotropin receptor mRNA expression and the possible roles of alternative splicing in gonadotropin receptor function.

Molecular cloning of a truncated isoform of the human follicle stimulating hormone receptor

Northern blot hybridization of human testicular poly (A)+ RNA to a human follicle stimulating hormone receptor probe revealed the existence of multiple mRNA transcripts. In order to investigate whether alternative splicing of the receptor occurs in the human testis we amplified the extracellular and the transmembrane domain of the human testicular follicle stimulating hormone receptor by reverse transcription polymerase chain reaction and subcloned the resulting DNA fragments. Sequence analysis of the recombinant clones revealed the existence of a truncated isoform of the human follicle stimulating hormone receptor which is spliced through a cassette exon mode without a change in the open reading frame, thereby deleting exon IX from the coding region of the receptor.