Estrogenic regulation of testicular expression of stem cell factor and c-kit: implications in germ cell survival and male fertility

Molecular insights into Sertoli cell function: how do metabolic disorders in childhood and adolescence affect spermatogonial fate?

Male infertility is a major public health concern globally with unknown etiology in approximately half of cases. The decline in total sperm count over the past four decades and the parallel increase in childhood obesity may suggest an association between these two conditions. Here, we review the molecular mechanisms through which obesity during childhood and adolescence may impair future testicular function. Several mechanisms occurring in obesity can interfere with the delicate metabolic processes taking place at the testicular level during childhood and adolescence, providing the molecular substrate to hypothesize a causal relationship between childhood obesity and the risk of low sperm counts in adulthood.

Obesity and male fertility disorders

Often associated with obesity, male infertility represents a widespread condition that challenges the wellbeing of the couple. In this article, we provide a comprehensive and critical analysis of studies exploring the association between obesity and male reproductive function, to evaluate the frequency of this association, and establish the effects of increased body weight on conventional and biofunctional sperm parameters and infertility. In an attempt to find possible molecular markers of infertility in obese male patients, the numerous mechanisms responsible for infertility in overweight/obese patients are reviewed in depth. These include obesity-related functional hypogonadism, insulin resistance, hyperinsulinemia, chronic inflammation, adipokines, irisin, gut hormones, gut microbiome, and sperm transcriptome. According to meta-analytic evidence, excessive body weight negatively influences male reproductive health. This can occurr through a broad array of molecular mechanisms. Some of these are not yet fully understood and need to be further elucidated in the future. A better understanding of the effects of metabolic disorders on spermatogenesis and sperm fertilizing capacity is very useful for identifying new diagnostic markers and designing therapeutic strategies for better clinical management of male infertility.

Therapeutic modulation of KIT ligand in melanocytic disorders with implications for mast cell diseases

KIT ligand and its associated receptor KIT serve as a master regulatory system for both melanocytes and mast cells controlling survival, migration, proliferation and activation. Blockade of this pathway results in cell depletion, while overactivation leads to mastocytosis or melanoma. Expression defects are associated with pigmentary and mast cell disorders. KIT ligand regulation is complex but efficient targeting of this system would be of significant benefit to those suffering from melanocytic or mast cell disorders. Herein, we review the known associations of this pathway with cutaneous diseases and the regulators of this system both in skin and in the more well-studied germ cell system. Exogenous agents modulating this pathway will also be presented. Ultimately, we will review potential therapeutic opportunities to help our patients with melanocytic and mast cell disease processes potentially including vitiligo, hair greying, melasma, urticaria, mastocytosis and melanoma.

Dendrobium officinale polysaccharides improved reproductive oxidative stress injury in male mice treated with cyclophosphamide

Polysaccharides from Dendrobium officinale polysaccharides (DOPs) are the main bioactive components of Dendrobium officinale, which have the functions of antioxidation and immune regulation. However, it is not clear whether DOPs have any effect on the prevention of reproductive disorders induced by oxidative stress. The purpose of this study was to explore the protective effect of DOPs on reproductive oxidative stress injury in male mice and its possible mechanism. In this study, the mouse model of reproductive injury was established by intraperitoneal injection of cyclophosphamide (CTX). The reproductive function was evaluated by relative testicular mass, sperm parameters, and sex hormone levels. The oxidative stress level of male mice with reproductive injury treated with DOPs was analyzed by the levels of 8-hydroxydeoxyguanosine (8-OHdG), malondialdehyde (MDA), and nitric oxide (NO) in sperm. The expression of follicle-stimulating hormone receptor (FSHR) mRNA, androgen-binding (ABP) mRNA, and c-kit mRNA was detected by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) to explore its mechanism. After CTX administration, the sperm density, sperm motility, normal sperm morphology, and sex hormone levels in mice were significantly lower than those in the control group (P < 0.05). At the same time, the expression of p53 protein was upregulated, and the expression of Bcl-2 protein was downregulated (P < 0.05). In addition, the expression of FSHR and ABP mRNA on Sertoli cells was also significantly inhibited (P < 0.05). DOPs can effectively reduce the oxidative stress injury of testicular tissue. After DOP treatment, the sperm quality and sex-related hormone levels of mice were significantly improved and positively correlated with the dose of DOPs (P < 0.05). Administration of DOPs can reduce the damage caused by oxidative stress by reducing the level of oxidative stress, improving the hormone environment in testes, and regulating the expression of specific genes in Sertoli cells and spermatogenic cells.

Zuogui Wan improves spermatogenesis of GC1-spg cells through modulating AR-related pathways

Zuogui Wan (ZGW) is a common prescription medication used in traditional Chinese medicine (TCM) to significantly improve the sperm quality and treat male infertility. This study evaluated the repair effect of ZGW and Levocarnitine (LEV) on GC1-spg cell injury induced by Glucosides of Tripterygium WilforDII Hook (GTW). The results showed that the ultrastructure and apoptosis rate of GC1- spg cells in LEV and ZGW group were considerably better than GTW. The transcriptional and translational level of CYP1A1, CYP17A1, androgen receptor (AR), SRD5A2 and proliferating cell nuclear antigen (PCNA) in GC-1spg cells of the LEV group were considerably elevated than GTW group (p < 0.05 or 0.01). Furthermore, the transcriptional and translational levels of CYP19A1, CYP17A1, AR, SRD5A2 and PCNA in GC-1spg cells in ZGW group were found to be considerably elevated than the LEV group (p < 0.05 or 0.01). The findings indicate that ZGW and LEV could increase the expression of PCNA, CYP17A1, CYP19A1, SRD5A2 and AR at transcriptional and translational levels, inhibit GC-1spg cell apoptosis and promoting cell proliferation, and the effect of ZGW was found to be significantly better than that of LEV.

Expression of G-Protein-Coupled Estrogen Receptor (GPER) in Whole Testicular Tissue and Laser-Capture Microdissected Testicular Compartments of Men with Normal and Aberrant Spermatogenesis

Simple Summary

Nowadays, there is no doubt that estrogens play an important role in male reproduction, affecting testicular cell differentiation, proliferation, apoptosis and metabolism. It is also widely believed that intratesticular balance of androgens and estrogens is crucial for the testicular development and function and that the increased testicular estrogen production may be associated with spermatogenic failure. There is also growing epidemiological evidence that the exposure of men to endocrine disruptors demonstrating estrogenic activity (xenoestrogens) may lead to impairment of male fertility via interference with estrogen signaling pathways. Besides the two classical nuclear estrogen receptors, the membrane-bound G protein-coupled estrogen receptor (GPER) was described in human testicular tissue. However, there are little data on its expression in testes with disturbed spermatogenesis. In this study, we investigated the GPER expression pattern in biopsies of azoospermic men with complete and aberrant spermatogenesis. Our results showed an increased expression of the GPER in testes with impaired spermatogenesis. Moreover, they indicate a possible involvement of estrogen signaling through GPER in disturbed function of Sertoli cells—the cells that support spermatogenic process.

Abstract

In this study, we retrospectively investigated GPER expression in biopsies of azoospermic men with complete (obstructive azoospermia—OA) and aberrant spermatogenesis (nonobstructive azoospermia—NOA). Each biopsy was histologically evaluated with morphometry. The testicular GPER expression was analyzed by the immunohistochemistry and RT-PCR technique in the whole testicular tissue and in seminiferous tubules and Leydig cells after laser-capture microdissection. In laser-microdissected compartments, we also analyzed transcriptional expression of selected Leydig (CYP17A1, HSD17B3, StAR) and Sertoli cell (AMH, SCF, BMP4) function markers. Immunohistochemical staining revealed expression of GPER in the cytoplasm of Leydig and Sertoli cells. Its stronger intensity was observed in Sertoli cells of NOA biopsies. The RT-PCR analysis of the GPER mRNA level unequivocally showed its increased expression in seminiferous tubules (i.e., Sertoli cells), not Leydig cells in NOA biopsies. This increased expression correlated positively with the transcriptional level of AMH—a marker of Sertoli cell immaturity, as well as FSH serum level in NOA but not in the OA group. Our results clearly demonstrate altered GPER expression in testes with primary spermatogenic impairment that might be related to Sertoli cell maturity/function.

Sertoli Cell-Germ Cell Interactions Within the Niche: Paracrine and Juxtacrine Molecular Communications

Male germ cell development depends on multiple biological events that combine epigenetic reprogramming, cell cycle regulation, and cell migration in a spatio-temporal manner. Sertoli cells are a crucial component of the spermatogonial stem cell niche and provide essential growth factors and chemokines to developing germ cells. This review focuses mainly on the activation of master regulators of the niche in Sertoli cells and their targets, as well as on novel molecular mechanisms underlying the regulation of growth and differentiation factors such as GDNF and retinoic acid by NOTCH signaling and other pathways.

β-estradiol promotes the growth of primary human fetal spermatogonial stem cells via the induction of stem cell factor in Sertoli cells

BACKGROUND

Mammalian spermatogenesis is responsible for male fertility and is supported by the self-renewal and differentiation of spermatogonial stem cells (SSCs). Sertoli cells provide a supportive microenvironment for SSCs, in part by the production of stem cell factor (SCF), which is a potent regulator of spermatogonia proliferation and survival.

METHODS

We investigated the novel role of β-estradiol in modulating the proliferation and apoptosis of fetal SSCs via the regulation of SCF secretion in Sertoli cells isolated from human fetal testes. The proliferation of SSCs in the co-culture system was determined by colony formation and BrdU incorporation assays. TUNEL assay was used to measure SSC apoptosis in co-culture in response to treatment with control, β-estradiol, or the combination of β-estradiol and the estrogen receptor inhibitor ICI 182780.

RESULTS

In the system with purified human fetal Sertoli cells (MIS+/c-Kit-/AP-), β-estradiol upregulated the production of SCF in a dose- and time-dependent manner. In the co-culture system of primary human fetal SSCs (c-Kit+/SSEA-4+/Oct-4+/AP+) and Sertoli cells (MIS+), β-estradiol markedly increased the proliferation of SSCs. Moreover, SSC apoptosis was significantly inhibited by β-estradiol and was completely reversed by the combination of β-estradiol and ICI 182780.

CONCLUSION

Here we report, for the first time, that β-estradiol can induce the increase of SCF expression in human fetal Sertoli cells and regulates the growth and survival of human fetal SSCs. These novel findings provide new perspectives on the current understanding of the role of estrogen in human spermatogenesis.

Testicular Testosterone and Estradiol Concentrations and Aromatase Expression in Men with Nonobstructive Azoospermia

CONTEXT

Spermatogenesis is strictly regulated by the intratesticular hormonal milieu, in which testosterone (T) and estradiol (E2) play pivotal roles. However, the optimal expression of aromatase and intratesticular T (ITT) and E2 (ITE2) levels are unknown.

OBJECTIVE

To investigate ITT/ITE2 and aromatase expression in men with nonobstructive azoospermia (NOA) and to elucidate the roles of aromatase in spermatogenesis, as determined based on sperm retrieval by microdissection testicular sperm extraction (micro-TESE).

DESIGN AND SETTING

A retrospective study at a reproductive center using serum, testicular specimens, and intratesticular fluid.

PATIENTS

Seventy-six men with NOA, including 4 men who received 3 months of anastrozole administration prior to micro-TESE, and 18 men with obstructive azoospermia.

INTERVENTIONS

Testicular aromatase expression was evaluated using immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (RT-PCR). Intratesticular T and ITE2 levels were determined using liquid chromatography-tandem mass spectrometry.

RESULTS

Aromatase was mainly located in Leydig cells, and the levels of its transcript and protein expression levels were increased in men with NOA. No correlation was observed between serum T/E2 and ITT/ITE2 levels, whereas significant associations were observed between decreased ITT and increased ITE2, aromatase expression, and sperm retrieval. Treatment with anastrozole increased the ITT/ITE2 ratio and decreased aromatase expression.

CONCLUSIONS

A close association between the expression of aromatase in Leydig cells and ITT/ITE2 was shown. Leydig cell aromatase is a factor that is independently correlated with spermatogenesis, and aromatase inhibitors may open a therapeutic window by increasing ITT/ITE2 in selected patients.

Overexpression of regucalcin mitigates the ageing-related changes in oxidative stress and sperm quality

Age-related changes, namely the increase in oxidative stress (OS) with the consequent sperm damage, result in decreased male fertility. Regucalcin (RGN) is a Ca²⁺-binding protein that has been shown to have beneficial effects on spermatogenesis by suppressing OS and chemical/radiation-induced damage. This work aims to evaluate whether RGN overexpression reduces the ageing-associated decline of male reproductive function. Sperm and testicular function analysis were performed in young-adult and senescent transgenic rats overexpressing RGN (Tg-RGN) comparatively with their wild-type (Wt) littermates. The gonadosomatic index (GI), tubular differentiation index and the expression levels of RGN and other proliferation regulators were evaluated. Moreover, the sperm parameters, OS analysis and immunolocalization of RGN were assessed, as well as morphometric evaluation of epididymal tubules. Both GI and sperm counts were reduced in the senescent Wt rats, but maintained in the Tg-RGN. Also, the levels of stem cell factor (SCF), c-Kit, and Akt were maintained in the testis of aged Tg-RGN rats, suggesting that the normal spermatogenic output was preserved over time in these animals, an effect not observed in Wt. Senescent Tg-RGN rats also presented lower sperm lipid peroxidation and total oxidant status relative to the Wt. Furthermore, aged Tg-RGN rats displayed higher sperm viability, higher frequency of sperm with normal morphology, and reduced incidence of head and neck/midpiece defects when compared with Wt, which may be a consequence of the lower OS levels found in the sperm of these animals. Interestingly, RGN expression increased with ageing in sperm, being mainly localized in the acrosome. Altogether, these findings indicate that the modulation of RGN levels may alleviate the age-related decline in sperm quality and testicular function.

MiR-4485-3p expression reduced in spermatozoa of men with idiopathic asthenozoospermia

Asthenozoospermia (AZS), which characterised by reduced forward sperm motility, is a common cause of male infertility. Recently, mitochondrial dysfunction reported in AZS men came to attention for finding the molecular aetiology of AZS. Mitochondria-related microRNAs (miRNAs) are the most important regulators of mitochondrial function through post-transcriptionally modulation of gene expression. Therefore, this study aims to evaluate the expression of four recently reported mitochondrial-related miRNAs (miR-4485-3p/4484/4461 and 4463) in the sperm sample of asthenozoospermic men. RNA was extracted from spermatozoa of 74 volunteers (39 patients with idiopathic AZS and 35 controls with normal fertility), and relative gene expression analysis was performed by quantitative PCR. We used SNORD48 as a normaliser gene, and quantification was calculated by 2^-ΔΔCt method. The expression of miR-4484 and miR-4461 was not detected in the spermatozoa of cases and controls. However, miR-4485-3p (p = .006) was significantly downregulated in the AZS men compared with the controls, but the miR-4463 expression was not significantly different between the two groups (p = .5). Bioinformatic analysis identified three target genes for miR-4485-3p (DNAH1, KIT and PARK7) that are related to male infertility. In conclusion, the downregulation of miR-4485-3p was associated with idiopathic AZS, which could be a molecular link between mitochondrial dysfunction and AZS.

Serum estradiol levels in infertile men with non-obstructive azoospermia

PURPOSE

To report the different patterns of estradiol levels in infertile men with non-obstructive azoospermia and correlate these levels with their clinical and laboratory findings.

MATERIALS AND METHODS

A retrospective study was launched, and a retrieval of data for infertile men with non-obstructive azoospermia (n = 166) and fertile controls (n = 40) was performed. The retrieved data included demographics, clinical findings, scrotal duplex, semen analysis, and hormonal assay (testosterone, follicle-stimulating hormone, luteinizing hormone, prolactin, and estradiol).

RESULTS

Our findings showed a wide spectrum of estradiol concentrations. The patients were arranged into three groups (high, normal, and low estradiol groups). The normal estradiol group was the most prevalent (71.1%). Testosterone, gonadotrophins, testicular volumes, and the number of patients with jobs in polluted workplaces showed significant differences among the study groups (p = 0.001, <0.001, <0.001, and 0.004, respectively). Age, body mass index, varicocele prevalence, prolactin, and smoking habits did not show any significant differences among the groups. Obesity was lacking in the low estradiol group, but it had significantly higher prevalence in the normal (p = 0.013) or high group (p = 0.023) compared with the controls.

CONCLUSION

Serum estradiol, in infertile men with non-obstructive azoospermia, may be present at different levels. It is recommended that estradiol be measured in infertile men with non-obstructive azoospermia when there is an alteration in testosterone concentration, obesity, a polluted workplace occupation, or before trying hormonal therapy. Extended studies are highly recommended to provide a clear clue whether alterations in estradiol concentrations in men with non-obstructive azoospermia are the cause or a consequence of the condition.

KIT as a therapeutic target for non-oncological diseases

KIT is a receptor tyrosine kinase that after binding to its ligand stem cell factor activates signaling cascades linked to biological processes such as proliferation, differentiation, migration and cell survival. Based on studies performed on SCF and/or KIT mutant animals that presented anemia, sterility, and/or pigmentation disorders, KIT signaling was mainly considered to be involved in the regulation of hematopoiesis, gametogenesis, and melanogenesis. More recently, novel animal models and ameliorated cellular and molecular techniques have led to the discovery of a widen repertoire of tissue compartments and functions that are being modulated by KIT. This is the case for the lung, heart, nervous system, gastrointestinal tract, pancreas, kidney, liver, and bone. For this reason, the tyrosine kinase inhibitors that were originally developed for the treatment of hemato-oncological diseases are being currently investigated for the treatment of non-oncological disorders such as asthma, rheumatoid arthritis, and alzheimer's disease, among others. The beneficial effects of some of these tyrosine kinase inhibitors have been proven to depend on KIT inhibition. This review will focus on KIT expression and regulation in healthy and pathologic conditions other than cancer. Moreover, advances in the development of anti-KIT therapies, including tyrosine kinase inhibitors, and their application will be discussed.

Derivation of male germ cells from induced pluripotent stem cells by inducers: A review

Induced pluripotent stem cells (iPSCs) refer to stem cells that are artificially produced using a new technology known as cellular reprogramming, which can use gene transduction in somatic cells. There are numerous potential applications for iPSCs in the field of stem cell biology becauase they are able to give rise to several different cell features of lineages such as three-germ layers. Primordial germ cells, generated via in vitro differentiation of iPSCs, have been demonstrated to produce functional gametes. Therefore, in this review we discussed past and recent advances in the in vitro differentiation of germ cells using pluripotent stem cells with an emphasis on iPSCs. Although this domain of research is still in its infancy, exploring development mechanisms of germ cells is promising, especially in humans, to promote future reproductive and developmental engineering technologies. While few studies have evaluated the ability and efficiency of iPSCs to differentiate toward male germ cells in vitro by different inducers, the given effect was investigated in this review.

Disturbed testicular expression of the estrogen-metabolizing enzymes CYP1A1 and COMT in infertile men with primary spermatogenic failure: possible negative implications on Sertoli cells

Estradiol (E₂ ) is normally metabolized to hydroxyestradiols and methoxyestradiols by CYP1A1, CYP1B1 and COMT. However, an altered production of these metabolites by a disturbed expression of these enzymes is associated with reproductive and non-reproductive pathologies. In vitro studies suggest that increased hydroxyestradiols and methoxyestradiols intratesticular generation is related to male infertility, but no studies have explored whether infertile men have a disturbed testicular expression of the enzymes that generate these E₂ metabolites. The aim of this study was to assess CYP1A1, CYP1B1 and COMT testicular expression at mRNA and protein level in men with spermatogenic impairment. Seventeen men with primary spermatogenic failure (13 with Sertoli cell-only syndrome and four with maturation arrest) and nine controls with normal spermatogenesis were subjected to testicular biopsy. mRNA was quantified using real-time RT-PCR and protein expression was evaluated using western blot and immunohistochemistry followed by integrated optic density analysis. Besides, the effects of hydroxyestradiols and methoxyestradiols on testosterone-induced transcriptional activity were evaluated in TM4 cells using a luciferase reporter assay system. Our results show that patients with Sertoli cell-only syndrome had significantly elevated COMT expression at the mRNA level, higher COMT immunoreactivity in their seminiferous tubules and increased protein expression of the soluble COMT isoform (S-COMT), whereas patients with maturation arrest had significantly elevated CYP1A1 mRNA levels and higher CYP1A1 immunoreactivity in interstitial space. Finally, 2-hydroxyestradiol decreased testosterone-induced transcriptional activity in Sertoli cells in vitro. In conclusion, male infertility is related to disturbed testicular expression of the enzymes responsible for producing hydroxyestradiols and/or methoxyestradiols. If these changes are related with increased intratesticular hydroxyestradiols and methoxyestradiols concentrations, they could elicit an impaired Sertoli cell function. Our results suggest CYP1A1 and COMT as new potential targets in treating male infertility.

17β-Oestradiol promotes differentiation of human embryonic stem cells into dopamine neurons via cross-talk between insulin-like growth factors-1 and oestrogen receptor β

Human embryonic stem cells (hESCs) can self‐renew and differentiate into all cell lineages. E2 is known to exhibit positive effects on embryo development. Although the importance of E2 in many physiological processes has been reported, to date few researchers have investigated the effects of E2 on hESCs differentiation. We studied the effects of E2 on dopamine (DA) neuron induction of hESCs and its related signalling pathways using the three‐stage protocol. In our study, 0.1 μM E2 were applied to hESCs‐derived human embryoid bodies (hEBs) and effects of E2 on neural cells differentiation were investigated. Protein and mRNA level assay indicated that E2 up‐regulated the expression of insulin‐like growth factors (IGF)‐1, ectoderm, neural precursor cells (NPC) and DA neuron markers, respectively. The population of hESC‐derived NPCs and DA neurons was increased to 92% and 93% to that of DMSO group, respectively. Furthermore, yield of DA neuron‐secreted tyrosine hydroxylase (TH) and dopamine was also increased. E2‐caused promotion was relieved in single inhibitor (ICI or JB1) group partly, and E2 effects were repressed more stronger in inhibitors combination (ICI plus JB1) group than in single inhibitor group at hEBs, hNPCs and hDA neurons stages. Owing to oestrogen receptors regulate multiple brain functions, when single or two inhibitors were used to treat neural differentiation stage, we found that oestrogen receptor (ER)β but not ERα is strongly repressed at the hNPCs and hDA neurons stage. These findings, for the first time, demonstrate the molecular cascade and related cell biology events involved in E2‐improved hNPC and hDA neuron differentiation through cross‐talk between IGF‐1 and ERβ in vitro.

The protective effect of regucalcin against radiation-induced damage in testicular cells

AIMS

Regucalcin (RGN), a protein broadly expressed in the male reproductive tract, has shown to have beneficial effects on spermatogenesis suppressing chemical-induced apoptosis. This study aimed to evaluate whether RGN overexpression ameliorates the spermatogenic phenotype after radiation treatment.

MAIN METHODS

Transgenic rats overexpressing RGN (Tg-RGN) and their wild-type (Wt) counterparts were exposed to a single dose of X-rays (6Gy), and at ten weeks after irradiation, the testicular status and the epididymal sperm parameters were evaluated. The expression of RGN and several cell cycle and apoptosis regulators, the enzymatic activity of caspase-3, and RGN immunostaining were also assessed.

KEY FINDINGS

Tg-RGN animals displayed higher gonadosomatic index, and augmented sperm viability and motility relatively to their Wt counterparts after irradiation, as well as higher frequency of normal sperm morphology and a diminished incidence of head-defects. The differences in reproductive parameters were underpinned by a lower rate of apoptosis, as evidenced by the reduced activity of caspase-3, lower levels of caspase-8, and increased Bcl-2/Bax ratio in the testis of Tg-RGN animals. Supporting the involvement of RGN in the anti-apoptotic response, an enhanced expression of RGN was observed in irradiated rats.

SIGNIFICANCE

Transgenic-overexpression of RGN protected against radiation-induced testicular damage, which strengthens the role of this protein protecting cells from the damage of external agents. These findings also indicated that the modulation of RGN testicular levels would be a mechanism for fertility preservation in men undergoing oncological treatment.

Efficacy of naringenin against permethrin-induced testicular toxicity in rats

Permethrin (PM), a synthetic pyrethroid insecticide, has broad toxicity spectra. We aimed to investigate the effects of PM on the testes of adult albino rats, examine the recovery response and evaluate the efficacy of naringenin (NG) supplementation. Adult male albino rats were randomly assigned to five groups of six each: control, NG (50 mg/kg), PM (70 mg/kg), recovery (after subsequent withdrawal of PM) and NG-PM group. All treatments were given by oral gavage for 6 weeks and another 3 weeks for the recovery group. At the time of sacrifice, each testis was weighed. Biochemical analysis of epididymal sperm count and serum testosterone level was performed. Testes were processed for histological, ultrastructural and c-Kit immunohistochemical study. PM toxicity was evidenced by a highly significant decrease in testicular weight, epididymal sperm count and serum testosterone level compared to control. Furthermore, testicular structure abnormalities and reduced c-Kit immunoreactions were observed. Stoppage of PM in the recovery group partially reversed PM-induced changes. There was a mild decrease in testicular weight and biochemical parameters compared to control. The structure of seminiferous tubules was partially retained. The NG-PM group showed an overall improvement in testicular weight and biochemical alterations which were confirmed by light and electron microscopic examination. In conclusion, PM induced testicular toxicity, which was ameliorated by NG co-administration. However, stoppage of PM exposure was associated with partial recovery.

Late-onset hypogonadism: the advantages of treatment with human chorionic gonadotropin rather than testosterone

The traditional pharmacological treatment of patients with late onset hypogonadism (LOH) is represented by different formulations of testosterone (T) or alternatively by the extractive human chorionic gonadotropin (HCG). The hormone replacement treatment (HRT) is associated with the potential increase of hematocrit, serum concentrations of prostate-specific antigen (PSA) and prostate volume. Moreover, the gynecomastia represent a condition frequently associated with HRT. Recent evidences showed the role of leydig cells in the 25-hydroxylation of vitamin D and the elevated frequency of hypovitaminosis D among LOH patients. Finally, another important aspect of LOH is represented by the frequency of secondary infertility due to age or to traditional HRT. This study evaluated 40 LOH patients treated for 6 months with extractive HCG (n = 10 patients) and three different formulations of T: transdermal (n = 10 patients), undecaonate (n = 10 patients) and enantate (n = 10 patients). Hormonal, anthropometric, metabolic and sperm parameters were evaluated and compared. Moreover, the main safety parameters and the results of the main questionnaires were evaluated. After treatment, HCG group showed serum concentrations of 25-OH-vitamin D significantly higher (p < 0.05) and serum concentrations of oestrogens significantly lower (p < 0.05) compared with other groups. Moreover, they showed a mean value of hematocrit, PSA and prostate volume significantly lower (p < 0.05) compared with other groups. Finally, all the groups treated with T showed a significant reduction (p < 0.05) of sperm density and of percentage of spermatozoa with progressive motility compared with HCG group.

Aging-associated changes in oxidative stress, cell proliferation, and apoptosis are prevented in the prostate of transgenic rats overexpressing regucalcin

Regucalcin (RGN) is a calcium (Ca(2+))-binding protein that displays a characteristic downregulated expression with aging in several tissues. Besides its role in regulating intracellular Ca(2+) homeostasis, RGN has been associated with the control of oxidative stress, cell proliferation, and apoptosis. Thus, the diminished expression of RGN with aging may contribute to the age-associated deterioration of cell function. In the present study, we hypothesized that the maintenance of high expression levels of RGN may prevent age-related alterations in the processes mentioned previously. First, we confirmed that RGN expression is significantly diminished in the prostate of 8-, 9-, 12-, and 24-months wild-type rats. Then, the effect of aging on lipid peroxidation, antioxidant defenses, cell proliferation, and apoptosis in the prostate of wild-type controls and transgenic rats overexpressing RGN (Tg-RGN) was investigated. The activity of glutathione and the antioxidant capacity were increased in Tg-RGN rats in response to the age-associated increase in thiobarbituric acid reactive substances levels, an effect not seen in wild type. Overexpression of RGN also counteracted the effect of aging increasing prostate cell proliferation. In contrast to wild-type animals, the prostate weight of Tg-RGN did not change with aging and was underpinned by the diminished expression of stem cell factor and c-kit, and increased expression of p53. In addition, aged Tg-RGN animals displayed increased expression (activity) of apoptosis regulators, therefore not showing the age-induced resistance to apoptosis observed in wild type. Altogether, these findings indicate the protective role of RGN against the development of age-related pathologies, such as, for example, prostate cancer.

Estrogens down-regulate the stem cell factor (SCF)/c-KIT system in prostate cells: Evidence of antiproliferative and proapoptotic effects

The development of prostate cancer (PCa) is intimately associated with the hormonal environment, and the sex steroids estrogens have been implicated in prostate malignancy. However, if some studies identified estrogens as causative agents of PCa, others indicated that these steroids have a protective role counteracting prostate overgrowth. The tyrosine kinase receptor c-KIT and its ligand, the stem cell factor (SCF), have been associated with the control of cell proliferation/apoptosis and prostate carcinogenesis, and studies show that estrogens regulate their expression in different tissues, though, in the case of prostate this remains unknown. The present study aims to evaluate the role of 17β-estradiol (E2) in regulating the expression of SCF/c-KIT in human prostate cell lines and rat prostate, and to investigate the consequent effects on prostate cell proliferation and apoptosis. qPCR, Western Blot, and immuno(cito)histochemistry analysis showed that E2-treatment decreased the expression of SCF and c-KIT both in human prostate cells and rat prostate. Furthermore, the diminished expression of SCF/c-KIT was underpinned by the diminished prostate weight and reduced proliferation index. On the other hand, the results of TUNEL labelling, the increased activity of caspase-3, and the augmented expression of caspase-8 and Fas system in the prostate of E2-treated animals indicated augmented apoptosis in response to E2. The obtained results demonstrated that E2 down-regulated the expression of SCF/c-KIT system in prostate cells, which was associated with antiproliferative and proapoptotic effects. Moreover, these findings support the protective role of estrogens in PCa and open new perspectives on the application of estrogen-based therapies.

Paradoxical and contradictory effects of imatinib in two cell line models of hormone-refractory prostate cancer

BACKGROUND

Imatinib mesylate is a chemotherapeutic drug that inhibits the tyrosine kinase activity of c-KIT and has been successfully used to treat leukemias and some solid tumors. However, its application for treatment of hormone-refractory prostate cancer (HRPC) has shown modest effectiveness and did not follow the outcomes in cultured cells or animal models. Moreover, the molecular pathways by which imatinib induces cytotoxicity in prostate cancer cells are poorly characterized.

METHODS

Two cell line models of HRPC (DU145 and PC3) were exposed to 20 μM of imatinib for 6-72 hr. MTS assay was used to assess cell viability during the course of experiment. Gene expression analysis of c-KIT, cell-cycle and apoptosis regulators, and angiogenic factors was determined by means of real-time PCR, western blot, and/or immunocytochemistry. The enzymatic activity of the apoptosis effector, caspase-3, was determined by a colorimetric assay.

RESULTS

Imatinib significantly decreased the viability of DU145 cells but paradoxically augmented the viability of PC3 cells. DU145 cells displayed diminished expression of anti-apoptotic Bcl-2 protein and augmented levels of caspase-8 and -9, as well as, increased enzymatic activity of caspase-3 in response to imatinib. No differences existed on the expression levels of apoptosis-related proteins in PC3 cells treated with imatinib, though the activity of caspase-3 was decreased. The mRNA levels of angiogenic factor VEGF were decreased in DU145-treated cells, whereas an opposite effect was seen in PC3. In addition, it was shown that DU145 and PC3 cells present a differential expression of c-KIT protein variants.

CONCLUSION

DU145 and PC3 cells displayed a contradictory behavior in response to imatinib, which was underpinned by a distinct expression pattern (or activity) of target regulators of cell-cycle, apoptosis, and angiogenesis. The paradoxical effect of imatinib in PC3 cells may be related with the differential expression of c-KIT protein variants. Moreover, the present findings helped to understand the discrepancies in the efficacy of imatinib as therapeutic option in HRPC.

Oestrogens as apoptosis regulators in mammalian testis: angels or devils?

In the mammalian testis, spermatogenesis is a highly coordinated process of germ cell development, which ends with the release of ‘mature’ spermatozoa. The fine regulation of spermatogenesis is strictly dependent on sex steroid hormones, which orchestrate the cellular and molecular events underlying normal development of germ cells. Sex steroids actions also rely on the control of germ cell survival, and the programmed cell death by apoptosis has been indicated as a critical process in regulating the size and quality of the germ line. Recently, oestrogens have emerged as important regulators of germ cell fate. However, the beneficial or detrimental effects of oestrogens in spermatogenesis are controversial, with independent reports arguing for their role as cell survival factors or as apoptosis-inducers. The dual behaviour of oestrogens, shifting from ‘angels to devils’ is supported by the clinical findings of increased oestrogens levels in serum and intratesticular milieu of idiopathic infertile men. This review aims to discuss the available information concerning the role of oestrogens in the control of germ cell death and summarises the signalling mechanisms driven oestrogen-induced apoptosis. The present data represent a valuable basis for the clinical management of hyperoestrogenism-related infertility and provide a rationale for the use of oestrogen-target therapies in male infertility.

The SCF/c-KIT system in the male: Survival strategies in fertility and cancer

Maintaining the delicate balance between cell survival and death is of the utmost importance for the proper development of germ cells and subsequent fertility. On the other hand, the fine regulation of tissue homeostasis by mechanisms that control cell fate is a factor that can prevent carcinogenesis. c-KIT is a type III receptor tyrosine kinase activated by its ligand, stem cell factor (SCF). c-KIT signaling plays a crucial role in cell fate decisions, specifically controlling cell proliferation, differentiation, survival, and apoptosis. Indeed, deregulating the SCF/c-KIT system by attenuation or overactivation of its signaling strength is linked to male infertility and cancer, and rebalancing its activity via c-KIT inhibitors has proven beneficial in treating human tumors that contain gain-of-function mutations or overexpress c-KIT. This review addresses the roles of SCF and c-KIT in the male reproductive tract, and discusses the potential application of c-KIT target therapies in disorders of the reproductive system.

An oncofetal and developmental perspective on testicular germ cell cancer

Germ cell tumors (GCTs) represent a diverse group of tumors presumably originating from (early fetal) developing germ cells. Most frequent are the testicular germ cell cancers (TGCC). Overall, TGCC is the most frequent malignancy in Caucasian males (20-40 years) and remains an important cause of (treatment related) mortality in these young men. The strong association between the phenotype of TGCC stem cell components and their totipotent ancestor (fetal primordial germ cell or gonocyte) makes these tumors highly relevant from an onco-fetal point of view. This review subsequently discusses the evidence for the early embryonic origin of TGCCs, followed by an overview of the crucial association between TGCC pathogenesis, genetics, environmental exposure and the (fetal) testicular micro-environment (genvironment). This culminates in an evaluation of three genvironmentally modulated hallmarks of TGCC directly related to the oncofetal pathogenesis of TGCC: (1) maintenance of pluripotency, (2) cell cycle control/cisplatin sensitivity and (3) regulation of proliferation/migration/apoptosis by KIT-KITL mediated receptor tyrosine kinase signaling. Briefly, TGCC exhibit identifiable stem cell components (seminoma and embryonal carcinoma) and progenitors that show large and consistent similarities to primordial/embryonic germ cells, their presumed totipotent cells of origin. TGCC pathogenesis depends crucially on a complex interaction of genetic and (micro-)environmental, i.e. genvironmental risk factors that have only been partly elucidated despite significant effort. TGCC stem cell components also show a high degree of similarity with embryonic stem/germ cells (ES) in the regulation of pluripotency and cell cycle control, directly related to their exquisite sensitivity to DNA damaging agents (e.g. cisplatin). Of note, (ES specific) micro-RNAs play a pivotal role in the crossover between cell cycle control, pluripotency and chemosensitivity. Moreover, multiple consistent observations reported TGCC to be associated with KIT-KITL mediated receptor tyrosine kinase signaling, a pathway crucially implicated in proliferation, migration and survival during embryogenesis including germ cell development. In conclusion, TGCCs are a fascinating model for onco-fetal developmental processes especially with regard to studying cell cycle control, pluripotency maintenance and KIT-KITL signaling. The knowledge presented here contributes to better understanding of the molecular characteristics of TGCC pathogenesis, translating to identification of at risk individuals and enhanced quality of care for TGCC patients (diagnosis, treatment and follow-up).