A comprehensive insight into the contribution of epigenetics in male infertility; focusing on immunological modifications.

Numerous recent studies have examined the impact epigenetics-including DNA methylation-has on spermatogenesis and male infertility. Differential methylation of several genes has been linked to compromised spermatogenesis and/or reproductive failure. Specifically, male infertility has been frequently associated with DNA methylation abnormalities of MEST and H19 inside imprinted genes and MTHFR within non-imprinted genes. Microbial infections mainly result in male infertility because of the immune response triggered by the bacteria' accumulation of immune cells, proinflammatory cytokines, and chemokines. Thus, bacterially produced epigenetic dysregulations may impact host cell function, supporting host defense or enabling pathogen persistence. So, it is possible to think of pathogenic bacteria as potential epimutagens that can alter the epigenome. It has been demonstrated that dysregulated levels of LncRNA correlate with motility and sperm count in ejaculated spermatozoa from infertile males. Therefore, a thorough understanding of the relationship between decreased reproductive capacity and sperm DNA methylation status should aid in creating new diagnostic instruments for this condition. To fully understand the mechanisms influencing sperm methylation and how they relate to male infertility, more research is required.

Evaluation of the relationships between oxidative stress, inflammation, hormonal status and sperm parameters in rats: Canonical correlation analysis.

Many endocrine or non-endocrine factors are involved in sperm production. Although reproductive hormones are very important for the initiation and maintenance of spermatogenesis, other factors, such as inflammation and oxidative stress, affect spermatogenesis. The aim of this study is to evaluate the relationships between sperm parameters and hormones, oxidative stress, and inflammation status. We conducted this study on 40 rats. Sperm parameters (motility, abnormal sperm rate, and dead sperm rate), oxidative stress (malondialdehyde, glutathione, glutathione peroxidase, and catalase), inflammation (NF-κß, TNF-α, IL-1ß, IL-6, and IL-10), and hormone parameters (follicle-stimulating hormone, luteinizing hormone, testosterone, melatonin, and corticosterone) were determined. Relationships between mentioned parameters were investigated by canonical correlation analysis. Canonical correlation coefficients for these data sets (sperm-oxidative stress, sperm-inflammation, and sperm-hormone parameters) were found to be strongly significant (rc= 0.875, p<0.001; rc= 0.868, p<0.001; rc= 0.886, p<0.001, respectively). The rate of explanation of oxidative stress, inflammation parameters and hormones by sperm parameters was 61.80 %, 56.10 % and 63.90 %, respectively. Canonical correlation analysis results have revealed that dead sperm rate is mostly related to nuclear factor-kappa beta (NF-κß), catalase, and corticosterone. CCA, which has taken into account the multiple relationships, has revealed that multidimensional evaluation of data sets can provide important and innovative information to researchers for the assessment of relationships between sperm, oxidative stress, inflammation, and hormone parameters.

Regulation of mammalian spermatogenesis by miRNAs.

Male fertility requires the continual production of sperm by the process of spermatogenesis. This process requires the correct timing of regulatory signals to germ cells during each phase of their development. MicroRNAs (miRNAs) in germ cells and supporting Sertoli cells respond to regulatory signals and cause down- or upregulation of mRNAs and proteins required to produce proteins that act in various pathways to support spermatogenesis. The targets and functional consequences of altered miRNA expression in undifferentiated and differentiating spermatogonia, spermatocytes, spermatids and Sertoli cells are discussed. Mechanisms are reviewed by which miRNAs contribute to decisions that promote spermatogonia stem cell self-renewal versus differentiation, entry into and progression through meiosis, differentiation of spermatids, as well as the regulation of Sertoli cell proliferation and differentiation. Also discussed are miRNA actions providing the very first signals for the differentiation of spermatogonia stem cells in a non-human primate model of puberty initiation.

The mechanisms and functions of microRNAs in mediating the fate determinations of human spermatogonial stem cells and Sertoli cells.

Human spermatogonial stem cells (SSCs) and Sertoli cells might have the applications in reproduction and regenerative medicine. Abnormal spermatogenesis results in male infertility, which seriously affects human reproduction and health. Spermatogenesis depends on the epigenetic and genetic regulation of male germ cells and somatic cells. A number of microRNAs (miRNAs) have been identified in human testicular tissues, and they are closely related to male fertility. Significantly, we and peers have recently demonstrated that numerous miRNAs are essential for regulating the self-renewal and apoptosis of human SSCs and Sertoli cells through controlling their mRNA and lncRNA targets. In this review, we critically discuss these findings regarding the important functions and mechanisms of miRNAs in mediating the fate determinations of human SSCs and Sertoli cells. Meanwhile, we illustrate the regulatory networks for miRNAs by forming the upstream and downstream regulators of mRNAs and lncRNAs in human SSCs, and we address that miRNAs regulate the decisions of Sertoli cells by targeting genes and via N6-methyladenosine (m6A). We also point out the future directions for further studies on this field. This review could offer an update on novel molecular targets for treating male infertility and new insights into epigenetic regulation of human spermatogenesis.

mTORC1/rpS6 and p-FAK-Y407 signaling regulate spermatogenesis: Insights from studies of the adjudin pharmaceutical/toxicant model.

In rodents and humans, the major cellular events at spermatogenesis include self-renewal of spermatogonial stem cells and undifferentiated spermatogonia via mitosis, commitment of spermatogonia to differentiation and transformation to spermatocytes, meiosis, spermiogenesis, and the release of spermatozoa at spermiation. While details of the morphological changes during these cellular events have been delineated, knowledge gap exists between the morphological changes in the seminiferous epithelium and the underlying molecular mechanism(s) that regulate these cellular events. Even though many of the regulatory proteins and biomolecules that modulate spermatogenesis are known based on studies using genetic models, the underlying regulatory mechanism(s), in particular signaling pathways/proteins, remain unexplored since much of the information regarding the signaling regulation is unknown. Studies in the past decade, however, have unequivocally demonstrated that the testis is using several signaling proteins and/or pathways to regulate multiple cellular events to modulate spermatogenesis. These include mTORC1/rpS6/Akt1/2 and p-FAK-Y407. While selective inhibitors and/or agonists and antagonists are available to examine some of these signaling proteins, their use have limitations due to their specificities and also potential systemic cytotoxicity. On the other hand, the use of genetic models has had profound implications for our understanding of the molecular regulation of spermatogenesis, and these knockout (null) models have also revealed the factors that are critical for spermatogenesis. Nonetheless, additional studies using in vitro and in vivo models are necessary to unravel the signaling pathways involved in regulating seminiferous epithelial cycle. Emerging data from studies, such as the use of the adjudin pharmaceutical/toxicant model, have illustrated that this non-hormonal male contraceptive drug is utilizing specific signaling pathways/proteins to induce specific defects in spermatogenesis, yielding mechanistic insights on the regulation of spermatogenesis. We sought to review these recent data in this article, highlighting an interesting approach that can be considered for future studies.

A laminin-based local regulatory network in the testis that supports spermatogenesis.

In adult rat testes, the basement membrane is structurally constituted by laminin and collagen chains that lay adjacent to the blood-testis barrier (BTB). It plays a crucial scaffolding role to support spermatogenesis. On the other hand, laminin-333 comprised of laminin-α3/ß3/γ3 at the apical ES (ectoplasmic specialization, a testis-specific cell-cell adherens junction at the Sertoli cell-step 8-19 spermatid interface) expressed by spermatids serves as a unique cell adhesion protein that forms an adhesion complex with α6ß1-integrin expressed by Sertoli cells to support spermiogenesis. Emerging evidence has shown that biologically active fragments are derived from basement membrane and apical ES laminin chains through proteolytic cleavage mediated by matrix metalloproteinase 9 (MMP9) and MMP2, respectively. Two of these laminin bioactive fragments: one from the basement membrane laminin-α2 chain called LG3/4/5-peptide, and one from the apical ES laminin-γ3 chain known as F5-peptide, are potent regulators that modify cell adhesion function at the Sertoli-spermatid interface (i.e., apical ES) but also at the Sertoli cell-cell interface designated basal ES at the blood-testis barrier (BTB) with contrasting effects. These findings not only highlight the physiological significance of these bioactive peptides that create a local regulatory network to support spermatogenesis, they also open a unique area of research. For instance, it is likely that several other bioactive peptides remain to be identified. These bioactive peptides including their downstream signaling proteins and cascades should be studied collectively in future investigations to elucidate the underlying mechanism(s) by which they coordinate with each other to maintain spermatogenesis. This is the goal of this review.

Male fertility during and after immune checkpoint inhibitor therapy: A cross-sectional pilot study.

BACKGROUND: Immune checkpoint inhibitors (ICIs) are widely used and may induce long-term survival in various types of cancer. Yet, there is scarce evidence on potential effects on patient fertility and the necessity of cryopreservation before treatment onset. The aim of our study was to assess the prevalence of male infertility after initiation of ICI treatment. METHODS: This is a monocenter, cross-sectional pilot study. Fertility was investigated by spermiogram, analysis of sexual hormones and questionnaires on sexual function and sexual activity. Male patients under the age of 60 years previously or currently treated with ICI for cutaneous malignancies or uveal melanoma were included. RESULTS: Twenty-five patients were included, with a median age of 49 years. Eighteen of 22 (82%) available spermiograms showed no pathologies, all patients reported a normal sexual function and sexual activity. Of four patients with pathological spermiogram, three patients were diagnosed with azoospermia and one with oligoasthenoteratozoospermia. Three patients had significant confounding factors (previous inguinal radiotherapy, chemotherapy and chronic alcohol abuse, and bacterial orchitis). One patient with normal spermiogram before ICI treatment presented 1 year after initiation with azoospermia, showing an asymptomatic, inflammatory infiltrate with predominantly neutrophil granulocytes, macrophages and T-lymphocytes in the ejaculate. Infectious causes were ruled out; andrological examination was unremarkable. A second case with reduced sperm counts during treatment may be ICI-induced also. CONCLUSIONS: Most patients had no restrictions in fertility, yet an inflammatory loss of spermatogenesis seems possible. Cryopreservation should be discussed with all patients with potential future desire for children before treatment.

Uropathogenic Escherichia coli Infection Compromises the Blood-Testis Barrier by Disturbing mTORC1-mTORC2 Balance.

The structural and functional destruction of the blood-testis barrier (BTB) following uropathogenic E. coli (UPEC) infection may be a critical component of the pathologic progress of orchitis. Recent findings indicate that the mammalian target of the rapamycin (mTOR)-signaling pathway is implicated in the regulation of BTB assembly and restructuring. To explore the mechanisms underlying BTB damage induced by UPEC infection, we analyzed BTB integrity and the involvement of the mTOR-signaling pathway using in vivo and in vitro UPEC-infection models. We initially confirmed that soluble virulent factors secreted from UPEC trigger a stress response in Sertoli cells and disturb adjacent cell junctions via down-regulation of junctional proteins, including occludin, zonula occludens-1 (ZO-1), F-actin, connexin-43 (CX-43), ß-catenin, and N-cadherin. The BTB was ultimately disrupted in UPEC-infected rat testes, and blood samples from UPEC-induced orchitis in these animals were positive for anti-sperm antibodies. Furthermore, we herein also demonstrated that mTOR complex 1 (mTORC1) over-activation and mTORC2 suppression contributed to the disturbance in the balance between BTB "opening" and "closing." More importantly, rapamycin (a specific mTORC1 inhibitor) significantly restored the expression of cell-junction proteins and exerted a protective effect on the BTB during UPEC infection. We further confirmed that short-term treatment with rapamycin did not aggravate spermatogenic degeneration in infected rats. Collectively, this study showed an association between abnormal activation of the mTOR-signaling pathway and BTB impairment during UPEC-induced orchitis, which may provide new insights into a potential treatment strategy for testicular infection.

SARS-COV-2 (Covid-19) and male fertility: Where are we?

Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), a single-stranded RNA virus, was found to be the causal agent of the disease called coronavirus disease. During December 2019, China informed the World Health Organization (WHO) of an outbreak of cases of pneumonia of unknown etiology, which caused severe-acute respiratory distress. The disease was termed coronavirus disease 2019 (Covid-19). Due to alarming levels of spread and severity, on the 11th of March 2020, the WHO declared the outbreak as a global pandemic. As of September 14, 2020, more than 29 million cases have been reported, with over 900,000 deaths globally. Since the outbreak, although not conclusive, discoveries have been made regarding the understanding of the epidemiology, etiology, clinical features, clinical treatment, and prevention of the disease. SARS-COV-2 has been detected in saliva, respiratory fluids, blood, urine, and faeces. Findings are however controversial regarding its presence in the semen or the testis. Hence, this review aimed to further analyse the literature concerning (i) the effects of previously identified human coronaviruses on male fertility (ii) the impact of Covid-19 on male fertility and (iii) the implication for general health in terms of infection and transmission.

Immuno-castration of female and male pigs with anti-gonadotrophin releasing hormone vaccine: Morphometric, histopathological and functional studies of the reproductive system.

Immuno-castration is increasingly recommended in pigs due to welfare reasons; however, there are few studies in females compared to males. This aim of this study was to investigate the effects of immuno-castration in female and male pigs. The weight, the morphometric and microscopic characteristics of the reproductive organs, and the hormone concentrations were studied in 12 immunocastrated females (IF) and 12 immunocastrated males (IM) and compared with control animals (C). At slaughter, IF tended to have greater body weights than CF (P =  0.051), whereas in IM and CM pigs there were not body weight differences (P =  0.140). The weight of the reproductive tract and size of all individual organs were less in IF compared with CF. Results from histological assessments indicated IF had more atretic follicles and a thinner endometrial mucosa than control females. Hormone concentrations were not different between CF and IF (P >  0.050). As a result of immuno-castration, there was impaired spermatogenesis in most males. Results from microscopic evaluations indicated there was a marked decrease of spermatogonial cells and size of Leydig cells in the testicles. Accessory gland structures were affected in CM and IM with there being differences in gross and microscopic characteristics. Testosterone concentrations, unlike estradiol, were different in IM compared to CM (P <  0.001). These results provide evidence that immuno-castration with the anti-gonadotrophin releasing hormone vaccine is effective in female and male pigs and induces morphological and endocrine changes incompatible with fertility.

Bacterial infection of the male reproductive system causing infertility.

Bacterial infections play a disruptive and hidden role in male reproductive failure. Different kinds of bacteria are often able to interfere with reproductive function in both sexes and lead to infertility. In this study, to further evaluate the role of bacterial infections in male reproduction we provided an extensive overview of so far researches investigating the effects of bacterial infections on male fertility. We searched Medline, PubMed, Scopus and Google scholar databases to identify the potentially relevant studies on bacterial infections and their implications in male infertility. All the bacteria included in this article have negative effects on the male reproductive function; however, there is ample evidence to blame bacteria such as Escherichia coli, Chlamydia trachomatis, Ureaplasma, Mycoplasma and Staphylococcus aureus for reduced fertility and deterioration of sperm parameters. More studies are needed to clarify the molecular mechanisms by which different bacteria exert their detrimental effects on male reproductive system. Getting more insight into probable mechanisms, would significantly facilitate the production of new, advanced, and effective remedies in the future. In view of all evidence, we strongly suggest increasing awareness among people and considering screening programs for patients seeking fertility both to avoid transmission and to improve fertility outcomes among them.

External and Genetic Conditions Determining Male Infertility.

We explain environmental and genetic factors determining male genetic conditions and infertility and evaluate the significance of environmental stressors in shaping defensive responses, which is used in the diagnosis and treatment of male infertility. This is done through the impact of external and internal stressors and their instability on sperm parameters and their contribution to immunogenetic disorders and hazardous DNA mutations. As chemical compounds and physical factors play an important role in the induction of immunogenetic disorders and affect the activity of enzymatic and non-enzymatic responses, causing oxidative stress, and leading to apoptosis, they downgrade semen quality. These factors are closely connected with male reproductive potential since genetic polymorphisms and mutations in chromosomes 7, X, and Y critically impact on spermatogenesis. Microdeletions in the Azoospermic Factor AZF region directly cause defective sperm production. Among mutations in chromosome 7, impairments in the cystic fibrosis transmembrane conductance regulator CFTR gene are destructive for fertility in cystic fibrosis, when spermatic ducts undergo complete obstruction. This problem was not previously analyzed in such a form. Alongside karyotype abnormalities AZF microdeletions are the reason of spermatogenic failure. Amongst AZF genes, the deleted in azoospermia DAZ gene family is reported as most frequently deleted AZF. Screening of AZF microdeletions is useful in explaining idiopathic cases of male infertility as well as in genetic consulting prior to assisted reproduction. Based on the current state of research we answer the following questions: (1) How do environmental stressors lessen the quality of sperm and reduce male fertility; (2) which chemical elements induce oxidative stress and immunogenetic changes in the male reproductive system; (3) how do polymorphisms correlate with changes in reproductive potential and pro-antioxidative mechanisms as markers of pathophysiological disturbances of the male reproductive condition; (4) how do environmental stressors of immunogenetic disorders accompany male infertility and responses; and (5) what is the distribution and prevalence of environmental and genetic risk factors.

Involvement of Asc and Nlrp3 inflammasomes in the testes following spinal cord injury.

OBJECTIVE: The exact mechanism, by which spinal cord injury (SCI) leads to a male subfertility is not well-known. Present study was conducted to determine the mechanisms that lead to the elevated end-product cytokines and inflammasomes in the testes of an SCI rat model. Moreover, we evaluated the inflammasome components following SCI in testis over a defined time periods. METHODS: Weight drop technique was used to induce SCI at the level of the T10 vertebra in male Wistar rats. The animals were sacrificed at specific time intervals (3, 7, 14, 21, and 28 day's post-SCI). mRNA levels of inflammasomes and cytokines were measured by real-time PCR, germ cells apoptosis was evaluated by TUNEL staining, and the epithelium of seminiferous tubules by Miller's and Johnsen's scores. RESULTS: The results showed activation of Nlrp3 in the testes of SCI animals at different time points. Expression of Nlrp3 and IL-1ß sharply increased 14 days after the SCI. Upregulation of IL-1ß and IL-18 at days 14 and 21 post-SCI might disintegrate the epithelium of seminiferous tubules at day 14 and induce germ cells apoptosis, increase abnormal sperm cells, and attenuate motility and viability at 21 days post-SCI. CONCLUSION: This study provided further evidence of innate immunity activation in testes that could lead to more disruption of spermatogenesis in SCI patients at specific times.

Repeated hormonal induction of spermiation affects the stress but not the immune response in pikeperch (Sander lucioperca).

Hormonal induction of spermiation, previously reported to be immunogenic in fishes, is a common hatchery practice in pikeperch, Sander lucioperca. The aim of the present study was to investigate the effects of repeated induction of spermiation in pikeperch, following application of either human chorionic gonadotropin (hCG) or salmon gonadoliberine analogue (sGnRHa) on sperm quality indices as well as on immune and stress response. Mature males of pikeperch (n = 7 per group) were stimulated twice with five days between injections of either hCG (hCG; 500 IU kg-1), sGnRHa (sGnRHa; 50 µg kg-1) or NaCl (control group; 1 ml kg-1) to assess spermatozoa motility with a computer-assisted sperm analysis (CASA) system. During second sampling, blood plasma was sampled for humoral innate immune (peroxidase and lysozyme activities, ACH50), stress (cortisol, glucose) and endocrine (testosterone) markers. In addition, the head kidney was dissected to assay the expression of several immune genes (such as il1, c3, hamp, tnf-α and lys genes). The results indicate that hormonal treatment significantly increased sperm production. Sperm sampled after the hormonal treatment maintained its quality throughout the study, regardless of the sampling time. However, it appears that the application of hCG induced elevated cortisol and glucose plasma levels compared to the control group. Almost all immune markers, except the relative expression of hepcidin (hamp gene), were unaffected by the two hormones applied. The results showed that the induction treatment of spermiation processes in pikeperch resulted in an important physiological stress response for which the intensity varied according to the hormonal agent used. However, this stress response (more profound following application of hCG) was weakly associated with innate immune functions. On the other hand, a significant negative correlation between the expression of several important immune markers (peroxidase activity, relative expression of c3 and il1 genes) and sperm quality indices indicates significant involvement of immune status on sperm quality. The results obtained shed light on immune-system-induced modifications to sperm quality. The data presented here highlight the need for careful revision of broodstock management and selection practices where welfare status as well as individual predispositions of fish to cope with the stress should be taken under the consideration.

Impairment of spermatogenesis and sperm motility by the high-fat diet-induced dysbiosis of gut microbes.

OBJECTIVE: High-fat diet (HFD)-induced metabolic disorders can lead to impaired sperm production. We aim to investigate if HFD-induced gut microbiota dysbiosis can functionally influence spermatogenesis and sperm motility. DESIGN: Faecal microbes derived from the HFD-fed or normal diet (ND)-fed male mice were transplanted to the mice maintained on ND. The gut microbes, sperm count and motility were analysed. Human faecal/semen/blood samples were collected to assess microbiota, sperm quality and endotoxin. RESULTS: Transplantation of the HFD gut microbes into the ND-maintained (HFD-FMT) mice resulted in a significant decrease in spermatogenesis and sperm motility, whereas similar transplantation with the microbes from the ND-fed mice failed to do so. Analysis of the microbiota showed a profound increase in genus Bacteroides and Prevotella, both of which likely contributed to the metabolic endotoxaemia in the HFD-FMT mice. Interestingly, the gut microbes from clinical subjects revealed a strong negative correlation between the abundance of Bacteroides-Prevotella and sperm motility, and a positive correlation between blood endotoxin and Bacteroides abundance. Transplantation with HFD microbes also led to intestinal infiltration of T cells and macrophages as well as a significant increase of pro-inflammatory cytokines in the epididymis, suggesting that epididymal inflammation have likely contributed to the impairment of sperm motility. RNA-sequencing revealed significant reduction in the expression of those genes involved in gamete meiosis and testicular mitochondrial functions in the HFD-FMT mice. CONCLUSION: We revealed an intimate linkage between HFD-induced microbiota dysbiosis and defect in spermatogenesis with elevated endotoxin, dysregulation of testicular gene expression and localised epididymal inflammation as the potential causes. TRIAL REGISTRATION NUMBER: NCT03634644.

Recombinant B2L and Kisspeptin-54 DNA Vaccine Induces Immunity Against Orf Virus and Inhibits Spermatogenesis In Rats.

Orf is a highly contagious zoonotic disease of small ruminants caused by Parapoxvirus. Kisspeptin, encoded by the KISS1 gene with its cognate receptor GPR-54 is recognized as an upstream orchestrator in the hypothalamic-pituitary-gonadal axis. This study was designed to construct a DNA vaccine that produces a fused peptide composed of a major immunodominant protein of the orf virus (B2L) and kisspeptin-54, a neuropeptide with recognized roles in mammalian reproductive biology. The administration of this recombinant vaccine is shown to produce a significant antibody and cell-mediated immune response directed against B2L compared to the control group (p < 0.05). Furthermore, we found that rats inoculated with PBK-asd vaccine up-regulated antigen-mediated splenocyte proliferation and significantly raised antigen-specific tumor necrosis factor-alpha (TNFα-), interferon-gamma (IFN-ϒ) and interleukin (IL-2) compared to the control group (p < 0.05). This recombinant vaccine also stimulated antibody responses to kisspeptin and decreased serum luteinizing hormone and testosterone levels. Moreover, the current recombinant vaccine caused testicular atrophy and arrested spermatogenesis. It is concluded that this recombinant B2L and Kisspeptin-54 vaccine could be a promising approach for construction of bivalent orf virus and immunocastration vaccine. Furthermore, we concluded that the orf virus envelope protein (B2L) could be used as an immunomodulator for kisspeptin-54 to produce a strong antibody response.

Unified single-cell analysis of testis gene regulation and pathology in five mouse strains.

To fully exploit the potential of single-cell functional genomics in the study of development and disease, robust methods are needed to simplify the analysis of data across samples, time-points and individuals. Here we introduce a model-based factor analysis method, SDA, to analyze a novel 57,600 cell dataset from the testes of wild-type mice and mice with gonadal defects due to disruption of the genes Mlh3, Hormad1, Cul4a or Cnp. By jointly analyzing mutant and wild-type cells we decomposed our data into 46 components that identify novel meiotic gene-regulatory programs, mutant-specific pathological processes, and technical effects, and provide a framework for imputation. We identify, de novo, DNA sequence motifs associated with individual components that define temporally varying modes of gene expression control. Analysis of SDA components also led us to identify a rare population of macrophages within the seminiferous tubules of Mlh3-/- and Hormad1-/- mice, an area typically associated with immune privilege.

Cytokines and male infertility.

Many male infertility cases have no apparent cause, being characterized as idiopathic. Both inflammation and obesity have long been associated with infertility. On one hand, inflammation, such as orchitis and male accessory gland infections (MAGIs), are regulated by inflammatory cytokines. The latter are also produced in the testis by Leydig and Sertoli cells, being associated with gap junctional communication at the blood-testis barrier. Furthermore, they regulate spermatogenesis through cell interaction, Toll-like receptors and production of reactive oxygen species. Additionally, they affect testosterone production, acting at many levels of the pituitary - gonadal axis. Any imbalance in their production may result in infertility. On the other hand, obesity has also been associated with infertility. Adipokines, cytokines produced by white adipose tissue, regulate the lipid and glucose metabolism and the inflammatory system. Recent data on leptin show that it regulates reproduction by adjusting hypothalamus - pituitary - gonadal axis at both the central and peripheral levels. In this regard, resistin, visfatin and the GH secretagogue peptic hormone ghrelin affect spermatogenesis, whereas data on adiponectin are rather scarce. In conclusion, inflammatory cytokines and adipokines seem to have a pivotal role in the regulation of spermatogenesis; any imbalance in this stable environment may lead to infertility. Nevertheless, further studies are needed to clarify their exact role.

Human testicular peritubular cells, mast cells and testicular inflammation.

In man, the wall of seminiferous tubules forms a testicular compartment, which contains several layers of smooth muscle-like, "myoid", peritubular cells and extracellular matrix. Its architecture and its cellular composition change in male infertility associated with impaired spermatogenesis. Increased deposits of extracellular matrix, changes in the smooth muscle-like phenotype of peritubular cells and accumulation of immune cells, especially mast cells, are among the striking alterations. Taken together, the changes indicate that inflammatory events take place in particular within this compartment. This short review summarises recent studies, which pinpoint possible mechanisms of the interplay between peritubular cells and mast cells, which may contribute to sterile inflammation and impairments of testicular function. These insights are based mainly on cellular studies, for which we used isolated human testicular peritubular cells (HTPCs), and on the examination of human testicular sections. Recent data on immunological properties of peritubular cells, unexpected roles of the extracellular matrix factor, biglycan, which is secreted by peritubular cells and functions of mast cell products (chymase, tryptase and ATP) are presented. We believe that the results may foster a better understanding of peritubular cells, their roles in the human testis and specifically their involvement in infertility.

Germ cell apoptosis and survival in testicular inflammation.

Male infertility is due to genetics, hormonal or environmental causes, or is idiopathic. Azoospermia is linked to local testicular microenvironment deregulation, with inflammatory cells present in the 15% of testicular biopsies of infertile patients. As widely reported, spermatogenesis and steroidogenesis are controlled by local immunoregulatory agents produced by immune and nonimmune cells. Moreover IL-6R, TNFR1, Fas and IL-1R are expressed on germ cells, indicating a direct action of pro-inflammatory agents on these cells. Beyond the known function of cytokines and nitric oxide on testicular function at the stable levels present in the normal testis, this review focalises on the effect of pro-inflammatory factors on germ cell survival and death when inflammatory conditions are established in the testis. As no cure for male infertility has been found up to the present, intracytoplasmic sperm injection is the therapeutic option for azoospermic patients who wish to achieve genetic parenthood. Therapies with antioxidant and anti-inflammatory agents in experimental models of testicular damage have been successful. However, clinical implementation is uncertain in cases with a prolonged inflammatory state of the testis. Therapies offering multiple approaches to treat infertility by restoring the spermatogonial stem cell niche and protecting germ cells from apoptosis should be considered.