Physiologic interactions between macrophages and Leydig cells

Chronic exposure to polystyrene microplastics induced LHR reduction and decreased testosterone levels through NF-κB pathway

The extensive utilization of plastic products in recent years has resulted in a significant contamination of microplastics (MPs). The ingestion of MPs by aquatic and terrestrial organisms facilitates their transmission to mammals through the food chain. Therefore, the toxicity of MPs has attracted widespread attention from researchers. Previous studies have shown a connection between being exposed to polystyrene MPs (PS-MPs) and issues with male reproductive function. Testosterone, a hormone essential for male reproductive function, is produced and secreted by specialized cells known as Leydig cells, which found in the testicular interstitium. In our prior research, we confirmed that exposure to PS-MPs caused a reduction in testosterone levels by interfering with the LH-mediated LHR/cAMP/PKA/StAR pathway, with LHR being pivotal in this mechanism. However, the molecular mechanism underlying PS-MPs-induced reduction of LHR remains unclear. In this study, mice were respectively given drinking water containing 1000 μg/L PS-MPs characterized by diameters of 0.5 μm, 4 μm, and 10 μm for a period of 180 days. Our findings indicated that exposure to PS-MPs resulted in the proliferation of macrophages as well as their polarization towards the M1 phenotype. Additionally, the presence of PS-MPs triggered the release of tumor necrosis factor alpha (TNF-α) from macrophages, thereby activating nuclear factor-κB (NF-κB) signaling pathway within Leydig cells. The translocation of NF-κB into nucleus facilitated its binding to the promoter region of LHR, which consequently led to the repression of LHR transcription. This transcriptional inhibition resulted in a subsequent suppression of testosterone synthesis and secretion. Overall, this study elucidates a theoretical basis for explaining the interference of PS-MPs on the testosterone synthesis and secretion in Leydig cells from the perspective of the interaction between cells in the testicular interstitium.

Role of serotonin, estrogen, and TNF-α in the paroxetine-impaired steroidogenesis and testicular macrophages polarization

BACKGROUND

Paroxetine, a selective serotonin reuptake inhibitor (SSRI) antidepressant, has caused male sexual dysfunction; however, the paroxetine mechanisms of action in testes are still unclear.

OBJECTIVES

Paroxetine serotonergic effects in testes were evaluated, focusing on steroidogenesis and the correlation between macrophages population and possible TNF-α-derived oxidative stress. We also verified whether the changes are reversible following treatment interruption.

MATERIALS AND METHODS

Adult rats received paroxetine (PG35 and PG65) or tap water (CG) for 35 days. PG65 was maintained without treatment for 30 more days. Intratesticular testosterone (IT), nitrite, and malondialdehyde concentrations were measured. To confirm serotonergic and estrogenic effects, Htr1b and Esr1 expressions were analyzed. The daily sperm production (DSP), frequency of abnormal seminiferous tubules (ST), SC number, ST area, and Leydig cells nuclear area (LCnu) were evaluated. TUNEL+ germ cells, M1 (CD68+ ), and M2 (Perls+ ) macrophages were quantified. 17β-HSD7, CYP19A1, NDRG2, oxytocin, TNF-α, and iNOS were evaluated by immunoreactions. Oxytocin and NDRG2 protein levels as well as Tnfa mRNA expression were also analyzed.

RESULTS

The Htr1b downregulation in testes confirmed the paroxetine serotonergic effect. The testicular sections showed abnormal ST frequency, ST atrophy and reduction of DSP, LCnu, SC number and Perls+ macrophages. TUNEL+ germ cells and LC were associated with strong NDRG2 immunoexpression. Paroxetine reduced IT levels and 17β-HSD7 immunoexpression in parallel to increased CYP19A1, oxytocin, TNF-α and iNOS. Esr1 and Tnfa overexpression and increased number of CD68+ macrophages were also observed together with high nitrite and malondialdehyde levels. Most parameters were not recovered in PG65.

CONCLUSIONS

Paroxetine serotonergic effect impairs LC steroidogenesis, via aromatization, increasing estrogen/testosterone ratio, which in turn upregulate NDRG2, promoting apoptosis, and impairing sperm production. Serotonin-estrogen pathways may be responsible for M2/M1 polarization, Tnfa upregulation, and induction of oxidative stress. The unrecovered testicular changes after treatment discontinuation are due to persistent paroxetine serotonin/estrogen effects.

Gasdermin D in macrophages drives orchitis by regulating inflammation and antigen presentation processes

Inflammation in the testes induced by infection and autoimmunity contributes significantly to male infertility, a public health issue. Current therapies using antibiotics and broad-spectrum anti-inflammatory drugs are ineffective against non-bacterial orchitis and induce side effects. This highlights the need to explore the pathogenesis of orchitis and develop alternative therapeutic strategies. In this study, we demonstrated that Gasdermin D (GSDMD) was activated in the testes during uropathogenic Escherichia coli (UPEC)-induced acute orchitis, and that GSDMD in macrophages induced inflammation and affected spermatogenesis during acute and chronic orchitis. In testicular macrophages, GSDMD promoted inflammation and antigen presentation, thereby enhancing the T-cell response after orchitis. Furthermore, the pharmacological inhibition of GSDMD alleviated the symptoms of UPEC-induced acute orchitis. Collectively, these findings provide the first demonstration of GSDMD's role in driving orchitis and suggest that GSDMD may be a potential therapeutic target for treating orchitis.

Benzophenone-2 exerts reproductive toxicity in male rats

Benzophenone derivatives such as benzophenone-2 (BP-2) belong to the group of endocrine disrupting compounds (EDCs). Increased exposure to EDCs is considered to be an important factor behind the decline of human fertility. The main aim of the present study was to determine the effect of BP-2 on testicular function specified by sperm analysis, the level of sex hormones and their receptors. Since BP-2 has been shown to activate the immune system, another aim of the research was to verify the hypothesis that the immune system may be contributing to the testis toxicity of this compound and for this purpose changes in macrophage and lymphocyte populations in the testes were determined. BP-2 at a dose of 100 mg/kg was administered dermally, twice daily at a dose of 100 mg/kg for 4-weeks. It was shown that BP-2 reduced the number and motility of sperm and increased the number of sperm showing morphological changes. By determining the concentration of sex hormones, a significant decrease in testosterone levels and an increase in the blood levels of 17β-estradiol were demonstrated. Similar to the results obtained from the blood samples, testosterone levels in the testes were lowered, which could affect sperm parameters. The effect of BP-2 on lowering testosterone levels and the number of sperm cells may be due to immunoactivation in the testes, because it has been detected that this compound significantly decreased the number of the immunosuppressive resident testicular macrophages (TMs) (CD68-CD163+), but increased pro-inflammatory TMs with monocyte-like properties (CD68+CD163-).

Do macrophages play a role in the adverse effects of endocrine disrupting chemicals (EDCs) on testicular functions?

During the past decades, several endocrine disrupting chemicals (EDCs) have been confirmed to affect male reproductive function and fertility in animal studies. EDCs are suspected to exert similar effects in humans, based on strong associations between levels of antiandrogenic EDCs in pregnant women and adverse reproductive effects in infants. Testicular macrophages (tMΦ) play a vital role in modulating immunological privilege and maintaining normal testicular homeostasis as well as fetal development. Although tMΦ were not historically studied in the context of endocrine disruption, they have emerged as potential targets to consider due to their critical role in regulating cells such as spermatogonial stem cells (SSCs) and Leydig cells. Few studies have examined the impact of EDCs on the ability of testicular cells to communicate and regulate each other's functions. In this review, we recapitulate what is known about tMΦ functions and interactions with other cell types in the testis that support spermatogenesis and steroidogenesis. We also surveyed the literature for reports on the effects of the EDCs genistein and DEHP on tMΦ, SSCs, Sertoli and Leydig cells. Our goal is to explore the possibility that EDC disruption of tMΦ interactions with other cell types may play a role in their adverse effects on testicular developmental programming and functions. This approach will highlight gaps of knowledge, which, once resolved, should improve the risk assessment of EDC exposure and the development of safeguards to protect male reproductive functions.

Prenatal exposure to bisphenol AF induced male offspring reproductive dysfunction by triggering testicular innate and adaptive immune responses

As an emerging endocrine-disrupting component with a chemical structure related to Bisphenol A (BPA), Bisphenol AF (BPAF) has become widely distributed in the environment and human surroundings. Although numerous studies have focused on its reproductive toxicity, the impact of prenatal BPAF exposure on the reproductive system of adult male offspring, particularly testicular morphology and function, as well as the underlying mechanisms, remains largely understudied. This study found prenatal BPAF exposure at a dose of 300 μg/kg b.w. induced a 32% loss of seminal vesicle weight, a 12% reduction in the anogenital distance index (AGI), and impairments to testicular morphology, such as a reduced diameter of seminiferous tubules and thickness of the seminiferous epithelium, as well as a more than 2 - fold decrease in testosterone level, and 41% and 19% reduction of sperm count and vitality, respectively, in the 10 week-old male offsprings. Testicular RNA-Seq data showed that 334 differential expressed genes (DEGs) were primarily involved in several immunological processes, including host defense response, innate and adaptive immune response, cellular response to interferon (IFN)-β and γ, antigen processing and presentation, regulation of T cell activation, etc. Importantly, our results revealed a pattern recognition receptor - absent in melanoma-2 (Aim2) was significantly increased in the testes of exposed males, thus triggering a testicular innate antiviral immunological response, leading to an increase of F4/80⁺ and CD11b⁺ macrophage. Subsequently, Aim2 activated the downstream signaling nuclear factor kappa-B (NF-κB), stimulated the transcription of IFN-β and -γ, and then induced cytokine production while upregulating MHC class II molecules to activate CD4⁺ and CD8⁺ Tcells, suggesting that an adaptive immune response was also elicited. The results demonstrated that prenatal BPAF exposure could provoke innate and adaptive immunological responses in the testes of adult males through the Aim2-NF-κB-IFNs signaling pathway. Our work provided insights into understanding the reproductive toxicity caused by BPAF and clarified the possible mechanisms, which offered a potential therapeutic target and treatment strategy for BPAF exposure-induced reproductive dysfunction.

Testicular macrophages are recruited during a narrow fetal time window and promote organ-specific developmental functions

A growing body of evidence demonstrates that fetal-derived tissue-resident macrophages have developmental functions. It has been proposed that macrophages promote testicular functions, but which macrophage populations are involved is unclear. Previous studies showed that macrophages play critical roles in fetal testis morphogenesis and described two adult testicular macrophage populations, interstitial and peritubular. There has been debate regarding the hematopoietic origins of testicular macrophages and whether distinct macrophage populations promote specific testicular functions. Here our hematopoietic lineage-tracing studies in mice show that yolk-sac-derived macrophages comprise the earliest testicular macrophages, while fetal hematopoietic stem cells (HSCs) generate monocytes that colonize the gonad during a narrow time window in a Sertoli-cell-dependent manner and differentiate into adult testicular macrophages. Finally, we show that yolk-sac-derived versus HSC-derived macrophages have distinct functions during testis morphogenesis, while interstitial macrophages specifically promote adult Leydig cell steroidogenesis. Our findings provide insight into testicular macrophage origins and their tissue-specific roles.

Emerging concepts on Leydig cell development in fetal and adult testis

Leydig cells (Lc) reside in the interstitial compartment of the testis and are the target of Luteinising hormone (LH) for Testosterone (T) production, thus critically regulates male fertility. Classical histological studies have identified two morphologically different populations of Lc during testicular development [fetal (FLc) and adult (ALc)]. Recent progress in ex vivo cell/organ culture, genome-wide analysis, genetically manipulated mouse models, lineage tracing, and single-cell RNA-seq experiments have revealed the diverse cellular origins with differential transcriptomic and distinct steroidogenic outputs of these populations. FLc originates from both coelomic epithelium and notch-active Nestin-positive perivascular cells located at the gonad-mesonephros borders, and get specified as Nr5a1 (previously known as Ad4BP/SF-1) expressing cells by embryonic age (E) 12.5 days in fetal mouse testes. These cells produce androstenedione (precursor of T, due to lack of HSD17β3 enzyme) and play critical a role in initial virilization and patterning of the male external genitalia. However, in neonatal testis, FLc undergoes massive regression/dedifferentiation and gradually gets replaced by T-producing ALc. Very recent studies suggest a small fraction (5-20%) of FLc still persists in adult testis. Both Nestin-positive perivascular cells and FLc are considered to be the progenitor populations for ALc. This minireview article summarizes the current understanding of Lc development in fetal and adult testes highlighting their common or diverse cellular (progenitor/stem) origins with respective functional significance in both rodents and primates. (227 words).

Overview of single-cell RNA sequencing analysis and its application to spermatogenesis research

Background

Single-cell transcriptomics allows parallel analysis of multiple cell types in tissues. Because testes comprise somatic cells and germ cells at various stages of spermatogenesis, single-cell RNA sequencing is a powerful tool for investigating the complex process of spermatogenesis. However, single-cell RNA sequencing analysis needs extensive knowledge of experimental technologies and bioinformatics, making it difficult for many, particularly experimental biologists and clinicians, to use it.

Methods

Aiming to make single-cell RNA sequencing analysis familiar, this review article presents an overview of experimental and computational methods for single-cell RNA sequencing analysis with a history of transcriptomics. In addition, combining the PubMed search and manual curation, this review also provides a summary of recent novel insights into human and mouse spermatogenesis obtained using single-cell RNA sequencing analyses.

Main Findings

Single-cell RNA sequencing identified mesenchymal cells and type II innate lymphoid cells as novel testicular cell types in the adult mouse testes, as well as detailed subtypes of germ cells. This review outlines recent discoveries into germ cell development and subtypes, somatic cell development, and cell-cell interactions.

Conclusion

The findings on spermatogenesis obtained using single-cell RNA sequencing may contribute to a deeper understanding of spermatogenesis and provide new directions for male fertility therapy.

Viral tropism for the testis and sexual transmission

The mammalian testis adopts an immune privileged environment to protect male germ cells from adverse autoimmune reaction. The testicular immune privileged status can be also hijacked by various microbial pathogens as a sanctuary to escape systemic immune surveillance. In particular, several viruses have a tropism for the testis. To overcome the immune privileged status and mount an effective local defense against invading viruses, testicular cells are well equipped with innate antiviral machinery. However, several viruses may persist an elongated duration in the testis and disrupt the local immune homeostasis, thereby impairing testicular functions and male fertility. Moreover, the viruses in the testis, as well as other organs of the male reproductive system, can shed to the semen, thus allowing sexual transmission to partners. Viral infection in the testis, which can impair male fertility and lead to sexual transmission, is a serious concern in research on known and on new emerging viruses. To provide references for our scientific peers, this article reviews research achievements and suggests future research focuses in the field.

Expression of CSF1, AR, and SRD5A2 during Postnatal Development of the Boar Reproductive Tract

Simple Summary

Understanding the initial development of the male reproductive system, including the prostate, should provide insight into malfunctions in the adult male. Although changes in circulating androgens during development are characterized in multiple species, potential changes in the androgen receptor, in the enzyme that converts testosterone to the presumably more potent dihydrotestosterone, and in colony stimulating factor 1, a critical mediator of macrophage influence on organ development, were previously unknown and anticipated to be influenced by androgens and estrogens. Gene expression in the testis, prostate, and seminal vesicles of these three mediators of development, including responses to reduced testosterone or estrogens, were evaluated. Each of these three genes had a unique temporal pattern of expression during postnatal reproductive tract development. However, surprisingly minimal effects of altered steroid signaling were reported on the expression of these presumed pivotal genes.

Abstract

The male reproductive system develops from a minimally functioning gonad and nonfunctioning accessory sex glands in the neonate; sex steroids, presumed to be primary influencers of these changes, have been characterized in multiple species. This study focused on the expression of the androgen receptor as the principal mediator of androgen-induced signaling; the 5α reductase enzyme that converts testosterone to the more active dihydrotestosterone; and colony stimulating factor 1, a mediator of macrophage influence on organ development in the pig. The time points chosen to evaluate normal developmental changes during the juvenile and prepubertal intervals included the inflection time points of 6.5 weeks of age at the nadir of circulating estradiol and testosterone concentrations in juveniles, and 11 weeks of age, when these concentrations begin to increase. The role of sex steroid signaling in the regulation of gene expression was evaluated by the blockade of androgen and estrogen receptors and reduction in endogenous estrogens. Expression of colony stimulating factor 1 in the testes gradually decreased during development; developmental profiles in the prostate and seminal vesicles were clearly different. Interference with sex steroid signaling had no effect on the expression of these three genes in testicular tissue and minimal and transient effects in prostate and seminal vesicles.

Sertoli Cell Immune Regulation: A Double-Edged Sword

The testis must create and maintain an immune privileged environment to protect maturing germ cells from autoimmune destruction. The establishment of this protective environment is due, at least in part, to Sertoli cells. Sertoli cells line the seminiferous tubules and form the blood-testis barrier (BTB), a barrier between advanced germ cells and the immune system. The BTB compartmentalizes the germ cells and facilitates the appropriate microenvironment necessary for spermatogenesis. Further, Sertoli cells modulate innate and adaptive immune processes through production of immunoregulatory compounds. Sertoli cells, when transplanted ectopically (outside the testis), can also protect transplanted tissue from the recipient’s immune system and reduce immune complications in autoimmune diseases primarily by immune regulation. These properties make Sertoli cells an attractive candidate for inflammatory disease treatments and cell-based therapies. Conversely, the same properties that protect the germ cells also allow the testis to act as a reservoir site for infections. Interestingly, Sertoli cells also have the ability to mount an antimicrobial response, if necessary, as in the case of infections. This review aims to explore how Sertoli cells act as a double-edged sword to both protect germ cells from an autoimmune response and activate innate and adaptive immune responses to fight off infections.

The Role of NLRP3 Inflammasome Activation and Oxidative Stress in Varicocele-Mediated Male Hypofertility

Varicocele (VC) is the most common abnormality identified in men evaluated for hypofertility. Increased levels of reactive oxygen species (ROS) and reduced antioxidants concentrations are key contributors in varicocele-mediated hypofertility. Moreover, inflammation and alterations in testicular immunity negatively impact male fertility. In particular, NLRP3 inflammasome activation was hypothesized to lead to seminal inflammation, in which the levels of specific cytokines, such as IL-1β and IL-18, are overexpressed. In this review, we described the role played by oxidative stress (OS), inflammation, and NLRP3 inflammasome activation in VC disease. The consequences of ROS overproduction in testis, including inflammation, lipid peroxidation, mitochondrial dysfunction, chromatin damage, and sperm DNA fragmentation, leading to abnormal testicular function and failed spermatogenesis, were highlighted. Finally, we described some therapeutic antioxidant strategies, with recognized beneficial effects in counteracting OS and inflammation in testes, as possible therapeutic drugs against varicocele-mediated hypofertility.

Reduction of testosterone levels in Schistosoma haematobium- or Schistosoma mansoni-infected men: a cross-sectional study in two schistosomiasis-endemic areas of the Adamawa region of Cameroon

BACKGROUND

The incidence of schistosomiasis-induced male reproductive dysfunction and infertility is probably underestimated compared to female genital schistosomiasis. This study aimed to investigate the impact of Schistosoma haematobium or S. mansoni infection on the reproductive function of men of reproductive age in Tibati and Wouldé, two endemic schistosomiasis areas in the Adamawa region of Cameroon.

METHODS

A total of 89 men of reproductive age (range 14-56 years) from two localities were enrolled in the study, with 51 in Tibati and 38 in Wouldé. Each participant was submitted to a questionnaire to document data on sociodemographic and stream contact behaviors. A medical examination was performed to measure the testes' circumference and evaluate genital tract pathologies. Stool and urine samples were collected and screened for the presence of S. haematobium or S. mansoni ova. Blood serum was used to assess the levels of transaminases and testosterone.

RESULTS

Schistosoma haematobium was present only in Tibati, with a prevalence of 31.37%. The S. mansoni prevalence was 3.92% at Tibati and 44.71% at Wouldé. The intensity of infection was 22.12 ± 9.57 eggs/10 mL for S. haematobium and 128.10 ± 3.76 epg for S. mansoni. Serum transaminase activity and the mean testicular circumference of Schistosoma-positive individuals were close to Schistosoma-negative individuals. However, the testes size was more prominent in S. mansoni-positive individuals than in S. haematobium-positive individuals (P < 0.05). The serum testosterone levels of S. haematobium- and S. mansoni-positive men were significantly reduced by 56.07% (P < 0.001) and 51.94% (P < 0.01), respectively, in comparison to those of Schistosoma-negative men. A significant and negative correlation was established between schistosomiasis and the low serum testosterone level. Male genital tract pathologies such as scrotal abnormalities, varicocele, nodular epididymis, inguinal hernia, and hydrocele were recorded in both Schistosoma-positive and Schistosoma-negative men. However, no significant link was established between schistosomiasis infection and these pathologies.

CONCLUSION

These results demonstrated that infection with S. haematobium or S. mansoni is associated with low production of the reproductive hormone testosterone and may be a significant cause of male infertility.

Immune Cells as Critical Regulators of Steroidogenesis in the Testis and Beyond

Steroidogenesis is an essential biological process for embryonic development, reproduction, and adult health. While specific glandular cells, such as Leydig cells in the testis, are traditionally known to be the principal players in steroid hormone production, there are other cell types that contribute to the process of steroidogenesis. In particular, immune cells are often an important component of the cellular niche that is required for the production of steroid hormones. For several decades, studies have reported that testicular macrophages and Leydig cells are intimately associated and exhibit a dependency on the other cell type for their proper development; however, the mechanisms that underlie the functional relationship between macrophages and Leydig cells are unclear. Beyond the testis, in certain instances immune cells themselves, such as certain types of lymphocytes, are capable of steroid hormone production, thus highlighting the complexity and diversity that underlie steroidogenesis. In this review we will describe how immune cells are critical regulators of steroidogenesis in the testis and in extra-glandular locations, as well as discuss how this area of research offers opportunities to uncover new insights into steroid hormone production.

Testicular 25-hydroxycholesterol: An alternate substrate for steroidogenesis in reptiles

The current study in wall lizards Hemidactylus flaviviridis was designed to ascertain that Leydig cells utilize testicular macrophage-derived 25-hydroxycholesterol (25-HC) for steroidogenesis. Leydig cells (LC) collected from regressed testes when incubated with 25-HC that was obtained from HPLC-eluted fraction of testicular macrophage-conditioned medium (TMCM), lyophilized and reconstituted in culture medium (0.5 µg/ml/well), produced considerably higher amount of testosterone. A similar observation was made when Leydig cells were incubated with varying concentrations of commercial 25-HC. Testosterone production by LC increased in a concentration-dependent manner. Taken together, it is evident that LC utilize 25-HC as a substrate for testosterone biosynthesis. To examine the gonadotropic regulation of steroid biosynthesis utilizing 25-HC as substrate, ovine follicle-stimulating hormone (FSH) that regulates both the testicular functions in lizards was used. Leydig cells were incubated with combinations of FSH and 25-HC as follows: 0 h FSH + 12 h 25-HC, 0 h 25-HC + 12 h FSH. As compared to respective controls, a marked increase in testosterone production was observed in response to FSH indicating that gonadotropin up-regulates uptake of 25-HC as a substrate for testosterone biosynthesis.

Varicocele-Mediated Male Infertility: From the Perspective of Testicular Immunity and Inflammation

Background

Varicocele (VC) is present in 35 - 40% of men with infertility. However, current surgical and antioxidant treatments are not completely effective. In addition to oxidative stress, it is likely that other factors such as testicular immune microenvironment disorder contribute to irreversible testicular. Evidence suggests that VC is associated with anti-sperm antibodies (ASAs), spermatogenesis and testosterone secretion abnormalities, and testicular cytokine production. Moreover, inhibition of inflammation can alleviate VC-mediated pathogenesis. The normal function of the testis depends on its immune tolerance mechanism. Testicular immune regulation is complex, and many infectious or non-infectious diseases may damage this precision system.

Results

The testicular immune microenvironment is composed of common immune cells and other cells involved in testicular immunity. The former includes testicular macrophages, T cells, dendritic cells (DCs), and mast cells, whereas the latter include Leydig cells and Sertoli cells (SCs). In animal models and in patients with VC, most studies have revealed an abnormal increase in the levels of ASAs and pro-inflammatory cytokines such as interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha in the seminal plasma, testicular tissue, and even peripheral blood. It is also involved in the activation of potential inflammatory pathways, such as the nucleotide-binding oligomerization domain-like receptor family pyrin domain containing (NLRP)-3 pathway. Finally, the development of VC-mediated infertility (VMI) may be facilitated by abnormal permeability of proteins, such as claudin-11, that constitute the blood-testis barrier (BTB).

Conclusions

The testicular immune response, including the production of ASAs and inflammatory factors, activation of inflammatory pathways, and destruction of the BTB may be involved in the pathogenesis of VMI it is necessary to further explore how patient outcomes can be improved through immunotherapy.

Impaired macrophages and failure of steroidogenesis and spermatogenesis in rat testes with cytokines deficiency induced by diacerein

The role of cytokines in testicular function under normal conditions has not been completely understood. Here, we evaluated testicular macrophages (TM), steroidogenesis by Leydig cells (LC) and seminiferous tubules integrity in cytokines-deficient rat testes induced by diacerein, an anti-inflammatory drug that inhibits interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-α). Male rats received daily 100 mg/kg of diacerein (DIAG; n = 8) or saline (CG; n = 8) for 30 days. Serum testosterone (T) levels were measured and the seminiferous tubule (ST) area, epithelial area (EA), frequency of damaged ST and number of Sertoli cells (SC) were evaluated. TUNEL method and immunoreactions for detection of pro-IL-1β, TNF-α, steroidogenic acute regulatory protein (StAR), 17β-hydroxysteroid dehydrogenase (17β-HSD), androgen receptor (AR) and scavenger receptor for hemoglobin-haptoglobin complexes (CD163), a TM marker, were performed. Testicular AR, 17β-HSD and IL-1β levels were detected by Western blot. Data were submitted to Student t test (p ≤ 0.05). In DIAG, T and testicular AR, 17β-HSD and IL-1β levels decreased significantly (p < 0.05). The number of TUNEL-positive interstitial cells increased and LC showed weak StAR, 17β-HSD and AR immunoexpression in association with reduced IL-1β immunoexpression and number of CD163-positive TM in the interstitial tissue from diacerein-treated rats. Numerous damaged ST were found in DIAG, and reduction in the EA were associated with germ cells death. Moreover, the number of SC reduced and weak AR and TNF-α immunoexpression was observed in SC and germ cells, respectively. The cytokines deficiency induced by diacerein impairs TM, LC and spermatogenesis, and points to a role of IL-1β in steroidogenesis under normal conditions. In the ST, the weak AR and TNF-α immunoexpression in SC and germ cells, respectively, reinforces the idea that TNF-α plays a role in the SC androgenic control.

Activation of C-C motif chemokine receptor 2 modulates testicular macrophages number, steroidogenesis, and spermatogenesis progression

The monocyte chemoattractant protein 1 (MCP-1) belongs to the CC chemokine family and acts in the recruitment of C-C motif chemokine receptor 2 (CCR2)-positive immune cell types to inflammation sites. In testis, the MCP-1/CCR2 axis has been associated with the macrophage population's functional regulation, which presents significant functions supporting germ cell development. In this context, herein, we aimed to investigate the role of the chemokine receptor CCR2 in mice testicular environment and its impact on male sperm production. Using adult transgenic mice strain that had the CCR2 gene replaced by a red fluorescent protein gene, we showed a stage-dependent expression of CCR2 in type B spermatogonia and early primary spermatocytes. Several parameters related to sperm production were reduced in the absence of CCR2 protein, such as Sertoli cell efficiency, meiotic index, and overall yield of spermatogenesis. Daily sperm production decreased by almost 40%, and several damages in the seminiferous tubules were observed. Significant reduction in the expression of important genes related to the Sertoli cell function (Cnx43, Vim, Ocln, Spna2) and meiosis initiation (Stra8, Pcna, Prdm9, Msh5) occurred in comparison to controls. Also, the number of macrophages significantly decreased in the absence of CCR2 protein, along with a disturbance in Leydig cell steroidogenic activity. In summary, our results show that the non-activation of the MCP-1/CCR2 axis disturbs the testicular homeostasis, interfering in macrophage population, meiosis initiation, blood-testis barrier function, and androgen synthesis, leading to the malfunction of seminiferous tubules, decreased testosterone levels, defective sperm production, and lower fertility index.

Ocimum tenuiflorum mitigates iron-induced testicular toxicity via modulation of redox imbalance, cholinergic and purinergic dysfunctions, and glucose metabolizing enzymes activities

Oxidative stress is a primary culprit in the pathophysiology of infertility conditions in males. This study investigated the effects of Ocimum tenuiflorum on redox imbalance, cholinergic and purinergic dysfunctions and glucose dysmetabolism in oxidative-mediated testicular toxicity using in vitro, ex vivo and in silico models. Induction of oxidative testicular injury was carried out by incubating normal testicular tissue with 0.1 mM FeSO₄ and treated by co-incubating with different concentrations of O. tenuiflorum infusion for 30 min at 37°C. O. tenuiflorum displayed significant ferric reducing power activity while scavenging DPPH and hydroxyl (OH˙) free radicals in vitro. Oxidative testicular injury significantly reduced the glutathione level and superoxide dismutase and catalase activities with concomitant elevation of malondialdehyde and nitric oxide levels and acetylcholinesterase, ATPase, fructose-1,6-bisphosphatase and glycogen phosphorylase (GlyP) activities. Incubation with the infusion significantly reversed these levels and activities. The phytochemical constituent of the infusion was detected by gas chromatography-mass spectroscopy analysis and revealed favourable binding energies when docked with some of the studied proteins. These results suggest O. tenuiflorum exerts a protective effect against Fe²⁺ induced testicular toxicity via mitigation of redox imbalance while modulating metabolic dysfunctions linked to male infertility.

Regulation of Cell Types Within Testicular Organoids

Organoids are 3-dimensional (3D) structures grown in vitro that emulate the cytoarchitecture and functions of true organs. Therefore, testicular organoids arise as an important model for research on male reproductive biology. These organoids can be generated from different sources of testicular cells, but most studies to date have used immature primary cells for this purpose. The complexity of the mammalian testicular cytoarchitecture and regulation poses a challenge for working with testicular organoids, because, ideally, these 3D models should mimic the organization observed in vivo. In this review, we explore the characteristics of the most important cell types present in the testicular organoid models reported to date and discuss how different factors influence the regulation of these cells inside the organoids and their outcomes. Factors such as the developmental or maturational stage of the Sertoli cells, for example, influence organoid generation and structure, which affect the use of these 3D models for research. Spermatogonial stem cells have been a focus recently, especially in regard to male fertility preservation. The regulation of the spermatogonial stem cell niche inside testicular organoids is discussed in the present review, as this research area may be positively affected by recent progress in organoid generation and tissue engineering. Therefore, the testicular organoid approach is a very promising model for male reproductive biology research, but more studies and improvements are necessary to achieve its full potential.

The endocrine disrupting effects of sodium arsenite in the rat testis is not mediated through macrophage activation

Arsenic (As) is an endocrine disrupting chemical that can disturb the male reproductive system. In a previous study, it was suggested that testicular macrophages could display a role in endocrine disruption induced by As exposure. This work aimed to evaluate the effects of chronic As exposure in the testis function of Wistar rats and examine the participation of macrophage activation and inflammatory response in these processes. We examined gene expression of steroidogenic machinery and immunological markers by RT-QPCR, plasma testosterone concentrations, sperm count and morphology, and histomorphometrical parameters after 60-days exposure to 1 or 5 mg.kg^-1.day^-1 of sodium arsenite, combined or not with 50 μg.kg^-1 of LPS administered one day before euthanasia. We have demonstrated that As exposure reduced the weight of androgen-dependent organs and induced changes in spermatogenesis, in particular at the highest dose. LPS and As co-exposure promoted a decrease in testosterone synthesis, but did not increase the overexpression of markers of macrophage activation seen in LPS-only rats. Our results suggest that As does not alter the testicular macrophage function, but under immunological challenges LPS and As can display a complex interaction, which could lead to endocrine disruption.

The Presence of Colony-Stimulating Factor-1 and Its Receptor in Different Cells of the Testis; It Involved in the Development of Spermatogenesis In Vitro

Spermatogenesis is a complex process, in which spermatogonial cells proliferate and differentiate in the seminiferous tubules of the testis to generate sperm. This process is under the regulation of endocrine and testicular paracrine/autocrine factors. In the present study, we demonstrated that colony stimulating factor-1 (CSF-1) is produced by mouse testicular macrophages, Leydig, Sertoli, peritubular cells and spermatogonial cells (such as CDH1-positively stained cells; a marker of spermatogonial cells). In addition, we demonstrated the presence of CSF-1 and its receptor (CSF-1R) in testicular macrophages, Leydig, Sertoli, peritubular cells and spermatogonial cells of human testis. We also show that the protein levels of CSF-1 were the highest in testis of 1-week-old mice and significantly decreased with age (2–12-week-old). However, the transcriptome levels of CSF-1 significantly increased in 2–3-week-old compared to 1-week-old, and thereafter significantly decreased with age. On the other hand, the transcriptome levels of CSF-1R was significantly higher in mouse testicular tissue of all examined ages (2–12-week-old) compared to 1-week-old. Our results demonstrate the involvement of CSF-1 in the induction the proliferation and differentiation of spermatogonial cells to meiotic and postmeiotic stages (BOULE- and ACROSIN-positive cells) under in vitro culture conditions, using methylcellulose culture system (MCS). Thus, it is possible to suggest that CSF-1 system, as a testicular paracrine/autocrine system, is involved in the development of different stages of spermatogenesis and may be used in the development of future therapeutic strategies for treatment of male infertility.

Varicocoele and oxidative stress: New perspectives from animal and human studies

BACKGROUND

Varicocoele (VCL), one of the main causes of male subfertility, negatively affects testicular function. Due to limited access to human testicular tissue, animal model studies have been used to evaluate molecular and, recently, epigenetic changes attributed to pathophysiology induced by VCL.

OBJECTIVES

This review aims to provide an update on the latest findings regarding the link between VCL-induced biochemical stress and molecular changes in germ cells and spermatozoa. Endocrine and antioxidant status, testicular chaperone-specific hemostasis failure, altered testicular ion balance, metabolic disorders, and altered carbon cycling during spermatogenesis are among the many features that will be presented.

DISCUSSION

Literature review coupled with our own findings suggests that ionic imbalance, hypoxia, hyperthermia, and altered blood flow could lead to severe chronic oxidative and nitrosative stress in patients with VCL leading to defective spermatogenesis and impairment of the integrity of all sperm cell components and compartments down to the epigenetic information they carry.

CONCLUSION

Since oxidative stress is an important feature of the reproductive pathology of VCL, therapeutic strategies such as the administration of appropriate antioxidants could be undertaken as a complementary non-invasive treatment line.

Pathomechanisms of Autoimmune Based Testicular Inflammation

Infection and inflammation of the male reproductive tract are relevant causes of infertility. Inflammatory damage occurs in the special immunosuppressive microenvironment of the testis, a hallmark termed testicular immune privilege, which allows tolerance to neo-antigens from developing germ cells appearing at puberty, long after the establishment of systemic immune tolerance. Experimental autoimmune orchitis (EAO) is a well-established rodent model of chronic testicular inflammation and organ specific autoimmunity that offers a valuable in vivo tool to investigate the pathological and molecular mechanisms leading to the breakdown of the testicular immune privilege. The disease is characterized by the infiltration of the interstitium by immune cells (mainly macrophages, dendritic cells, and T cells), formation of autoantibodies against testicular antigens, production of pro-inflammatory mediators such as NO, MCP1, TNFα, IL6, or activins and dysregulation of steroidogenesis with reduced levels of serum testosterone. EAO leads to sloughing of germ cells, atrophic seminiferous tubules and fibrotic remodeling, parameters all found similarly to changes in human biopsies from infertile patients with inflammatory infiltrates. Interestingly, testosterone supplementation during the course of EAO leads to expansion of the regulatory T cell population and inhibition of disease development. Knowledge of EAO pathogenesis aims to contribute to a better understanding of human testicular autoimmune disease as an essential prerequisite for improved diagnosis and treatment.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Granulocyte-macrophage colony stimulating factor (GM-CSF) is fully expressed in the genital tract, seminal plasma and spermatozoa of male pigs

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a pro-inflammatory cytokine identified in boar seminal plasma (SP) but until now unexplored in terms of place of production and its association to spermatozoa. This study aimed to explore these aspects by evaluating the presence of GM-CSF in porcine reproductive organs (testes, epididymis and accessory sex glands), SP and mature spermatozoa (from cauda epididymis and ejaculated) using Western blot (WB), immunohistochemistry and immunocytochemistry. Positive labelling was obtained in tissues, SP and spermatozoa. In reproductive organs, WB revealed three forms of GM-CSF with different glycosylation degrees (15, 31 and 40 kDa). In SP and epididymal fluid, the GM-CSF appeared only in its active form while in spermatozoa the GM-CSF form present varied among sperm sources. Non-viable spermatozoa showed more GM-CSF than viable spermatozoa (14.87 ± 1.98 RU vs. 7.25 ± 0.52 RU) of fluorescence intensity. In conclusion, GM-CSF is widely present in the reproductive tract of male pigs, attached to the spermatozoa already in the epididymis as well as verted to SP. Consequently, the GM-CSF ought to regulate male genital tract and sperm function as well as mediating initial inflammatory responses and further mediating later immune actions by the female to semen deposition.

Rebuilding the human testis in vitro

Increasing rates of male infertility have led to a greater need for relevant model systems to gain further insight into male fertility and its failings. Spermatogenesis and hormone production occur within distinct regions of the testis. Defined by specialized architecture and a diverse population of cell types, it is no surprise that disruption of this highly organized microenvironment can lead to infertility. To date, no robust in vitro system has facilitated full spermatogenesis resulting in the production of fertilization‐competent human spermatozoa. Here, we review a selection of current in vitro systems available for modelling the human testis microenvironment with focus on the progression of spermatogenesis and recapitulation of the testis microenvironment.

CircRNA-9119 suppresses poly I:C induced inflammation in Leydig and Sertoli cells via TLR3 and RIG-I signal pathways

Background

Circular RNAs (circRNAs) contribute to the epigenetic modulation of pathological and physiological conditions. The understanding of the impact of circRNAs on generation of testicular inflammatory reactions is insufficient.

Methods

Our research adopted a poly I:C-triggered testicular inflammation murine model and cell assays.

Results

Microarray data and quantitative evaluation revealed the elevation in the concentrations of Toll-like receptor 3 (TLR3), circRNA-9119, and retinoic acid inducible gene-I (RIG-I) and repression in the levels of miR-136 and miR-26a. Inhibition of circRNA-9119 expression impaired the inflammatory reactions in the separated Leydig and Sertoli cells subjected to poly I:C treatment. CircRNA-9119 suppressed the expression of miR-136 and miR-26a by acting as a microRNA sponge. miR-136 and miR-26a repressed the expression of RIG-I and TLR3 through the expected target region in Leydig and Sertoli cells in vitro. Inhibition of miR-136 and miR-26a expression, at least in part, restored the expression of inflammatory cytokines, which were inhibited upon circRNA-9119 expression silencing. Furthermore, the expression of circRNA-9119 was positively associated with RIG-I and TLR3 mRNA and protein levels. The expression of inflammatory genes triggered by poly I:C treatment was noticeably suppressed after RIG-I and TLR3 knockout.

Conclusions

Our results suggest that circRNA-9119 may serve as a competing endogenous RNA that insulated miR-136 and miR-26a and consequently defended RIG-I and TLR3 mRNAs against miR-26a/miR-136-mediated inhibition of testicular cells. Moreover, RIG-I and TLR3 contributed to the modulation of poly I:C-triggered inflammatory cytokine generation during orchitis in testicular cells.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0094-1) contains supplementary material, which is available to authorized users.

Expression pattern of galectin-1 and galectin-3 in rat testes and epididymis during postnatal development

Galectins are a family of lectins-binding beta-galactosides involved in a variety of extracellular and intracellular processes, thereby contributing to homeostasis, cell adhesion, cellular turnover, and immunity. This study aimed to determine the localization and expression of galectin-1 (Gal-1) and galectin-3 (Gal-3) in the testis and epididymis of rats at postnatal [(prepubertal (day 5), pubertal (day 20), postpubertal (day 50) and mature (day 70)] periods by using immunohistochemistry and Western blotting. Gal-1 and Gal-3 were differentially expressed in different types of cells in the testis and epididymis during postnatal development. While we detected Gal-1 expression in some spermatogenic cells and Leydig cells in the testis, not in the epididymal epithelium, Gal-3 was expressed in Sertoli cells, peritubular myoid cells, Leydig cells, smooth muscles and interstitial CD68-positive macrophages. Epithelial cells of the corpus and cauda epididymis showed an intense Gal-3 expression. Gal-1 expression was higher in the testis than in the epididymis on days 50 and 70. The expression of Gal-3 in the testis increased from the prepubertal to mature period. While the expression difference of Gal-3 was not statistically significant in the testis and epididymis until puberty, Gal-3 expression in the postpubertal and mature periods was higher in the epididymis. The expression of Gal-3 in the corpus and cauda epididymis was higher than that in the caput epididymis. In conclusion, our findings suggest that puberty has potential regulatory effect on the expression of galectins in testis and epididymis of rats. Gal-1 and 3 may play a role in the development of the reproductive system and the preservation of the immune-privileged environment in the testis, due to their pro-apoptotic and anti-apoptotic functions. The presence of intense expression of Gal-3 in the corpus and cauda epididymis may contribute to the maturation and storage of spermatozoa.

Testicular macrophages: Guardians of fertility

Macrophages are innate immune cells present in essentially every organ of the body with dedicated tissue specific functions. We will present in this review the unique properties and functions of macrophage populations residing in the testis, an immune-privileged organ. Testicular macrophages (tMΦ) could be seen as guardians of fertility due to their immunosuppressive functions protecting spermatogenesis from auto immune-attack. They exhibit testis specific functions with essential roles in normal testis homeostasis and fetal testicular development. Recently, two distinct testicular macrophage populations have been characterized based on different localization, morphology, gene expression profiles, developmental origin and postnatal development. We will discuss the importance of these two testicular macrophage populations for organ specific functions such as testosterone production and spermatogenesis, as well as their role in establishing immuno-privilege highlighting the contributions of macrophages to male fertility.

Loss of hamster Leydig cells during regression after exposure to a short photoperiod

The aim of the present study was to evaluate the changes that occur in hamster Leydig cells during regression. Animals were divided into control, mild regression (MR), strong regression (SR) and total regression (TR) groups. Leydig cells were characterised by light and electron microscopy. Terminal deoxyribonucleotidyl transferase-mediated dUTP–digoxigenin nick end-labelling (TUNEL) and proliferating cell nuclear antigen (PCNA) antibodies were used to detect apoptosis and proliferation respectively. Three types of Leydig cells (A, B and C) could be differentiated. Type A cells were small in size compared with Leydig cells from animals exposed to a long photoperiod, which was a result of a decreased cytoplasm and nucleus. Type B cells were even smaller than Type A cells in regression groups. Type C exhibited cytoplasm vacuolisation. The percentage of Type C cells from the control group was much lower than in the MR, SR and TR groups. (P < 0.05). In the SR and TR groups, there was a significant decrease in the percentage of Type B cells compared with the control and MR groups (P < 0.05). The total number of Leydig cells decreased during testicular regression (P < 0.05). The total number of Type A and B cells was significantly lower in the MR, SR and TR groups compared with the control group (P < 0.05). There were no significant differences in the proliferation and apoptosis index in the groups studied. The findings of the present study indicate that there are three types of Leydig cells (A, B and C) in all hamsters studied and that regression causes an increase in the number of Type C cells, so that the reduction in the number Leydig cells during the phases of regression studied must be the result of necrosis and/or necroptosis.

Testicular abnormalities in mice with Y chromosome deficiencies

We recently investigated mice with Y chromosome gene contribution limited to two, one, or no Y chromosome genes in respect to their ability to produce haploid round spermatids and live offspring following round spermatid injection. Here we explored the normalcy of germ cells and Sertoli cells within seminiferous tubules, and the interstitial tissue of the testis in these mice. We performed quantitative analysis of spermatogenesis and interstitial tissue on Periodic acid-Schiff and hematoxylin-stained mouse testis sections. The seminiferous epithelium of mice with limited Y gene contribution contained various cellular abnormalities, the total number of which was higher than in the males with an intact Y chromosome. The distribution of specific abnormality types varied among tested genotypes. The males with limited Y genes also had an increased population of testicular macrophages and internal vasculature structures. The data indicate that Y chromosome gene deficiencies in mice are associated with cellular abnormalities of the seminiferous epithelium and some changes within the testicular interstitium.

Macrophages in Endocrine Glands, with Emphasis on Pancreatic Islets

We review here the macrophages found in endocrine tissues, placing emphasis on those residing in the islets of Langerhans of the pancreas. The islets represent the endocrine organ where macrophages have been examined in great detail and where our own studies and experience have been directed.

Purification and identification of 25-hydroxycholesterol in a reptile: Seasonal variation and hormonal regulation

The present in vitro study, for the first time, demonstrates the production of 25-hydroxycholestrol (25-HC) by testicular macrophages of a non-mammalian vertebrate. The ether extracts of testicular macrophage-conditioned medium (TMCM) were fractionated on a C18 reversed phase high-performance liquid chromatography (HPLC) column using methanol as the mobile phase. The mass spectrometry (MS) fragmentation pattern of HPLC-purified 25-HC was found to be identical to that of authentic 25-HC. Further, a significant seasonal variation in 25-HC concentration was observed with maximal level in regressed and minimal during breeding phase. To understand the hormonal control of 25-HC production, testicular macrophages from regressed phase testes were incubated with 0.5μg/ml of ovine follicle stimulating hormone (FSH) and 0.1, 1 and 10μg/ml of testosterone (T). FSH considerably enhanced 25-HC production by testicular macrophages. In contrast, T markedly inhibited 25-HC production in a dose-dependent manner. In addition, T significantly inhibited FSH-induced 25-HC production, though pre-treatment with T was more effective as compared to post-treatment with T to FSH. Our findings on production, seasonal variation and hormonal control of 25-HC suggest the functional significance of 25-HC in the testis of reptiles.

Pro-steroidogenic and pro-spermatogenic actions of nitric oxide (NO) on the catfish, Clarias batrachus: An in vivo study

In an earlier study we have demonstrated reproductive-stage dependent, cell specific existence of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS)/NO system in testis of the catfish, Clarias batrachus. The present study is an extension to examine the role of NO in steroidogenesis and spermatogenesis through in vivo administration of a NO donor, sodium nitroprusside (SNP) and a NOS inhibitor, N-nitro-l-arginine methyl ester (l-NAME) during the quiescence and recrudescence phase of the reproductive cycle of the catfish. Effects of these chemicals were assessed on the gonadosomatic index (GSI), levels of circulating & testicular testosterone, NO, activities of 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) in testis, expression of different NOS isoforms and testicular morphology in relation to spermatogenesis. SNP treatment increased the GSI, testicular and circulating testosterone & NO, activities of testicular 3β-HSD & 17β-HSD, and expression of NOS isoforms. It also increased the area and perimeters of interstitium and seminiferous tubules in the testis. It accelerated the spermatogenesis, as was evident from the large number of spermatids/spermatozoa in seminiferous tubules and very few spermatogonial cells/primary spermatocytes in comparison to the control testis. On the contrary, l-NAME significantly suppressed GSI, testosterone & NO levels in serum and testis, and activities of testicular 3β-HSD & 17β-HSD. It also suppressed the expression of NOSs in testis. Though l-NAME did not alter the spermatogonial mitotic proliferation with the advancement of testicular recrudescence, it halted the progression of spermatogenesis (meiotic division and spermatozoa formation) as was clear from the increase in spermatogonial cells and very few advanced germ cells in the seminiferous tubules in l-NAME treated testis, compared to the control testis. The above noted effects were highly pronounced in the recrudescing catfish. Their effects were very marginal and at a particular dose levels of SNP and l-NAME in the quiescent testis. This study distinctly provides evidence of pro-steroidogenic and pro-spermatogenic role of NO. This study also demonstrates the existence of eNOS in fish testis for the first time. The positive feedback control of expression of all isoform of NOS in testis by NO is also noteworthy.

Role of the testis interstitial compartment in spermatogonial stem cell function

Intricate cellular and molecular interactions ensure that spermatogonial stem cells (SSCs) proceed in a step-wise differentiation process through spermatogenesis and spermiogenesis to produce sperm. SSCs lie within the seminiferous tubule compartment, which provides a nurturing environment for the development of sperm. Cells outside of the tubules, such as interstitial and peritubular cells, also help direct SSC activity. This review focuses on interstitial (interstitial macrophages, Leydig cells and vasculature) and peritubular (peritubular macrophages and peritubular myoid cells) cells and their role in regulating the SSC self-renewal and differentiation in mammals. Leydig cells, the major steroidogenic cells in the testis, influence SSCs through secreted factors, such as insulin growth factor 1 (IGF1) and colony-stimulating factor 1 (CSF1). Macrophages interact with SSCs through various potential mechanisms, such as CSF1 and retinoic acid (RA), to induce the proliferation or differentiation of SSCs respectively. Vasculature influences SSC dynamics through CSF1 and vascular endothelial growth factor (VEGF) and by regulating oxygen levels. Lastly, peritubular myoid cells produce one of the most well-known factors that is required for SSC self-renewal, glial cell line-derived neurotrophic factor (GDNF), as well as CSF1. Overall, SSC interactions with interstitial and peritubular cells are critical for SSC function and are an important underlying factor promoting male fertility.

The New Director of "the Spermatogonial Niche": Introducing the Peritubular Macrophage

In this issue of Cell Reports, DeFalco et al. (2015) characterize a novel macrophage population associated with the peritubular lamina of mouse testes. These macrophages may create a niche not for the self-renewal of stem cells but rather the induction of their differentiation.

Cellular changes in the hamster testicular interstitium with ageing and after exposure to short photoperiod

The aim of this study was to evaluate the cellular changes that occur in the hamster testicular interstitium in two very different physiological situations involving testicular involution: ageing and exposure to a short photoperiod. The animals were divided into an ‘age group’ with three subgroups – young, adult and old animals – and a ‘regressed group’ with animals subjected to a short photoperiod. The testicular interstitium was characterised by light and electron microscopy. Interstitial cells were studied histochemically with regard to their proliferation, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end labelling (TUNEL+) and testosterone synthetic activity. We identified two types of Leydig cell: Type A cells showed a normal morphology, while Type B cells appeared necrotic. With ageing, pericyte proliferation decreased but there was no variation in the index of TUNEL-positive Leydig cells. In the regressed group, pericyte proliferation was greater and TUNEL-positive cells were not observed in the interstitium. The testicular interstitium suffered few ultrastructural changes during ageing and necrotic Leydig cells were observed. In contrast, an ultrastructural involution of Leydig cells with no necrosis was observed in the regressed group. In conclusion, the testicular interstitium of Mesocricetus auratus showed different cellular changes in the two groups (age and regressed), probably due to the irreversible nature of ageing and the reversible character of changes induced by short photoperiod.

Biology of the Sertoli Cell in the Fetal, Pubertal, and Adult Mammalian Testis

A healthy man typically produces between 50 × 10(6) and 200 × 10(6) spermatozoa per day by spermatogenesis; in the absence of Sertoli cells in the male gonad, this individual would be infertile. In the adult testis, Sertoli cells are sustentacular cells that support germ cell development by secreting proteins and other important biomolecules that are essential for germ cell survival and maturation, establishing the blood-testis barrier, and facilitating spermatozoa detachment at spermiation. In the fetal testis, on the other hand, pre-Sertoli cells form the testis cords, the future seminiferous tubules. However, the role of pre-Sertoli cells in this process is much less clear than the function of Sertoli cells in the adult testis. Within this framework, we provide an overview of the biology of the fetal, pubertal, and adult Sertoli cell, highlighting relevant cell biology studies that have expanded our understanding of mammalian spermatogenesis.

Intratesticular alpha1-adrenergic receptors mediate stress-disturbed transcription of steroidogenic stimulator NUR77 as well as steroidogenic repressors DAX1 and ARR19 in Leydig cells of adult rats

The aim of the present study was to define the role of testicular α1-adrenergic receptors (α1-ADRs) in stress-triggered adaptation of testosterone-producing Leydig cells of adult rats. Results showed that in vivo blockade of testicular α1-ADRs prevented partial recovery of circulating androgen levels registered after 10× repeated immobilization stress (10 × IMO). Moreover, α1-ADR-blockade diminished 10 × IMO-triggered recovery of Leydig cell androgen production, and abolished mitochondrial membrane potential recovery. In the same cells, 10 × IMO-induced increase in Star transcript was abolished, Lhcgr transcript decreased, while transcription of other steroidogenic proteins was not changed. α1-ADR-blockade recovered stress-induced decrease of Nur77, one of the main steroidogenic stimulator, while significantly reduced 10 × IMO-increased in the transcription of the main steroidogenic repressors, Arr19 and Dax1. In vitro experiments revealed an adrenaline-induced α1-ADR-mediated decrease in Nur77 transcription in Leydig cells. Adrenaline-induced increase of repressor Dax1 also involves ADRs in Leydig cells. Accordingly, α1-ADRs participate in some of the stress-triggered effects on the steroidogenic machinery of Leydig cells.

Steroidogenic fate of the Leydig cells that repopulate the testes of young and aged Brown Norway rats after elimination of the preexisting Leydig cells

The capacity of Brown Norway rat Leydig cells to produce testosterone (T) decreases with aging. In a previous study, we reported that a new generation of Leydig cells can be restored in both young and old rat testes after a single injection of ethane dimethanesulfonate (EDS), and that the abilities of the new Leydig cells in young and old rats to produce T were equivalent. Our objective herein was to compare the steroidogenic fate of the new Leydig cells over time. Young (3 month-old) and old (18 month-old) rats were injected with EDS to eliminate the existing Leydig cells. Ten weeks after EDS, Leydig cells had been restored and T production by the new Leydig cells isolated from young and old rat testes was equivalent. Thirty weeks after EDS treatment of young rats, the ability of the new Leydig cells to produce T had not diminished from 10 weeks post-EDS. In contrast, at 30 weeks post-EDS, T production by new cells in old rat testes was reduced significantly from the 10-week level. Serum T levels at 10 and 30 weeks were consistent with Leydig cell T production. Serum LH levels did not differ in any group. Thus, although the Leydig cells restored to both young and old rats after EDS initially produced T at high, equivalent levels, the cells in the old testes did not maintain this ability. These results suggest that: 1) the cells from which new populations of Leydig cells are derived may differ depending upon the age of the rat; and/or 2) factors extrinsic to the new Leydig cells in young and old testes differ, and it is these differences that are responsible for reductions in T by the newly formed Leydig cells in the testes of old rats.

Macrophages Contribute to the Spermatogonial Niche in the Adult Testis

The testis produces sperm throughout the male reproductive lifespan by balancing self-renewal and differentiation of spermatogonial stem cells (SSCs). Part of the SSC niche is thought to lie outside the seminiferous tubules of the testis; however, specific interstitial components of the niche that regulate spermatogonial divisions and differentiation remain undefined. We identified distinct populations of testicular macrophages, one of which lies on the surface of seminiferous tubules, in close apposition to areas of tubules enriched for undifferentiated spermatogonia. These macrophages express spermatogonial proliferation- and differentiation-inducing factors, such as colony-stimulating factor 1 (CSF1) and enzymes involved in retinoic acid (RA) biosynthesis. We show that transient depletion of macrophages leads to a disruption in spermatogonial differentiation. These findings reveal an unexpected role for macrophages in the spermatogonial niche in the testis and raise the possibility that macrophages play previously unappreciated roles in stem/progenitor cell regulation in other tissues.

Prolonged in vivo administration of testosterone-enanthate, the widely used and abused anabolic androgenic steroid, disturbs prolactin and cAMP signaling in Leydig cells of adult rats

This study was designed to systematically analyze and define the effects of 1-day, 2-weeks, 10-weeks intramuscular administration of testosterone-enanthate, widely used and abused anabolic androgenic steroid (AAS), on main regulators of steroidogenesis and steroidogenic genes expression in testosterone-producing Leydig cells of adult rats. The results showed that prolonged (10-weeks) intramuscular administration of testosterone-enanthate, in clinically relevant dose, significantly increased prolactin, but decreased Prlr2 and Gnrhr in pituitary of adult rat. The levels of testosterone, Insl3, cAMP and mitochondrial membrane potential of Leydig cells were significantly reduced. This was followed by decreased expression of some steroidogenic enzymes and regulatory proteins such as Lhcgr, Prlr1/2, Tspo, Star, Cyp11a1, Cyp17a1, Dax1. Oppositely, Hsd3b1/2, Hsd3b5, Hsd17b4, Ar, Arr19 increased. In the same cells, transcriptional milieu of cAMP signaling elements was disturbed with remarkable up-regulation of PRKA (the main regulator of steroidogenesis). Increased prolactin together with stimulated transcription of Jak2/Jak3 could account for increased Hsd3b1/2 and Hsd3b5 in Leydig cells following 10-weeks in vivo treatment with testosterone-enanthate. In vitro studies revealed that testosterone is capable to increase level of Prlr1, Prlr2, Hsd3b1/2, Hsd3b5 in Leydig cells. Accordingly, testosterone-induced changes in prolactin receptor signaling together with up-regulation of PRKA, Hsd3b1/2, Hsd3b5, Ar in Leydig cells, could be the possible mechanism that contribute to the establishment of a new adaptive response to maintain homeostasis and prevent loss of steroidogenic function. Presented data provide new molecular insights into the relationship between disturbed testosterone homeostasis and mammalian reproduction and are important in terms of wide use and abuse of AASs and human reproductive health.