Exploring human testicular peritubular cells: identification of secretory products and regulation by tumor necrosis factor-alpha

Dysregulated serum and seminal plasma levels of surfactant protein D and MCP-1 in men with genital tract infection/inflammation

PROBLEM

Surfactant protein D (SP-D), a multimeric collectin expressed by testicular mucosal epithelia and is positively regulated by testosterone. It exerts antimicrobial effects, modulates inflammation and rescued spermatogenesis in a murine model. Various cytokines and chemokines, including MCP-1, play a key role in regulating the inflammation in rat and human testis. The study aimed to investigate the role of SP-D and involvement of chemokines and cytokines in the male infertility associated with urogenital infections or inflammation.

METHOD OF STUDY

The cross-sectional study evaluated levels of SP-D, testosterone, estradiol and the cytokines/chemokines including MCP-1 in the serum and semen samples of fertile and infertile Indian men with and without urogenital infections/inflammation (n = 76).

RESULTS

Both fertile and infertile males with urogenital infection/inflammation had significantly lower levels of SP-D and higher levels of the chemokine, Monocyte chemoattractant protein 1 (MCP-1) in the serum and seminal plasma. Seminal plasma of these males exhibited significantly higher proportion of proteolytically degraded forms of SP-D. The serum SP-D levels positively correlated with testosterone/estradiol (TE) ratio. There was no significant correlation between the SP-D levels in seminal plasma and sperm count/motility. With a significant area under the Receiver Operating Characteristic curves, the serum and seminal plasma SP-D levels exhibited significant potential to predict infertility with high sensitivity and specificity in men with genital infections/inflammation.

CONCLUSIONS

The circulating and seminal plasma SP-D levels were decreased in men with urogenital infection and inflammation. This could be due to their engagement at the site of infection, dysregulated expression owing to the altered hormonal profile and increased proteolytic degradation.

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.

Pleiotropic actions of melatonin in testicular peritubular myoid cells of immature Syrian hamsters

BACKGROUND

Peritubular myoid cells are emerging as key regulators of testicular function in adulthood. However, little is known about the role of testicular peritubular myoid cells (TPMCs) in the development of the male gonad. We found that, compared to testes of young adult hamsters, gonads of 21 day-old animals show increased melatonin concentration, seminiferous tubular wall thickening and a heterogeneous packaging of its collagen fibers thus raising the question whether melatonin may be involved in the regulation of TPMCs.

METHODS

We established primary cultures of TPMCs from immature hamsters (ihaTPMCs), which we found express melatonergic receptors.

RESULTS

Exogeneous melatonin decreased the levels of inflammatory markers (NLRP3 inflammasome, IL1β) but increased the expression of cyclooxygenase 2 (COX2, key enzyme mediating prostaglandin synthesis) and of the glial cell line-derived neurotrophic factor (GDNF) in ihaTPMCs. Melatonin also stimulated ihaTPMCs proliferation and the expression of extracellular matrix proteins such as collagen type I and IV. Furthermore, collagen gel contraction assays revealed an enhanced ability of ihaTPMCs to contract in the presence of melatonin.

CONCLUSION

Melatonin regulates immune and inflammatory functions as well as contractile phenotype of the peritubular wall in the hamster testis.

GENERAL SIGNIFICANCE

If transferable to the in vivo situation, melatonin-dependent induction of ihaTPMCs to produce factors known to exert paracrine effects in other somatic cell populations of the gonad suggests that the influence of melatonin may go beyond the peritubular wall and indicates its contribution to testicular development and the establishment of a normal and sustainable spermatogenesis.

Cell-Specific Expression Pattern of Toll-Like Receptors and Their Roles in Animal Reproduction

Toll-like receptors (TLRs), a part of the innate immune system, have critical roles in protection against infections and involve in basic pathology and physiology. Secreted molecules from the body or pathogens could be a ligand for induction of the TLR system. There are many immune and non-immune types of cells that express at a least single TLR on their surface or cytoplasm. Those cells may be a player in a defense system or in the physiological regulation mechanisms. Reproductive tract and organs contain different types of cells that have essential functions such as hormone production, providing an environment for embryo/fetus, germ cell production, etc. Although lower parts of reproductive organs are in a relationship with outsider contaminants (bacteria, viruses, etc.), upper parts should be sterile to provide a healthy pregnancy and germ cell production. In those areas, TLRs bear controller or regulator roles. In this chapter, we will provide current information about physiological functions of TLR in the cells of the reproductive organs and tract, and especially about their roles in follicle selection, maturation, follicular atresia, ovulation, corpus luteum (CL) formation and regression, establishment and maintenance of pregnancy, sperm production, maturation, capacitation as well as the relationship between TLR polymorphism and reproduction in domestic animals. We will also discuss pathogen-associated molecular patterns (PAMPs)-induced TLRs that involve in reproductive inflammation/pathology.

Age-Related Alterations in the Testicular Proteome of a Non-Human Primate

Aging of human testis and associated cellular changes is difficult to assess. Therefore, we used a translational, non-human primate model to get insights into underlying cellular and biochemical processes. Using proteomics and immunohistochemistry, we analyzed testicular tissue of young (age 2 to 3) and old (age 10 to 12) common marmosets (Callithrix jacchus). Using a mass spectrometry-based proteomics approach, we identified 63,124 peptides, which could be assigned to 5924 proteins. Among them, we found proteins specific for germ cells and somatic cells, such as Leydig and Sertoli cells. Quantitative analysis showed 31 differentially abundant proteins, of which 29 proteins were more abundant in older animals. An increased abundance of anti-proliferative proteins, among them CDKN2A, indicate reduced cell proliferation in old testes. Additionally, an increased abundance of several small leucine rich repeat proteoglycans and other extracellular matrix proteins was observed, which may be related to impaired cell migration and fibrotic events. Furthermore, an increased abundance of proteins with inhibitory roles in smooth muscle cell contraction like CNN1 indicates functional alterations in testicular peritubular cells and may mirror a reduced capacity of these cells to contract in old testes.

Testicular adenosine acts as a pro-inflammatory molecule: role of testicular peritubular cells

Extracellular ATP has been described to be involved in inflammatory cytokine production by human testicular peritubular cells (HTPCs). The ectonucleotidases ENTPD1 and NT5E degrade ATP and have been reported in rodent testicular peritubular cells. We hypothesized that if a similar situation exists in human testis, ATP metabolites may contribute to cytokine production. Indeed, ENTPD1 and NT5E were found in situ and in vitro in HTPCs. Malachite green assays confirmed enzyme activities in HTPCs. Pharmacological inhibition of ENTPD1 (by POM-1) significantly reduced pro-inflammatory cytokines evoked by ATP treatment, suggesting that metabolites of ATP, including adenosine, are likely involved. We focused on adenosine and detected three of the four known adenosine receptors in HTPCs. One, A2B, was also found in situ in peritubular cells of human testicular sections. The A2B agonist BAY60-6583 significantly elevated levels of IL6 and CXCL8, a result also obtained with adenosine and its analogue NECA. Results of siRNA-mediated A2B down-regulation support a role of this receptor. In mouse peritubular cells, in contrast to HTPCs, all four of the known adenosine receptors were detected; when challenged with adenosine, cytokine expression levels significantly increased. Organotypic short-term testis cultures yielded comparable results and indicate an overall pro-inflammatory action of adenosine in the mouse testis. If transferable to the in vivo situation, our results may implicate that interference with the generation of ATP metabolites or interference with adenosine receptors could reduce inflammatory events in the testis. These novel insights may provide new avenues for treatment of sterile inflammation in male subfertility and infertility.

Testicular immune cells and vasculature in Klinefelter syndrome from childhood up to adulthood

STUDY QUESTION

Is the distribution of immune cells and the testicular vasculature altered in testicular biopsies from patients with Klinefelter syndrome (KS)?

SUMMARY ANSWER

Increased numbers of macrophages and mast cells, an increased expression of decorin and an increased blood vessel density were found in KS samples compared to controls.

WHAT IS KNOWN ALREADY

Most KS patients are infertile due to an early germ cell loss. From puberty onwards, testicular fibrosis can be detected. How this fibrotic process is initiated remains unknown.

STUDY DESIGN, SIZE, DURATION

In this study, the number of macrophages, mast cells and their secretory products were evaluated in KS, Sertoli cell only (SCO) and control patient samples. The association between immune cell numbers and level of fibrosis in KS tissue was examined. In addition, the vascularization within these testicular tissue biopsies was studied. For immunohistochemical evaluation, KS patients at different stages of testicular development were included: prepubertal (aged 4-7 years; n = 4), peripubertal (aged 11-17 years; n = 21) and adult (aged >18 years; n = 37) patients. In addition, testicular tissue biopsies of adult SCO (n = 33) and control samples for the three KS age groups (prepubertal n = 9; peripubertal n = 5; adult n = 25) were analysed. Gene expression analysis was performed on adult testicular tissue from KS (n = 5), SCO (n = 5) and control (n = 5) patients.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Adult (>18 years) KS, SCO and control testicular tissue biopsies were obtained during a testicular sperm extraction procedure. KS peripubertal (11-18 years), prepubertal (<11 years) and age-matched control biopsies were obtained from the biobank of the university hospital. Immunohistochemistry was used to determine the tubular structure (H/PAS), the number of spermatogonia (MAGE-A4), macrophages (CD68) and mast cells (tryptase) and the blood vessel density (Von Willebrand factor). In addition, quantitative real-time polymerase chain reaction was used to determine the expression of secretory products of macrophages and mast cells (tryptase, tumour necrosis factor alpha and decorin).

MAIN RESULTS AND THE ROLE OF CHANCE

A significant increase in the number of macrophages (P < 0.0001) and mast cells (P = 0.0008) was found in the peritubular compartment of testes of adult KS patients compared to control samples. However, no association between the number of immune cells and the degree of fibrosis was observed. In adult SCO samples, a significant increase was seen for peritubular macrophage (P < 0.0001) and mast cell (P < 0.0001) numbers compared to control samples. In the interstitial compartment, a significant increase in mast cell number was found in adult SCO samples compared to KS (P < 0.0001) and control (P < 0.0001) tissue. A significant difference (P = 0.0431) in decorin expression could be detected in adult KS compared to control patients. Decorin expression was mostly seen in the walls of the seminiferous tubules. When comparing the vascularization between KS patients and age-matched controls, a significant increase (P = 0.0081) in blood vessel density could be observed only in prepubertal KS testicular tissue.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

As controls for this study, testicular tissue biopsies of men who underwent a vasectomy reversal or orchiectomy were used, but these men may not represent fertile controls. In addition, a high variability in immune cell numbers, secretory products expression and number of blood vessels could be observed amongst all patient samples.

WIDER IMPLICATIONS OF THE FINDINGS

Increased numbers of macrophages and mast cells have previously been described in non-KS infertile men. Our results show that these increased numbers can also be detected in KS testicular tissue. However, no association between the number of macrophages or mast cells and the degree of fibrosis in KS samples could be detected. Decorin has previously been described in relation to fibrosis, but it has not yet been associated with testicular fibrosis in KS. Our results suggest a role for this proteoglycan in the fibrotic process since an increased expression was observed in adult KS tissue compared to controls. Impaired vascularization in KS men was suggested to be responsible for the KS-related disturbed hormone levels. Our results show a significant difference in blood vessel density, especially for the smallest blood vessels, between prepubertal KS samples and age-matched controls. This is the first study to report differences between KS and control testicular tissue at prepubertal age.

STUDY FUNDING/COMPETING INTEREST(S)

The project was funded by grants from the Vrije Universiteit Brussel (E.G.) and the scientific Fund Willy Gepts from the UZ Brussel (D.V.S.). D.V.S. is a post-doctoral fellow of the Fonds voor Wetenschappelijk Onderzoek (FWO; 12M2819N). No conflict of interest is declared for this research project.

Hypertension and reproductive dysfunction: a possible role of inflammation and inflammation-associated lymphangiogenesis in gonads

Hypertension is one of the most prevalent diseases that leads to end organ damage especially affecting the heart, kidney, brain, and eyes. Numerous studies have evaluated the association between hypertension and impaired sexual health, in both men and women. The detrimental effects of hypertension in men includes erectile dysfunction, decrease in semen volume, sperm count and motility, and abnormal sperm morphology. Similarly, hypertensive females exhibit decreased vaginal lubrication, reduced orgasm, and several complications in pregnancy leading to fetal and maternal morbidity and mortality. The adverse effect of hypertension on male and female fertility is attributed to hormonal imbalance and changes in the gonadal vasculature. However, mechanistic studies investigating the impact of hypertension on gonads in more detail on a molecular basis remain scarce. Hence, the aim of the current review is to address and summarize the effects of hypertension on reproductive health, and highlight the importance of research on the effects of hypertension on gonadal inflammation and lymphatics.

Microfluidics in male reproduction: is ex vivo culture of primate testis tissue a future strategy for ART or toxicology research?

The significant rise in male infertility disorders over the years has led to extensive research efforts to recapitulate the process of male gametogenesis in vitro and to identify essential mechanisms involved in spermatogenesis, notably for clinical applications. A promising technology to bridge this research gap is organ-on-chip (OoC) technology, which has gradually transformed the research landscape in ART and offers new opportunities to develop advanced in vitro culture systems. With exquisite control on a cell or tissue microenvironment, customized organ-specific structures can be fabricated in in vitro OoC platforms, which can also simulate the effect of in vivo vascularization. Dynamic cultures using microfluidic devices enable us to create stimulatory effect and non-stimulatory culture conditions. Noteworthy is that recent studies demonstrated the potential of continuous perfusion in OoC systems using ex vivo mouse testis tissues. Here we review the existing literature and potential applications of such OoC systems for male reproduction in combination with novel bio-engineering and analytical tools. We first introduce OoC technology and highlight the opportunities offered in reproductive biology in general. In the subsequent section, we discuss the complex structural and functional organization of the testis and the role of the vasculature-associated testicular niche and fluid dynamics in modulating testis function. Next, we review significant technological breakthroughs in achieving in vitro spermatogenesis in various species and discuss the evidence from microfluidics-based testes culture studies in mouse. Lastly, we discuss a roadmap for the potential applications of the proposed testis-on-chip culture system in the field of primate male infertility, ART and reproductive toxicology.

Regulation of Human Spermatogenesis

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].

ITGA6+ Human Testicular Cell Populations Acquire a Mesenchymal Rather than Germ Cell Transcriptional Signature during Long-Term Culture

Autologous spermatogonial stem cell transplantation is an experimental technique aimed at restoring fertility in infertile men. Although effective in animal models, in vitro propagation of human spermatogonia prior to transplantation has proven to be difficult. A major limiting factor is endogenous somatic testicular cell overgrowth during long-term culture. This makes the culture both inefficient and necessitates highly specific cell sorting strategies in order to enrich cultured germ cell fractions prior to transplantation. Here, we employed RNA-Seq to determine cell type composition in sorted integrin alpha-6 (ITGA6+) primary human testicular cells (n = 4 donors) cultured for up to two months, using differential gene expression and cell deconvolution analyses. Our data and analyses reveal that long-term cultured ITGA6+ testicular cells are composed mainly of cells expressing markers of peritubular myoid cells, (progenitor) Leydig cells, fibroblasts and mesenchymal stromal cells and only a limited percentage of spermatogonial cells as compared to their uncultured counterparts. These findings provide valuable insights into the cell type composition of cultured human ITGA6+ testicular cells during in vitro propagation and may serve as a basis for optimizing future cell sorting strategies as well as optimizing the current human testicular cell culture system for clinical use.

Role of GPER-Mediated Signaling in Testicular Functions and Tumorigenesis

Estrogen signaling plays important roles in testicular functions and tumorigenesis. Fifteen years ago, it was discovered that a member of the G protein-coupled receptor family, GPR30, which binds also with high affinity to estradiol and is responsible, in part, for the rapid non-genomic actions of estrogens. GPR30, renamed as GPER, was detected in several tissues including germ cells (spermatogonia, spermatocytes, spermatids) and somatic cells (Sertoli and Leydig cells). In our previous review published in 2014, we summarized studies that evidenced a role of GPER signaling in mediating estrogen action during spermatogenesis and testis development. In addition, we evidenced that GPER seems to be involved in modulating estrogen-dependent testicular cancer cell growth; however, the effects on cell survival and proliferation depend on specific cell type. In this review, we update the knowledge obtained in the last years on GPER roles in regulating physiological functions of testicular cells and its involvement in neoplastic transformation of both germ and somatic cells. In particular, we will focus our attention on crosstalk among GPER signaling, classical estrogen receptors and other nuclear receptors involved in testis physiology regulation.

Palmitic Acid Targets Human Testicular Peritubular Cells and Causes a Pro-Inflammatory Response

Palmitic acid (PA) is a major fatty acid, derived from diet and endogenous production, which is being linked to inflammation. While such actions of PA at the level of the testis remain difficult to examine, we reasoned that studies in human testicular cells may be instructive. Human testicular peritubular cells (HTPCs) can be isolated from men and cultured. They have contractile properties but also produce Interleukin 6 (IL6), express the inflammasome member NLRP3, and via glia cell line derived neurotrophic factor (GDNF), they contribute to the spermatogonial stem cell niche. We found that PA at 100 µM significantly increased the levels of IL6, while NLRP3 or the related Interleukin 1 beta (IL1beta) were not affected. The contractility marker calponin (CNN1) and the growth factor GDNF were likewise not affected. ELISA studies confirmed the stimulatory PA actions on IL6. Hence, PA derived from diet and/or endogenous sources may be able to foster a pro-inflammatory milieu in the testis. A possible link of these results to diet and high fat intake and obesity is indicated by the about 12-fold elevated testicular levels of IL6 in testes of obese rhesus monkeys (n = 3), fed with a Western Style diet. They had elevated 2–5-fold increased body fat and increased circulating triglyceride levels. Further consequences of PA and obesity for testicular functions remain to be evaluated.

The inflammatory mediators TNFα and nitric oxide arrest spermatogonia GC-1 cell cycle

During an inflammatory process of the testis, the network of somatic, immune, and germ cell interactions is altered leading to organ dysfunction. In testicular biopsies of infertile men, spermatogenesis impairment is associated with reduced spermatogonia proliferation, increased number of immune cells, and content of pro-inflammatory cytokines. TNFα-TNFR and nitric oxide (NO)-NO synthase systems are up-regulated in models of testicular damage and in human testis with maturation arrest. The purpose of this study was to test the hypothesis that TNFα-TNFR system and NO alter the function of spermatogonia in the inflamed testis. We studied the effect of TNFα and NO on GC-1 spermatogonia cell cycle progression and death by flow cytometry. GC-1 cells expressed TNFR1 and TNFR2 (immunofluorescence). TNFα (10 and 50 ng/ml) and DETA-Nonoate (0.5 and 2 mM), a NO releaser, increased the percentage of cells in S-phase of the cell cycle and reduced the percentage in G1, inducing also cell apoptosis. TNFα effect was not mediated by oxidative stress unlike NO, since the presence of N-acetyl-l-cysteine (2.5 and 5.0 mM) prevented NO induced cell cycle arrest and death. GC-1 spermatogonia overpass NO induced cell cycle arrest but no TNFα, since after removal of NO, spermatogonia progressed through the cell cycle. We propose TNFα and NO might contribute to impairment of spermatogenesis by preventing adequate functioning of the spermatogonia population. Our results showed that TNFα and NO impaired spermatogonia cell cycle, inducing GC-1 arrest in the S phase.

Insights into replicative senescence of human testicular peritubular cells

There is evidence for an age-related decline in male reproductive functions, yet how the human testis may age is not understood. Human testicular peritubular cells (HTPCs) transport sperm, contribute to the spermatogonial stem cell (SSC) niche and immune surveillance, and can be isolated and studied in vitro. Consequences of replicative senescence of HTPCs were evaluated to gain partial insights into human testicular aging. To this end, early and advanced HTPC passages, in which replicative senescence was indicated by increased cell size, altered nuclear morphology, enhanced β-galactosidase activity, telomere attrition and reduced mitochondrial DNA (mtDNA), were compared. These alterations are typical for senescent cells, in general. To examine HTPC-specific changes, focused ion beam scanning electron microscopy (FIB/SEM) tomography was employed, which revealed a reduced mitochondrial network and an increased lysosome population. The results coincide with the data of a parallel proteomic analysis and indicate deranged proteostasis. The mRNA levels of typical contractility markers and growth factors, important for the SSC niche, were not significantly altered. A secretome analysis identified, however, elevated levels of macrophage migration inhibitory factor (MIF) and dipeptidyl peptidase 4 (DPP4), which may play a role in spermatogenesis. Testicular DPP4 may further represent a possible drug target.

Characterization of a non-human primate model for the study of testicular peritubular cells-comparison with human testicular peritubular cells

STUDY QUESTION

Are monkey testicular peritubular cells (MKTPCs) from the common marmoset monkey (Callithrix jacchus) a suitable translational model for the study of human testicular peritubular cells (HTPCs)?

SUMMARY ANSWER

MKTPCs can be isolated and propagated in vitro, retain characteristic markers for testicular peritubular cells and their proteome strongly (correlation coefficient of 0.78) overlaps with the proteome of HTPCs.

WHAT IS KNOWN ALREADY

Smooth-muscle-like peritubular cells form the wall of seminiferous tubules, transport sperm, are immunologically active, secrete a plethora of factors and may contribute to the spermatogonial stem cell niche. Mechanistic studies are hampered by heterogeneity of human samples.

STUDY DESIGN, SIZE, DURATION

We established a culture method for MKTPCs and characterized these cells from six young adult animals (2-3 years). To examine whether they qualify as a translational model we also examined HTPCs from seven men and compared the proteomes of both groups.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used explant cultures to obtain MKTPCs, which express smooth muscle markers (calponin (CNN1), smooth muscle actin (ACTA2)), lack FSH-receptors (FSHR) and LH-receptors (LHCGR), but possess androgen receptors (AR). MKTPCs can be passaged at least up to eight times, without discernable phenotypic changes. Mass-spectrometry-based analyses of the MKTPC and HTPC proteomes were performed.

MAIN RESULTS AND THE ROLE OF CHANCE

We established a method for isolation and cultivation of MKTPCs, and provide a comprehensive analysis of their protein repertoire. The results let us conclude that MKTPCs are suitable as a non-human primate model to study peritubular cell functions.

LARGE SCALE DATA

List of identified proteins in MKTPCs by liquid chromatography-tandem mass spectrometry is accessible at the ProteomeXchange (identifier PXD009394).

LIMITATIONS, REASON FOR CAUTION

This is an in vitro cellular non-human primate model used to provide a window into the role of these cells in the human testis.

WIDER IMPLICATIONS OF THE FINDINGS

Previous studies with HTPCs from patients revealed a degree of heterogeneity, possibly due to age, lifestyle and medical history of the individual human donors. We anticipate that the new translational model, derived from young healthy non-human primates, may allow us to circumvent these issues and may lead to a better understanding of the role of peritubular cells.

STUDY FUNDING AND COMPETION OF INTEREST(S)

This work was supported by grants from the Deutsche Forschungsgemeinschaft (MA 1080/27-1; AR 362/9-1; BE 2296/8-1). The authors declare no competing financial interests.

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.

Evaluation of Periodontal Status among Men Undergoing Infertility Treatment

Aims:

It has been estimated that >30% of male infertility cases are of idiopathic etiology. Recent studies revealed a positive connection between periodontal pockets and sperm submotility, which proposes that periodontitis may have a role in male infertility and inadequate semen quality. The aim of the present investigation was to inspect the relationship between male fertility parameters and the periodontal status of male patients attending in vitro treatment (IVF) clinic.

Materials and Methods:

The study participants comprised 85 men going to the facility for sperm investigation before semen insemination. The nature of sperm was surveyed by the WHO 2010 criteria. On the same day, male patients were examined for periodontal parameters.

Results:

The patients were determined to have either gingivitis (24.7%) or periodontitis (75.3%). Normospermia was credited to 23.5% and oligozoospermia to 43.5%. Sperm submotility was seen in 76.4% of patients. A higher number of sites with clinical attachment loss showed a positive correlation with sperm submotility and sperm count.

Conclusions:

The findings of the present study showed a conceivable relationship between male infertility, decreased semen quality, and periodontal diseases in men visiting IVF centers. Periodontitis may subsequently play a role in male infertility.

The cell-cell junctions of mammalian testes: II. The lamellar smooth muscle monolayer cells of the peritubular wall are laterally connected by vertical adherens junctions-a novel architectonic cell-cell junction system

The testes of sexually mature males of six mammalian species (men, bulls, boars, rats, mice, guinea pigs) have been studied using biochemical as well as light and electron microscopical techniques, in particular immunolocalizations. In these tissues, the peritubular walls represent lamellar encasement structures wrapped around the seminiferous tubules as a bandage system of extracellular matrix layers, alternating with monolayers of very flat polyhedral "lamellar smooth muscle cells" (LSMCs), the number of which varies in different species from 1 to 5 or 6. These LSMCs are complete SMCs containing smooth muscle α-actin (SMA), myosin light and heavy chains, α-actinin, tropomyosin, smoothelin, intermediate-sized filament proteins desmin and/or vimentin, filamin, talin, dystrophin, caldesmon, calponin, and protein SM22α, often also cytokeratins 8 and 18. In the monolayers, the LSMCs are connected by adherens junctions (AJs) based on cadherin-11, in some species also with P-cadherin and/or E-cadherin, which are anchored in cytoplasmic plaques containing β-catenin and other armadillo proteins, in some species also striatin family proteins, protein myozap and/or LUMA. The LSMC cytoplasm is rich in myofilament bundles, which in many regions are packed in paracrystalline arrays, as well as in "dense bodies," "focal adhesions," and caveolae. In addition to some AJ-like end-on-end contacts, the LSMCs are laterally connected by numerous vertical AJ-like junctions located in variously sized and variously shaped, overlapping (alter super alterum) lamelliform cell protrusions. Consequently, the LSMCs of the peritubular wall monolayers are SMCs sensu stricto which are laterally connected by a novel architectonic system of arrays of vertical AJs located in overlapping cell protrusions.

Isolation of human testicular cells and co-culture with embryonic stem cells

Our overall goal is to create a three-dimensional human cell-based testicular model for toxicological and spermatogenesis studies. Methods to purify the major somatic testicular cells, namely Leydig cells (LCs), peritubular myoid cells (PCs) and Sertoli cells (SCs), from rats, mice and guinea pigs have been reported. In humans, the isolation of populations enriched for primary LCs, PCs or SCs also have described. One objective of this study was to determine if populations of cells enriched for all three of these cell types can be isolated from testes of single human donors, and we were successful in doing so from testes of three donors. Testes tissues were enzymatically digested, gravity sedimented and Percoll filtered to isolate populations enriched for LCs, PCs and SCs. LCs and PCs were identified by colorimetric detection of the expression of prototypical enzymes. Division of PCs and SCs in culture has been reported. We observed that primary human LCs could divide in culture by incorporation of 5-ethynyl-2'-deoxyuridine. SCs were identified and their functionality was demonstrated by the formation of tight junctions as shown by the expression of tight junction proteins, increased transepithelial electrical resistance, polarized secretion of biomolecules and inhibition of lucifer yellow penetration. Furthermore, we found that human SC feeder layers could facilitate germ cell progression of human embryonic stem cells (hESCs) by microarray analysis of gene expression.

Alpha 1 adrenergic receptor-mediated inflammatory responses in human testicular peritubular cells

Stress activates the sympathetic nervous system and is linked to impaired fertility in man. We hypothesized that catecholamines by acting on testicular cells have a role in these events, possibly by fostering an inflammatory environment. The cells of the wall of seminiferous tubules, human testicular peritubular cells (HTPCs), express adrenergic receptors (ADRs) α1B, α1D, β1 and β2. A selective α1-ADR agonist, phenylephrine, increased intracellular Ca²⁺-levels in cultured HTPCs and induced COX-2, IL-6 and MCP-1 mRNA expression without affecting IL-1β mRNA. These changes were paralleled by a significant increase in the secretion of IL-6 and MCP-1. Epinephrine was also effective, but salbutamol, a selective β2-ADR agonist was not. Our results suggest that stress-associated elevation of catecholamines may be able to promote inflammatory events by targeting peritubular cells in the human testis. Blockage of α1-ADRs may therefore be a novel way to interfere with stress-related impairment of male reproductive functions.

Ca2+ Signaling and IL-8 Secretion in Human Testicular Peritubular Cells Involve the Cation Channel TRPV2

Peritubular cells are part of the wall of seminiferous tubules in the human testis and their contractile abilities are important for sperm transport. In addition, they have immunological roles. A proteomic analysis of isolated human testicular peritubular cells (HTPCs) revealed expression of the transient receptor potential channel subfamily V member 2 (TRPV2). This cation channel is linked to mechano-sensation and to immunological processes and inflammation in other organs. We verified expression of TRPV2 in peritubular cells in human sections by immunohistochemistry. It was also found in other testicular cells, including Sertoli cells and interstitial cells. In cultured HTPCs, application of cannabidiol (CBD), a known TRPV2 agonist, acutely induced a transient increase in intracellular Ca²⁺ levels. These Ca²⁺ transients could be blocked both by ruthenium red, an unspecific Ca²⁺ channel blocker, and tranilast (TRA), an antagonist of TRPV2, and were also abolished when extracellular Ca²⁺ was removed. Taken together this indicates functional TRPV2 channels in peritubular cells. When applied for 24 to 48 h, CBD induced expression of proinflammatory factors. In particular, mRNA and secreted protein levels of the proinflammatory chemokine interleukin-8 (IL-8/CXCL8) were elevated. Via its known roles as a major mediator of the inflammatory response and as an angiogenic factor, this chemokine may play a role in testicular physiology and pathology.

Prostaglandin E2 (PGE2) is a testicular peritubular cell-derived factor involved in human testicular homeostasis

In man, blockage of prostaglandin (PG)-production e.g. by non-steroidal anti-inflammatory drug (NSAIDs) may have negative testicular side effects, implying beneficial actions of PGs in the testis. We examined human testicular samples and isolated human testicular peritubular cells (HTPCs) to explore sites of PG-synthesis and targets. HTPCs express cyclooxygenase 1 (COX1) and secrete PGE2. Receptors (EP1, 2, 4) were specifically identified in peritubular cells. In HTPCs PGE2 significantly increased mRNA levels of the contractility protein calponin, but did not induce contractions. PGE2, as well as EP1 and EP4 receptor agonists, significantly increased glia cell line derived neurotrophic factor (GDNF) mRNA and/or protein levels. Importantly, the NSAID ibuprofen reduced PGE2 and this action also lowered SMA and calponin mRNA levels and levels of secreted GDNF protein. The results reveal an unknown PGE2 system in the human testis, in involving peritubular cells, which may be prone to interference by NSAIDs.

NLRP3 in somatic non-immune cells of rodent and primate testes

NLRP3 is part of the NLRP3 inflammasome and a global sensor of cellular damage. It was recently discovered in rodent Sertoli cells. We investigated NLRP3 in mouse, human and non-human primate (marmoset and rhesus macaque) testes, employing immunohistochemistry. Sertoli cells of all species expressed NLRP3, and the expression preceded puberty. In addition, peritubular cells of the adult human testes expressed NLRP3. NLRP3 and associated genes (PYCARD, CASP1, IL1B) were also found in isolated human testicular peritubular cells and the mouse Sertoli cell line TM4. Male infertility due to impairments of spermatogenesis may be related to sterile inflammatory events. We observed that the expression of NLRP3 was altered in the testes of patients suffering from mixed atrophy syndrome, in which tubules with impairments of spermatogenesis showed prominent NLRP3 staining. In order to explore a possible role of NLRP3 in male infertility, associated with sterile testicular inflammation, we studied a mouse model of male infertility. These human aromatase-expressing transgenic mice (AROM+) develop testicular inflammation and impaired spermatogenesis during aging, and the present data show that this is associated with strikingly elevated Nlrp3 expression in the testes compared to WT controls. Interference by aromatase inhibitor treatment significantly reduced increased Nlrp3 levels. Thus, throughout species NLRP3 is expressed by somatic cells of the testis, which are involved in testicular immune surveillance. We conclude that NLRP3 may be a novel player in testicular immune regulation.

Insights into the role of androgen receptor in human testicular peritubular cells

Contractile smooth muscle-like peritubular cells build the wall of seminiferous tubules in men. They are crucial for sperm transport and complement the functions of Sertoli cells by secreting factors, including glial cell line-derived neurotrophic factor. Previous studies revealed that they also secrete the chemokine C-X-C motif chemokine ligand 12 (CXCL12), which has known roles in spermatogenesis. Peritubular cells express the androgen receptor (AR), which is retained in isolated human testicular peritubular cells. We aimed to explore AR-regulated functions in human testicular peritubular cells. Bearing in mind that infertile men often have high aromatase activity, which may lower intratesticular androgen concentrations, an animal model for male infertility was studied. These mice display an age-dependent loss in spermatogenesis due to high aromatase activity. Human testicular peritubular cells were exposed to dihydrotestosterone or the antiandrogen flutamide. We studied AR, smooth muscle cell markers, glial cell line-derived neurotrophic factor and 15 secreted factors previously identified, including CXCL12. We used qPCR, Western blotting, ELISA or selected reaction monitoring (SRM). In the animal model for male infertility, we employed qPCR and immunohistochemistry. Dihydrotestosterone increased AR and flutamide prevented these actions. The smooth muscle cell markers calponin and smooth muscle actin were likewise increased, while cell size or cellular proliferation was not changed. Dihydrotestosterone did not increase glial cell line-derived neurotrophic factor or CXCL12 secretion but increased levels of serine proteinase inhibitor (SERPIN) E1. The animal model for male infertility with high aromatase activity showed reduced numbers of AR-immunoreactive testicular peritubular cells, suggesting that altered androgen and/or oestrogen levels could influence AR-mediated responses in peritubular cells. Androgens act on human testicular peritubular cells to enhance AR levels, their contractile phenotype and to modulate the secretion of some secreted factors. This study suggests that some aspects of human peritubular cell functions are regulated by androgens.

ATP-mediated Events in Peritubular Cells Contribute to Sterile Testicular Inflammation

Peritubular myoid cells, which form the walls of seminiferous tubules in the testis, are functionally unexplored. While they transport sperm and contribute to the spermatogonial stem cell niche, specifically their emerging role in the immune surveillance of the testis and in male infertility remains to be studied. Recently, cytokine production and activation of Toll-like receptors (TLRs) were uncovered in cultured peritubular cells. We now show that human peritubular cells express purinergic receptors P2RX4 and P2RX7, which are functionally linked to TLRs, with P2RX4 being the prevalent ATP-gated ion channel. Subsequent ATP treatment of cultured peritubular cells resulted in up-regulated (pro-)inflammatory cytokine expression and secretion, while characteristic peritubular proteins, that is smooth muscle cell markers and extracellular matrix molecules, decreased. These findings indicate that extracellular ATP may act as danger molecule on peritubular cells, able to promote inflammatory responses in the testicular environment.

Cytokines in Male Fertility and Reproductive Pathologies: Immunoregulation and Beyond

Germline development in vivo is dependent on the environment formed by somatic cells and the differentiation cues they provide; hence, the impact of local factors is highly relevant to the production of sperm. Knowledge of how somatic and germline cells interact is central to achieving biomedical goals relating to restoring, preserving or restricting fertility in humans. This review discusses the growing understanding of how cytokines contribute to testicular function and maintenance of male reproductive health, and to the pathologies associated with their abnormal activity in this organ. Here we consider both cytokines that signal through JAKs and are regulated by SOCS, and those utilizing other pathways, such as the MAP kinases and SMADs. The importance of cytokines in the establishment and maintenance of the testis as an immune-privilege site are described. Current research relating to the involvement of immune cells in testis development and disease is highlighted. This includes new data relating to testicular cancer which reinforce the understanding that tumorigenic cells shape their microenvironment through cytokine actions. Clinical implications in pathologies relating to local inflammation and to immunotherapies are discussed.

Sterile inflammation as a factor in human male infertility: Involvement of Toll like receptor 2, biglycan and peritubular cells

Changes in the wall of seminiferous tubules in men with impaired spermatogenesis imply sterile inflammation of the testis. We tested the hypothesis that the cells forming the wall of seminiferous tubules, human testicular peritubular cells (HTPCs), orchestrate inflammatory events and that Toll like receptors (TLRs) and danger signals from the extracellular matrix (ECM) of this wall are involved. In cultured HTPCs we detected TLRs, including TLR2. A TLR-2 ligand (PAM) augmented interleukin 6 (IL-6), monocyte chemo-attractant protein-1 (MCP-1) and pentraxin 3 (PTX3) in HTPCs. The ECM-derived proteoglycan biglycan (BGN) is secreted by HTPCs and may be a TLR2-ligand at HTPCs. In support, recombinant human BGN increased PTX3, MCP-1 and IL-6 in HTPCs. Variable endogenous BGN levels in HTPCs derived from different men and differences in BGN levels in the tubular wall in infertile men were observed. In testes of a systemic mouse model for male infertility, testicular sterile inflammation and elevated estradiol (E2) levels, BGN was also elevated. Hence we studied the role of E2 in HTPCs and observed that E2 elevated the levels of BGN. The anti-estrogen ICI 182,780 blocked this action. We conclude that TLR2 and BGN contribute to sterile inflammation and infertility in man.

Stem cell therapy for the treatment of Leydig cell dysfunction in primary hypogonadism

The production of testosterone occurs within the Leydig cells of the testes. When production fails at this level from either congenital, acquired, or systemic disorders, the result is primary hypogonadism. While numerous testosterone formulations have been developed, none are yet fully capable of replicating the physiological patterns of testosterone secretion. Multiple stem cell therapies to restore androgenic function of the testes are under investigation. Leydig cells derived from bone marrow, adipose tissue, umbilical cord, and the testes have shown promise for future therapy for primary hypogonadism. In particular, the discovery and utilization of a group of progenitor stem cells within the testes, known as stem Leydig cells (SLCs), has led not only to a better understanding of testicular development, but of treatment as well. When combining this with an understanding of the mechanisms that lead to Leydig cell dysfunction, researchers and physicians will be able to develop stem cell therapies that target the specific step in the steroidogenic process that is deficient. The current preclinical studies highlight the complex nature of regenerating this steroidogenic process and the problems remain unresolved. In summary, there appears to be two current directions for stem cell therapy in male primary hypogonadism. The first method involves differentiating adult Leydig cells from stem cells of various origins from bone marrow, adipose, or embryonic sources. The second method involves isolating, identifying, and transplanting stem Leydig cells into testicular tissue. Theoretically, in-vivo re-activation of SLCs in men with primary hypogonadism due to age would be another alternative method to treat hypogonadism while eliminating the need for transplantation.

Spermatogenesis in humans and its affecting factors

Spermatogenesis is an extraordinary complex process. The differentiation of spermatogonia into spermatozoa requires the participation of several cell types, hormones, paracrine factors, genes and epigenetic regulators. Recent researches in animals and humans have furthered our understanding of the male gamete differentiation, and led to clinical tools for the better management of male infertility. There is still much to be learned about this intricate process. In this review, the critical steps of human spermatogenesis are discussed together with its main affecting factors.

Testis peritubular myoid cells increase their motility and express matrix-metalloproteinase 9 (MMP-9) after interaction with embryonal carcinoma cells

Today cancer research studies have highlighted the role of the cancer-stroma interaction in the regulation of invasive processes. However, very little is known about cell-to-cell relationships between germinal cancer cells and the somatic ones belong to their close environment, particularly at early invasion stages. Here, we have studied the potential role of the seminiferous peritubular myoid cells (PTCs), as potential part of the reactive stroma, like tumor myofibroblast, in the progression of embryonal carcinoma (EC). To this end, we show results on the in vitro interactions between F9 murine embryonal carcinoma cells (EC cells) and primary cultures of murine PTCs, using contact-dependent and contact-independent 2D co-cultures. In these circumstances, when EC cells interact with PTCs they change their migratory behavior and matrix-metalloproteinase 9 (MMP-9) was up-regulated in PTCs. Additionally, among a variety of cytokines implicated in tumor-stroma cross-talk, we have examined in more detail the influence of tumor necrosis factor alpha (TNF-α). In this regard, it was observed that this cytokine induced a MMP-9 secretion by PTCs in a pattern dependent on its concentration, whereas does not increase the migration capacity of cancer cells. All together, our results provide evidence for a role played by peritubular myoid cells and cancer-cell secreted TNF- α for a change in the tumor microenvironment during the early stages of EC progression.

Human testicular peritubular cells secrete pigment epithelium-derived factor (PEDF), which may be responsible for the avascularity of the seminiferous tubules

Male fertility depends on spermatogenesis, which takes place in the seminiferous tubules of the testis. This compartment is devoid of blood vessels, which are however found in the wall of the seminiferous tubules. Our proteomic study using cultured human testicular peritubular cells (HTPCs) i.e. the cells, which form this wall, revealed that they constitutively secrete pigment epithelium-derived factor, PEDF, which is known to exert anti-angiogenic actions. Immunohistochemistry supports its presence in vivo, in the human tubular wall. Co-culture studies and analysis of cell migration patterns showed that human endothelial cells (HUVECs) are repulsed by HTPCs. The factor involved is likely PEDF, as a PEDF-antiserum blocked the repulsing action. Thus testicular peritubular cells, via PEDF, may prevent vascularization of human seminiferous tubules. Dihydrotestosterone (DHT) increased PEDF (qPCR) in HTPCs, however PEDF expression in the testis of a non-human primate occurs before puberty. Thus PEDF could be involved in the establishment of the avascular nature of seminiferous tubules and after puberty androgens may further reinforce this feature. Testicular microvessels and blood flow are known to contribute to the spermatogonial stem cell niche. Hence HTPCs via control of testicular microvessels may contribute to the regulation of spermatogonial stem cells, as well.

Cyclooxygenase and prostaglandins in somatic cell populations of the testis

Prostaglandins (PGs) are synthesized through the action of the rate-limiting enzyme cyclooxygenase (COX) and further specific enzymes. The development ofCox-deficient mice in the 1990s gave insights into the reproductive roles of PGs. FemaleCox-knockout mice were subfertile or infertile. Interestingly, fertility was not affected in male mice deficient inCox, suggesting that PGs may not be critical for the functioning of the testis. However, this conclusion has recently been challenged by observations of important roles for PGs in both physiological and pathological processes in the testis. The two key somatic cell types in the testis, Leydig and Sertoli cells, express the inducible isoenzyme COX2 and produce PGs. Testicular COX2 expression in these somatic cells is regulated by hormonal input (FSH, prolactin (PRL), and testosterone) as well as by IL1β. PGs modulate steroidogenesis in Leydig cells and glucose uptake in Sertoli cells. Hence, the COX2/PG system in Leydig and Sertoli cells acts as a local modulator of testicular activity, and consequently may regulate spermatogenic efficiency. In addition to its expression in Leydig and Sertoli cells, COX2 has been detected in the seminiferous tubule wall, and in testicular macrophages and mast cells of infertile patients. These observations highlight the possible relevance of PGs in testicular inflammation associated with idiopathic infertility. Collectively, these data indicate that the COX2/PG system plays crucial roles not only in testicular physiology (i.e., development, steroidogenesis, and spermatogenesis), but more importantly in the pathogenesis or maintenance of infertility status in the male gonad. Further studies of these actions could lead to new therapeutic approaches to idiopathic male infertility.

Free German abstract

A German translation of this abstract is freely available athttp://www.reproduction-online.org/content/149/4/R169/suppl/DC1.

Free Spanish abstract

A Spanish translation of this abstract is freely available athttp://www.reproduction-online.org/content/149/4/R169/suppl/DC2.

Peritubular myoid cells have a role in postnatal testicular growth

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

Human testicular peritubular cells host putative stem Leydig cells with steroidogenic capacity

AIM

We aim to examine the steroidogenic phenotype and the differentiation potential of human testicular peritubular cells (HTPCs) and to explore their possible relationship to the adult Leydig cell lineage.

BACKGROUND

The cells of the adult Leydig cell lineage may reside in the peritubular compartment of the testis. This suggestion is supported by the facts that the rodent peritubular cells can be differentiated toward this lineage and that cAMP enhances their steroidogenic potential.

METHODS

Human testicular biopsies, and derived HTPCs, were analyzed by immunohistochemistry, RT-PCR, and Western blotting. After stimulation by forskolin or platelet-derived growth factor-BB, quantitative RT-PCR was used to compare the levels of mRNAs encoding proteins involved in steroidogenesis and steroid production was analyzed by liquid chromatography and tandem mass spectrometry.

RESULTS

Immunohistochemical analysis revealed that the peritubular cells that form the outer part of the tubular wall express platelet derived growth factor receptor-α. Furthermore, the pluripotency markers (POU domain class 5 transcription factor 1, GATA-binding protein 4), stem Leydig cell markers (platelet derived growth factor receptor-A, leukemia inhibitory factor receptor), and mRNAs encoding proteins involved in steroidogenesis (nuclear receptor subfamily 5, group A, member 1; steroidogenic acute regulatory protein; CYP11A1; CYP17A1; 3β-hydroxysteroid dehydrogenase) were expressed by the HTPCs. Stimulation with forskolin increased the expression of the steroidogenic markers, which was accompanied by the production of pregnenolone and progesterone by HTPCs in vitro. Treatment with platelet-derived growth factor-BB induced expression of steroidogenic acute regulatory protein.

CONCLUSIONS

Our results indicate that the tubular wall of the human testis is a reservoir for cells of the adult Leydig cell lineage and that the steroidogenic potential of these cells can be activated in culture.

Innate and adaptive immune responses in male and female reproductive tracts in homeostasis and following HIV infection

The male and female reproductive tracts are complex microenvironments that have diverse functional demands. The immune system in the reproductive tract has the demanding task of providing a protective environment for a fetal allograft while simultaneously conferring protection against potential pathogens. As such, it has evolved a unique set of adaptations, primarily under the influence of sex hormones, which make it distinct from other mucosal sites. Here, we discuss the various components of the immune system that are present in both the male and female reproductive tracts, including innate soluble factors and cells and humoral and cell-mediated adaptive immunity under homeostatic conditions. We review the evidence showing unique phenotypic and functional characteristics of immune cells and responses in the male and female reproductive tracts that exhibit compartmentalization from systemic immunity and discuss how these features are influenced by sex hormones. We also examine the interactions among the reproductive tract, sex hormones and immune responses following HIV-1 infection. An improved understanding of the unique characteristics of the male and female reproductive tracts will provide insights into improving clinical treatments of the immunological causes of infertility and the design of prophylactic interventions for the prevention of sexually transmitted infections.

The immune privilege of testis and gravid uterus: same difference?

The fetus in the gravid uterus and the developing spermatogenic cells in the adult testis both comprise special challenges for the host immune system. Protection of the neoantigens of the fetus and male germ cells from immune attack, defined as immune privilege, is fundamental for the propagation of species. Immune privilege is not simply the absence of leukocytes, but involves immune and non-immune cells acting synergistically together at multiple levels to create a unique tolerogenic environment. A number of the pathways are shared by the testis and gravid uterus. Amongst them steroid hormones, namely testosterone in the male and progesterone in the female, seem to function as key molecules that govern the local production of immunoregulatory factors which finally control the overall immune environment.

Trial of recombinant follicle-stimulating hormone pretreatment for GnRH-induced fertility in patients with congenital hypogonadotropic hypogonadism

CONTEXT AND OBJECTIVE

The optimal strategy for inducing fertility in men with congenital hypogonadotropic hypogonadism (CHH) is equivocal. Albeit a biologically plausible approach, pretreatment with recombinant FSH (rFSH) before GnRH/human chorionic gonadotropin administration has not been sufficiently assessed. The objective of the study was to test this method.

DESIGN AND SETTING

This was a randomized, open-label treatment protocol at an academic medical center.

PATIENTS AND INTERVENTIONS

GnRH-deficient men (CHH) with prepubertal testes (<4 mL), no cryptorchidism, and no prior gonadotropin therapy were randomly assigned to either 24 months of pulsatile GnRH therapy alone (inducing endogenous LH and FSH release) or 4 months of rFSH pretreatment followed by 24 months of GnRH therapy. Patients underwent serial testicular biopsies, ultrasound assessments of testicular volume, serum hormone measurements, and seminal fluid analyses.

RESULTS

rFSH treatment increased inhibin B levels into the normal range (from 29 ± 9 to 107 ± 41 pg/mL, P < .05) and doubled testicular volume (from 1.1 ± 0.2 to 2.2 ± 0.3 mL, P < .005). Histological analysis showed proliferation of both Sertoli cells (SCs) and spermatogonia, a decreased SC to germ cell ratio (from 0.74 to 0.35), and SC cytoskeletal rearrangements. With pulsatile GnRH, the groups had similar hormonal responses and exhibited significant testicular growth. All men receiving rFSH pretreatment developed sperm in their ejaculate (7 of 7 vs 4 of 6 in the GnRH-only group) and showed trends toward higher maximal sperm counts.

CONCLUSIONS

rFSH pretreatment followed by GnRH is successful in inducing testicular growth and fertility in men with CHH with prepubertal testes. rFSH not only appears to maximize the SC population but also induces morphologic changes, suggesting broader developmental roles.

Human testicular peritubular cells: more than meets the eye

In healthy men, several layers of inconspicuously flat cells and extracellular matrix (ECM) proteins build the wall of the seminiferous tubules. The cells of this wall, peritubular cells, are not well characterized. They are smooth-muscle-like and contractile and transport immotile sperm, a function important for male fertility. However, their full functional importance, especially their potential contribution to the paracrine regulation of the male gonad, is unknown. In men with impaired spermatogenesis, the architecture of the tubular wall is frequently altered. Deposits of ECM and morphological changes of peritubular cells imply that functions of peritubular cells may be fundamentally altered. To be able to study human peritubular cells and their functions, a culture method was established. It is based on small biopsies of patients with obstructive azoospermia but normal spermatogenesis (human testicular peritubular cells, HTPCs) and non-obstructive azoospermia, impaired spermatogenesis, and testicular fibrosis (HTPCFs). Results obtained from cellular studies and parallel examinations of biopsies provide insights into the repertoire of the secretion products, contractile properties, and plasticity of human peritubular cells. They produce ECM components, including the proteoglycan decorin, which may influence paracrine signaling between testicular cells. They may contribute to the spermatogonial stem cell niche via secreted factors. They are regulated by mast cell and macrophage products, and in response produce factors that can fuel inflammatory changes. They possess a high degree of plasticity, which results in hypertrophy and loss of contractile abilities. The data collectively indicate important roles of inconspicuous testicular peritubular cells in human male fertility and infertility.

Partial loss of contractile marker proteins in human testicular peritubular cells in infertility patients

Fibrotic remodelling of the testicular tubular wall is common in human male infertility caused by impaired spermatogenesis. We hypothesized that this morphological change bears witness of an underlying fundamentally altered state of the cells building this wall, that is, peritubular smooth muscle-like cells. This could include a loss of the contractile abilities of these cells and thus be a factor in male infertility. Immune cells are increased in the tubular wall in these cases, hence local immune cell-related factors, including a prostaglandin (PG) metabolite may be involved. To explore these points in the human, we used testicular biopsies, in which tubules with normal spermatogenesis and impaired spermatogenesis are next to each other [mixed atrophy (MA)], normal biopsies and cultured human testicular peritubular cells. Proteins essential for contraction, myosin heavy chain (MYH11), calponin (Cal) and relaxation, cGMP-dependent protein kinase 1 (cGKI), were readily detected by immunohistochemistry and were equally distributed in all peritubular cells of biopsies with normal spermatogenesis. In all biopsies, vascular smooth muscle cells also stained and served as important intrinsic controls, which showed that in MA samples when spermatogenesis was impaired, staining was restricted to only few peritubular cells or was absent. When spermatogenesis was normal, regular peritubular staining became obvious. This pattern suggests complex regulatory influences, which in face of the identical systemic hormonal situation in MA patients, are likely caused by the local testicular micromilieu. The PG metabolite 15dPGJ2 may represent such a factor and it reduced Cal protein levels in peritubular cells from patients with/without impaired spermatogenesis. The documented phenotypic switch of peritubular, smooth muscle-like cells in MA patients may impair the abilities of the afflicted seminiferous tubules to contract and relax and must now be considered as a part of the complex events in male infertility.