Region-specific innate antiviral responses of the human epididymis

Regional modulation of toll-like receptor signaling pathway genes in acute epididymitis in mice

BACKGROUND

Region-specific immune environments in the epididymis influence the immune responses to uropathogenic Escherichia coli (UPEC) infection, a relevant cause of epididymitis in men. Toll-like receptors (TLRs) are essential to orchestrate immune responses against bacterial infections. The epididymis displays region-specific inflammatory responses to bacterial-derived TLR agonists, such as lipopolysaccharide (LPS; TLR4 agonist) and lipoteichoic acid (LTA; TLR2/TLR6 agonist), suggesting that TLR-associated signaling pathways could influence the magnitude of inflammatory responses in epididymitis.

OBJECTIVES

To investigate the expression and regulation of key genes associated with TLR4 and TLR2/TLR6 signaling pathways during epididymitis induced by UPEC, LPS, and LTA in mice.

MATERIAL AND METHODS

Epididymitis was induced in mice using UPEC, ultrapure LPS, or LTA, injected into the interstitial space of the initial segment or the lumen of the vas deferens close to the cauda epididymidis. Samples were harvested after 1, 5, and 10 days for UPEC-treated animals and 6 and 24 h for LPS-/LTA-treated animals. Ex vivo epididymitis was induced by incubating epididymal regions from naive mice with LPS or LTA. RT-qPCR and Western blot assays were conducted.

RESULTS

UPEC infection up-regulated Tlr2, Tlr4, and Tlr6 transcripts and their associated signaling molecules Cd14, Ticam1, and Traf6 in the cauda epididymidis but not in the initial segment. In these epididymal regions, LPS and LTA differentially modulated Tlr2, Tlr4, Tlr6, Cd14, Myd88, Ticam1, Traf3, and Traf6 expression levels. NFKB and AP1 activation was required for LPS- and LTA-induced up-regulation of TLR-associated signaling transcripts in the cauda epididymidis and initial segment, respectively.

CONCLUSION

The dynamic modulation of TLR4 and TLR2/TLR6 signaling pathways gene expression during epididymitis indicates bacterial-derived antigens elicit an increased tissue sensitivity to combat microbial infection in a spatial manner in the epididymis. Differential activation of TLR-associated signaling pathways may contribute to fine-tuning inflammatory responses along the epididymis.

Identification and Functional Assignment of Genes Implicated in Sperm Maturation of Tibetan Sheep

While traveling through the epididymis, immature sheep spermatozoa undergo a sequence of processes that ultimately give them the capacity to swim and fertilize an egg. Different gene expression patterns may be found in the epididymal caput, corpus, and cauda, conferring variant or unique biological roles during epididymis development and sperm maturation. To search for candidate genes associated with ovine sperm maturation and assess their possible modulating mechanisms, we characterized gene expression in each epididymal segment derived from pre- and post-pubertal Tibetan sheep by RNA sequencing. Compared with pre-puberty, 7730 (3724 upregulated and 4006 downregulated), 7516 (3909 upregulated and 3607 downregulated), and 7586 (4115 elevated and 3471 downregulated) genes were found to be differentially expressed in the post-pubertal caput, corpus, and cauda epididymis, respectively, and real-time quantitative PCR verified the validity of the gathered expression patterns. Based on their functional annotations, most differential genes were assigned to the biological processes and pathways associated with cellular proliferation, differentiation, immune response, or metabolic activities. As for the post-pubertal epididymis, 2801, 197, and 186 genes were specifically expressed in the caput, corpus, and cauda, respectively. Functional annotation revealed that they were mainly enriched to various distinct biological processes associated with reproduction (including the caput binding of sperm to the zona pellucida; fertilization in the caput and corpus; and meiosis in the caput and cauda) and development (such as cell differentiation and developmental maturation in the caput; cell proliferation and metabolism in the corpus; and regulation of tube size and cell division/cell cycle in the cauda). Additionally, we focused on the identification of genes implicated in immunity and sperm maturation, and subsequent functional enrichment analysis revealed that immune-related genes mainly participated in the biological processes or pathways associated with the immune barrier (such as JAM3 and ITGA4/6/9) and immunosuppression (such as TGFB2, TGFBR1, TGFBR2, and SMAD3), thus protecting auto-immunogenic spermatozoa. Additionally, sperm maturation was mostly controlled by genes linked with cellular processes, including cell growth, proliferation, division, migration, morphogenesis, and junction. Altogether, these results suggest that most genes were differentially expressed in developmental epididymal regions to contribute to microenvironment development and sperm maturation. These findings help us better understand the epididymal biology, including sperm maturation pathways and functional differences between the epididymal regions in Tibetan sheep and other sheep breeds.

Dual SMAD inhibition enhances the longevity of human epididymis epithelial cells

Primary human epididymis epithelial (HEE) cells are valuable reagents for functional studies on the human epididymis. We used them previously to determine the transcriptional networks that establish cell identity along the length of the epididymis from caput, corpus, and cauda. These studies on HEE cells and organoids derived from them revealed important cellular properties. However, similar to other primary cells, HEE cells undergo replicative senescence and de-differentiation in culture. A cocktail of small molecules was shown elsewhere to extend longevity of epithelial basal cells. The components included transforming growth factor β (TGF-β)/bone morphogenetic protein (BMP) antagonists, WNT agonist, and Rho-associated and coiled-coil containing protein kinase (ROCK) inhibitor (ROCKi), which together prevented the senescence-related upregulation of TGF-β signaling pathway members. Here, we treat HEE cells with the same cocktail and observed enhanced replicative potential and prolonged expression of markers of HEE differentiation. This treatment expands the differentiated HEE cell population available from individual epididymis tissue samples that can be used for molecular, cellular, and functional studies.

An atlas of human proximal epididymis reveals cell-specific functions and distinct roles for CFTR

Spermatozoa released from the testis are unable to fertilize an egg without a coordinated process of maturation in the lumen of the epididymis. Relatively little is known about the molecular events that integrate this critical progression along the male genital ducts in man. Here, we use single cell RNA-sequencing to construct an atlas of the human proximal epididymis. We find that the CFTR, which is pivotal in normal epididymis fluid transport, is most abundant in surface epithelial cells in the efferent ducts and in rare clear cells in the caput epididymis, suggesting region-specific functional properties. We reveal transcriptional signatures for multiple cell clusters, which identify the individual roles of principal, apical, narrow, basal, clear, halo, and stromal cells in the epididymis. A marked cell type-specific distribution of function is seen along the duct with local specialization of individual cell types integrating processes of sperm maturation.

The Immune Characteristics of the Epididymis and the Immune Pathway of the Epididymitis Caused by Different Pathogens

The epididymis is an important male accessory sex organ where sperm motility and fertilization ability develop. When spermatozoa carrying foreign antigens enter the epididymis, the epididymis shows "immune privilege" to tolerate them. It is well-known that a tolerogenic environment exists in the caput epididymis, while pro-inflammatory circumstances prefer the cauda epididymis. This meticulously regulated immune environment not only protects spermatozoa from autoimmunity but also defends spermatozoa against pathogenic damage. Epididymitis is one of the common causes of male infertility. Up to 40% of patients suffer from permanent oligospermia or azoospermia. This is related to the immune characteristics of the epididymis itself. Moreover, epididymitis induced by different pathogenic microbial infections has different characteristics. This article elaborates on the distribution and immune response characteristics of epididymis immune cells, the role of epididymis epithelial cells (EECs), and the epididymis defense against different pathogenic infections (such as uropathogenic Escherichia coli, Chlamydia trachomatis, and viruses to provide therapeutic approaches for epididymitis and its subsequent fertility problems.

The epididymal immune balance: a key to preserving male fertility

Up to 15% of male infertility has an immunological origin, either due to repetitive infections or to autoimmune responses mainly affecting the epididymis, prostate, and testis. Clinical observations and epidemiological data clearly contradict the idea that the testis confers immune protection to the whole male genital tract. As a consequence, the epididymis, in which posttesticular spermatozoa mature and are stored, has raised some interest in recent years when it comes to its immune mechanisms. Indeed, sperm cells are produced at puberty, long after the establishment of self-tolerance, and they possess unique surface proteins that cannot be recognized as self. These are potential targets of the immune system, with the risk of inducing autoantibodies and consequently male infertility. Epididymal immunity is based on a finely tuned equilibrium between efficient immune responses to pathogens and strong tolerance to sperm cells. These processes rely on incompletely described molecules and cell types. This review compiles recent studies focusing on the immune cell types populating the epididymis, and proposes hypothetical models of the organization of epididymal immunity with a special emphasis on the immune response, while also discussing important aspects of the epididymal immune regulation such as tolerance and tumour control.

Postnatal differentiation and regional histological variations in the ductus epididymidis of the Congjiang Xiang pig

The Congjiang Xiang pig is a rare Chinese miniature breed whose epididymal histologic features through the postnatal development are poorly understood. To clarify the histomorphological differences between each region of epididymis during postnatal development, 24 male Congjiang Xiang pigs aged from neonatal (15 d), peri-puberty (30 d), puberty (60 d) to adult (180 d) stages, were examined. Postnatal differentiation of the different regions (I-V) of the epididymis started from birth and continued until maturity that showed regional variations. Developmental progression was disto-proximal. At the neonatal stage, Wolffian duct differentiation starts in the distal region, then ascends to the middle region which forms regions V, IV and III, respectively. A simple lined cuboidal in the epidydimal epithelial, which gradually differentiated into a pseudostratified columnar with stereocilia from neonatal to post-pubertal. After puberty cell rearrangement occurred in the epithelium, differentiation accelerated, and spermatozoon seen in the lumen, especially the lumen of region II. In region III, both halo and apical cells were frequently observed. At the post-pubertal stage, clear cells were frequently observed in Region IV-V, and the epididymal duct was markedly increased in size and fully packed with spermatozoa. The information presented in this study will be helpful for future evaluations of Congjiang Xiang pig fertility. After puberty cell rearrangement occurred in the epithelium, differentiation accelerated, and spermatozoon seen in the lumen, especially the lumen of region II. In region III, both halo and apical cells were frequently observed. At the post-pubertal stage, clear cells were frequently observed in Region IV-V, and the epididymal duct was markedly increased in size and fully packed with spermatozoa. The information presented in this study will be helpful for future evaluations of Congjiang Xiang pig fertility.

From Ancient to Emerging Infections: The Odyssey of Viruses in the Male Genital Tract

The male genital tract (MGT) is the target of a number of viral infections that can have deleterious consequences at the individual, offspring, and population levels. These consequences include infertility, cancers of male organs, transmission to the embryo/fetal development abnormalities, and sexual dissemination of major viral pathogens such as human immunodeficiency virus (HIV) and hepatitis B virus. Lately, two emerging viruses, Zika and Ebola, have additionally revealed that the human MGT can constitute a reservoir for viruses cleared from peripheral circulation by the immune system, leading to their sexual transmission by cured men. This represents a concern for future epidemics and further underlines the need for a better understanding of the interplay between viruses and the MGT. We review here how viruses, from ancient viruses that integrated the germline during evolution through old viruses (e.g., papillomaviruses originating from Neanderthals) and more modern sexually transmitted infections (e.g., simian zoonotic HIV) to emerging viruses (e.g., Ebola and Zika) take advantage of genital tract colonization for horizontal dissemination, viral persistence, vertical transmission, and endogenization. The MGT immune responses to viruses and the impact of these infections are discussed. We summarize the latest data regarding the sources of viruses in semen and the complex role of this body fluid in sexual transmission. Finally, we introduce key animal findings that are relevant for our understanding of viral infection and persistence in the human MGT and suggest future research directions.

Differential gene expression profiles of human efferent ducts and proximal epididymis

BACKGROUND

Gene expression patterns along the epididymis are established by specific transcription factor networks that coordinate region-specific functions. In rodents, the epididymis can be divided in up to 19 segments. Based on gross anatomy, the human epididymis is divided into caput, corpus, and cauda segments together with efferent ducts that occupy the proximal part of this organ.

OBJECTIVES

To determine to which extent gene expression pattern is segmented along the efferent ducts and the proximal region of the epididymis in men of reproductive age.

MATERIALS AND METHODS

Epididymal transcriptome profiling was performed on eight distinct regions from three donors. Microarray analysis was performed on a gene-chip microarray. Differentially expressed genes (DEGs)>2-fold change (P < .05) were clustered in relation to their intensity profiles. Overrepresented biological functions from gene ontology were searched using DAVID 6.8. Expression profiles were validated by qRT-PCR quantification of selected genes.

RESULTS

There were no DEGs among segments 1-3 of efferent ducts region neither among segments 4-6 of the caput epididymis. 1058 DEGs were identified between efferent ducts and the epididymis, whereas 444 and 846 DEGs distinguished the caput from the corpus (section 7) and cauda (section 8) epididymis, respectively. A total of 131 DEGs were detected between corpus (7) and cauda (8) transcriptomes. Up-regulated DEGs in the efferent ducts were predominantly related to cilium assembly/movement and cell differentiation. Fertilization, defense, and immune responses were associated with caput epididymis (4-6), while spermatogenesis and protein binding were found all along the epididymis (4-8).

DISCUSSION

The proximal human epididymis is exclusively occupied by efferent ducts with a distinct DEG profile compared with the downstream epididymal segments. Moreover, gene expression profiling revealed two regions in the human epididymis: the caput and the distal corpus/cauda region.

CONCLUSIONS

Human epididymal transcriptome reveals limited DEGs, and efferent ducts have a distinct DEGs profile.

Of vessels and cells: the spatial organization of the epididymal immune system

BACKGROUND

One third of infertility cases in couples worldwide has an exclusive male origin and immune disorders, essentially due to repetitive infections, are emerging an cause of male infertility. As the place of sperm maturation, epididymis must be preserved from excessive immune responses that may arise following infections of the male genital tract. At the same time, epididymis must set and maintain a tolerogenic environment in order not to destroy sperm cells that enter the tissue at puberty, long after the immune system has been taught to recognize self pathogens. The immune cells that populate the epididymis have raised growing interest over the last thirty years but they may be not sufficient to understand the immune balance existing in this organ, between immune response to pathogens and tolerance to spermatozoa. Indeed, immune cells are the most motile cells in the organism and need blood and lymphatic vessels to traffic between lymphoid organs and sites of infection to induce efficient responses.

OBJECTIVES

To review the literature on the blood and lymphatic vessels, and on the immune cells present at steady state in the rodent epididymis (rat and mouse).

MATERIALS AND METHODS

PubMed database was searched for studies reporting on the spatial organization of the rodent epididymal vasculature and immune cell types at steady state. This search was combined with recent findings from our team.

RESULTS

At steady state, the rodent epididymis presents with dense blood and lymphatic networks, and a large panel of immune cells distributed across the interstitum and epithelium along the organ.

CONCLUSIONS

The immune system of the rodent epididymis is highly organized. Exploring its functions, especially in an infectious context, is the essential coming step before any transposition to human.

Transcriptional networks in the human epididymis

BACKGROUND

The epithelial lining of the human epididymis is critical for sperm maturation. This process requires distinct specialized functions in the head, body, and tail of the duct. These region-specific properties are maintained by distinct gene expression profiles which are governed by transcription factor networks, non-coding RNAs, and other factors.

MATERIALS AND METHODS

We used genome-wide protocols including DNase-seq, RNA-seq and ChIP-seq to characterize open (active) chromatin, the transcriptome and occupancy of specific transcription factors (TFs) respectively, in caput, corpus, and cauda segments of adult human epididymis tissue and primary human epididymis epithelial (HEE) cell cultures derived from them. RNA-seq following TF depletion or activation, combined with gene ontology analysis also determined TF targets.

RESULTS

Among regional differentially expressed transcripts were epithelial-selective transcription factors (TFs), microRNAs, and antiviral response genes. Caput-enriched TFs included hepatocyte nuclear factor 1 (HNF1) and the androgen receptor (AR), both of which were also predicted to occupy cis-regulatory elements identified as open chromatin in HEE cells. HNF1 targets were identified genome-wide using ChIP-seq, in HEE cells. Next, siRNA-mediated depletion of HNF1 revealed a pivotal role for this TF in coordinating epithelial water and solute transport in caput epithelium. The importance of AR in HEE cells was shown by AR ChIP-seq, and by RNA-seq after synthetic androgen (R1881) treatment. AR has a distinct transcriptional program in the HEE cells and likely recruits different co-factors (RUNX1 and CEBPβ) in comparison to those used in prostate epithelium.

DISCUSSION AND CONCLUSION

Our data identify many transcription factors that regulate the development and differentiation of HEE cells. Moreover, a comparison between immature and adult HEE cells showed key TFs in the transition to fully differentiated function of this epithelium. These data may help identify new targets to treat male infertility and have the potential to open new avenues for male contraception.