Sperm-associated antigen 11A is expressed exclusively in the principal cells of the mouse caput epididymis in an androgen-dependent manner

Distinct actions of testicular endocrine and lumicrine signaling on the proximal epididymal transcriptome

The epididymal function and gene expression in mammals are under the control of the testis. Sex steroids are secreted from the testis and act on the epididymis in an endocrine manner. There is another, non-sex steroidal secreted signaling, named lumicrine signaling, in which testis-derived secreted proteins go through the male reproductive tract and act on the epididymis. The effects of such multiple regulations on the epididymis by the testis have been investigated for many genes. The recent development of high-throughput next-generation sequencing now enables us a further comparative survey of endocrine and lumicrine action-dependent gene expression. In the present study, testis-derived endocrine and lumicrine actions on epididymal gene expression were comparatively investigated by RNA-seq transcriptomic analyses. This investigation utilized experimental animal models in which testis-derived endocrine and/or lumicrine actions were interfered with, such as unilateral or bilateral orchidectomy. By bilateral orchidectomy, which interferes with both endocrine and lumicrine actions, 431 genes were downregulated. By unilateral orchidectomy, which also interferes with endocrine and lumicrine actions by the unilateral testis, but the endocrine action was compensated by the contralateral testis, 283 genes were downregulated. The content of such genes downregulated by unilateral orchidectomy was like those of lumicrine action-interfered efferent duct-ligation, W/Wv, and Nell2-/- mice. When genes affected by unilateral and bilateral orchidectomy were compared, 154 genes were commonly downregulated, whereas 217 genes were specifically downregulated only by bilateral orchidectomy, indicating the distinction between endocrine and lumicrine actions on the proximal epididymal transcriptome. Comparative transcriptome analyses also showed that the expressions of genes emerging since Amniota were notably impacted by bilateral orchidectomy, unilateral orchidectomy, and lumicrine action-interfering treatments; the degree of influence from these treatments varied based on the evolutionary stage beyond Amniota. These findings unveil an evolutional transition of regulated gene expression in the proximal epididymis by two different testis-derived signaling mechanisms.

Busulfan administration replicated the characteristics of the epididymal initial segment observed in mice lacking testis-epididymis lumicrine signaling

The physiological functions of the mammalian epididymis are typically regulated by the testes. In addition to sex steroids secreted by testicular Leydig cells, which act on the epididymis in an endocrine manner, there is a non-sex-steroidal signaling pathway known as the lumicrine pathway. This lumicrine signaling pathway involves ligand proteins secreted from germ cells within the testicular seminiferous tubules traversing the male reproductive tract, which induce epithelial differentiation in the epididymis. These findings prompted an inquiry into whether treatments influencing testis physiology can disrupt epididymal function by interfering with testis-epididymis communication. Busulfan, an alkylating agent commonly used to deplete testicular germ cells in reproductive biology, has not been sufficiently explored because of its effects on the epididymis. This study investigated the effects of busulfan administration on the proximal epididymis using histological and transcriptomic analyses. Notably, busulfan, as opposed to the vehicle dimethyl sulfoxide (DMSO), altered the morphology of the initial segment of the epididymis, leading to a reduction in the cell height of the luminal epithelium. RNA sequencing identified 185 significantly downregulated genes in the proximal epididymis of busulfan-administered mice compared to DMSO-administered mice. Comparative transcriptome analyses revealed similarities between the epididymal transcriptome of busulfan-administered mice and lumicrine-deficient mice, such as efferent-duct-ligated W/Wv and Nell2-/- mice. However, this differed from that of bilaterally orchidectomized mice, in which both the endocrine and lumicrine signaling pathways were simultaneously ablated. Collectively, these results suggested that the harmful effects of busulfan on the proximal epididymis are secondary consequences of the ablation of testis-epididymis lumicrine signaling.

Conditioned medium and secretome from epididymal epithelial cell cultures improve sperm kinetics and capacitation

Background and Aim

Sperm maturation occurs in the epididymis through interactions with existing molecules inside the lumen. However, the mechanism of epididymis molecular transfer is currently unclear. This study was aimed to determine the necessity of the epididymal epithelial cells (EECs) in the process of sperm maturation in terms of sperm kinetics and tyrosine phosphorylation.

Materials and Methods

A true experimental research design was used in this study. The medium tested was a primary culture of mice caput epididymal cells (cells and culture medium), conditioned medium (CM) (supernatant of EECs), and secretome (CM filtered at 0.22 μm). Sperm was cocultured in EEC culture, CM, and secretome for 1, 2, 3, or 4 h. The original culture medium was used as the control. Sperm kinetic analysis was performed after the indicated times using computer-assisted sperm analysis, and tyrosine phosphorylation was detected using the Western blot technique.

Results

A primary culture of caput EECs was successfully generated. The results showed increased sperm motility and progressive movement after 3 h of incubation (p < 0.05). There was a significant decrease in the average path velocity (VAP) values after 4 h of incubation (p < 0.05), but there was no significant change in the 1, 2, and 3 h incubation groups. The EEC culture-CM and secretome groups showed a significant increased progressivity and VAP percentage values compared with the control medium (p < 0.05). In terms of percentage motility, the culture and CM groups were significantly different from the control medium, but the secretome group was not.

Conclusion

The sperm kinetics of sperm cultured in CM, secretome, and EEC were significantly increased after 3 h of incubation, suggesting that CM and secretome can be used to replace EECs, especially when analyzing molecules secreted by the epididymal epithelium during sperm maturation. The results of this study highlight the potential of CM and secretome as therapy mediums for sperm kinetic abnormalities.

Effect of C-Type Natriuretic Peptide (CNP) on Spermatozoa Maturation in Adult Rat Epididymis

C-type natriuretic peptide (CNP) is highly expressed in male reproductive tissues, such as the epididymis. The aim of this study is to explore the role of CNP in the maturation of rat epididymal spermatozoa. First, the expression levels of CNP and its specific natriuretic peptide receptor-B (NPR-B) were detected in various tissues of rats and epididymis at different stages after birth. Then a castrated rat model was established to analyze the relationship between testosterone and CNP/NPR-B expression in the epididymis. Finally, CNP and different inhibitors (NPR-B inhibitors, cGMP inhibitors) were used to incubate epididymal sperm in vitro to examine sperm mobility and expression of sperm maturation-related factors. The results showed CNP/NPR-B mRNAs were expressed in all tissues of rats, but were extremely highly expressed in male genital ducts (seminal vesicle, prostate and epididymis). The expression of CNP/NPR-B in epididymis was the highest at birth and the fifth week after birth. In the epididymis, CNP/NPR-B were highly expressed in the caput and located in the epididymal epithelial cells. After castration, the expression of CNP/NPR-B decreased sharply and was restored quickly after testosterone supplementation. In vitro, CNP could significantly promote the acquisition of epididymal sperm motility through the NPR-B/cGMP pathway and induce the expression of sperm maturation-related factors (such as Bin1b, Catsper 1, Dnah17, Fertilin). This study shows that CNP plays a role in epididymal sperm maturation. The mechanism of CNP is to promote the acquisition of epididymal sperm fluidity through the NPR-B/cGMP signaling pathway and also to regulate sperm maturation-related genes. Moreover, the expression of CNP/NPR-B was regulated by testosterone.

Various gene modification techniques to discover molecular targets for nonhormonal male contraceptives: A review

The identification and characterization of relevant targets are necessary for developing nonhormonal male contraceptives. The molecules must demonstrate that they are necessary for reproduction. As a result, a sophisticated technique is required to identify the molecular targets for nonhormonal male contraceptives. Genetic modification (GM) techniques are one method that can be applied. This technique has been widely used to study gene function that effected male fertility and has resulted in the discovery of numerous nonhormonal male contraceptive target molecules. We examined GM techniques and approaches used to investigate genes involved in male fertility as potential targets for nonhormonal contraceptives. The discovery of nonhormonal contraceptive candidate molecules was increased by using GM techniques, especially the Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 method. The discovery of candidate nonhormonal contraceptive molecules can be a wide-open research for the development of nonhormonal male contraceptives. Therefore, we are believing that one day nonhormonal male contraceptives will be released.

Defensins: defenders of human reproductive health

BACKGROUND

Reproductive tract infection is an important factor leading to male and female infertility. Among female infertility factors, microbial and viral infections are the main factors affecting female reproductive health and causing tubal infertility, ectopic tubal pregnancy and premature delivery. Among male infertility factors, 13-15% of male infertility is related to infection. Defensins are cationic antibacterial and antiviral peptides, classified into α-defensins, β-defensins and θ-defensins. Humans only have α-defensins and β-defensins. Apart from their direct antimicrobial functions, defensins have an immunomodulatory function and are involved in many physiological processes. Studies have shown that defensins are widely distributed in the female reproductive tract (FRT) and male reproductive tract (MRT), playing a dual role of host defence and fertility protection. However, to our knowledge, the distribution, regulation and function of defensins in the reproductive tract and their relation to reproduction have not been reviewed.

OBJECTIVE AND RATIONALE

This review summarizes the expression, distribution and regulation of defensins in the reproductive tracts to reveal the updated research on the dual role of defensins in host defence and the protection of fertility.

SEARCH METHODS

A systematic search was conducted in PubMed using the related keywords through April 2022. Related data from original researches and reviews were integrated to comprehensively review the current findings and understanding of defensins in the human reproductive system. Meanwhile, female and male transcriptome data in the GEO database were screened to analyze defensins in the human reproductive tracts.

OUTCOMES

Two transcriptome databases from the GEO database (GSE7307 and GSE150852) combined with existing researches reveal the expression levels and role of the defensins in the reproductive tracts. In the FRT, a high expression level of α-defensin is found, and the expression levels of defensins in the vulva and vagina are higher than those in other organs. The expression of defensins in the endometrium varies with menstrual cycle stages and with microbial invasion. Defensins also participate in the local immune response to regulate the risk of spontaneous preterm birth. In the MRT, a high expression level of β-defensins is also found. It is mainly highly expressed in the epididymal caput and corpus, indicating that defensins play an important role in sperm maturation. The expression of defensins in the MRT varies with androgen levels, age and the status of microbial invasion. They protect the male reproductive system from bacterial infections by neutralizing lipopolysaccharide and downregulating pro-inflammatory cytokines. In addition, animal and clinical studies have shown that defensins play an important role in sperm maturation, motility and fertilization.

WIDER IMPLICATIONS

As a broad-spectrum antimicrobial peptide without drug resistance, defensin has great potential for developing new natural antimicrobial treatments for reproductive tract infections. However, increasing evidence has shown that defensins can not only inhibit microbial invasion but can also promote the invasion and adhesion of some microorganisms in certain biological environments, such as human immunodeficiency virus. Therefore, the safety of defensins as reproductive tract anti-infective drugs needs more in-depth research. In addition, the modulatory role of defensins in fertility requires more in-depth research since the current conclusions are based on small-size samples. At present, scientists have made many attempts at the clinical transformation of defensins. However, defensins have problems such as poor stability, low bioavailability and difficulties in their synthesis. Therefore, the production of safe, effective and low-cost drugs remains a challenge.

RNA-Seq reveals the functional specificity of epididymal caput, corpus, and cauda genes of cattleyak

The first filial generation of the cattleyaks demonstrates hybrid vigor; however, the male cattleyaks are infertile and restrict productivity and breeding. The discovery of genes in a segment-specific approach offers valuable information and understanding concerning fertility status, yet the biology of cattleyak epididymis is still progressing. Comparative transcriptome analysis was performed on segment pairs of cattleyak epididymis. The caput versus corpus epididymis provided the highest (57.8%) differentially expressed genes (DEGs), corpus versus cauda (25.1%) followed, whereas caput versus cauda pair (17.1%) had the least DEGs. The expression levels of genes coding EPHB6, TLR1, MUC20, MT3, INHBB, TRPV5, EI24, PAOX, KIF12, DEPDC5, and KRT25, which might have the potentials to regulate the homeostasis, innate immunity, differentiation, motility, transport, and sperm maturation-related function in epididymal cells, were downregulated in the distal segment of epididymis. Top enriched KEGG pathways included mTOR, axon guidance, and taste transduction signaling pathways. EIF4B, EPHB6, and TAS2R42 were enriched in the pathways, respectively. Identifying key, new, and unexplored DEGs among the epididymal segments and further analyzing them could boost cattleyak fertility by maximizing sperm quality from genetically better sires and also facilitate better understanding of the epididymal biology.

Mouse CD52 is predominantly expressed in the cauda epididymis, regulated by androgen and lumicrine factors

Background:

Sperm maturation takes place through contact between sperm and proteins produced in the epididymal lumen. CD52 had been characterised in the sperm; however, the expression and its regulation in the epididymis are mostly unknown.

Aim:

This study aimed to analyse the expression and regulation of CD52 in the mouse epididymis.

Setting and Design:

Experimental design was used in this study.

Materials and Methods:

Epididymis tissues from mice strain Deutch Democratic Yokohama were used as sources of total RNA. Bioinformatic tool was used to predict signal peptides. Quantitative real-time reverse transcription–polymerase chain reaction was used to analyse tissue distribution, androgen, testicular factors dependency and postnatal development.

Statistical Analysis:

One-way analysis of variance was used to analyse differences between treatment and control untreated group. P < 0.05 was determined as a significant difference.

Results:

CD52 amino acid sequence contains a signal peptide, indicating it is a secretory protein. CD52 exhibited region-specific expression in the epididymis, with the highest level being in the cauda. CD52 expression was regulated by androgen indicated by a significant downregulation at day 1 and day 3 following a castration (P < 0.05). Dependency on androgen was confirmed by injection of exogenous testosterone which prevented downregulation by 50%. Moreover, lumicrine factors also influenced CD52 expression indicated by ligation of efferent duct which also reduced expression at day 1 to day 5 following the ligation (P < 0.05). CD52 expression was developmentally regulated. This was shown by increase in the level of expression starting at day 15 postnatally.

Conclusion:

CD52 shows characteristics of genes involved in sperm maturation in the epididymis.

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.

Mouse defensin beta 20 (Defb20) is expressed specifically in the caput region of the epididymis and regulated by androgen and testicular factors

Sperm cells undergo maturation during their transit throughout the epididymis. This process takes place in region-specific manner in which sperm are battered by proteins secreted by epithelium lining the epididymal duct. Most of the genes that encode for the proteins involved in the sperm maturation remain uncharacterized. Previous studies showed that family of β-defensins preferentially eaxpressed in male reproductive tracts and play an important role in both innate immunity and sperm fertility. In this study we characterized Defb20 to gain insight on its role in sperm maturation. Bioinformatic tools were used to analyzed functional domains and signal peptide. qRT-PCR analyses were used to analyzed tissue distribution, dependency on androgen and testicular factors and developmental-regulated expression analysis. Defb20 sequence contains important domains such as N-myristoilation and kinase binding sites which are putatively involved in the protein activation and protein-plasma membrane interaction. Moreover, DEFB20 contains a signal peptide indicating characteristic of secretory proteins. Defb20 was expressed exclusively in the epididymis with the highest expression in the caput region and was down-regulated by gonadectomy. Defb20 was also regulated by testicular factors in which the expression was down-regulated after efferent duct ligation (EDL). The dependency on the androgen was further confirmed by postnatal expression analysis in which Defb20 began to express at day-20 postnatal indicating specific stage of expression after initial development of the testis. In conclusion, Defb20 have a potential to be involved in the epididymal sperm maturation process.

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.

Seasonal expressions of SPAG11A and androgen receptor in the epididymis of the wild ground squirrels (<em>Citellus dauricus</em> Brandt)

Sperm-associated antigen 11A (SPAG11A), a protein expressed exclusively in the epididymis, plays a vital and special role in regulating mammalian sperm maturation. The aim of this study was to investigate the seasonal expressions of SPAG11A and androgen receptor (AR) in the epididymis of the wild ground squirrels (Spermophilus dauricus Brandt). Morphologically, the results showed that epididymis length and weight in the breeding season were significantly higher than those of the non-breeding season. Histologically, the results revealed that enlarged lumen diameters, thickened epithelium and abundant sperm in the breeding season while reduced lumen diameters and epithelium with no sperm in the non-breeding season. SPAG11A was intensely expressed in cytoplasm and nucleus of epithelial cells and smooth muscle cells in the breeding season, and weaker staining in the non-breeding season. In the lumen of epididymis, SPAG11A immunostaining in the sperm of the epididymal corpus and cauda was higher than those in the caput during the breeding season. The immunostaining of AR was only presented in nucleus of smooth muscle cells and epithelial cells in the epididymis from the breeding season rather than the non-breeding season. The results of real-time quantitative PCR also showed that the mRNA levels of SPAG11A and AR in the epididymis during the breeding season were significantly higher than those of the non-breeding season. In addition, the circulating testosterone, follicle- stimulating hormone and luteinizing hormone levels in the squirrels were higher in the breeding season compared with those in the non-breeding season. Taken together, these results implied that SPAG11A might be involved in regulating seasonal changes in epididymal functions of the wild ground squirrels.

Unusual interplay of contrasting selective pressures on β-defensin genes implicated in male fertility of the Buffalo (Bubalus bubalis)

BACKGROUND

The buffalo, despite its superior milk-producing ability, suffers from reproductive limitations that constrain its lifetime productivity. Male sub-fertility, manifested as low conception rates (CRs), is a major concern in buffaloes. The epididymal sperm surface-binding proteins which participate in the sperm surface remodelling (SSR) events affect the survival and performance of the spermatozoa in the female reproductive tract (FRT). A mutation in an epididymal secreted protein, beta-defensin 126 (DEFB-126/BD-126), a class-A beta-defensin (CA-BD), resulted in decreased CRs in human cohorts across the globe. To better understand the role of CA-BDs in buffalo reproduction, this study aimed to identify the BD genes for characterization of the selection pressure(s) acting on them, and to identify the most abundant CA-BD transcript in the buffalo male reproductive tract (MRT) for predicting its reproductive functional significance.

RESULTS

Despite the low protein sequence homology with their orthologs, the CA-BDs have maintained the molecular framework and the structural core vital to their biological functions. Their coding-sequences in ruminants revealed evidence of pervasive purifying and episodic diversifying selection pressures. The buffalo CA-BD genes were expressed in the major reproductive and non-reproductive tissues exhibiting spatial variations. The Buffalo BD-129 (BuBD-129) was the most abundant and the longest CA-BD in the distal-MRT segments and was predicted to be heavily O-glycosylated.

CONCLUSIONS

The maintenance of the structural core, despite the sequence divergence, indicated the conservation of the molecular functions of the CA-BDs. The expression of the buffalo CA-BDs in both the distal-MRT segments and non-reproductive tissues indicate the retention the primordial microbicidal activity, which was also predicted by in silico sequence analyses. However, the observed spatial variations in their expression across the MRT hint at their region-specific roles. Their comparison across mammalian species revealed a pattern in which the various CA-BDs appeared to follow dissimilar evolutionary paths. This pattern appears to maintain only the highly efficacious CA-BD alleles and diversify their functional repertoire in the ruminants. Our preliminary results and analyses indicated that BuBD-129 could be the functional ortholog of the primate DEFB-126. Further studies are warranted to assess its molecular functions to elucidate its role in immunity, reproduction and fertility.

The epididymal amyloid matrix: structure and putative functions

BACKGROUND

We previously demonstrated the normal mouse epididymal lumen contains a non-pathological amyloid matrix that surrounds spermatozoa and plays important roles in sperm maturation and protection.

OBJECTIVE

The objective herein was to present a review of this work, including studies showing the amyloid structures of four members of the CRES (cystatin-related epididymal spermatogenic) subgroup are integral and essential components of the amyloid matrix.

METHODS

We used conformation-dependent reagents that recognize the cross-β-sheet structure characteristic of amyloid, including thioflavin S (ThS), thioflavin T (ThT), anti-amyloid antibodies, and X-ray diffraction, as well as negative-stain transmission electron microscopy (TEM) to visualize amyloid structures in the epididymal lumen. Antibodies that specifically detect each CRES subgroup family member were also used in indirect immunofluorescence analysis.

RESULTS AND DISCUSSION

The epididymal lumen contains an amyloid matrix that surrounds maturing spermatozoa and represents a functional amyloid. Alterations in the structure of the amyloid matrix by the loss of the CRES subgroup members or the overexpression of cystatin C result in epididymal pathologies, including infertility. Preliminary data suggest the epididymal amyloid matrix is structurally and functionally similar to bacterial biofilms.

CONCLUSION

Together, these results suggest the amyloid matrix serves important roles in epididymal function including sperm maturation and protection.

Novel androgen-induced activity of an antimicrobial β-defensin: Regulation of Wolffian duct morphogenesis

The Wolffian duct (WD) undergoes morphological changes induced by androgens to form the epididymis, which is an organ essential for sperm maturation. Androgen action in WD epithelium involves paracrine factors of mesenchymal origin that function by still poorly understood mechanisms. Here we studied the antimicrobial β-defensin SPAG11C as a new player in duct morphogenesis, localized prenatally in the WD mesenchyme. Organotypic culture of rat WDs and tissues from Androgen Receptor (AR) knockout mice (ARKO) were used. Our results show that androgen/AR signaling differentially regulated SPAG11C expression at mRNA and protein levels in the developing WD. WDs incubated with recombinant human SPAG11C were shorter and less coiled as a result of reduced epithelial cell proliferation, but not increased apoptosis. Our results suggested β-defensin SPAG11C as an androgen-target required for WD morphogenesis. This highlights the multifunctional repertoire of the β-defensin protein family and their potential contribution to the in utero environment that determines male reproductive success.

Functional expression of G protein-coupled receptor 30 in immature rat epididymal epithelium

The aim of this study is to investigate the functional role of G protein-coupled receptor 30 (GPR30) in the epididymis. We found that GPR30 is expressed in the epithelium of the immature rat epididymis and is involved in chloride secretion into the caudal epididymis lumen. The short-circuit current (Isc) experiments showed that in primary cultured caudal epididymis epithelium, activation of GPR30 by its specific agonist G1 induced a mono-phasic current increase, and G15, the specific antagonist of GPR30, could completely inhibit the current induced by G1. The G1-induced Isc was largely blocked by application of the non-specific chloride channel inhibitor diphenylamine-dicarboxylic acid (DPC), or by the cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor CFTR_inh-172 , suggesting that the current was mainly mediated through CFTR. In addition, after stimulating GPR30 by G1, the intracellular concentration of cAMP in the epithelium was significantly increased, indicating that the cAMP signal pathway is involved and could be responsible for the CFTR activation. Finally, to further investigate the function of GPR30 in vivo, G15 was administrated into rats subcutaneously. The osmotic pressure of the micro perfusion solution from epididymis was measured and the sperms were collected. Results showed that there was an osmotic pressure increase of the perfusion solution from G15 treated rats. When the GPR30 was inhibited by G15 endogenously, the motility of sperms decreased. Our data demonstrated that GPR30 is involved in the formation of caudal epididymis fluid micro-environment thus affecting sperm motility.

β-defensins and the epididymis: contrasting influences of prenatal, postnatal, and adult scenarios

β-defensins are components of host defense, with antimicrobial and pleiotropic immuno-modulatory properties. Research over the last 15 years has demonstrated abundant expression of a variety of β-defensins in the postnatal epididymis of different species. A gradient of region- and cell-specific expression of these proteins is observed in the epithelium of the postnatal epididymis. Their secretion into the luminal fluid and binding to spermatozoa as they travel along the epididymis has suggested their involvement in reproduction-specific tasks. Therefore, continuous attention has been given to various β-defensins for their role in sperm function and fertility. Although β-defensins are largely dependent on androgens, the underlying mechanisms regulating their expression and function in the epididymis are not well understood. Recent investigation has pointed out to a new and interesting scenario where β-defensins emerge with a different expression pattern in the Wolffian duct, the embryonic precursor of the epididymis, as opposed to the adult epididymis, thereby redefining the concept concerning the multifunctional roles of β-defensins in the developing epididymis. In this review, we summarize some current views of β-defensins in the epididymis highlighting our most recent data and speculations on their role in the developing epididymis during the prenatal-to-postnatal transition, bringing attention to the many unanswered questions in this research area that may contribute to a better understanding of epididymal biology and male fertility.

Identification of New Epididymal Luminal Fluid Proteins Involved in Sperm Maturation in Infertile Rats Treated by Dutasteride Using iTRAQ

Background: Spermatozoa become mature and acquire fertilizing capacity during their passage through the epididymal lumen. In this study, we identified new epididymal luminal fluid proteins involved in sperm maturation in infertile rats by dutasteride, a dual 5α-reductase inhibitor, in order to provide potential epididymal targets for new contraceptives and infertility treatment. Methods: Male rats were treated with dutasteride for 28 consecutive days. We observed the protein expression profiles in the epididymal luminal fluids in infertile and normal rats using isobaric tags for relative and absolute quantitation (iTRAQ) technique. The confidence of proteome data was validated by enzyme-linked immunosorbent assays. Results: 1045 proteins were tested, and 23 of them presented different expression profiling in the infertile and normal rats. The seven proteins were down-regulated, and 16 proteins were up-regulated. Among the seven proteins which were significantly down-regulated by dutasteride in the epididymal luminal fluids, there were three β-defensins (Defb2, Defb18 and Defb39), which maybe the key proteins involved in epididymal sperm maturation and male fertility. Conclusions: We report for the first time that dutasteride influences the protein expression profiling in the epididymal luminal fluids of rats, and this result provides some new epididymal targets for male contraception and infertility therapy.

Major protein alterations in spermatozoa from infertile men with unilateral varicocele

BACKGROUND

The etiology of varicocele, a common cause of male factor infertility, remains unclear. Proteomic changes responsible for the underlying pathology of unilateral varicocele have not been evaluated. The objective of this prospective study was to employ proteomic techniques and bioinformatic tools to identify and analyze proteins of interest in infertile men with unilateral varicocele.

METHODS

Spermatozoa from infertile men with unilateral varicocele (n=5) and from fertile men (control; n=5) were pooled in two groups respectively. Proteins were extracted and separated by 1-D SDS-PAGE. Bands were digested and identified on a LTQ-Orbitrap Elite hybrid mass spectrometer system. Bioinformatic analysis identified the pathways and functions of the differentially expressed proteins (DEP).

RESULTS

Sperm concentration, motility and morphology were lower, and reactive oxygen species levels were higher in unilateral varicocele patients compared to healthy controls. The total number of proteins identified were 1055, 1010 and 1042 in the fertile group, and 795, 713 and 763 proteins in the unilateral varicocele group. Of the 369 DEP between both groups, 120 proteins were unique to the fertile group and 38 proteins were unique to the unilateral varicocele group. Compared to the control group, 114 proteins were overexpressed while 97 proteins were underexpressed in the unilateral varicocele group. We have identified 29 proteins of interest that are involved in spermatogenesis and other fundamental reproductive events such as sperm maturation, acquisition of sperm motility, hyperactivation, capacitation, acrosome reaction and fertilization. The major functional pathways of the 359 DEP related to the unilateral varicocele group involve metabolism, disease, immune system, gene expression, signal transduction and apoptosis. Functional annotations showed that unilateral varicocele mostly affected small molecule biochemistry and post-translational modification proteins. Proteins expressed uniquely in the unilateral varicocele group were cysteine-rich secretory protein 2 precursor (CRISP2) and arginase-2 (ARG2).

CONCLUSIONS

The expression of these proteins of interest are altered and possibly functionally compromised in infertile men with unilateral varicocele. If validated, these proteins may lead to potential biomarker(s) and help better understand the mechanism involved in the pathophysiology of unilateral varicocele in infertile men.

Androgenic regulation of beta-defensins in the mouse epididymis

BACKGROUND

The majority of beta-defensin family members are exclusively expressed in the epididymis, and some members have been shown to play essential roles in sperm maturation and fertility in rats, mice and humans. Therefore, beta-defensins are hypothesized to be potential targets for contraception and infertility diagnosis and treatment. Clarifying the regulatory mechanisms for the expression of these genes is necessary. Androgen/androgen receptor (AR) signaling plays an important regulatory role in epididymal structure and function. However, very little is known about the androgenic regulation on the production and secretion of the epididymal beta-defensins.

METHODS

The expression of beta-defensins was detected by quantitative RT-PCR. The androgen dependence of beta-defensins was determined by bilateral orchiectomy and androgen supplementation. The androgen response elements (AREs) in the promoters of beta-defensins were identified using the MatInspector software. The binding of AR to AREs was assayed by ChIP-PCR/qPCR.

RESULTS

We demonstrated that 23 mouse caput epididymal beta-defensins were differentially regulated by androgen/androgen receptor. Six genes, Defb18, 19, 20, 39, 41, and 42, showed full regulation by androgens. Ten genes, Defb15, 30, 34, 37, 40, 45, 51, 52, 22 and Spag11a, were partially regulated by androgens. Defb15, 18, 19, 20, 30, 34, 37, 39, 41, 42, 22 and Spag11a were associated with androgen receptor binding sites in their promoter or intronic regions, indicating direct regulation of AR. Six genes, Defb1, 12, 13, 29, 35, and spag11b/c, exhibited an androgen-independent expression pattern. One gene, Defb25, was highly dependent on testicular factors rather on androgens.

CONCLUSIONS

The present study provides novel insights into the mechanisms of androgen regulation on epididymal beta-defensins, enabling a better understanding of the function of beta-defensins in sperm maturation and fertility.

Importance of β-defensins in sperm function

Recent work in humans and mouse has confirmed the involvement of the host defence β-defensin peptides in male fertility. We discuss here the work that has implicated β-defensins in sperm function including the identification of the epididymis as the predominant site of expression of the peptides and the in vivo consequences of mutation and deletion. The potential dual role of these peptides in the regulation of infection and control of sperm maturation is compelling and may combine their antimicrobial activity with the ability of these molecules to interact with cell membrane receptors and modulate ion transport.