CFTR gene mutations and polymorphism are associated with non-obstructive azoospermia: From case-control study

Global Practice Patterns in the Evaluation of Non-Obstructive Azoospermia: Results of a World-Wide Survey and Expert Recommendations

PURPOSE

Non-obstructive azoospermia (NOA) represents the persistent absence of sperm in ejaculate without obstruction, stemming from diverse disease processes. This survey explores global practices in NOA diagnosis, comparing them with guidelines and offering expert recommendations.

MATERIALS AND METHODS

A 56-item questionnaire survey on NOA diagnosis and management was conducted globally from July to September 2022. This paper focuses on part 1, evaluating NOA diagnosis. Data from 367 participants across 49 countries were analyzed descriptively, with a Delphi process used for expert recommendations.

RESULTS

Of 336 eligible responses, most participants were experienced attending physicians (70.93%). To diagnose azoospermia definitively, 81.7% requested two semen samples. Commonly ordered hormone tests included serum follicle-stimulating hormone (FSH) (97.0%), total testosterone (92.9%), and luteinizing hormone (86.9%). Genetic testing was requested by 66.6%, with karyotype analysis (86.2%) and Y chromosome microdeletions (88.3%) prevalent. Diagnostic testicular biopsy, distinguishing obstructive azoospermia (OA) from NOA, was not performed by 45.1%, while 34.6% did it selectively. Differentiation relied on physical examination (76.1%), serum hormone profiles (69.6%), and semen tests (68.1%). Expectations of finding sperm surgically were higher in men with normal FSH, larger testes, and a history of sperm in ejaculate.

CONCLUSIONS

This expert survey, encompassing 367 participants from 49 countries, unveils congruence with recommended guidelines in NOA diagnosis. However, noteworthy disparities in practices suggest a need for evidence-based, international consensus guidelines to standardize NOA evaluation, addressing existing gaps in professional recommendations.

The interactome of cystic fibrosis transmembrane conductance regulator and its role in male fertility: A critical review

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic adenosine monophosphate (cAMP)-regulated chloride and bicarbonate ion channel found in many human cells. Its unique biochemical characteristics and role as a member of the adenosine triphosphate (ATP)-binding cassette transporters superfamily are pivotal for the transport of several substrates across cellular membranes. CFTR is known to interact, physically and functionally, with several other cellular proteins. Hence, its properties are essential for moving various substances across cell membranes and ensuring correct cell functioning. Genetic mutations or environmental factors may disrupt CFTR's function resulting in different possible phenotypes due to gene variations that affect not only CFTR's function, localization, and processing within cells, but also those of its interactors. This has been reported as an underlying cause of various diseases, including cystic fibrosis. The severe clinical implications of cystic fibrosis have driven intense research into the role of CFTR in lung function but its significance to fertility, particularly in men, has been comparatively understudied. However, ongoing and more recent research into CFTR and its interacting proteins in the testis or specific testicular cells is beginning to shed light on this field. Herein, we provide a comprehensive and up-to-date overview of the CFTR, its interactome, and its crucial role in male reproduction, highlighting recent discoveries and advancements in understanding the molecular mechanisms involved. The comprehension of these complex interactions may pave the way for potential therapeutic approaches to improve fertility of men suffering from alterations in the function of CFTR.

Identification of a novel mutation in chibby family member 2 in a non-obstructive azoospermic patient

Azoospermia constitutes a significant factor in male infertility, defined by the absence of spermatozoa in the ejaculate, afflicting 15% of infertile men. However, a subset of azoospermic cases remains unattributed to known genetic variants. Prior investigations have identified the chibby family member 2 (CBY2) as prominently and specifically expressed in the testes of both humans and mice, implicating its potential involvement in spermatogenesis. In this study, we conducted whole exome sequencing (WES) on an infertile family to uncover novel genetic factors contributing to azoospermia. Our analysis revealed a homozygous c .355 C>A variant of CBY2 in a non-obstructive azoospermic patient. This deleterious variant significantly diminished the protein expression of CBY2 both in vivo and in vitro, leading to a pronounced disruption of spermatogenesis at the early round spermatid stage post-meiosis. This disruption was characterized by a nearly complete loss of elongating and elongated spermatids. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and co-immunoprecipitation assays demonstrated the interaction between CBY2 and Piwi-like protein 1 (PIWIL1). Immunofluorescence staining further confirmed the co-localization of CBY2 and PIWIL1 in the testes during the spermatogenic process in both humans and mice. Additionally, diminished PIWIL1 expression was observed in the testicular tissue from the affected patient. Our findings suggest that the homozygous c .355 C>A variant of CBY2 compromises CBY2 function, contributing to defective spermatogenesis at the round spermiogenic stage and implicating its role in the pathogenesis of azoospermia.

Insights Into Cystic Fibrosis Gene Mutation Frequency, Clinical Findings, and Complications Among Pakistani Patients

Background Cystic fibrosis (CF) is a genetic disorder with diverse symptoms. Understanding its genetic basis and prevalence is crucial for effective management and treatment. Objective The study aimed to provide comprehensive insights into the frequency of CF gene mutations, clinical presentations, and complications among the Pakistani population. Methodology A cohort comprising 892 patients, ranging in age from 18 to more than 40 years, was selected on the basis of clinical and genetic criteria for the diagnosis of CF. Polymerase chain reaction (PCR) was used to look for 34 variants in the CFTR gene in blood samples. Statistical analysis, which included figuring out the number of mutations, the average age of diagnosis, and the genetic diversity of the samples, was performed to analyze the percentage of patients with specific mutations, offering insights into the genetic diversity. Results In our comprehensive analysis of 892 patient samples, 77.47% (n=691) displayed consanguinity, indicating a family history. The prevailing symptoms included chronic cough (88.67%; n=791), recurrent respiratory infections (76.68%; n=684), and fatigue (73.76%; n=658). The major complications comprised pulmonary infections (22%; n=197), cystic fibrosis-related diabetes (21%; n=187), and malabsorption (20%: n=178). A paired t-test revealed a mean difference of 5.750 with a standard deviation of 9.147, a 95% confidence interval from -0.061 to 11.561, a t-value of 2.178 with 11 degrees of freedom, and a two-tailed p-value of 0.052, suggesting a potential trend towards significance. Nevertheless, the asymptotic significance values of 1.000 and 0.998 for both groups indicate no significant difference. Furthermore, the study identified 12 cystic fibrosis gene mutations, with F508del and N1303K being the most prevalent. Conclusion This research revealed significant consanguinity, confirmed typical CF symptoms, and identified common complications and prevalent CFTR gene mutations (with F508del and N1303K being the most common), providing insights for genetic guidance and treatment in the Pakistani community.

The prevalence of common CFTR gene mutations and polymorphisms in infertile Iranian men with very severe oligozoospermia

Due to progress in infertility etiology, several genetic bases of infertility are revealed today. This study aimed to investigate the distribution of mutations in the CFTR gene, M470V polymorphism, and IVS8 poly T. Furthermore, we aimed to examine the hotspot exons (4, 7, 9, 10, 11, 20, and 21 exons) to find a new mutation in cystic fibrosis transmembrane conductance regulator (CFTR) gene among infertile Iranian men very severe oligozoospermia (<1 million sperm/mL ejaculate fluid). In the present case-control study, 200 very severe oligozoospermia (20-60s) and 200 fertile men (18-65s) were registered. Five common CFTR mutations were genotyped using the ARMS-PCR technique. The M470V polymorphism was checked out by real-time PCR, and poly T and exons were sequenced. The F508del was the most common (4.5%) CFTR gene mutation; G542X and W1282X were detected with 1.5% and 1%, respectively. N1303K and R117H were detected in 0.5% of cases. F508del was seen as a heterozygous compound with G542X in one patient and with W1282X in the other patient. Also, in the case of M470V polymorphism, there are differences between the case and control groups (p=0.013). Poly T assay showed statistical differences in some genotypes. The study showed no new mutation in the exons mentioned above. Our results shed light on the genetic basis of men with very severe oligozoospermia in the Iranian population, which will support therapy decisions among infertile men.

Overview Of Current NGS Testing For Male Factor Infertility

Aim — Infertility is a global health problem. The next-generation sequencing and panel testing are offering new opportunities to further diagnose the reason for male infertility. The aim of this paper is to provide a better insight into the currently available panels for male infertility due to impaired spermatogenesis. Methods — We conducted research in the Genetic testing registry by using the keywords „infertility“, „male infertility“. We also gathered information about the number of tested genes, coverage of the panels, turnaround time, and any additional tests, which could be ordered. Results — As a result there were eleven laboratories, offering panel testing for male infertility, which tested for 230 different genes, but 65 genes (28.26%) from the different panels had an uncertain role for the tested condition. Cystic fibrosis transmembrane conductance regulator was the only gene, suggested by all laboratories. Conclusions — Next-generation sequencing could be extremely helpful in the diagnostic process of male infertility. However, clinicians should be aware that some of the included genes have an uncertain role for male infertility.

A Catalog of Human Genes Associated With Pathozoospermia and Functional Characteristics of These Genes

Genetic causes of the global decline in male fertility are among the hot spots of scientific research in reproductive genetics. The most common way to evaluate male fertility in clinical trials is to determine semen quality. Lower semen quality is very often accompanied by subfertility or infertility, occurs in many diseases and can be caused by many factors, including genetic ones. The following forms of lowered semen quality (pathozoospermia) are known: azoospermia, oligozoospermia, asthenozoospermia, teratozoospermia, and some combined forms. To systematize information about the genetic basis of impaired spermatogenesis, we created a catalog of human genes associated with lowered semen quality (HGAPat) and analyzed their functional characteristics. The catalog comprises data on 126 human genes. Each entry of the catalog describes an association between an allelic variant of the gene and a particular form of lowered semen quality, extracted from the experimental study. Most genes included into the catalog are located on autosomes and are associated with such pathologies as non-obstructive azoospermia, oligozoospermia or asthenozoospermia. Slightly less than half of the included genes (43%) are expressed in the testes in a tissue-specific manner. Functional annotation of genes from the catalog showed that spermatogenic failure can be associated with mutations in genes that control biological processes essential for spermiogenesis (regulating DNA metabolism, cell division, formation of cellular structures, which provide cell movement) as well as with mutations in genes that control cellular responses to unfavorable conditions (stress factors, including oxidative stress and exposure to toxins).

Evaluation of association between methylenetetrahydrofolate reductase and azoospermia: A meta-analysis

BACKGROUND

Infertility affects childbearing age couples all over the world. One of the important reasons for infertility is genetic factors. Our study evaluated the association between methylenetetrahydrofolate reductase (MTHFR) and azoospermia.

METHODS

Multiple databases like MEDLINE, EMBASE, Cochrane library, and China journal full-text database were used to search for relevant studies, and full-text articles involved in the evaluation of MTHFR and azoospermia. The results were evaluated using STATA 12.0. Heterogeneity analysis, sensitivity analysis, and bias analysis were also performed on the data.

RESULTS

Thirteen related studies eventually met the inclusion criteria. Significant association between C677T polymorphism and azoospermia (relative risk [RR] = 0.94 [0.90, 0.99], I2 = 60.9%, P = .002), and between A1298C polymorphism and azoospermia (RR = 0.98 [0.94, 1.02], I2 = 56.3%, P = .011) was observed. Meanwhile, in subgroup analysis, Caucasians had higher risk than Mongolians in association between MTHFR and azoospermia.

CONCLUSION

There was association between MTHFR polymorphism and azoospermia. Caucasian populations had higher risk than Mongolian populations in association between MTHFR and azoospermia.

CFTR gene variants as a reason for impaired spermatogenesis: a pilot study and a Meta-analysis of published data

There is increasing data that IVS8-5T variand and TG repeats could lead to impaired spermatogenesis. To investigate this we performed Sanger sequencing on 50 Bulgarian men with a sperm count below 5 × 10⁶/mL and 20 normal fertile men. Frequencies of the results were compared among the two groups. A meta-analysis was perfomed by using the data for 6,423 patients and 5,834 control subjects, tested for the IVS8-5T polymorphism. One case subject (2.0%) was homozygote for the 5 T/5T variant whereas two (4.0%) were heterozygotes for the 5 T/7T variant. No 5 T alleles were found in the control group. The genotypes of the two groups showed a statistically significant difference (p = 0.04, α < 0.05). Also, the odds ratio was 3.73, but this was unsignificant (p = 0.38). All control subjects had 11 TG repeats and for the test group: 47 (94.0%) men with 11 TG repeats and three (6.00%) with 10 TG repeats. Fisher's test showed no significant difference (p = 0.55). The meta-analysis showed that IVS8-5T variant was a risk factor for impaired spermatogenesis (OR = 2.84, p < 0.05) and this was more prominent for non-European (OR = 4.50, p < 0.05) compared to European (OR = 1.28, p < 0.05) men. The IVS8 - 5 T variant could be associated with disorders of sperm production.

Male Infertility in Humans: An Update on Non-obstructive Azoospermia (NOA) and Obstructive Azoospermia (OA)

Non-obstructive azoospermia (NOA) and obstructive azoospermia (OA) are two common causes of infertility that affect a considerable number of men. However, few studies were performed to understand the molecular etiology of these disorders. Studies based on bioinformatics and genetic analyses in recent years, however, have yielded insightful information and have identified a number of genes that are involved in these disorders. In this review, we briefly summarize and evaluate these findings. We also discuss findings based on epigenetic modifications of sperm DNAs that affect a number of genes pertinent to NOA and OA. The information summarized in this Chapter should be helpful to investigators in future functional studies of NOA and OA.

Sperm retrieval and intracytoplasmic sperm injection outcomes in men with cystic fibrosis disease versus congenital bilateral absence of the vas deferens

Recent data suggest that cystic fibrosis transmembrane conductance regulator (CFTR) gene alterations negatively impact male fertility beyond obstruction. We sought to compare gene alterations, sperm retrieval rates, and intracytoplasmic sperm injection (ICSI) outcomes among men with cystic fibrosis (CF) disease and congenital bilateral absence of the vas deferens (CBAVD) only. We retrospectively evaluated all men who underwent surgical sperm retrieval at two academic, high-volume andrology centers from 2010 to 2018. Only men with documented CFTR alterations and obstructive azoospermia from either CBAVD or CF were included. Differences between groups for CFTR abnormality, sperm retrieval, and ICSI outcomes were statistically analyzed. Overall,39 patients were included with 10 in the CF and 29 in the CBAVD groups. Surgical sperm retrieval rates were significantly lower in the CF group for sperm concentration (14.8 × 10⁶ ml^-1vs 61.4 × 10⁶ m^-1, P = 0.02) and total motile sperm count (2.9 million vs 11.4 million, P = 0.01). This difference was only predicted by homozygous delta F508 CFTR mutations (P < 0.05). The CF group also demonstrated a significantly higher rate of rescue testicular sperm extraction (70.0% vs 27.6%, P < 0.03) and lower fertilization rate with ICSI (32.5% vs 68.9%, P < 0.01). In conclusion, those with CF demonstrated lower sperm quality, greater difficulty with sperm retrieval, and worse ICSI outcomes compared with CBAVD-only patients. Homozygous delta F508 CFTR mutations appear to significantly impair spermatogenesis and sperm function.

Molecular genetics of infertility: loss-of-function mutations in humans and corresponding knockout/mutated mice

BACKGROUND

Infertility is a major issue in human reproductive health, affecting an estimated 15% of couples worldwide. Infertility can result from disorders of sex development (DSD) or from reproductive endocrine disorders (REDs) with onset in infancy, early childhood or adolescence. Male infertility, accounting for roughly half of all infertility cases, generally manifests as decreased sperm count (azoospermia or oligozoospermia), attenuated sperm motility (asthenozoospermia) or a higher proportion of morphologically abnormal sperm (teratozoospermia). Female infertility can be divided into several classical types, including, but not limited to, oocyte maturation arrest, premature ovarian insufficiency (POI), fertilization failure and early embryonic arrest. An estimated one half of infertility cases have a genetic component; however, most genetic causes of human infertility are currently uncharacterized. The advent of high-throughput sequencing technologies has greatly facilitated the identification of infertility-associated gene mutations in patients over the past 20 years.

OBJECTIVE AND RATIONALE

This review aims to conduct a narrative review of the genetic causes of human infertility. Loss-of-function mutation discoveries related to human infertility are summarized and further illustrated in tables. Corresponding knockout/mutated animal models of causative genes for infertility are also introduced.

SEARCH METHODS

A search of the PubMed database was performed to identify relevant studies published in English. The term 'mutation' was combined with a range of search terms related to the core focus of the review: infertility, DSD, REDs, azoospermia or oligozoospermia, asthenozoospermia, multiple morphological abnormalities of the sperm flagella (MMAF), primary ciliary dyskinesia (PCD), acephalic spermatozoa syndrome (ASS), globozoospermia, teratozoospermia, acrosome, oocyte maturation arrest, POI, zona pellucida, fertilization defects and early embryonic arrest.

OUTCOMES

Our search generated ∼2000 records. Overall, 350 articles were included in the final review. For genetic investigation of human infertility, the traditional candidate gene approach is proceeding slowly, whereas high-throughput sequencing technologies in larger cohorts of individuals is identifying an increasing number of causative genes linked to human infertility. This review provides a wide panel of gene mutations in several typical forms of human infertility, including DSD, REDs, male infertility (oligozoospermia, MMAF, PCD, ASS and globozoospermia) and female infertility (oocyte maturation arrest, POI, fertilization failure and early embryonic arrest). The causative genes, their identified mutations, mutation rate, studied population and their corresponding knockout/mutated mice of non-obstructive azoospermia, MMAF, ASS, globozoospermia, oocyte maturation arrest, POI, fertilization failure and early embryonic arrest are further illustrated by tables. In this review, we suggest that (i) our current knowledge of infertility is largely obtained from knockout mouse models; (ii) larger cohorts of clinical cases with distinct clinical characteristics need to be recruited in future studies; (iii) the whole picture of genetic causes of human infertility relies on both the identification of more mutations for distinct types of infertility and the integration of known mutation information; (iv) knockout/mutated animal models are needed to show whether the phenotypes of genetically altered animals are consistent with findings in human infertile patients carrying a deleterious mutation of the homologous gene; and (v) the molecular mechanisms underlying human infertility caused by pathogenic mutations are largely unclear in most current studies.

WILDER IMPLICATIONS

It is important to use our current understanding to identify avenues and priorities for future research in the field of genetic causes of infertility as well as to apply mutation knowledge to risk prediction, genetic diagnosis and potential treatment for human infertility.

Cellular mechanism underlying oxytocin-stimulated Cl- secretion in rat cauda epididymal epithelium

The neurohypophyseal hormone oxytocin (OT) plays critical roles in lactation and parturition, while its function in male reproduction system is largely unknown. This study aims to investigate the effect of OT on regulating transepithelial ion transport in rat cauda epididymal epithelium. With the use of RT-PCR, Western blot, and immunohistochemical analysis, we found that OT receptor (OTR) was expressed and localized at the basal membrane of rat cauda epididymal epithelium. The short-circuit current (I_sc) measurement showed that basolateral application of OT to the primary cultured rat cauda epididymal epithelial cells elicited an increase in I_sc, which was abrogated by pretreating the epithelial cells with CFTR_inh-172, a blocker of cystic fibrosis transmembrane conductance regulator (CFTR). Pretreatment with the prostaglandin H synthase inhibitors indomethacin and piroxicam, or the nonselective antagonists of prostaglandin E2 (PGE₂) receptor EP2 or EP4, AH-6809, and AH-23848, significantly attenuated OT-stimulated I_sc response. Furthermore, the generation of PGE₂ was measured using enzyme-linked immunosorbent assay, demonstrating that OT induced a substantial increase in PGE₂ release from primary cultured rat cauda epididymal epithelial cells. In conclusion, activation of OTR by OT triggered PGE₂ release, resulting in CFTR-dependent Cl^- secretion through paracrine/autocrine pathways in rat cauda epididymal epithelium.

Cystic fibrosis gene mutations and polymorphisms in Saudi men with infertility

BACKGROUND

Some mutations of the cystic fibrosis transmembrane regulator (CFTR) gene may impair spermatogenesis or cause a congenital absence of the vas deferens that manifests as isolated male infertility.

OBJECTIVE

Assess the frequency and analyze the spectrum of CFTR gene variations in Saudi men with primary infertility.

DESIGN

Prospective, cross-sectional.

SETTING

Tertiary care specialist hospital in Jeddah.

PATIENTS AND METHODS

Genomic DNA was extracted from peripheral blood samples of Saudi men who presented with primary infertility to the outpatient andrology clinic with either azoospermia or oligoasthenoteratozoospermia. Polymerase chain reaction and direct sequencing were used to identify all variants of the CFTR gene.

MAIN OUTCOME MEASURES

Proportion of the patients with a mutant CFTR gene and the spectrum of CFTR gene variations.

SAMPLE SIZE

50 infertile Saudi men.

RESULTS

This study identified 10 CFTR gene variants in 7 (14%) subjects (100 chromosomes). The detected variants and polymorphisms were: c.1408G>A, c.4389G>A, c.2562T>G, c.869+11C>T, c.2909-92G>A, c.3469-65C>A, c.1210-6delT, c.1210-6T>A, c.2988+1G>A, and c.1210-13GT>TG.

CONCLUSION

We demonstrated that 14% of the study subjects had one or more CFTR mutations and these were compounded in most of the affected patients. The spectrum of CFTR gene mutations in these subjects was similar to the mutations reported in other studies throughout the world.

LIMITATIONS

Small sample size and the lack of a control group.

CONFLICTS OF INTEREST

None.

Gene therapy-emulating small molecule treatments in cystic fibrosis airway epithelial cells and patients

Background

Several small molecule corrector and potentiator drugs have recently been licensed for Cystic Fibrosis (CF) therapy. However, other aspects of the disease, especially inflammation, are less effectively treated by these drugs. We hypothesized that small molecule drugs could function either alone or as an adjuvant to licensed therapies to treat these aspects of the disease, perhaps emulating the effects of gene therapy in CF cells. The cardiac glycoside digitoxin, which has been shown to inhibit TNFα/NFκB signaling in CF lung epithelial cells, may serve as such a therapy.

Methods

IB3–1 CF lung epithelial cells were treated with different Vertex (VX) drugs, digitoxin, and various drug mixtures, and ELISA assays were used to assess suppression of baseline and TNFα-activated secretion of cytokines and chemokines. Transcriptional responses to these drugs were assessed by RNA-seq and compared with gene expression in AAV-[wildtype]CFTR-treated IB3–1 (S9) cells. We also compared in vitro gene expression signatures with in vivo data from biopsied nasal epithelial cells from digitoxin-treated CF patients.

Results

CF cells exposed to digitoxin exhibited significant suppression of both TNFα/NFκB signaling and downstream secretion of IL-8, IL-6 and GM-CSF, with or without co-treatment with VX drugs. No evidence of drug-drug interference was observed. RNA-seq analysis showed that gene therapy-treated CF lung cells induced changes in 3134 genes. Among these, 32.6% were altered by digitoxin treatment in the same direction. Shared functional gene ontology themes for genes suppressed by both digitoxin and gene therapy included inflammation (84 gene signature), and cell-cell interactions and fibrosis (49 gene signature), while genes elevated by both were enriched for epithelial differentiation (82 gene signature). A new analysis of mRNA data from digitoxin-treated CF patients showed consistent trends in expression for genes in these signatures.

Conclusions

Adjuvant gene therapy-emulating activities of digitoxin may contribute to enhancing the efficacy of currently licensed correctors and potentiators in CF patients.

Two novel and correlated CF-causing insertions in the (TG)mTn tract of the CFTR gene

Two novel and related pathogenic variants of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene were structurally and functionally characterized. These alterations have not been previously described in literature. Two patients with diagnosis of Cystic Fibrosis (CF) based on the presence of one mutated allele, p.Phe508del, pathological sweat test and clinical symptoms were studied. To complete the genotypes of both patients, an extensive genetic and functional analysis of the CFTR gene was performed. Extensive genetic characterization confirmed the presence of p.Phe508del pathogenic variant and revealed, in both patients, the presence of an insertion of part of intron 10 in intron 9 of the CFTR gene, within the (TG)m repeat, with a variable poly-T stretch. The molecular lesions resulted to be very similar in both patients, with only a difference in the number of T in the poly-T stretch. The functional characterization at RNA level revealed a complete anomalous splicing, without exon 10, from the allele with the insertion of both patients. Consequently, the alleles with the insertions are expected not to contribute to the formation of a functional CFTR protein. Molecular and functional features of these alterations are compatible with the definition of novel CF-causing variants of the CFTR gene. This also allowed the completion of the genetic characterization of both patients.

Mapping the sites of localization of epithelial sodium channel (ENaC) and CFTR in segments of the mammalian epididymis

The sperm produced in the seminiferous tubules pass through the rete testis, efferent ducts, and epididymis. The epididymis has three distinct regions known as caput, corpus, and cauda. The transit through the epididymis is an essential process in sperm maturation. The lumen of each epididymal region has a unique fluid composition regulated by many ion channels and transporters in the epithelial cells. The objective of this study was to map the sites of localization of ion channels ENaC and CFTR along the length of the mouse and rat epididymis using confocal microscopic imaging. The integrity of the fine structure of the tissues was verified by fluorescent phalloidin staining of actin filaments visualized by high-resolution confocal microscopy. The 2D and 3D images showed preservation of the stereocilia. Based on these images we determined morphometric parameters of the epithelial cells and ducts. ENaC and CFTR immunofluorescence appeared almost continuously on the apical membrane of caput and in smooth muscle myoid cells. In cauda, CFTR expression was observed continuously in long stretches of epithelium interrupted by clusters of cells that showed no CFTR expression. Similar patterns of localization were observed in both mouse and rat samples. Mutations in the CFTR gene are known to result in male infertility. Based on the widespread presence of ENaC along the epididymis we suggest that mutations in ENaC subunits may also be associated with male infertility. The diverse phenotypes associated with CFTR mutations may be due to malfunction of CFTR at specific subcellular locations in the male reproductive system.

Chromosomal abnormalities in 1663 infertile men with azoospermia: the clinical consequences

STUDY QUESTION

What is the prevalence of chromosomal abnormalities in azoospermic men and what are the clinical consequences in terms of increased risk for absent spermatogenesis, miscarriages and offspring with congenital malformations?

SUMMARY ANSWER

The prevalence of chromosomal abnormalities in azoospermia was 14.4%, and the number of azoospermic men needed to be screened (NNS) to identify one man with a chromosomal abnormality with increased risk for absence of spermatogenesis was 72, to prevent one miscarriage 370-739 and to prevent one child with congenital malformations 4751-23 757.

WHAT IS KNOWN ALREADY

Infertility guidelines worldwide advise screening of non-iatrogenic azoospermic men for chromosomal abnormalities, but only few data are available on the clinical consequences of this screening strategy.

STUDY DESIGN, SIZE, DURATION

This retrospective multicentre cross-sectional study of non-iatrogenic azoospermic men was performed at the University Hospital Brussels, Belgium, and the University Medical Centre Groningen, The Netherlands, between January 2000 and July 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Analysis of clinical registries retrospectively identified 1663 non-iatrogenic azoospermic men with available results of karyotyping and FSH serum levels. Iatrogenic azoospermia was an exclusion criterion, defined as azoospermia after spermatotoxic medical treatment, exogenous androgen suppletion or vasectomy and/or vasovasostomy. Also, men with a clinical diagnosis of anejaculation or hypogonadotropic hypo-androgenism and/or FSH values <1.0 U/l were excluded. Chromosomal abnormalities were categorized according to their (theoretical) impact on clinical consequences for the patient (i.e. an increased risk for absence of spermatogenesis) and adverse pregnancy outcomes (i.e. miscarriage or offspring with congenital malformations), in both normogonadotropic (FSH < 10 U/l) and hypergonadotropic (FSH ≥ 10 U/l) azoospermia. We estimated the NNS for chromosomal abnormalities to identify one man with absence of spermatogenesis and to prevent one miscarriage or one child with congenital malformations, and calculated the surgical sperm retrieval rates per chromosomal abnormality.

MAIN RESULTS AND THE ROLE OF CHANCE

The overall prevalence of chromosomal abnormalities in azoospermia was 14.4% (95% CI 12.7-16.1%), its prevalence being higher in hypergonadotropic azoospermia (20.2%, 95% CI 17.8-22.7%) compared to normogonadotropic azoospermia (4.9%, 95% CI 3.2-6.6%, P < 0.001). Klinefelter syndrome accounted for 83% (95% CI 77-87%) of abnormalities in hypergonadotropic azoospermia. The NNS to identify one man with increased risk for absence of spermatogenesis was 72, to prevent one miscarriage 370-739, and to prevent one child with congenital malformations 4751-23 757. There was no clinically significant difference in NNS between men with normogonadotropic and hypergonadotropic azoospermia. The surgical sperm retrieval rate was significantly higher in azoospermic men with a normal karyotype (60%, 95% CI 57.7-63.1%) compared to men with a chromosomal abnormality (32%, 95% CI 25.9-39.0%, P < 0.001). The sperm retrieval rate in Klinefelter syndrome was 28% (95% CI 20.7-35.0%).

LIMITATIONS, REASONS FOR CAUTION

The absolute number of chromosomal abnormalities associated with clinical consequences and adverse pregnancy outcomes in our study was limited, thereby increasing the role of chance. Further, as there are currently no large series on outcomes of pregnancies in men with chromosomal abnormalities, our conclusions are partly based on assumptions derived from the literature.

WIDER IMPLICATIONS OF THE FINDINGS

The NNS found can be used in future cost-effectiveness studies and the evaluation of current guidelines on karyotyping in non-iatrogenic azoospermia.

STUDY FUNDING/COMPETING INTEREST(S)

None to declare.

Localization of epithelial sodium channel (ENaC) and CFTR in the germinal epithelium of the testis, Sertoli cells, and spermatozoa

Spermatogenesis starts within the seminiferous tubules of the testis by mitotic division of spermatogonia that produces spermatocytes. Meiotic division of these spermatocytes produces haploid spermatids that differentiate into spermatozoa. In this study, we examined the expression of ENaC and CFTR (a Cl^- channel) in rat testicular sections using confocal microscopic immunofluorescence. The structural integrity of the seminiferous tubule sections was verified by precise phalloidin staining of the actin fibers located abundantly at both basal and adluminal tight junctions. The acrosome forming regions in the round spermatids were stained using an FITC coupled lectin (wheat germ agglutinin). In all phases of the germ cells (spermatogonia, spermatocytes, and spermatids) ENaC was localized in cytoplasmic pools. Prior to spermiation, ENaC immunofluorescence appeared along the tails of the spermatids. In spermatozoa isolated from the epididymis, ENaC was localized at the acrosome and a central region of the sperm flagellum. The mature sperm are transcriptionally silent. Hence, we suggest that ENaC subunits in cytoplasmic pools in germ cells serve as the source of ENaC subunits located along the tail of spermatozoa. The locations of ENaC is compatible with a possible role in the acrosomal reaction and sperm mobility. In contrast to ENaC, CFTR immunofluorescence was most strongly observed specifically within the Sertoli cell nuclei. Based on the nuclear localization of CFTR we suggest that, in addition to its role as an ion channel, CFTR may have an independent role in gene regulation within the nuclei.