Causes and Clinical Features of Infertile Men With Nonobstructive Azoospermia and Histopathologic Diagnosis of Hypospermatogenesis

The MAEL expression in mitochondria of human spermatozoa and the association with asthenozoospermia

PURPOSE

The maelstrom spermatogenic transposon silencer (MAEL) function in postmeiotic germ cells remains unclear, and its protein localization in human testis and spermatozoa awaits determination. This study aims to clarify the MAEL expression in human spermatogenesis and to explore its role in sperm function.

MATERIALS AND METHODS

Twenty-seven asthenozoospermic men, 40 normozoospermic controls, and three obstructive azoospermic men were enrolled. The transcripts of MAEL in the seminiferous epithelium and MAEL downstream targets were identified by bioinformatics analysis. MAEL protein expression in human testis and ejaculated sperms were examined by immunohistochemical and immunogold staining, respectively. The roles of MAEL in mitochondria function were investigated by siRNA knockdown in human H358 cells. The association between MAEL protein levels and clinical sperm features was evaluated.

RESULTS

Abundant MAEL was expressed in spermatid and spermatozoa of the human testis. Remarkably, MAEL was located in the mitochondria of ejaculated sperm, and bioinformatics analysis identified GPX4 and UBL4B as MAEL's downstream targets. Knockdown of MAEL sabotaged mitochondria function and reduced adenosine triphosphate (ATP) production in H358 cells. MAEL, GPX4, and UBL4B expression levels were significantly decreased in asthenozoospermic sperms than in controls. The MAEL protein levels were positively correlated with GPX4 and UBL4B in human sperm. Total motile sperm count (TMSC) was positively correlated with protein levels of MAEL, GPX4, and UBL4B in ejaculated sperms.

CONCLUSIONS

We highlight prominent MAEL expression in the intratesticular spermatid and the mitochondria of ejaculated spermatozoa. MAEL directly binds to GPX4 and UBL4B, and loss of MAEL induces mitochondrial dysfunction. MAEL-mitochondrial function-motility relationship might advance our understanding of the causes of asthenozoospermia.

The Role of Long Noncoding RNAs on Male Infertility: A Systematic Review and In Silico Analysis

Male infertility is a complex disorder affecting many couples worldwide. Long noncoding RNAs (lncRNAs) regulate important cellular processes; however, a comprehensive understanding of their role in male infertility is limited. This systematic review investigates the differential expressions of lncRNAs in male infertility or variations in lncRNA regions associated with it. The PRISMA guidelines were used to search Pubmed and Web of Science (1 June 2022). Inclusion criteria were human participants, patients diagnosed with male infertility, and English language speakers. We also performed an in silico analysis investigating lncRNAs that are reported in many subtypes of male infertility. A total of 625 articles were found, and after the screening and eligibility stages, 20 studies were included in the final sample. Many lncRNAs are deregulated in male infertility, and interactions between lncRNAs and miRNAs play an important role. However, there is a knowledge gap regarding the impact of variants found in lncRNA regions. Furthermore, eight lncRNAs were identified as differentially expressed in many subtypes of male infertility. After in silico analysis, gene ontology (GO) and KEGG enrichment analysis of the genes targeted by them revealed their association with bladder and prostate cancer. However, pathways involved in general in tumorigenesis and cancer development of all types, such as p53 pathways, apoptosis, and cell death, were also enriched, indicating a link between cancer and male infertility. This evidence, however, is preliminary. Future research is needed to explore the exact mechanism of action of the identified lncRNAs and investigate the association between male infertility and cancer.

Outcomes and affecting factors for ICSI and microTESE treatments in nonobstructive azoospermia patients with different etiologies: A retrospective analysis

INTRODUCTION

Nonobstructive azoospermia (NOA) is a common and severe form of male infertility. Microdissection testicular sperm extraction (microTESE) combined with intracytoplasmic sperm injection (ICSI) is an optimal treatment for men with NOA. However, the outcomes and affecting factors of ICSI for NOA patients with different etiologies receiving microTESE treatment are still unclear.

METHODS

A total of 335 NOA patients undergoing microTESE from January 2017 to December 2021 were included in this retrospective analysis. The patients were divided into five groups (idiopathic, Klinefelter syndrome (KS), Y chromosome microdeletions (YCMDs), cryptorchidism and mumps orchitis) according to the etiologies. The clinical characteristics and outcomes of microTESE and ICSI were collected and comparisons were performed between clinical characteristics of patients who had successful sperm retrieval (SSR) and sperm retrieval failure (SRF). In addition, relationships between clinical characteristics and rates of SSR were explored by Kendall correlation analysis.

RESULTS

The overall SSR rate was 40.90%. SSR rate of the idiopathic group (31.22%) was the lowest and was much lower than that of other groups (KS: 48.65%, 28/58; YCMDs: 60.87%; cryptorchidism: 80.95%; mumps orchitis: 75.00%). The overall fertilization rate was 72.26%. No group differences were found among five groups (idiopathic: 73.91%; KS: 71.43%; YCMDs: 64.29%; cryptorchidism: 70.59%; mumps orchitis: 77.78%). The overall clinical pregnancy rate was 66.67%. No group differences were found among five groups (idiopathic: 68.63%; KS: 65.00%; YCMDs: 44.44%; cryptorchidism: 66.67%; mumps orchitis: 85.71%). The overall live birth rate was 66.67%. No group differences were found among five groups (idiopathic: 71.43%; KS: 53.85%; YCMDs: 50.00%; cryptorchidism: 75.00%; mumps orchitis: 66.67%). For SSR patients, the average age was significantly lower in the idiopathic group, while the average testicular volume was significantly greater in the cryptorchidism and mumps orchitis groups. However, no significant differences were found in the level of follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) between patients who had SSR and SRF. In addition, negative relationships were found between age and rates of SSR in idiopathic NOA patients while positive relationships were found between testis volume and rates of SSR in patients with cryptorchidism and mumps orchitis.

CONCLUSION

Patients with idiopathic NOA had lowest SSR. In addition, the age in idiopathic NOA patients was a predictor for SSR while testicular volume in NOA patients with cryptorchidism and mumps orchitis was a predictor for SSR. However, the relationships between clinical characteristics and clinical outcomes in NOA patients were preliminary, and further validation needed to be carried out in a larger sample to increase statistical capacity before a definitive conclusion could be drawn.

Chronic testicular Chlamydia muridarum infection impairs mouse fertility and offspring development†

With approximately 131 million new genital tract infections occurring each year, Chlamydia is the most common sexually transmitted bacterial pathogen worldwide. Male and female infections occur at similar rates and both cause serious pathological sequelae. Despite this, the impact of chlamydial infection on male fertility has long been debated, and the effects of paternal chlamydial infection on offspring development are unknown. Using a male mouse chronic infection model, we show that chlamydial infection persists in the testes, adversely affecting the testicular environment. Infection increased leukocyte infiltration, disrupted the blood:testis barrier and reduced spermiogenic cell numbers and seminiferous tubule volume. Sperm from infected mice had decreased motility, increased abnormal morphology, decreased zona-binding capacity, and increased DNA damage. Serum anti-sperm antibodies were also increased. When both acutely and chronically infected male mice were bred with healthy female mice, 16.7% of pups displayed developmental abnormalities. Female offspring of chronically infected sires had smaller reproductive tracts than offspring of noninfected sires. The male pups of infected sires displayed delayed testicular development, with abnormalities in sperm vitality, motility, and sperm-oocyte binding evident at sexual maturity. These data suggest that chronic testicular Chlamydia infection can contribute to male infertility, which may have an intergenerational impact on sperm quality.

A magnetic resonance imaging study in etiology of nonobstructive azoospermia

BACKGROUND

Testicular magnetic resonance imaging parameters, including apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalized metabolite concentrations represent useful noninvasive fingerprints of nonobstructive azoospermia. Nonobstructive azoospermia etiology might correlate with the spermatogenesis status.

OBJECTIVES

To assess the possible association between apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalised metabolite concentrations with nonobstructive azoospermia etiology.

MATERIALS AND METHODS

This retrospective study included 48 consecutive men with nonobstructive azoospermia and 18 age-matched controls. All participants underwent scrotal magnetic resonance imaging. The testicular apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalized metabolite concentrations were calculated. nonobstructive azoospermia men were classified into three groups, based on etiology: group 1, idiopathic; group 2, genetic causes; and group 3, non-genetic causes. Parametric and nonparametric statistical tests were used to evaluate differences in magnetic resonance imaging parameters between nonobstructive azoospermia groups and normal testes (group 4). Regression analysis was performed to assess the most predictive magnetic resonance imaging factor of nonobstructive azoospermia etiology.

RESULTS

Differences in mean apparent diffusion coefficient (p < .001), fractional anisotropy (p < .001), magnetization transfer ratio (p < .001), and normalized concentrations of total choline (p = .005), glucose (p = .012), myo-inositol (p = .024), and lipids (p = .010) were observed among groups. Regression analysis failed to identify the most discriminating magnetic resonance imaging feature for nonobstructive azoospermia etiology.

DISCUSSION AND CONCLUSION

Apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalized concentrations of total choline, glucose, myo-inositol, and lipids are helpful in discriminating nonobstructive azoospermia etiology. Magnetic resonance imaging may provide useful, noninvasive information on the microstructural and biochemical milieu of nonobstructive azoospermia testes.

DNA methylation in human sperm: a systematic review

BACKGROUND

Studies in non-human mammals suggest that environmental factors can influence spermatozoal DNA methylation, and some research suggests that spermatozoal DNA methylation is also implicated in conditions such as subfertility and imprinting disorders in the offspring. Together with an increased availability of cost-effective methods of interrogating DNA methylation, this premise has led to an increasing number of studies investigating the DNA methylation landscape of human spermatozoa. However, how the human spermatozoal DNA methylome is influenced by environmental factors is still unclear, as is the role of human spermatozoal DNA methylation in subfertility and in influencing offspring health.

OBJECTIVE AND RATIONALE

The aim of this systematic review was to critically appraise the quality of the current body of literature on DNA methylation in human spermatozoa, summarize current knowledge and generate recommendations for future research.

SEARCH METHODS

A comprehensive literature search of the PubMed, Web of Science and Cochrane Library databases was conducted using the search terms 'semen' OR 'sperm' AND 'DNA methylation'. Publications from 1 January 2003 to 2 March 2020 that studied human sperm and were written in English were included. Studies that used sperm DNA methylation to develop methodologies or forensically identify semen were excluded, as were reviews, commentaries, meta-analyses or editorial texts. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) criteria were used to objectively evaluate quality of evidence in each included publication.

OUTCOMES

The search identified 446 records, of which 135 were included in the systematic review. These 135 studies were divided into three groups according to area of research; 56 studies investigated the influence of spermatozoal DNA methylation on male fertility and abnormal semen parameters, 20 studies investigated spermatozoal DNA methylation in pregnancy outcomes including offspring health and 59 studies assessed the influence of environmental factors on spermatozoal DNA methylation. Findings from studies that scored as 'high' and 'moderate' quality of evidence according to GRADE criteria were summarized. We found that male subfertility and abnormal semen parameters, in particular oligozoospermia, appear to be associated with abnormal spermatozoal DNA methylation of imprinted regions. However, no specific DNA methylation signature of either subfertility or abnormal semen parameters has been convincingly replicated in genome-scale, unbiased analyses. Furthermore, although findings require independent replication, current evidence suggests that the spermatozoal DNA methylome is influenced by cigarette smoking, advanced age and environmental pollutants. Importantly however, from a clinical point of view, there is no convincing evidence that changes in spermatozoal DNA methylation influence pregnancy outcomes or offspring health.

WIDER IMPLICATIONS

Although it appears that the human sperm DNA methylome can be influenced by certain environmental and physiological traits, no findings have been robustly replicated between studies. We have generated a set of recommendations that would enhance the reliability and robustness of findings of future analyses of the human sperm methylome. Such studies will likely require multicentre collaborations to reach appropriate sample sizes, and should incorporate phenotype data in more complex statistical models.

Serum estradiol levels in infertile men with non-obstructive azoospermia

PURPOSE

To report the different patterns of estradiol levels in infertile men with non-obstructive azoospermia and correlate these levels with their clinical and laboratory findings.

MATERIALS AND METHODS

A retrospective study was launched, and a retrieval of data for infertile men with non-obstructive azoospermia (n = 166) and fertile controls (n = 40) was performed. The retrieved data included demographics, clinical findings, scrotal duplex, semen analysis, and hormonal assay (testosterone, follicle-stimulating hormone, luteinizing hormone, prolactin, and estradiol).

RESULTS

Our findings showed a wide spectrum of estradiol concentrations. The patients were arranged into three groups (high, normal, and low estradiol groups). The normal estradiol group was the most prevalent (71.1%). Testosterone, gonadotrophins, testicular volumes, and the number of patients with jobs in polluted workplaces showed significant differences among the study groups (p = 0.001, <0.001, <0.001, and 0.004, respectively). Age, body mass index, varicocele prevalence, prolactin, and smoking habits did not show any significant differences among the groups. Obesity was lacking in the low estradiol group, but it had significantly higher prevalence in the normal (p = 0.013) or high group (p = 0.023) compared with the controls.

CONCLUSION

Serum estradiol, in infertile men with non-obstructive azoospermia, may be present at different levels. It is recommended that estradiol be measured in infertile men with non-obstructive azoospermia when there is an alteration in testosterone concentration, obesity, a polluted workplace occupation, or before trying hormonal therapy. Extended studies are highly recommended to provide a clear clue whether alterations in estradiol concentrations in men with non-obstructive azoospermia are the cause or a consequence of the condition.

UBE2W down-regulation promotes cell apoptosis and correlates with hypospermatogenesis

Ubiquitin conjugating enzyme (E2) is crucial for mediating N-terminal ubiquitination. Recent study reports that UBE2W is involved in male infertility. However, the correlation between UBE2W expression and hypospermatogenesis is unclear. The present study is to explore the biological role of UBE2W and its association with hypospermatogenesis. Results showed that the sexpression levels of UBE2W in mouse testes were gradually elevated from 2 to 10 weeks, while were significantly deceased in the testes with hypospermatogenesis. When UBE2W expression was successfully down-regulated in spermatogenic cells, the rate of apoptosis was significantly increased and the P53/Bcl-2/caspase 6/caspase 9 signal pathways were activated. Thus, these data indicate that UBE2W down-regulation promotes cell apoptosis and correlates with hypospermatogenesis, which may be helpful for the diagnosis of male infertility.

PGAM1 knockdown is associated with busulfan‑induced hypospermatogenesis and spermatogenic cell apoptosis

Phosphoglycerate mutase 1 (PGAM1) is reported to be involved in spermatogenic dysfunction. However, the association between PGAM1 and busulfan-induced hypospermatogenesis and spermatogenic cell apoptosis remains unclear. The aim of the current study was to investigate the association between PGAM1 expression and busulfan-induced hypospermatogenesis, and the effect of PGAM1 expression on spermatogenic cell apoptosis. PGAM1 expression was detected in mouse models of busulfan-induced hypospermatogenesis by western blotting, reverse transcription-quantitative polymerase chain reaction and immunohistochemistry. Then, spermatogenic cell apoptosis in mouse models of busulfan-induced hypospermatogenesis was assessed by TUNEL assay. The effect and potential mechanism of PGAM1 downregulation on spermatogenic cells were further investigated. The results indicated that PGAM1 expression was significantly downregulated in the mouse models of busulfan-induced hypospermatogenesis, compared with those with normal spermatogenesis (P<0.05). Furthermore, the TUNEL assay revealed that the apoptosis of spermatogenic cells was accelerated in the mouse model of busulfan-induced hypospermatogenesis. In addition, PGAM1 knockdown promoted the apoptosis of spermatogenic cells in vitro, which was associated with the P53/Caspase 3/Caspase 6/Caspase 9 signaling pathway. In conclusion, these data indicate that PGAM1 knockdown is associated with busulfan-induced hypospermatogenesis and contributes to spermatogenic cell apoptosis by regulating the P53/Caspase 3/Caspase 6/Caspase 9 signaling pathway.

MAEL promoter hypermethylation is associated with de-repression of LINE-1 in human hypospermatogenesis

STUDY QUESTION

Does the hypermethylation of the maelstrom spermatogenic transposon silencer (MAEL) promoter and subsequent de-repression of transposable elements represent one of the causes of spermatogenic failure in infertile men?

SUMMARY ANSWER

Experimental hypermethylation of a specific region (-131 to +177) of the MAEL promoter leads to decreased expression of MAEL with increased expression of the transposable element LINE-1 (L1) and in infertile men methylation of the MAEL promoter is associated with the severity of spermatogenic failure.

WHAT IS KNOWN ALREADY

MAEL induces transposon repression in the male germline and is required for mammalian meiotic progression and post-meiotic spermiogenesis. Patients with non-obstructive azoospermia (NOA), defined as no sperm in the ejaculate due to spermatogenic failure, and histopathologically proven hypospermatogenesis (HS) is not uncommon and its etiology is largely unknown.

STUDY DESIGN, SIZE, DURATION

Luciferase reporter assay and a targeted DNA methylation model were used to explore the effects of hypermethylation of MAEL promoter on gene expression. Germ cell-enriched testicular cells from infertile patients were used to determine the methylation levels of MAEL and expressions of MAEL and L1.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Twenty-six patients with histopathologically proven NOA and HS and 12 patients with obstructive azoospermia and normal spermatogenesis (NS) were enrolled in this study. Demographic and clinical information were obtained. The severity of HS was determined by a spermatogenic scoring system. The methylation levels of 26 CpGs in the MAEL promoter was measured, and quantitative real-time RT-PCR was used to determine the expressional levels of MAEL and L1.

MAIN RESULTS AND THE ROLE OF CHANCE

Targeted DNA methylation of MAEL promoter suppressed MAEL expression and de-repressed L1 activity in vitro. Patients with HS had significantly higher mean methylation levels of 26 consecutive CpGs in the MAEL promoter, compared to patients with NS. The MAEL methylation levels were negatively correlated with MAEL transcript levels and higher methylation level of MAEL was associated with severe spermatogenic defect. L1 transcript level was significantly higher in patients with HS. No differences in age, frequency of testicular insults and genetic anomalies was noted between patients with high or low MAEL methylation levels.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Because of the difficulty in the use of human germ cells for study, the in vitro targeted DNA methylation model was performed by using human NCI-H358 cells to explore the effects of MAEL methylation on transposable elements activity. Because the germ cell-enriched testicular cells isolated from a testicular sample were relatively few, the purity of cell populations was not determined.

WIDER IMPLICATIONS OF THE FINDINGS

Measurement of the methylation level of MAEL gene may be feasible to predict the severity of spermatogenic failure or the outcome of testicular sperm retrieval.

STUDY FUNDING/COMPETING INTERESTS

This work was supported through grants from the Ministry of Science and Technology of Taiwan (100-2314-B-006-017) and National Cheng Kung University Hospital, Tainan, Taiwan (NCKUH 20120266). The authors declare no conflicts of interest.

A multi-scale analysis of bull sperm methylome revealed both species peculiarities and conserved tissue-specific features

BACKGROUND

Spermatozoa have a remarkable epigenome in line with their degree of specialization, their unique nature and different requirements for successful fertilization. Accordingly, perturbations in the establishment of DNA methylation patterns during male germ cell differentiation have been associated with infertility in several species. While bull semen is widely used in artificial insemination, the literature describing DNA methylation in bull spermatozoa is still scarce. The purpose of this study was therefore to characterize the bull sperm methylome relative to both bovine somatic cells and the sperm of other mammals through a multiscale analysis.

RESULTS

The quantification of DNA methylation at CCGG sites using luminometric methylation assay (LUMA) highlighted the undermethylation of bull sperm compared to the sperm of rams, stallions, mice, goats and men. Total blood cells displayed a similarly high level of methylation in bulls and rams, suggesting that undermethylation of the bovine genome was specific to sperm. Annotation of CCGG sites in different species revealed no striking bias in the distribution of genome features targeted by LUMA that could explain undermethylation of bull sperm. To map DNA methylation at a genome-wide scale, bull sperm was compared with bovine liver, fibroblasts and monocytes using reduced representation bisulfite sequencing (RRBS) and immunoprecipitation of methylated DNA followed by microarray hybridization (MeDIP-chip). These two methods exhibited differences in terms of genome coverage, and consistently, two independent sets of sequences differentially methylated in sperm and somatic cells were identified for RRBS and MeDIP-chip. Remarkably, in the two sets most of the differentially methylated sequences were hypomethylated in sperm. In agreement with previous studies in other species, the sequences that were specifically hypomethylated in bull sperm targeted processes relevant to the germline differentiation program (piRNA metabolism, meiosis, spermatogenesis) and sperm functions (cell adhesion, fertilization), as well as satellites and rDNA repeats.

CONCLUSIONS

These results highlight the undermethylation of bull spermatozoa when compared with both bovine somatic cells and the sperm of other mammals, and raise questions regarding the dynamics of DNA methylation in bovine male germline. Whether sperm undermethylation has potential interactions with structural variation in the cattle genome may deserve further attention.