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

A comparison of the expression patterns and diagnostic capability of the ncRNAs NEAT1 and miR-34a in non-obstructive azoospermia and severe oligospermia

Infertility is a major global health problem, affecting 8-12% of couples worldwide, with male causes contributing to approximately 50% of cases. Notably, around 15% of infertile men are azoospermic. Consequently, there is a critical necessity to find noninvasive biomarkers to help in diagnosing and assessing the susceptibility of patients with various infertility disorders. This study is designed to determine the roles of NEAT1 and miR-34a as diagnostic and susceptibility biomarkers for non-obstructive azoospermia and severe oligospermia. The interactions between these non-coding RNA (ncRNAs) were explored, along with their correlations to hormonal profiles and clinical parameters like sperm count and motility. The potential of serum NEAT1 and miR-34a as diagnostic biomarkers for these conditions was explored. The study included 100 participants: 40 non-obstructive azoospermia patients, 40 severe oligospermia patients, and 20 healthy controls. Quantitative real-time PCR and transcriptomics-based bioinformatics tools were employed to explore the co-expression networks and molecular interactions of NEAT1, miR-34a, SIRT1, and their associated hormonal and genetic pathways. Results indicated that NEAT1 was significantly downregulated in severe oligospermia patients, while its levels in non-obstructive azoospermia patients did not differ significantly from healthy controls. Furthermore, serum miR-34a expression was considerably upregulated in both patient groups compared to controls. This study highlights the promise of serum NEAT1 and miR-34a as diagnostic markers for non-obstructive azoospermia and severe oligospermia. These findings provide valuable insights into male infertility and indicate potential avenues for personalized treatment strategies.

Integrative Analysis of Whole-Genome and Transcriptomic Data Reveals Novel Variants in Differentially Expressed Long Noncoding RNAs Associated with Asthenozoospermia

Background/Objectives: Asthenozoospermia, characterized by reduced sperm motility, is a common cause of male infertility. Emerging evidence suggests that noncoding RNAs, particularly long noncoding RNAs (lncRNAs), play a critical role in the regulation of spermatogenesis and sperm function. Coding regions have a well-characterized role and established predictive value in asthenozoospermia. However, this study was designed to complement previous findings and provide a more holistic understanding of asthenozoospermia, this time focusing on noncoding regions. This study aimed to identify and prioritize variants in differentially expressed (DE) lncRNAs found exclusively in asthenozoospermic men, focusing on their impact on lncRNA structure and lncRNA-miRNA-mRNA interactions. Methods: Whole-genome sequencing (WGS) was performed on samples from asthenozoospermic and normozoospermic men. Additionally, an RNA-seq dataset from normozoospermic and asthenozoospermic individuals was analyzed to identify DE lncRNAs. Bioinformatics analyses were conducted to map unique variants on DE lncRNAs, followed by prioritization based on predicted functional impact. The structural impact of the variants and their effects on lncRNA-miRNA interactions were assessed using computational tools. Gene ontology (GO) and KEGG pathway analyses were employed to investigate the affected biological processes and pathways. Results: We identified 4173 unique variants mapped to 258 DE lncRNAs. After prioritization, 5 unique variants in 5 lncRNAs were found to affect lncRNA structure, while 20 variants in 17 lncRNAs were predicted to disrupt miRNA-lncRNA interactions. Enriched pathways included Wnt signaling, phosphatase binding, and cell proliferation, all previously implicated in reproductive health. Conclusions: This study identifies specific variants in DE lncRNAs that may play a role in asthenozoospermia. Given the limited research utilizing WGS to explore the role of noncoding RNAs in male infertility, our findings provide valuable insights and a foundation for future studies.

ΜicroRNA (miRNA) Variants in Male Infertility: Insights from Whole-Genome Sequencing

BACKGROUND/OBJECTIVES

Male infertility is a complex condition with various underlying genetic factors. microRNAs (miRNAs) play a crucial role in gene regulation, and their disruption can significantly impact fertility. This study aimed to identify variants within miRNA genes and elucidate their impact on male infertility.

METHODS

Whole genome sequencing was performed on blood samples from men with asthenozoospermia, oligozoospermia, and teratozoospermia, compared to normozoospermic controls. The analysis revealed a significant number of unique variants in each infertile group. We subsequently focused on variants in miRNA regions, followed by an in silico analysis to investigate the role of the identified variants and miRNAs in male infertility.

RESULTS

Focused analysis on miRNA genes identified 19 exclusive variants in teratozoospermic men, 24 in asthenozoospermic, and 27 in oligozoospermic, all mapping to pre-miRNAs or mature miRNAs. Functional analyses using Gene Ontology (GO) and KEGG pathways highlighted key biological processes and pathways disrupted by these variants and miRNA-mRNA interactions, including transcription regulation, signaling, and cancer-related pathways. Furthermore, six variants (rs17797090, rs1844035, rs7210937, rs451887, rs12233076, and rs6787734) were common across the infertile groups, suggesting their importance in male infertility or their potential as biomarkers. Common variants were also validated in another clinically relevant group of men. Some miRNAs with identified variants, such as hsa-miR-449b and hsa-miR-296, have been previously implicated in male infertility and exhibit differential expression between fertile and infertile men, according to the literature, too.

CONCLUSION

These results provide new insights into the genetic basis of male infertility and open avenues for future research and therapeutic interventions.

Cadmium exposure and its association with oxidative stress, MT1A methylation, and idiopathic male infertility in Egypt: A case-control study

Idiopathic male infertility, a significant health concern, lacks a clear etiology. Cadmium (Cd), a widespread environmental pollutant known to impact male reproductive health negatively, can accumulate in mussels, a common food source in Egypt. This study investigated the link between ecological Cd exposure, oxidative stress, MT1A methylation, and idiopathic male infertility in two regions of Alexandria. Thirty-three infertile men and 33 fertile controls were included. Cd levels were measured in mussels from the study sites and in participants' blood and semen. Biomarkers reflecting Cd exposure and its effects were assessed. Mussel Cd levels exceeded regulatory limits. Infertile men revealed significantly higher blood and semen Cd levels, reduced semen quality, increased oxidative stress, and elevated MT1A methylation compared to controls. MT1A methylation was inversely correlated with sperm count and is the strongest predictor of idiopathic male infertility, demonstrating the lowest p-value and considerable effect size. This study suggests that environmental Cd exposure, potentially through mussel consumption, may contribute to idiopathic male infertility in Egypt by increasing oxidative stress, inducing epigenetic modifications, and impairing semen quality. These findings underscore the need for further research into the mechanisms underlying Cd-induced male infertility and the development of preventative strategies.

Potential hazards of bisphenol A on the male reproductive system: Induction of programmed cell death in testicular cells

A common industrial chemical known as bisphenol A (BPA) has been linked to endocrine disruption and can interfere with hormonal signaling pathways in humans and animals. This comprehensive review aims to explore the detrimental consequences of BPA on reproductive organ performance and apoptosis induction, shedding light on the emerging body of evidence from laboratory animal studies. Historically, most studies investigating the connection between BPA and reproductive tissue function have mainly leaned on laboratory animal models. These studies have provided crucial insights into the harmful effects of BPA on several facets of reproduction. This review consolidates an increasing literature that correlates exposure to BPA in the environment with a negative impact on human health. It also integrates findings from laboratory studies conducted on diverse species, collectively bolstering the mounting evidence that environmental BPA exposure can be detrimental to both humans and animals, particularly to reproductive health. Furthermore, this article explores the fundamental processes by which BPA triggers cell death and apoptosis in testicular cells. By elucidating these mechanisms, this review aids a deeper understanding of the complex interactions between BPA and reproductive tissues.

Genetic Insights into Azoospermia and Severe Oligozoospermia: Discovering Seven SNPs through GWAS and In Silico Analysis

Azoospermia and severe oligozoospermia represent the most extreme forms of male infertility. Despite their prevalence, the genetic foundations of these conditions are not well understood, with only a limited number of genetic factors identified so far. This study aimed to identify single-nucleotide polymorphisms (SNPs) linked to both azoospermia and severe oligozoospermia. We conducted a genome-wide association study (GWAS) involving 280 Greek males with normal semen parameters and 85 Greek males diagnosed with either azoospermia or severe oligozoospermia. Following rigorous quality control measures, our analysis identified seven SNPs associated with azoospermia/severe oligozoospermia. An in silico functional annotation was subsequently used to further investigate their role. These SNPs, found in regions not previously associated with male reproductive disorders, suggest novel genetic pathways that may contribute to these forms of infertility and pave the way for future studies. Additionally, this study sheds light on the significant role of noncoding RNAs in the pathogenesis of male infertility, with three of the identified SNPs situated in long intergenic non-coding RNAs (lincRNAs). Our findings highlight the intricate genetic landscape of azoospermia and severe oligozoospermia, underlining the necessity for more detailed studies to fully grasp the underlying mechanisms and their potential for informing diagnostic and therapeutic strategies.

Sperm epigenetics and male infertility: unraveling the molecular puzzle

BACKGROUND

The prevalence of infertility among couples is estimated to range from 8 to 12%. A paradigm shift has occurred in understanding of infertility, challenging the notion that it predominantly affects women. It is now acknowledged that a significant proportion, if not the majority, of infertility cases can be attributed to male-related factors. Various elements contribute to male reproductive impairments, including aberrant sperm production caused by pituitary malfunction, testicular malignancies, aplastic germ cells, varicocele, and environmental factors.

MAIN BODY

The epigenetic profile of mammalian sperm is distinctive and specialized. Various epigenetic factors regulate genes across different levels in sperm, thereby affecting its function. Changes in sperm epigenetics, potentially influenced by factors such as environmental exposures, could contribute to the development of male infertility.

CONCLUSION

In conclusion, this review investigates the latest studies pertaining to the mechanisms of epigenetic changes that occur in sperm cells and their association with male reproductive issues.

Identification of potential biomarkers and pathways for asthenozoospermia by bioinformatics analysis and experiments

Background

Asthenozoospermia, a type of male infertility, is primarily caused by dysfunctional sperm mitochondria. Despite previous bioinformatics analysis identifying potential key lncRNAs, miRNAs, hub genes, and pathways associated with asthenospermia, there is still a need to explore additional molecular mechanisms and potential biomarkers for this condition.

Methods

We integrated data from Gene Expression Omnibus (GEO) (GSE22331, GSE34514, and GSE160749) and performed bioinformatics analysis to identify differentially expressed genes (DEGs) between normozoospermia and asthenozoospermia. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to gain insights into biological processes and signaling pathways. Weighted Gene Co-expression Network Analysis (WGCNA) identified gene modules associated with asthenozoospermia. Expression levels of key genes were assessed using datasets and experimental data. Gene Set Enrichment Analysis (GSEA) and correlation analysis identified pathways associated with the hub gene and explore the relationship between the ZNF764 and COQ9 and mitochondrial autophagy-related genes. Competitive endogenous RNA (ceRNA) networks were constructed, and in vitro experiments using exosome samples were conducted to validate this finding.

Results

COQ9 was identified as a marker gene in asthenozoospermia, involved in autophagy, ATP-dependent chromatin remodeling, endocytosis, and cell cycle, etc. The ceRNA regulatory network (LINC00893/miR-125a-5p/COQ9) was constructed, and PCR demonstrated that LINC00893 and COQ9 were downregulated in asthenozoospermia, while miR-125a-5p and m6A methylation level of LINC00893 were upregulated in asthenozoospermia compared to normozoospermic individuals.

Conclusion

The ceRNA regulatory network (LINC00893/miR-125a-5p/COQ9) likely plays a crucial role in the mechanism of asthenozoospermia. However, further functional experiments are needed to fully understand its significance.

Impacts of non-coding RNAs in the pathogenesis of varicocele

Two classes of non-coding RNAs, namely lncRNAs and miRNAs have been reported to be involved in the pathogenesis of varicocele. MIR210HG, MLLT4-AS1, gadd7, and SLC7A11-AS1 are among lncRNAs whose expression has been changed in patients with varicocele in association with the sperm quality. Animal studies have also suggested contribution of NONRATG001060, NONRATG002949, NONRATG013271, NONRATG027523 and NONRATG023747 lncRNAs in this pathology. Meanwhile, expression of some miRNAs, such as miR-210-3p, miR-21, miR-34a, miR-122a, miR-181a, miR-34c and miR-192a has been altered in this condition. Some of these transcripts have the potential to predict the sperm quality. We summarize the impacts of lncRNAs and miRNAs in the pathogenesis of varicocele.

Exploring the regulatory role of Linc00893 in asthenozoospermia: Insights into sperm motility and SSC viability

The role of long intergenic noncoding RNA 00893 (Linc00893) in asthenozoospermia (AS) and its impact on sperm motility remains unclear The present study explored the effect of Linc00893 on AS, specifically its effect on sperm motility and its relationship with spermatogonial stem cell (SSC) vitality and myosin heavy chain 9 (MYH9) protein expression. Linc00893 expression was analyzed in semen samples using reverse transcription‑quantitative PCR, revealing a significant downregulation in samples from individuals with AS compared with those from healthy subjects. This downregulation was found to be negatively correlated with parameters of sperm motility. To further understand the role of Linc00893, small interfering RNA was used to knockdown its expression in SSCs. This knockdown led to a marked decrease in cell vitality and an increase in apoptosis. Notably, Linc00893 knockdown was shown to inhibit MYH9 expression by competitively binding with microRNA‑107, a finding verified by dual‑luciferase reporter and RNA immunoprecipitation assays. Furthermore, using the GSE160749 dataset from the Gene Expression Omnibus database, it was revealed that MYH9 protein expression was downregulated in AS samples. Subsequently, lentiviral vectors were constructed to induce overexpression of MYH9, which in turn reduced SSC apoptosis and counteracted the apoptosis triggered by Linc00893 knockdown. In conclusion, the present study identified the role of Linc00893 in AS, particularly its regulatory impact on sperm motility, SSC vitality and MYH9 expression. These findings may provide information on the potential regulatory mechanisms in AS development, and identify Linc00893 and MYH9 as possible targets for diagnosing and treating AS‑related disorders.

Unveiling the Genetic Complexity of Teratozoospermia: Integrated Genomic Analysis Reveals Novel Insights into lncRNAs' Role in Male Infertility

Male infertility is a global health issue, affecting over 20 million men worldwide. Genetic factors are crucial in various male infertility forms, including teratozoospermia. Nonetheless, the genetic causes of male infertility remain largely unexplored. In this study, we employed whole-genome sequencing and RNA expression analysis to detect differentially expressed (DE) long-noncoding RNAs (lncRNAs) in teratozoospermia, along with mutations that are exclusive to teratozoospermic individuals within these DE lncRNAs regions. Bioinformatic tools were used to assess variants' impact on lncRNA structure, function, and lncRNA-miRNA interactions. Our analysis identified 1166 unique mutations in teratozoospermic men within DE lncRNAs, distinguishing them from normozoospermic men. Among these, 64 variants in 23 lncRNAs showed potential regulatory roles, 7 variants affected 4 lncRNA structures, while 37 variants in 17 lncRNAs caused miRNA target loss or gain. Pathway Enrichment and Gene Ontology analyses of the genes targeted by the affected miRNAs revealed dysregulated pathways in teratozoospermia and a link between male infertility and cancer. This study lists novel variants and lncRNAs associated for the first time with teratozoospermia. These findings pave the way for future studies aiming to enhance diagnosis and therapy in the field of male infertility.

Circular RNAs and Their Role in Male Infertility: A Systematic Review

Male infertility is a global health problem that is on the rise. Today, many noncoding RNAs (ncRNAs) are associated with male infertility. Circular RNAs (circRNAs) have recently drawn attention, but a comprehensive understanding of the role of circRNAs in male infertility is limited. This systematic review investigates the differential expression of circRNAs in male infertility or circRNAs that could serve as candidate biomarkers. The PRISMA guidelines were used to search PubMed and Web of Science on 11 January 2023. Inclusion criteria were human participants, experimental studies aiming to associate circRNAs with male infertility reporting differentially expressed circRNAs, and the English language. A total of 156 articles were found, and after the screening and eligibility stages, 13 studies were included in the final sample. Many circRNAs are deregulated in male infertility, and their interactions with miRNAs play an important role in affecting cellular processes and pathways. CircRNAs could also be used as biomarkers to screen patients before sperm retrieval. However, most studies focus on the role of circRNAs in azoospermia, and there is a knowledge gap regarding other subtypes of male infertility. Future research is needed to explore the exact mechanism of action of circRNAs and investigate their use as biomarkers.

Morphological and Molecular Bases of Male Infertility: A Closer Look at Sperm Flagellum

Infertility is a major health problem worldwide without an effective therapy or cure. It is estimated to affect 8-12% of couples in the reproductive age group, equally affecting both genders. There is no single cause of infertility, and its knowledge is still far from complete, with about 30% of infertile couples having no cause identified (named idiopathic infertility). Among male causes of infertility, asthenozoospermia (i.e., reduced sperm motility) is one of the most observed, being estimated that more than 20% of infertile men have this condition. In recent years, many researchers have focused on possible factors leading to asthenozoospermia, revealing the existence of many cellular and molecular players. So far, more than 4000 genes are thought to be involved in sperm production and as regulators of different aspects of sperm development, maturation, and function, and all can potentially cause male infertility if mutated. In this review, we aim to give a brief overview of the typical sperm flagellum morphology and compile some of the most relevant information regarding the genetic factors involved in male infertility, with a focus on sperm immotility and on genes related to sperm flagellum development, structure, or function.