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

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.