Common SNP in hsa-miR-196a-2 increases hsa-miR-196a-5p expression and predisposes to idiopathic male infertility in Chinese Han population

Small RNAs, spermatogenesis, and male infertility: a decade of retrospect

Small non-coding RNAs (sncRNAs), being the top regulators of gene expression, have been thoroughly studied in various biological systems, including the testis. Research over the last decade has generated significant evidence in support of the crucial roles of sncRNAs in male reproduction, particularly in the maintenance of primordial germ cells, meiosis, spermiogenesis, sperm fertility, and early post-fertilization development. The most commonly studied small RNAs in spermatogenesis are microRNAs (miRNAs), PIWI-interacting RNA (piRNA), small interfering RNA (siRNA), and transfer RNA-derived small RNAs (ts-RNAs). Small non-coding RNAs are crucial in regulating the dynamic, spatial, and temporal gene expression profiles in developing germ cells. A number of small RNAs, particularly miRNAs and tsRNAs, are loaded on spermatozoa during their epididymal maturation. With regard to their roles in fertility, miRNAs have been studied most often, followed by piRNAs and tsRNAs. Dysregulation of more than 100 miRNAs has been shown to correlate with infertility. piRNA and tsRNA dysregulations in infertility have been studied in only 3-5 studies. Sperm-borne small RNAs hold great potential to act as biomarkers of sperm quality and fertility. In this article, we review the role of small RNAs in spermatogenesis, their association with infertility, and their potential as biomarkers of sperm quality and fertility.

Unraveling the harmful effect of oxidative stress on male fertility: A mechanistic insight

Male infertility is a widely debated issue that affects males globally. There are several mechanisms involved. Oxidative stress is accepted to be the main contributing factor, with sperm quality and quantity affected by the overproduction of free radicals. Excess reactive oxygen species (ROS) cannot be controlled by the antioxidant system and, thus, potentially impact male fertility and hamper sperm quality parameters. Mitochondria are the driving force of sperm motility; irregularities in their function may lead to apoptosis, alterations to signaling pathway function, and, ultimately, compromised fertility. Moreover, it has been observed that the prevalence of inflammation may arrest sperm function and the production of cytokines triggered by the overproduction of ROS. Further, oxidative stress interacts with seminal plasma proteomes that influence male fertility. Enhanced ROS production disturbs the cellular constituents, particularly DNA, and sperms are unable to impregnate the ovum. Here, we review the latest information to better understand the relationship between oxidative stress and male infertility, the role of mitochondria, the cellular response, inflammation and fertility, and the interaction of seminal plasma proteomes with oxidative stress, as well as highlight the influence of oxidative stress on hormones; collectively, all of these factors are assumed to be important for the regulation of male infertility. This article may help improve our understanding of male infertility and the strategies to prevent it.

Infertility in Men: Advances towards a Comprehensive and Integrative Strategy for Precision Theranostics

Male infertility is an increasing and serious medical concern, though the mechanism remains poorly understood. Impaired male reproductive function affects approximately half of infertile couples worldwide. Multiple factors related to the environment, genetics, age, and comorbidities have been associated with impaired sperm function. Present-day clinicians rely primarily on standard semen analysis to diagnose male reproductive potential and develop treatment strategies. To address sperm quality assessment bias and enhance analysis accuracy, the World Health Organization (WHO) has recommended standardized sperm testing; however, conventional diagnostic and therapeutic options for male infertility, including physical examination and semen standard analysis, remain ineffective in relieving the associated social burden. Instead, assisted reproductive techniques are becoming the primary therapeutic approach. In the post-genomic era, multiomics technologies that deeply interrogate the genome, transcriptome, proteome, and/or the epigenome, even at single-cell level, besides the breakthroughs in robotic surgery, stem cell therapy, and big data, offer promises towards solving semen quality deterioration and male factor infertility. This review highlights the complex etiology of male infertility, especially the roles of lifestyle and environmental factors, and discusses advanced technologies/methodologies used in characterizing its pathophysiology. A comprehensive combination of these innovative approaches in a global and multi-centric setting and fulfilling the suitable ethical consent could ensure optimal reproductive and developmental outcomes. These combinatorial approaches should allow for the development of diagnostic markers, molecular stratification classes, and personalized treatment strategies. Since lifestyle choices and environmental factors influence male fertility, their integration in any comprehensive approach is required for safe, proactive, cost-effective, and noninvasive precision male infertility theranostics that are affordable, accessible, and facilitate couples realizing their procreation dream.

Role of microRNAs in etiology of azoospermia and their application as non-invasive biomarkers in diagnosis of azoospermic patients

Azoospermia is a common cause of male infertility without any sperm in the semen and consists of ∼1% of all males and ∼15% of infertile ones. Currently, no accurate non-invasive diagnostic method exists for patients with azoospermia and testis biopsy is mandatory to determine if any spermatozoa exist in the testes. Studies have clarified that the expression of some distinct microRNAs shows alterations in azoospermic patients. MicroRNAs play critical roles during spermatogenesis and their dysregulation can defect this process. Here, we review studied microRNAs involved in the pathogenesis of azoospermia and their target genes. Moreover, we will imply the utility of seminal plasma microRNAs as non-invasive diagnostic biomarkers for azoospermia. We hope such studies could help patients with azoospermia in both diagnosis and treatment, in order that they could father their own biological children.

Next-generation sequencing analysis reveals segmental patterns of microRNA expression in yak epididymis

MicroRNAs (miRNAs) have emerged as potent regulators of gene expression and are widely expressed in biological systems. In reproduction, they have been shown to have a significant role in the acquisition and maintenance of male fertility, whereby deletion of Dicer in mouse germ cells leads to infertility. Evidence indicates that this role of miRNAs extends from the testis into the epididymis, controlling gene expression and contributing to regional variations in gene expression. In this study, RNA sequencing technology was used to investigate miRNA expression patterns in the yak epididymis. Region-specific miRNA expression was found in the yak epididymis. In all, 683 differentially expressed known miRNAs were obtained; 190, 186 and 307 differentially expressed miRNAs were identified for caput versus corpus, corpus versus cauda and caput versus cauda region pairs respectively. Kyoto Encyclopedia of Genes and Genomes results showed endocytosis as the most enriched pathway across region pairs, followed by protein processing in the endoplasmic reticulum, phagosome, spliceosome and biosynthesis of amino acids in region pair-specific hierarchical order. Gene ontology results showed varied enrichment in terms including cell, biogenesis, localisation, binding and locomotion across region pairs. In addition, significantly higher miR-34c expression was seen in the yak caput epididymidis relative to the corpus and cauda epididymidis.

Seminal Plasma Transcriptome and Proteome: Towards a Molecular Approach in the Diagnosis of Idiopathic Male Infertility

As the “-omic” technology has largely developed, its application in the field of medical science seems a highly promising tool to clarify the etiology, at least in part, of the so-called idiopathic male infertility. The seminal plasma (SP) is made-up of secretions coming from the male accessory glands, namely epididymis, seminal vesicles, and prostate. It is not only a medium for sperm transport since it is able to modulate the female reproductive environment and immunity, to allow the acquisition of sperm competence, to influence the sperm RNA content, and even embryo development. The aim of this systematic review was to provide an updated and comprehensive description of the main transcripts and proteins reported by transcriptome and proteome studies performed in the human SP of patients with idiopathic infertility, in the attempt of identifying possible candidate molecular targets. We recurrently found that micro RNA (miR)-34, miR-122, and miR-509 are down-regulated in patients with non-obstructive azoospermia (NOA) and oligozoospermia compared with fertile controls. These molecules may represent interesting targets whose predictive role in testicular sperm extraction (TESE) or assisted reproductive techniques (ART) outcome deserves further investigation. Furthermore, according to the available proteomic studies, ECM1, TEX101, lectingalactoside-binding andsoluble 3 binding protein (LGALS3BP) have been reported as accurate predictors of TESE outcome. Interestingly, ECM1 is differently expressed in patients with different ART outcomes. Further prospective, ample-sized studies are needed to validate these molecular targets that will help in the counseling of patients with NOA or undergoing ART.

MiR-4485-3p expression reduced in spermatozoa of men with idiopathic asthenozoospermia

Asthenozoospermia (AZS), which characterised by reduced forward sperm motility, is a common cause of male infertility. Recently, mitochondrial dysfunction reported in AZS men came to attention for finding the molecular aetiology of AZS. Mitochondria-related microRNAs (miRNAs) are the most important regulators of mitochondrial function through post-transcriptionally modulation of gene expression. Therefore, this study aims to evaluate the expression of four recently reported mitochondrial-related miRNAs (miR-4485-3p/4484/4461 and 4463) in the sperm sample of asthenozoospermic men. RNA was extracted from spermatozoa of 74 volunteers (39 patients with idiopathic AZS and 35 controls with normal fertility), and relative gene expression analysis was performed by quantitative PCR. We used SNORD48 as a normaliser gene, and quantification was calculated by 2^-ΔΔCt method. The expression of miR-4484 and miR-4461 was not detected in the spermatozoa of cases and controls. However, miR-4485-3p (p = .006) was significantly downregulated in the AZS men compared with the controls, but the miR-4463 expression was not significantly different between the two groups (p = .5). Bioinformatic analysis identified three target genes for miR-4485-3p (DNAH1, KIT and PARK7) that are related to male infertility. In conclusion, the downregulation of miR-4485-3p was associated with idiopathic AZS, which could be a molecular link between mitochondrial dysfunction and AZS.

Genetic Landscape of Nonobstructive Azoospermia and New Perspectives for the Clinic

Nonobstructive azoospermia (NOA) represents the most severe expression of male infertility, involving around 1% of the male population and 10% of infertile men. This condition is characterised by the inability of the testis to produce sperm cells, and it is considered to have an important genetic component. During the last two decades, different genetic anomalies, including microdeletions of the Y chromosome, karyotype defects, and missense mutations in genes involved in the reproductive function, have been described as the primary cause of NOA in many infertile men. However, these alterations only explain around 25% of azoospermic cases, with the remaining patients showing an idiopathic origin. Recent studies clearly suggest that the so-called idiopathic NOA has a complex aetiology with a polygenic inheritance, which may alter the spermatogenic process. Although we are far from a complete understanding of the molecular mechanisms underlying NOA, the use of the new technologies for genetic analysis has enabled a considerable increase in knowledge during the last years. In this review, we will provide a comprehensive and updated overview of the genetic basis of NOA, with a special focus on the possible application of the recent insights in clinical practice.

Genetic Polymorphisms in miR-146a, miR-196a2 and miR-125a Genes and its Association in Prostate Cancer

The increase in incidence of prostate cancer in the Indian Population stresses the need to identify genetic markers for susceptibility and prognosis. Recent studies show that microRNAs play an important role in tumorigenesis by altering proliferation, differentiation and cell death. Gene polymorphisms not only in promoter region but also within miRNA gene have been shown to affect expression. The present study was aimed to analyze the role of miR-146a, miR-196a2 and miR-125a gene polymorphisms in prostate cancer. Genotyping of three SNPs rs73318382, rs57095329, rs2910164 in miRNA146a, rs11614913 in miR-196a2 and rs41275794, rs12976445, rs10404453 and rs1297533 in miR-125a was performed in 100 cases and 100 controls. Statistical analysis revealed the heterozygous AG genotype of the rs57095329 was significantly decreased in the cases when compared to the controls (OR-0.45, CI -0.24 to 0.85, p value-0.02) indicating an inverse association of this genotype with prostate cancer. Further the heterozygous CT of miR-196a2 (rs11614913) (OR-1.88, CI-1.06 to 3.35, p-0.02) and homozygous CC of miR-125a (rs12976445) (OR-2.55, CI -1.15 to 4.65, p-0.03) showed increased risk for prostate cancer. Combined analysis of all the genotypes revealed that the haplotype combination AGGCGTGG (OR = 0.09 at CI 95% (0.01-0.65) showed an inverse association with prostate cancer. Stratified analysis based on the age and tumor grade revealed no significant association.

Association of miR-146a, miR-149, miR-196a2, and miR-499 Polymorphisms with Ossification of the Posterior Longitudinal Ligament of the Cervical Spine

Background

Ossification of the posterior longitudinal ligament (OPLL) of the spine is considered a multifactorial and polygenic disease. We aimed to investigate the association between four single nucleotide polymorphisms (SNPs) of pre-miRNAs [miR-146aC>G (rs2910164), miR-149T>C (rs2292832), miR-196a2T>C (rs11614913), and miR-499A>G (rs3746444)] and the risk of cervical OPLL in the Korean population.

Methods

The genotypic frequencies of these four SNPs were analyzed in 207 OPLL patients and 200 controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay.

Findings

For four SNPs in pre-miRNAs, no significant differences were found between OPLL patients and controls. However, subgroup analysis based on OPLL subgroup (continuous: continuous type plus mixed type, segmental: segmental and localized type) showed that miR-499GG genotype was associated with an increased risk of segmental type OPLL (adjusted odds ratio = 4.314 with 95% confidence interval: 1.109–16.78). In addition, some allele combinations (C-T-T-G, G-T-T-A, and G-T-C-G of miR-146a/-149/-196a2/-499) and combined genotypes (miR-149TC/miR-196a2TT) were associated with increased OPLL risk, whereas the G-T-T-G and G-C-C-G allele combinations were associated with decreased OPLL risk.

Conclusion

The results indicate that GG genotype of miR-499 is associated with significantly higher risks of OPLL in the segmental OPLL group. The miR-146a/-149/-196a2/-499 allele combinations may be a genetic risk factor for cervical OPLL in the Korean population.