mir-34b/c and mir-449a/b/c are required for spermatogenesis, but not for the first cleavage division in mice

How do lifestyle and environmental factors influence the sperm epigenome? Effects on sperm fertilising ability, embryo development, and offspring health

Recent studies support the influence of paternal lifestyle and diet before conception on the health of the offspring via epigenetic inheritance through sperm DNA methylation, histone modification, and small non-coding RNA (sncRNA) expression and regulation. Smoking may induce DNA hypermethylation in genes related to anti-oxidation and insulin resistance. Paternal diet and obesity are associated with greater risks of metabolic dysfunction in offspring via epigenetic alterations in the sperm. Metabolic changes, such as high blood glucose levels and increased body weight, are commonly observed in the offspring of fathers subjected to chronic stress, in addition to an enhanced risk of depressive-like behaviour and increased sensitivity to stress in both the F0 and F1 generations. DNA methylation is correlated with alterations in sperm quality and the ability to fertilise oocytes, possibly via a differentially regulated MAKP81IP3 signalling pathway. Paternal exposure to toxic endocrine-disrupting chemicals (EDCs) is also linked to the transgenerational transmission of increased predisposition to disease, infertility, testicular disorders, obesity, and polycystic ovarian syndrome (PCOS) in females through epigenetic changes during gametogenesis. As the success of assisted reproductive technology (ART) is also affected by paternal diet, BMI, and alcohol consumption, its outcomes could be improved by modifying factors that are dependent on male lifestyle choices and environmental factors. This review discusses the importance of epigenetic signatures in sperm-including DNA methylation, histone retention, and sncRNA-for sperm functionality, early embryo development, and offspring health. We also discuss the mechanisms by which paternal lifestyle and environmental factors (obesity, smoking, EDCs, and stress) may impact the sperm epigenome.

MicroRNAs as diagnostic biomarkers in diabetes male infertility: a systematic review

This study conducts an in-depth review of the correlation between testis tissue changes and circulating microRNAs (miRNA) in diabetes-induced male reproductive complications, drawing upon both animal and clinical studies. The original articles published in English that specifically investigate miRNAs linked to male infertility in humans or animals with either type I or ΙΙ diabetes mellitus were included. The relevant articles were gathered from the PubMed, Google Scholar, Cochrane Library, and ScienceDirect databases. The quality of study was assessed utilizing the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Prevalence Studies. We collected an overall number of 1989 citations relating to our research subject. Following the elimination of articles based on the criteria, a total of 20 papers were included in the study. Aberrant expression profiles of 25 miRNAs were identified in diabetes associated with male reproductive issues, with 15 miRNAs exhibiting increased expression and 10 miRNAs showing decreased expression. Among the chosen publications, eighteen were identified as low-risk and two were classed as moderate quality. The dysregulated miRNAs were linked to testicular injury, disrupted steroid production, decreased sperm development and quality, and erectile dysfunction. The results demonstrate that the miRNA-mRNA network is linked to the pathological progression of diabetic testicular damage or erectile dysfunction. From a therapeutic perspective, the identification of circulating miRNAs could be beneficial in the timely identification and prevention of diabetes problems, such as diabetes-induced male infertility. Among all signaling pathways influenced by modified miRNAs, the Bax-caspase-3, MAPK, PI3K-Akt, and eNOS-cGMP-PKC were the main deregulated pathways.

Transcriptomics of bovine sperm and oocytes

Traditionally, sperm and embryos were studied using microscopy to assess morphology and motility. However, OMICS technologies, especially transcriptomic analysis, are now being used to screen the molecular dynamics of fertility markers at cellular and molecular levels, with high sensitivity. Transcriptomics is the study of the transcriptome - RNA transcripts produced by the genome - using high-throughput methods to understand how the RNAs are expressed. In this review, we have discussed gene contributions to sperm structure and function and their role in fertilization and early embryo development. Further, we identified miRNAs shared by sperm, oocytes, and early embryos and their roles in fertilization and early embryo development.

Transmission of reduced levels of miR-34/449 from sperm to preimplantation embryos is a key step in the transgenerational epigenetic inheritance of the effects of paternal chronic social instability stress

The transgenerational effects of exposing male mice to chronic social instability (CSI) stress are associated with decreased sperm levels of multiple members of the miR-34/449 family that persist after their mating through preimplantation embryo (PIE) development. Here we demonstrate the importance of these miRNA changes by showing that restoring miR-34c levels in PIEs derived from CSI stressed males prevents elevated anxiety and defective sociability normally found specifically in their adult female offspring. It also restores, at least partially, levels of sperm miR-34/449 normally reduced in their male offspring who transmit these sex-specific traits to their offspring. Strikingly, these experiments also revealed that inducing miR-34c levels in PIEs enhances the expression of its own gene and that of miR-449 in these cells. The same induction of embryo miR-34/449 gene expression likely occurs after sperm-derived miR-34c is introduced into oocytes upon fertilization. Thus, suppression of this miRNA amplification system when sperm miR-34c levels are reduced in CSI stressed mice can explain how a comparable fold-suppression of miR-34/449 levels can be found in PIEs derived from them, despite sperm containing ~50-fold lower levels of these miRNAs than those already present in PIEs. We previously found that men exposed to early life trauma also display reduced sperm levels of miR-34/449. And here we show that miR-34c can also increase the expression of its own gene, and that of miR-449 in human embryonic stem cells, suggesting that human PIEs derived from men with low sperm miR-34/449 levels may also contain this potentially harmful defect.

Harnessing the power of miRNAs for precision diagnosis and treatment of male infertility

Infertility is a multifactorial reproductive system disorder, and most infertility cases occur in men. Semen testing is now thought to be the most important diagnostic test for infertile men; nonetheless, because of its limitations, the cause of infertility remains unknown for 40% of infertile men. Semen assessment's shortcomings indicate the need for improved and innovative diagnostic techniques and biomarkers worldwide. Non-coding RNAs with a length of roughly 18-22 nucleotides are called microRNAs (miRNAs). Most of our protein-coding genes are post-transcriptionally regulated by them. These molecules are unusual in bodily fluids, and aberrant variations in their expression can point to specific conditions like infertility. As a result, fresh potential biomarkers for the diagnosis and prognosis of various forms of male infertility may be represented by miRNAs. This review examined the most recent research revealing the association between different miRNAs' functions in male infertility and their expression patterns. Also, it aims to figure out the most recent strategies that could be applied for using such miRNAs as possible therapeutic targets for infertility treatment.

The Relationship between The Expression of Sperm MicroRNA-149b and 34c and Sperm Quality in Men with Oligoasthenoteratozoospermia in Endometriosis

BACKGROUND

The objective of this study was to investigate the correlation between the expression levels of sperm microRNA-149b and 34c and sperm quality in men diagnosed with oligoasthenoteratozoospermia.

MATERIALS AND METHODS

In the experimental study, we recruited 30 infertile men with oligoasthenoteratozoospermia and 30 control samples. In this study, miR-149b and miR 34c expression using reverse transcription polymerase chain reaction (RT-PCR) were evaluated. Semen samples were collected and subjected to initial analysis, including semen parameters, following the protocol provided by the World Health Organization (WHO). The levels of total antioxidant capacity (TAC) and malondialdehyde (MDA) were measured using an ELISA kit.

RESULTS

The expression levels of miR-149b and miR-34c were significantly downregulated in men with oligoasthenoteratozoospermia compared to age-matched normozoospermic men, as determined by RT-qPCR (P=0.001, and P=0.003 respectively). Correlation analysis revealed a positive correlation between the expression levels of mmiR-149b and miR-34c and various sperm parameters, including sperm count, motility, morphology, viability, sperm mitochondrial membrane potential, sperm capacity, and TAC. Additionally, an inverse correlation was observed between the expression levels of miR-149b, miR-34c, DNA fragmentation, and MDA levels.

CONCLUSION

The findings of this study indicate that the decreased expression of miR-149b and miR-34c is associated with oligoasthenoteratozoospermia, potentially affecting fundamental semen parameters. These results provide a basis for future research aimed at exploring potential therapeutic interventions for male infertility.

ARL13B controls male reproductive tract physiology through primary and Motile Cilia

ARL13B is a small regulatory GTPase that controls ciliary membrane composition in both motile cilia and non-motile primary cilia. In this study, we investigated the role of ARL13B in the efferent ductules, tubules of the male reproductive tract essential to male fertility in which primary and motile cilia co-exist. We used a genetically engineered mouse model to delete Arl13b in efferent ductule epithelial cells, resulting in compromised primary and motile cilia architecture and functions. This deletion led to disturbances in reabsorptive/secretory processes and triggered an inflammatory response. The observed male reproductive phenotype showed significant variability linked to partial infertility, highlighting the importance of ARL13B in maintaining a proper physiological balance in these small ducts. These results emphasize the dual role of both motile and primary cilia functions in regulating efferent duct homeostasis, offering deeper insights into how cilia related diseases affect the male reproductive system.

Astrocyte-Derived Exosomes Regulate Sperm miR-34c Levels to Mediate the Transgenerational Effects of Paternal Chronic Social Instability Stress

The effects of chronically stressing male mice can be transmitted across generations by stress-specific changes in their sperm miRNA content that induce stress-specific phenotypes in their offspring. But how each stress paradigm alters the levels of distinct sets of sperm miRNAs is not known. We showed previously that exposure of male mice to chronic social instability (CSI) stress results in elevated anxiety and reduced sociability specifically in their female offspring across multiple generations because it reduces miR-34c levels in sperm of stressed males and their unstressed male offspring. Here we describe evidence that a strocyte-derived exos omes ( A-Exos ) carrying miR-34c mediate how CSI stress has this transgenerational effect on sperm. We found that CSI stress decreases miR-34c carried by A-Exos in the prefrontal cortex and amygdala, as well as in the blood of males. Importantly, miR-34c A-Exos levels are also reduced in these tissues in their F1 male offspring, who despite not being exposed to stress exhibit reduced sperm miR-34c levels and transmit the same stress-associated traits to their male and female offspring. Furthermore, restoring A-Exos miR-34c content in the blood of CSI-stressed males by intravenous injection of miR-34c-containing A-Exos restores miR-34c levels in their sperm. These findings reveal an unexpected role for A-Exos in maintaining sperm miR-34c levels by a process that when suppressed by CSI stress mediates this example of transgenerational epigenetic inheritance.

MicroRNA Analysis of In Vitro Differentiation of Spermatogonial Stem Cells Using a 3D Human Testis Organoid System

Spermatogenesis produces male gametes from spermatogonial stem cells (SSC), beginning at puberty. Modern-day laboratory techniques allow for the long-term culture of SSC and in vitro spermatogenesis. The specific biochemical processes that occur during spermatogenesis remain poorly understood. One particular element of spermatogenesis that has yet to be characterized is the role of microRNAs (miRNA), short, non-transcribed RNAs that act as post-translational regulators of gene activity. In this study, we seek to describe the presence of miRNA in a two-dimensional (2D) SSC culture and a 3D human testis organoid (HTO) system. Testicular cells were isolated from the frozen tissue of three brain-dead subjects, propagated in cultures for four to five weeks, and used to form 3D HTOs. Following organoid formation, differentiation of testicular cells was induced. RNA was isolated from the whole testis tissue (WT) showing in vivo conditions, HTO Day Zero (2D SSC culture), Day 2 HTOs, and Day 23 differentiated HTOs, then analyzed for changes in miRNA expression using the Nanostring nCounter miRNA panel. One hundred ninety-five miRNAs met the criteria for expression in WT, 186 in 2D culture, 190 in Day 2 HTOs, and 187 in differentiated HTOs. One hundred thirty-three miRNAs were common across all conditions, and 41, 17, 6, and 11 miRNAs were unique for WT, 2D culture, Day 2 HTOs, and differentiated HTOs, respectively. Twenty-two miRNAs were similar between WT and differentiated HTOS. We evaluated the miRNA expression profiles of progressively complex stages of testicular cell culture, culminating in a 3D organoid model capable of meiotic differentiation, and compared these to WT. We identified a great variance between the native tissue and the culture system; however, some miRNAs are preserved. These data may provide avenues for deeper understanding of spermatogenesis and the ability to improve this process in the laboratory. Research on miRNA continues to be an essential avenue for understanding human spermatogenesis.

Specific microRNAs in stallion spermatozoa are potential biomarkers of high functionality

Males of some species, from horses to humans, require medical help for subfertility problems. There is an urgent need for novel molecular assays that reflect spermatozoal function. In the last 25 years, studies examined RNAs in spermatozoa as a window into gene expression during their development and, more recently, for their functions in early embryo development. In clinics, more dense spermatozoa are isolated by density gradient centrifugation before use in artificial insemination to increase pregnancy rates. The objectives of the current study were to discover and quantify the microRNAs in stallion spermatozoa and identify those with differential expression levels in more dense versus less dense spermatozoa. First, spermatozoa from seven stallions were separated into more dense and less dense populations by density gradient centrifugation. Next, small RNAs were sequenced from each of the 14 RNA samples. We identified 287 different mature microRNAs within the 11,824,720 total mature miRNA reads from stallion spermatozoa. The most prevalent was miR-10a/b-5p. The less dense spermatozoa had fewer mature microRNAs and more microRNA precursor sequences than more dense spermatozoa, perhaps indicating that less dense spermatozoa are less mature. Two of the most prevalent microRNAs in more dense stallion spermatozoa were predicted to target mRNAs that encode proteins that accelerate mRNA decay. Nine microRNAs were more highly expressed in more dense spermatozoa. Three of those microRNAs were predicted to target mRNAs that encode proteins involved in protein decay. Both mRNA and protein decay are very active in late spermiogenesis but not in mature spermatozoa. The identified microRNAs may be part of the mechanism to shut down those processes. The microRNAs with greater expression in more dense spermatozoa may be useful biomarkers for spermatozoa with greater functional capabilities.

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.

MicroRNAs in spermatogenesis dysfunction and male infertility: clinical phenotypes, mechanisms and potential diagnostic biomarkers

Infertility affects approximately 10-15% of couples worldwide who are attempting to conceive, with male infertility accounting for 50% of infertility cases. Male infertility is related to various factors such as hormone imbalance, urogenital diseases, environmental factors, and genetic factors. Owing to its relationship with genetic factors, male infertility cannot be diagnosed through routine examination in most cases, and is clinically called 'idiopathic male infertility.' Recent studies have provided evidence that microRNAs (miRNAs) are expressed in a cell-or stage-specific manner during spermatogenesis. This review focuses on the role of miRNAs in male infertility and spermatogenesis. Data were collected from published studies that investigated the effects of miRNAs on spermatogenesis, sperm quality and quantity, fertilization, embryo development, and assisted reproductive technology (ART) outcomes. Based on the findings of these studies, we summarize the targets of miRNAs and the resulting functional effects that occur due to changes in miRNA expression at various stages of spermatogenesis, including undifferentiated and differentiating spermatogonia, spermatocytes, spermatids, and Sertoli cells (SCs). In addition, we discuss potential markers for diagnosing male infertility and predicting the varicocele grade, surgical outcomes, ART outcomes, and sperm retrieval rates in patients with non-obstructive azoospermia (NOA).

The miR-34b/MEK/ERK pathway is regulated by NR5A1 and promotes differentiation in primary bovine Sertoli cells

Sertoli cells play a key role in testicular development and spermatogenesis. It has been suggested that Sertoli cells differentiate after their proliferation ceases. Our previous study showed that miR-34b inhibits proliferation by targeting MAP2K1 mediated MEK/ERK signaling pathway in bovine immature Sertoli cells. Subsequent studies have revealed that the differentiation marker androgen receptor is upregulated during this process. However, the effect of the miR-34b/MEK/ERK pathway on immature bovine Sertoli cell differentiation and the underlying molecular mechanisms are yet to be explored. In this study, we determined that the miR-34b/MEK/ERK pathway was involved in the differentiation of primary Sertoli cells (PSCs) in response to retinoic acid. Transfection of an miR-34b mimic into PSCs promoted cell differentiation, whereas transfection of an miR-34b inhibitor into PSCs delayed it. Pharmacological inhibition of MEK/ERK signaling by AZD6244 promoted PSCs differentiation. Mechanistically, miR-34b promoted PSCs differentiation by inhibiting the MEK/ERK signaling pathway. Through a combination of bioinformatics analysis, dual-luciferase reporter assay, quantitative real-time PCR, and western blotting, nuclear receptor subfamily 5 group A member 1 (NR5A1) was identified as an upstream negative transcription factor of miR-34b. Furthermore, NR5A1 knockdown promoted Sertoli cell differentiation, whereas NR5A1 overexpression had the opposite effect. Together, this study revealed a new NR5A1/miR-34b/MEK/ERK axis that plays a significant role in Sertoli cell differentiation and provides a theoretical and experimental framework for further clarifying the regulation of cell differentiation in bovine PSCs.

Exploring testicular miRNA profiles during developmental stages in Dezhou donkeys: A preliminary insight

Testicular development and spermatogenesis are complex phenomena controlled by various genetic factors, including miRNA-based post-transcriptional gene expression regulation. Exploring the miRNA expression patterns during testicular development in Dezhou donkeys would enhance our understanding of equine fertility and spermatogenesis. In this investigation, we examined the testicular miRNA profiles at various stages of development. The experimental animals were divided into three groups based on their developmental stages: 2 months old (juvenile: n = 3), 12 months old (adolescent; n = 3) and 24 months old (adult; n = 3) donkeys. Total RNA was extracted from dissected testicles for miRNA sequencing and analysis. In total, 586 miRNAs, including 451 known miRNAs and 135 novel miRNAs, were identified. Among identified miRNAs, 315 displayed age-dependent expression differences. The levels of miRNA expression in the juvenile group were significantly higher than in the adolescent or adult groups. The MiR-483 exhibited the maximum fold change between juvenile and adolescent groups. Several screened genes, including SLC45A4 and TFCP2L1, have been linked to male reproductive pathways in donkeys. In addition, miR-744 was predicted to regulate SPIN2B, a gene implicated in spermatocyte cell cycle progression and genomic integrity of spermatozoa. These results contribute to our comprehension of microRNA regulation during testicular development and spermatogenesis in Dezhou donkeys. The identified microRNAs and their target genes have the potential to serve as biomarkers for evaluating the reproductive capacity of stud donkeys.

The Role of microRNA in Spermatogenesis: Is There a Place for Fertility Preservation Innovation?

Oncological treatments have dramatically improved over the last decade, and as a result, survival rates for cancer patients have also improved. Quality of life, including concerns about fertility, has become a major focus for both oncologists and patients. While oncologic treatments are often highly effective at suppressing neoplastic growth, they are frequently associated with severe gonadotoxicity, leading to infertility. For male patients, the therapeutic option to preserve fertility is semen cryopreservation. In prepubertal patients, immature testicular tissue can be sampled and stored to allow post-cure transplantation of the tissue, immature germ cells, or in vitro spermatogenesis. However, experimental techniques have not yet been proven effective for restoring sperm production for these patients. MicroRNAs (miRNAs) have emerged as promising molecular markers and therapeutic tools in various diseases. These small regulatory RNAs possess the unique characteristic of having multiple gene targets. MiRNA-based therapeutics can, therefore, be used to modulate the expression of different genes involved in signaling pathways dysregulated by changes in the physiological environment (disease, temperature, ex vivo culture, pharmacological agents). This review discusses the possible role of miRNA as an innovative treatment option in male fertility preservation-restoration strategies and describes the diverse applications where these new therapeutic tools could serve as fertility protection agents.

Seasonal patterns of miRNA and mRNA expression profiles in the testes of plateau zokors (Eospalax baileyi)

The gonads of seasonal breeding animals undergo periodic annual changes in morphology, physiological hormones, and gene expression levels. To clarify the regulatory mechanism of miRNAs in the seasonal testicular development and spermatogenesis of plateau zokors, the miRNA expression profiles in their testicles during breeding and non-breeding seasons were analyzed. In total, 447 miRNAs, including 366, 81, and 167 known, novel, and differentially expressed (DE) miRNAs, respectively, were determined in the testes. Compared to the non-breeding season, 90 DE miRNAs were upregulated and 77 DE miRNAs were downregulated during the breeding season. By analysing the miRNA and mRNA expression profiles, we predicted 2096 significant target mRNAs. According to the miRNA-mRNA interaction network, target mRNAs with DE miRNAs were related to testicular development and spermatogenesis. GO indicated that target mRNAs were enriched in spermatogenesis, cell differentiation, multicellular biological development, and flagellated sperm movement and were associated with regulating testicular development and spermatogenesis. KEGG suggested that target mRNAs were enriched in lipid and fructose metabolism and provided energy and material for spermatogenesis. The target mRNA of rno-miR-24-3p was determined to be Polyubiquitin-B (UBB). Our results provide a reference for revealing the mechanism by which miRNAs regulate testicular development and spermatogenesis in plateau zokors, which has important implications for understanding the regulation of seasonal reproduction in animals.

Small Non-Coding RNAs in Male Reproduction

Male reproductive functions are strictly regulated in order to maintain sperm production and fertility. All processes are controlled by precise regulation of gene expression, which creates specific gene expression programs for different developmental stages and cell types, and forms the functional basis for the reproductive system. Small non-coding RNAs (sncRNAs) are involved in gene regulation by targeting mRNAs for translational repression and degradation through complementary base pairing to recognize their targets. This review article summarizes the current knowledge on the function of different classes of sncRNAs, in particular microRNAs (miRNAs) and PIWI-interacting RNAs (piRNAs), during male germ cell differentiation, with the focus on sncRNAs expressed in the germline. Although transcriptionally inactive, mature spermatozoa contain a complex population of sncRNAs, and we also discuss the recently identified role of sperm sncRNAs in the intergenerational transmission of epigenetic information on father's environmental and lifestyle exposures to offspring. Finally, we summarize the current information on the utility of sncRNAs as potential biomarkers of infertility that may aid in the diagnosis and prediction of outcomes of medically assisted reproduction.

Characterization and identification of extracellular vesicles-coupled miRNA profiles in seminal plasma of fertile and subfertile rabbit bucks

Seminal plasma (SP) provides essential nutrients, transport, and protection to the spermatozoa during their journey through the male and female reproductive tracts. Extracellular vesicles (EVs) are one of the main components of the SP with several biomolecular cargoes, including miRNAs, that can influence spermatozoa functions and interact with the cells of the female reproductive tract. This study aimed to isolate, characterize, and identify the miRNA expression profiles in the SP-EVs isolated from fertile (F) and subfertile (S) rabbit bucks that could serve as fertility biomarkers. In this study, the methods to isolate and identify EVs including exosomes, from SP of 3 F and S bucks have been developed. Ultracentrifugation and size exclusion chromatography analysis were using to isolate EVs from SP of F and S males that were qualitative and quantitively characterised using transmission electron microscopy, nanoparticle tracking analysis and western blotting. In addition, total RNA, including miRNA, was isolated, sequenced and identified from SP-EVs samples. Different SP-EVs concentrations (8.53 × 1011 ± 1.04 × 1011 and 1.84 × 1012 ± 1.75 × 1011 particles/mL of SP; P = 0.008), with a similar average size (143.9 ± 11.9 and 115.5 ± 2.4 nm; P = 0.7422) in F and S males, respectively was observed. Particle size was not significantly correlated with any kinetic parameter. The concentration of SP-EVs was positively correlated with the percentage of abnormal forms (r = 0.94; P < 0.05) and with the percentage of immotile spermatozoa (r = 0.88; P < 0.05). Small-RNA-seq analysis identified a total of 267 and 244 expressed miRNAs in the F and S groups, respectively. Two miRNAs (let-7b-5p and let-7a-5p) were the top most abundant miRNAs in both groups. Differential expression analysis revealed that 9 miRNAs including miR-190b-5p, miR-193b-5p, let-7b-3p, and miR-378-3p, and another 9 miRNAs including miR-7a-5p, miR-33a-5p, miR-449a-5p, and miR-146a-5p were significantly up- and downregulated in the F compared to the S group, respectively. The SP from F and S rabbit males contains EVs with different miRNA cargo correlated with spermatogenesis, homeostasis, and infertility, which could be used as biomarkers for male fertility and potential therapies for assisted reproductive technologies.

Expression of miR-138 in cryopreserved bovine sperm is related to their fertility potential

BACKGROUND

MicroRNAs (miRNAs) are small, single-stranded, non-coding RNA molecules of 22-24 nucleotides that regulate gene expression. In the last decade, miRNAs have been described in sperm of several mammals, including cattle. It is known that miRNAs can act as key gene regulators of early embryogenesis in mice and humans; however, little is known about the content, expression, and function of sperm-borne miRNAs in early bovine embryo. In this study, total sperm RNA was isolated from 29 cryopreserved sperm samples (each coming from a separate bull) using a RNeasy kit and treatment with DNase I. RNA concentration and purity were determined through an Epoch spectrophotometer and an Agilent Bioanalyzer. The expression of 10 candidate miRNAs in bovine sperm (bta-miR-10a, bta-miR-10b, bta-miR-138, bta-miR-146b, bta-miR-19b, bta-miR-26a, bta-miR-34a, bta-miR-449a, bta-miR-495 and bta-miR-7), previously identified in testis and/or epididymis, was evaluated with RT-qPCR. The cel-miR-39-3p was used as a spike-in exogenous control. Nonparametric Mann-Whitney tests were run to evaluate which miRNAs were differentially expressed between bulls with high fertility [HF; non-return rates (NRR) ranging from 39.5 to 43.5] and those with subfertility (SF; NRR ranging from 33.3 to 39.3). Several sperm functionality parameters (e.g., viability, membrane stability or oxygen consumption, among others) were measured by multiplexing flow cytometry and oxygen sensing technologies.

RESULTS

RNA concentration and purity (260/280 nm ratio) (mean ± SD) from the 29 samples were 99.3 ± 84.6 ng/µL and 1.97 ± 0.72, respectively. Bioanalyzer results confirmed the lack of RNA from somatic cells. In terms of the presence or absence of miRNAs, and after applying the Livak method, 8 out of 10 miRNAs (bta-miR-10b, -138, -146b, -19b, -26a, -449a, -495, -7) were consistently detected in bovine sperm, whereas the other two (bta-miR-10a, and -34a) were absent. Interestingly, the relative expression of one miRNA (bta-miR-138) in sperm was significantly lower in the SF than in the HF group (P = 0.038). In addition to being associated to fertility potential, the presence of this miRNA was found to be negatively correlated with sperm oxygen consumption. The expression of three other miRNAs (bta-miR-19b, bta-miR-26a and bta-miR-7) was also correlated with sperm function variables.

CONCLUSIONS

In conclusion, although functional validation studies are required to confirm these results, this study suggests that sperm bta-miR-138 is involved in fertilization events and beyond, and supports its use as a fertility biomarker in cattle.

In vivo functions of miRNAs in mammalian spermatogenesis

MicroRNAs (miRNAs) are believed to play important roles in mammalian spermatogenesis mainly because spermatogenesis is more or less disrupted when genes encoding key enzymes for miRNA biogenesis are mutated. However, it is challenging to study the functions of individual miRNAs due to their family-wise high sequence similarities and the clustered genomic distributions of their genes, both of which expose difficulties in using genetic methods. Accumulating evidence shows that a number of miRNAs indeed play important roles in mammalian spermatogenesis and the underlying mechanisms start to be understood. In this mini review, we focus on highlighting the roles of miRNAs in mammalian spermatogenesis elucidated mainly by using in vivo genetic methods and on discussing the underlying mechanisms. We propose that studies on the roles of miRNAs in spermatogenesis should and can be conducted in a more fruitful way given the progress in traditional methods and the birth of new technologies.

The impact of epigenetic landscape on ovarian cells in infertile older women undergoing IVF procedures

The constant decline in fertility and older reproductive age is the major cause of low clinical pregnancy rates in industrialised countries. Epigenetic mechanisms impact on proper embryonic development in women undergoing in vitro fertilisation (IVF) protocols. Here, we describe the main epigenetic modifications that may influence female reproduction and could affect IVF success.

In Silico Analysis of miRNA-Mediated Genes in the Regulation of Dog Testes Development from Immature to Adult Form

High-throughput in-silico techniques help us understand the role of individual proteins, protein-protein interaction, and their biological functions by corroborating experimental data as epitomized biological networks. The objective of this investigation was to elucidate the association of miRNA-mediated genes in the regulation of dog testes development from immature to adult form by in-silico analysis. Differentially expressed (DE) canine testis miRNAs between healthy immature (2.2 ± 0.13 months; n = 4) and mature (11 ± 1.0 months; n = 4) dogs were utilized in this investigation. In silico analysis was performed using miRNet, STRING, and ClueGo programs. The determination of mRNA and protein expressions of predicted pivotal genes and their association with miRNA were studied. The results showed protein-protein interaction for the upregulated miRNAs, which revealed 978 enriched biological processes GO terms and 127 KEGG enrichment pathways, and for the down-regulated miRNAs revealed 405 significantly enriched biological processes GO terms and 72 significant KEGG enrichment pathways (False Recovery Rate, p < 0.05). The in-silico analysis of DE-miRNA's associated genes revealed their involvement in the governing of several key biological functions (cell cycle, cell proliferation, growth, maturation, survival, and apoptosis) in the testis as they evolve from immature to adult forms, mediated by several key signaling pathways (ErbB, p53, PI3K-Akt, VEGF and JAK-STAT), cytokines and hormones (estrogen, GnRH, relaxin, thyroid hormone, and prolactin). Elucidation of DE-miRNA predicted genes' specific roles, signal transduction pathways, and mechanisms, by mimics and inhibitors, which could perhaps offer diagnostic and therapeutic targets for infertility, cancer, and birth control.

Sperm-borne microRNA-34c regulates maternal mRNA degradation and preimplantation embryonic development in mice

BACKGROUND

Studies have shown that sperm-borne microRNAs (miRNAs) are involved in mammalian preimplantation embryonic development. In humans, spermatozoan miR-34c levels are correlated with in vitro fertilization outcomes, such as embryo quality and the clinical pregnancy and live birth rates. In rabbits and cows, miR-34c improves the developmental competence of embryos generated by somatic cell nuclear transfer. However, the mechanisms underlying the regulation of embryonic development by miR-34c remain unknown.

METHODS

Female C57BL/6 mice (6-8 weeks old) were superovulated, and pronucleated zygotes were collected and microinjected with an miR-34c inhibitor or a negative-control RNA. The embryonic development of the microinjected zygotes was evaluated, and the messenger RNA (mRNA) expression profiles of the embryos at the two-cell, four-cell and blastocyst stages (five embryos per group) were determined by RNA sequencing analysis. Gene expression levels were verified by reverse transcription-quantitative polymerase chain reaction. Cluster analysis and heat map visualization were performed to detect differentially expressed mRNAs. Pathway and process enrichment analyses were performed using ontology resources. Differentially expressed mRNAs were systematically analyzed using the Search Tool for the Retrieval of Interacting Genes/Proteins database to determine their biological functions.

RESULTS

Embryonic developmental potential was significantly reduced in zygotes microinjected with the miR-34c inhibitor compared with those microinjected with a negative-control RNA. Two-cell stage embryos microinjected with an miR-34c inhibitor presented altered transcriptomic profiles, with upregulated expression of maternal miR-34c target mRNAs and classical maternal mRNAs. Differentially expressed transcripts were mainly of genes associated with lipid metabolism and cellular membrane function at the two-cell stage, with cell-cycle phase transition and energy metabolism at the four-cell stage; and with vesicle organization, lipid biosynthetic process and endomembrane system organization at the blastocyst stage. We also showed that genes related to preimplantation embryonic development, including Alkbh4, Sp1, Mapk14, Sin3a, Sdc1 and Laptm4b, were significantly downregulated after microinjection of an miR-34c inhibitor.

CONCLUSIONS

Sperm-borne miR-34c may regulate preimplantation embryonic development by affecting multiple biological processes, such as maternal mRNA degradation, cellular metabolism, cell proliferation and blastocyst implantation. Our data demonstrate the importance of sperm-derived miRNAs in the development of preimplantation embryos.

Early life nutrition affects the molecular ontogeny of testicular development in the young bull calf

Enhanced early life nutrition accelerates sexual development in the bull calf through neuroendocrine-signalling mediated via the hypothalamic-pituitary-testicular axis. Our aim was to assess the impact of contrasting feeding regimes in bull calves during the first 12 weeks of life on the testes transcriptome and proteome. Holstein-Friesian bull calves were offered either a high (HI) or moderate (MOD) plane of nutrition, designed to support target growth rates of 1.0 and 0.5 kg/day, respectively. At 12 weeks of age all calves were euthanized, testicular parenchyma sampled, and global transcriptome (miRNAseq and mRNAseq) and proteome analyses undertaken. Bioinformatic analyses revealed 7 differentially expressed (DE) miRNA and 20 DE mRNA. There were no differentially abundant proteins between the two dietary groups. Integration of omics results highlighted a potential role for the cadherin gene, CDH13, in earlier reproductive development. Furthermore, co-regulatory network analysis of the proteomic data revealed CDH13 as a hub protein within a network enriched for processes related to insulin, IGF-1, androgen and Sertoli cell junction signalling pathways as well as cholesterol biosynthesis. Overall, results highlight a potential role for CDH13 in mediating earlier reproductive development as a consequence of enhanced early life nutrition in the bull calf.

Sperm DNA Fragmentation and Sperm-Borne miRNAs: Molecular Biomarkers of Embryo Development?

The evaluation of morpho-functional sperm characteristics alone is not enough to explain infertility or to predict the outcome of Assisted Reproductive Technologies (ART): more sensitive diagnostic tools are needed in clinical practice. The aim of the present study was to analyze Sperm DNA Fragmentation (SDF) and sperm-borne miR-34c-5p and miR-449b-5p levels in men of couples undergoing ART, in order to investigate any correlations with fertilization rate, embryo quality and development. Male partners (n = 106) were recruited. Semen analysis, SDF evaluation and molecular profiling analysis of miR-34c-5p and miR-449b-5p (in 38 subjects) were performed. Sperm DNA Fragmentation evaluation- a positive correlation between SDF post sperm selection and the percentage of low-quality embryos and a negative correlation with viable embryo were found. SDF > 2.9% increased the risk of obtaining a non-viable embryo by almost 4-fold. Sperm miRNAs profile—we found an association with both miRNAs and sperm concentration, while miR-449b-5p is positively associated with SDF. Moreover, the two miRNAs are positively correlated. Higher levels of miR-34c-5p compared to miR-449b-5p increases by 14-fold the probability of obtaining viable embryos. This study shows that SDF, sperm miR-34c-5p, and miR-449b-5p have a promising role as biomarkers of semen quality and ART outcome.

The Male-Biased Expression of miR-2954 Is Involved in the Male Pathway of Chicken Sex Differentiation

Many expression data showed miRNAs have a potential function on regulating gonadal differentiation in animals, but their function is rarely studied in vivo, especially in chickens. Using the comprehensive expression profiles analysis, the specific male-biased miR-2954, which is significantly higher expressed in male embryos and gonads at all detected stages, was firstly screened during the early stages of chicken embryogenesis and gonadogenesis. In sex-reversed female gonads treated with aromatase inhibitors, the expression of miR-2954 was increased, which was consistent with the up-regulation of DMRT1 and SOX9. The injection of vivo-morpholino of miR-2954 significantly inhibited the expression of miR-2954 in chicken embryos, and the down-regulation of miR-2954 decreased the expression of testis-associated genes DMRT1 and SOX9, while the expression of ovary-associated genes and the gonadal morphology did not change obviously. These results confirm that miR-2954 coincides with testicular differentiation in chicken embryos, but whether it might be an upstream cell autonomous factor to sex development in birds still need to be further determined.

The Sperm Small RNA Transcriptome: Implications beyond Reproductive Disorder

Apart from the paternal half of the genetic material, the male gamete carries assorted epigenetic marks for optimal fertilization and the developmental trajectory for the early embryo. Recent works showed dynamic changes in small noncoding RNA (sncRNA) in spermatozoa as they transit through the testicular environment to the epididymal segments. Studies demonstrated the changes to be mediated by epididymosomes during the transit through the adluminal duct in the epididymis, and the changes in sperm sncRNA content stemmed from environmental insults significantly altering the early embryo development and predisposing the offspring to metabolic disorders. Here, we review the current knowledge on the establishment of the sperm sncRNA transcriptome and their role in male-factor infertility, evidence of altered offspring health in response to the paternal life experiences through sperm sncRNA species and, finally, their implications in assisted reproductive technology in terms of epigenetic inheritance.

The potential of sertoli cells (SCs) derived exosomes and its therapeutic efficacy in male reproductive disorders

In the male reproductive system, seminiferous tubules in testis are lined by a complex stratified epithelium containing two distinct populations of cells, spermatogenic cells that develop into spermatozoa, and sertoli cells (SCs) that mainly support and nourish spermatogenic cell lineage as well as exerting powerful effect on men reproductive capacity. Different varieties of proteins, hormones, exosomes and growth factors are secreted by SCs. There are different kinds of junctions found between SCs called BTB. It was elucidated that complete absence of BTB or its dysfunction leads to infertility. To promote spermatogenesis, crosstalk of SCs with spermatogenic cells plays an important role. The ability of SCs to support germ cell productivity and development is related to its various products carrying out several functions. Exosomes (EXOs) are one of the main EVs with 30-100 nm size generating from endocytic pathway. They are produced in different parts of male reproductive system including epididymis, prostate and SCs. The most prominent characteristics of SC-based exosomes is considered mutual interaction of sertoli cells with spermatogonial stem cells and Leydig cells mainly through establishment of intercellular communication. Exosomes have gotten a lot of interest because of their role in pathobiological processes and as a cell free therapy which led to developing multiple exosome isolation methods based on different principles. Transmission of nucleic acids, proteins, and growth factors via SC-based exosomes and exosomal miRNAs are proved to have potential to be valuable biomarkers in male reproductive disease. Among testicular abnormalities, non-obstructive azoospermia and testicular cancer have been more contributed with SCs performance. The identification of key proteins and miRNAs involved in the signaling pathways related with spermatogenesis, can serve as diagnostic and regenerative targets in male infertility.

Correlation between Sperm Micro Ribonucleic Acid-34b and -34c Levels and Clinical Outcomes of Intracytoplasmic Sperm Injection in Men with Male Factor Infertility

Few studies have examined the correlation between sperm miRNA levels and clinical outcomes of intracytoplasmic sperm injection (ICSI). In this study, we aimed to assess the correlation of sperm miR-34b, miR-34c, miR-122, and miR-429 levels with ICSI outcomes in men with teratozoospermia and asthenozoospermia. TaqMan microRNA quantitative polymerase chain reaction was used to evaluate the relative expression of miRNAs in sperm. The relative miRNA levels quantified using a comparative method found that the four miRNAs were not associated with fertilization rate and early embryo development. However, revels of miR-34b and miR-34c in teratozoospermia sperm of the live birth group were significantly higher than those in the non-live birth group. Receiver operating characteristic curve analysis revealed that the optimal cut-off delta cycle threshold values of miR-34b and miR-34c were 8.630 and 7.883, respectively. Statistical analysis found that the levels of miR-34b and the miR-34c in teratozoospermic and asthenozoospermic sperm above the thresholds were not associated with the fertilization rate and the high-quality embryo rate above 50%; however, they were more likely to exhibit higher implantation, pregnancy, and live birth rates. miR-34b and miR-34c were significantly associated with ICSI clinical outcomes in male factor infertility, especially teratozoospermia. Further validation is required before it becomes a clinically valid reference indicator.

Investigation of Sperm and Seminal Plasma Candidate MicroRNAs of Bulls with Differing Fertility and In Silico Prediction of miRNA-mRNA Interaction Network of Reproductive Function

Simple Summary

The objective of this study was to identify differentially expressed (DE) sperm and seminal plasma microRNAs (miRNAs) in high- and low-fertile Holstein bulls (four bulls per group), integrate miRNAs to their target genes, and categorize target genes based on predicted biological processes. Out of 84 bovine-specific, prioritized miRNAs analyzed by RT-PCR, 30 were differentially expressed in high-fertile sperm and seminal plasma compared to low-fertile sperm and seminal plasma, respectively (p ≤ 0.05, fold regulation ≥5 magnitudes). Interestingly, expression levels of DE-miRNAs in sperm and seminal plasma followed a similar pattern. Highly scored integrated genes of DE-miRNAs predicted various biological and molecular functions, cellular process, and pathways. Further in silico analysis revealed categorized genes may have a plausible association with pathways regulating sperm structure and function, fertilization, and embryo and placental development. In conclusion, highly DE-miRNAs in bovine sperm and seminal plasma could be used as a tool for predicting reproductive functions. Since the identified miRNA-mRNA interactions were mostly based on predictions from public databases, the causal regulations of miRNA-mRNA and the underlying mechanisms require further functional characterization in future studies.

Abstract

Recent advances in high-throughput in silico techniques portray experimental data as exemplified biological networks and help us understand the role of individual proteins, interactions, and their biological functions. The objective of this study was to identify differentially expressed (DE) sperm and seminal plasma microRNAs (miRNAs) in high- and low-fertile Holstein bulls (four bulls per group), integrate miRNAs to their target genes, and categorize the target genes based on biological process predictions. Out of 84 bovine-specific, prioritized miRNAs analyzed by RT-PCR, 30 were differentially expressed in high-fertile sperm and seminal plasma compared to low-fertile sperm and seminal plasma, respectively (p ≤ 0.05, fold regulation ≥ 5 magnitudes). The expression levels of DE-miRNAs in sperm and seminal plasma followed a similar pattern. Highly scored integrated genes of DE-miRNAs predicted various biological and molecular functions, cellular process, and pathways. Further, analysis of the categorized genes showed association with pathways regulating sperm structure and function, fertilization, and embryo and placental development. In conclusion, highly DE-miRNAs in bovine sperm and seminal plasma could be used as a tool for predicting reproductive functions. Since the identified miRNA-mRNA interactions were mostly based on predictions from public databases, the causal regulations of miRNA-mRNA and the underlying mechanisms require further functional characterization in future studies.

Germline FOXJ2 overexpression causes male infertility via aberrant autophagy activation by LAMP2A upregulation

Spermatogenesis is a complex biological process that produces haploid spermatozoa and requires precise regulation by many tissue-specific factors. In this study, we explored the role and mechanism of Fork head box J2 (FOXJ2, which is highly expressed in spermatocytes) in the regulation of spermatogenesis using a germline-specific conditional Foxj2 knock-in mouse model (Stra8-Cre; Foxj2 ^tg/tg mouse). Foxj2 overexpression in mouse testes led to spermatogenesis failure, which started at the initiation of meiosis, and resulted in male infertility. Lysosomes and autophagy-related genes were upregulated in Stra8-cre; Foxj2 ^tg/tg mouse testes and the number of autolysosomes in the spermatocytes in Stra8-cre; Foxj2 ^tg/tg mice was increased. Chromatin immunoprecipitation-PCR and Dual-luciferase reporter assays showed that Lamp2 (encoding lysosome-associated membrane protein-2) was a target of FOXJ2. Foxj2 overexpression increased the expression levels of Lamp2a and Hsc70 (70-kDa cytoplasmic heat shock protein) in the Stra8-cre; Foxj2 ^tg/tg mouse testes. Our results suggested that Foxj2 overexpression in the germ cells of mouse testes affects chaperone-mediated autophagy by upregulating LAMP2A, leading to spermatogenesis failure at the initiation of meiosis, thus resulting in male infertility. Our findings provide a new insight into the function of FOXJ2 in spermatogenesis and the significance of autophagy regulation in spermatogenesis.

Association between metabolic disorders and seminal plasma miRNA levels: a pilot study

BACKGROUND

Excess weight and metabolic disorders have a negative impact on male reproductive functions. The mechanisms involved are numerous and complex and epigenetic mechanisms may also be involved, notably through the small non-coding RNAs. Among them, microRNAs (miRNAs) are of particular interest. This preliminary study aimed to identify the miRNAs differentially enriched in seminal plasma related to metabolic disorders and if some are also associated with spermatic parameters alterations. One hundred and sixty men between 18 to 45 years, partners of infertile couple, were included in this cohort. The miRNAs associated with metabolism were selected from the literature and assayed by quantitative real-time PCR using TaqMan gene expression assays. A subset of those with an interesting profile in seminal plasma were secondarily tested in blood.

RESULTS

Among the 11 selected miRNAs, seven were detected in seminal plasma (miR10b, miR19a, miR19b, miR34b, miR34c, miR133b, miRlet7c). A negative correlation was observed between seminal miR19a levels and metabolic syndrome, blood glucose and C-peptide. Seminal miR19b levels were also negatively correlated with metabolic syndrome. Seminal miR34c levels were negatively correlated with body mass index (BMI) and waist circumference. Seminal miR133b levels were positively correlated with BMI, waist circumference and leptin levels. Interestingly, modifications of miRNAs in seminal plasma seem specific since highlighted above correlations were not retrieved in the blood plasma for the miR19a, 19b, 10b, 34c.

CONCLUSION

Few metabolic and anthropometric disorders are correlated with the level of specific miRNAs in seminal plasma. Further studies will be required to decipher if other small non-coding RNAs may also be correlated with metabolic and anthropometric disorders and to assess their potential implication in the alteration of reproductive functions in men with obesity or metabolic disorders.

CLINICAL STUDY

Metabolic Syndrome and Male Infertility (Metasperme): Trial registration:  NCT01974947 . Registered 18 July 2013.

Characteristics of miRNAs Present in Bovine Sperm and Associations With Differences in Fertility

Small non-coding RNAs have been linked to different phenotypes in bovine sperm, however attempts to identify sperm-borne molecular biomarkers of male fertility have thus far failed to identify a robust profile of expressed miRNAs related to fertility. We hypothesized that some differences in bull fertility may be reflected in the levels of different miRNAs in sperm. To explore such differences in fertility that are not due to differences in visible metrics of sperm quality, we employed Next Generation Sequencing to compare the miRNA populations in Bos taurus sperm from bulls with comparable motility and morphology but varying Sire Conception Rates. We identified the most abundant miRNAs in both populations (miRs -34b-3p; -100-5p; -191-5p; -30d-4p; -21-5p) and evaluated differences in the overall levels and specific patterns of isomiR expression. We also explored correlations between specific pairs of miRNAs in each population and identified 10 distinct pairs of miRNAs that were positively correlated in bulls with higher fertility and negatively correlated in comparatively less fertile individuals. Furthermore, 8 additional miRNA pairs demonstrated the opposite trend; negatively correlated in high fertility animals and positively correlated in less fertile bulls. Finally, we performed pathway analysis to identify potential roles of miRNAs present in bull sperm in the regulation of specific genes that impact spermatogenesis and embryo development. Together, these results present a comprehensive picture of the bovine sperm miRNAome that suggests multiple potential roles in fertility.

The Transmission of Intergenerational Epigenetic Information by Sperm microRNAs

Epigenetic information is transmitted from one generation to the next, modulating the phenotype of offspring non-genetically in organisms ranging from plants to mammals. For intergenerational non-genetic inheritance to occur, epigenetic information must accumulate in germ cells. The three main carriers of epigenetic information-histone post-translational modifications, DNA modifications, and RNAs-all exhibit dynamic patterns of regulation during germ cell development. For example, histone modifications and DNA methylation are extensively reprogrammed and often eliminated during germ cell maturation and after fertilization during embryogenesis. Consequently, much attention has been given to RNAs, specifically small regulatory RNAs, as carriers of inherited epigenetic information. In this review, we discuss examples in which microRNAs have been implicated as key players in transmitting paternal epigenetic information intergenerationally.

Sex-Biased miRNAs in the Gonads of Adult Chinese Alligator (Alligator sinensis) and Their Potential Roles in Sex Maintenance

MicroRNA (miRNA) is a category of single-stranded non-coding small RNA (sRNA) that regulates gene expression by targeting mRNA. It plays a key role in the temperature-dependent sex determination of Chinese alligator (Alligator sinensis), a reptile whose sex is determined solely by the temperature during the incubation period and remains stable thereafter. However, the potential function of miRNAs in the gonads of adult Chinese alligators is still unclear. Here, we prepared and sequenced sRNA libraries of adult female and male alligator gonads, from breeding (in summer) and hibernating (in winter) animals. We obtained 130 conserved miRNAs and 683 novel miRNAs, which were assessed for sex bias in summer and winter; a total of 65 miRNAs that maintained sex bias in both seasons were identified. A regulatory network of sex-biased miRNAs and genes was constructed. Sex-biased miRNAs targeted multiple genes in the meiosis pathway of adult Chinese alligator oocytes and the antagonistic gonadal function maintenance pathway, such as MOS, MYT1, DMRT1, and GDF9. Our study emphasizes the function of miRNA in the epigenetic mechanisms of sex maintenance in crocodilians.

Genetic Regulation of N6-Methyladenosine-RNA in Mammalian Gametogenesis and Embryonic Development

Emerging evidence shows that m⁶A is the most abundant modification in eukaryotic RNA molecules. It has only recently been found that this epigenetic modification plays an important role in many physiological and pathological processes, such as cell fate commitment, immune response, obesity, tumorigenesis, and relevant for the present review, gametogenesis. Notably the RNA metabolism process mediated by m⁶A is controlled and regulated by a series of proteins termed writers, readers and erasers that are highly expressed in germ cells and somatic cells of gonads. Here, we review and discuss the expression and the functional emerging roles of m⁶A in gametogenesis and early embryogenesis of mammals. Besides updated references about such new topics, readers might find in the present work inspiration and clues to elucidate epigenetic molecular mechanisms of reproductive dysfunction and perspectives for future research.

Essential Roles of Efferent Duct Multicilia in Male Fertility

Cilia are microtubule-based hair-like organelles on the cell surface. Cilia have been implicated in various biological processes ranging from mechanosensation to fluid movement. Ciliary dysfunction leads to a plethora of human diseases, known as ciliopathies. Although non-motile primary cilia are ubiquitous, motile multicilia are found in restricted locations of the body, such as the respiratory tract, the oviduct, the efferent duct, and the brain ventricles. Multicilia beat in a whip-like motion to generate fluid flow over the apical surface of an epithelium. The concerted ciliary motion provides the driving force critical for clearing airway mucus and debris, transporting ova from the ovary to the uterus, maintaining sperm in suspension, and circulating cerebrospinal fluid in the brain. In the male reproductive tract, multiciliated cells (MCCs) were first described in the mid-1800s, but their importance in male fertility remained elusive until recently. MCCs exist in the efferent ducts, which are small, highly convoluted tubules that connect the testis to the epididymis and play an essential role in male fertility. In this review, we will introduce multiciliogenesis, discuss mouse models of male infertility with defective multicilia, and summarize our current knowledge on the biological function of multicilia in the male reproductive tract.

The gene regulatory role of non-coding RNAs in non-obstructive azoospermia

Non-coding RNAs are classified as small non-coding RNAs, long non-coding RNAs and circular RNAs, which are involved in a variety of biological processes, including cell differentiation, proliferation, apoptosis and pathological conditions of various diseases. Many studies have shown that non-coding RNAs are related to spermatogenesis, maturation, apoptosis, function, etc. In addition, the expression of non-coding RNAs in testicular tissue and semen of patients with non-obstructive azoospermia was different. However, the role of non-coding RNAs in the pathogenesis of non-obstructive azoospermia has not been fully elucidated, and the role of non-coding RNAs in non-obstructive azoospermia is rarely reviewed. Here we summarize the research progress of non-coding RNAs in the pathogenesis of non-obstructive azoospermia.

Effect of Sperm Cryopreservation on miRNA Expression and Early Embryonic Development

Although sperm preservation is a common means of personal fertility preservation, its effects on embryonic development potential need further investigation. The purpose of this study was to identify key microRNA (miRNA) in cryopreserved sperm and determine the changes of these miRNAs and their target genes during embryonic development using cryopreserved sperm. Moreover, the embryonic development potential of cryopreserved sperm was estimated in assisted reproductive technology (ART), where key miRNAs and target genes were validated in sperm and subsequent embryos. Clinical data of embryonic development from cryopreserved sperm indicated a significant decrease in fertilization rate in both in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cases, as well as a reduction in blastocyst formation rate in ICSI cases. Meanwhile there was a significant increase in blocked embryo ratio of Day1, Day2, and Day3.5 embryos when frozen-thawed mouse sperm was used, compared with fresh mouse sperm, suggesting a potential negative effect of sperm cryopreservation on embryonic development. From frozen-thawed and fresh sperm in humans and mice, respectively, 21 and 95 differentially expressed miRNAs (DEmiRs) were detected. miR-148b-3p were downregulated in both human and mouse frozen-thawed sperm and were also decreased in embryos after fertilization using cryopreserved sperm. Target genes of miR-148b-3p, Pten, was identified in mouse embryos using quantitative real-time PCR (qRT-PCR) and Western blot (WB). In addition, common characters of cryopreservation of mouse oocytes compared with sperm were also detected; downregulation of miR-148b-3p was also confirmed in cryopreserved oocytes. In summary, our study suggested that cryopreservation of sperm could change the expression of miRNAs, especially the miR-148b-3p across humans and mice, and may further affect fertilization and embryo development by increasing the expression of Pten. Moreover, downregulation of miR-148b-3p induced by cryopreservation was conserved in mouse gametes.

Small Noncoding RNAs in Reproduction and Infertility

Infertility has been reported as one of the most common reproductive impairments, affecting nearly one in six couples worldwide. A large proportion of infertility cases are diagnosed as idiopathic, signifying a deficit in information surrounding the pathology of infertility and necessity of medical intervention such as assisted reproductive therapy. Small noncoding RNAs (sncRNAs) are well-established regulators of mammalian reproduction. Advanced technologies have revealed the dynamic expression and diverse functions of sncRNAs during mammalian germ cell development. Mounting evidence indicates sncRNAs in sperm, especially microRNAs (miRNAs) and transfer RNA (tRNA)-derived small RNAs (tsRNAs), are sensitive to environmental changes and mediate the inheritance of paternally acquired metabolic and mental traits. Here, we review the critical roles of sncRNAs in mammalian germ cell development. Furthermore, we highlight the functions of sperm-borne sncRNAs in epigenetic inheritance. We also discuss evidence supporting sncRNAs as promising biomarkers for fertility and embryo quality in addition to the present limitations of using sncRNAs for infertility diagnosis and treatment.

Sperm-borne sncRNAs: potential biomarkers for semen fertility?

Semen infertility or sub-fertility, whether in humans or livestock species, remains a major concern for clinicians and technicians involved in reproduction. Indeed, they can cause tragedies in human relationships or have a dramatic overall negative impact on the sustainability of livestock breeding. Understanding and predicting semen fertility issues is therefore crucial and quality control procedures as well as biomarkers have been proposed to ensure sperm fertility. However, their predictive values appeared to be too limited and additional relevant biomarkers are still required to diagnose sub-fertility efficiently. During the last decade, the study of molecular mechanisms involved in spermatogenesis and sperm maturation highlighted the regulatory role of a variety of small non-coding RNAs (sncRNAs) and led to the discovery that sperm sncRNAs comprise both remnants from spermatogenesis and post-testicular sncRNAs acquired through interactions with extracellular vesicles along epididymis. This has led to the hypothesis that sncRNAs may be a source of relevant biomarkers, associated either with sperm functionality or embryo development. This review aims at providing a synthetic overview of the current state of knowledge regarding implication of sncRNA in spermatogenesis defects and their putative roles in sperm maturation and embryo development, as well as exploring their use as fertility biomarkers.

New Insight into Molecular and Hormonal Connection in Andrology

Hormones and cytokines are known to regulate cellular functions in the testes. These biomolecules induce a broad spectrum of effects on various level of spermatogenesis, and among them is the modulation of cell junction restructuring between Sertoli cells and germ cells in the seminiferous epithelium. Cytokines and androgens are closely related, and both correct testicular development and the maintenance of spermatogenesis depend on their function. Cytokines also play a crucial role in the immune testicular system, activating and directing leucocytes across the endothelial barrier to the inflammatory site, as well as in increasing their adhesion to the vascular wall. The purpose of this review is to revise the most recent findings on molecular mechanisms that play a key role in male sexual function, focusing on three specific molecular patterns, namely, cytokines, miRNAs, and endothelial progenitor cells. Numerous reports on the interactions between the immune and endocrine systems can be found in the literature. However, there is not yet a multi-approach review of the literature underlying the role between molecular patterns and testicular and sexual function.

Comprehensive Analysis of miRNAs and Target mRNAs between Immature and Mature Testis Tissue in Chinese Red Steppes Cattle

Simple Summary

MicroRNAs are small molecules that can regulate the relative abundance of their target genes by binding to the 3′ untranslated region of the target genes at the post-transcriptional level to affect various biological processes, such as biosynthesis, fat metabolism and proliferation, apoptosis, and cell differentiation. Fertility is one of the most important economic traits in livestock production. Bulls require the continuous production of high-quality spermatozoa in abundance. The quality of semen is an exceptionally important factor affecting the fertilization rate of the dairy cow and is also associated with the increasing conception rate in the process of artificial insemination. Therefore, accurately predicting fertility potential for a semen sample from donor bull for artificial insemination is crucial for consistently high reproductive efficiency. The present study performed a genome-wide sequencing analysis of microRNAs and mRNAs between immature and mature testes of Chinese Red Steppes. These results provide novel candidate microRNAs and functional genes related to bull reproduction traits and the networks between microRNAs and target genes, which will provide a useful genetic mechanism and epigenetic information for marker-assisted selection of bulls with excellent sperm quality in the future.

Abstract

This study aims to screen potential regulators and regulate fecundity networks between microRNAs (miRNAs) and target genes. The bovine testes of immature and mature Chinese Red Steppes were performed by genome-wide analysis of mRNAs and miRNAs. Compared with testicular tissues of newborns, 6051 upregulated genes and 7104 downregulated genes in adult cattle were identified as differentially expressed genes (DEGs). The DEGs were significantly enriched in 808 GO terms (p < 0.05) including male gonad development, male genitalia development, spermatogenesis, and sperm motility. Moreover, DEGs were also significantly enriched in 105 KEGG pathways (p < 0.05), including cGMP-PKG signaling pathway and calcium signaling pathway. To explore the expression of miRNA-regulated gene expression, 896 differentially expressed target genes negatively regulated with the expression levels of 31 differentially expressed miRNAs (DERs) were predicted and analyzed, and a network-integrated analysis was constructed. Furthermore, real-time PCR was performed to verify the expression levels of DEGs and DERs. Our results identified novel candidate DEGs and DERs correlated with male reproduction and intricate regulating networks between miRNAs and genes, which will be valuable for future genetic and epigenetic studies of sperm development and maturity, as well as providing valuable insights into the molecular mechanisms of male fertility and spermatogenesis in cattle.

Sperm miR-34c-5p Transcript Content and Its Association with Sperm Parameters in Unexplained Infertile Men

MicroRNAs (miRNAs) play an essential role in regulatory functions during gametogenesis. There is evidence that dysregulation of miR-34c-5p is implicated in the pathogenesis of male infertility. Whether miR-34c-5p expression could represent the semen quality and be useful in prediction of the fertilizing ability in normozoospermic men was examined in this study. Normozoospermic infertile patients (n = 15) and fertile men (n = 15) were recruited from the Infertility Clinic of Ahvaz, Iran. Sperm contents of miR-34c-5p transcript in were assessed using real-time polymerase chain reaction. No significant differences were seen in semen characteristics between patients and fertile men. Infertile patients showed significant (p = 0.019) lower contents of sperm miR-34c-5p than fertile controls. Men with lower transcript contents of miR-34c-5p exhibit lower sperm motility and normal morphology. Sperm miR-34c-5p transcript with a relatively good diagnostic power discriminated unexplained infertile men (AUC = 0.751, 95% CI: 0.568-0.934; p = 0.019). Our findings show that sperm contents of miR-34c-5p transcript could reflect the quality of spermatozoa in etiology of unexplained male infertility and be helpful in predicting a successful pregnancy.

Sperm Functional Genome Associated With Bull Fertility

Bull fertility is an important economic trait in sustainable cattle production, as infertile or subfertile bulls give rise to large economic losses. Current methods to assess bull fertility are tedious and not totally accurate. The massive collection of functional data analyses, including genomics, proteomics, metabolomics, transcriptomics, and epigenomics, helps researchers generate extensive knowledge to better understand the unraveling physiological mechanisms underlying subpar male fertility. This review focuses on the sperm phenomes of the functional genome and epigenome that are associated with bull fertility. Findings from multiple sources were integrated to generate new knowledge that is transferable to applied andrology. Diverse methods encompassing analyses of molecular and cellular dynamics in the fertility-associated molecules and conventional sperm parameters can be considered an effective approach to determine bull fertility for efficient and sustainable cattle production. In addition to gene expression information, we also provide methodological information, which is important for the rigor and reliability of the studies. Fertility is a complex trait influenced by several factors and has low heritability, although heritability of scrotal circumference is high and that it is a known fertility maker. There is a need for new knowledge on the expression levels and functions of sperm RNA, proteins, and metabolites. The new knowledge can shed light on additional fertility markers that can be used in combination with scrotal circumference to predict the fertility of breeding bulls. This review provides a comprehensive review of sperm functional characteristics or phenotypes associated with bull fertility.

Fine-tuning multiciliated cell differentiation at the post-transcriptional level: contribution of miR-34/449 family members

Cell differentiation is a process that must be precisely regulated for the maintenance of tissue homeostasis. Differentiation towards a multiciliated cell fate is characterized by well-defined stages, where a transcriptional cascade is activated leading to the formation of multiple centrioles and cilia. Centrioles migrate and dock to the apical cell surface and, acting as basal bodies, give rise to multiple motile cilia. The concerted movement of cilia ensures directional fluid flow across epithelia and defects either in their number or structure can lead to disease phenotypes. Micro-RNAs (miRNAs; miRs) are small, non-coding RNA molecules that play an important role in post-transcriptional regulation of gene expression. miR-34b/c and miR-449a/b/c specifically function throughout the differentiation of multiciliated cells, fine-tuning the expression of many different centriole- and cilia-related genes. They strictly regulate the expression levels of genes that are required both for commitment towards the multiciliated cell fate (e.g. Notch) and for the establishment and maintenance of this fate by regulating the expression of transcription factors and structural components of the pathway. Herein we review miR-34 and miR-449 spatiotemporal regulation along with their roles during the different stages of multiciliogenesis.

Oviductal motile cilia are essential for oocyte pickup but dispensable for sperm and embryo transport

Mammalian oviducts play an essential role in female fertility by picking up ovulated oocytes and transporting and nurturing gametes (sperm/oocytes) and early embryos. However, the relative contributions to these functions from various cell types within the oviduct remain controversial. The oviduct in mice deficient in two microRNA (miRNA) clusters (miR-34b/c and miR-449) lacks cilia, thus allowing us to define the physiological role of oviductal motile cilia. Here, we report that the infundibulum without functional motile cilia failed to pick up the ovulated oocytes. In the absence of functional motile cilia, sperm could still reach the ampulla region, and early embryos managed to migrate to the uterus, but the efficiency was reduced. Further transcriptomic analyses revealed that the five messenger ribonucleic acids (mRNAs) encoded by miR-34b/c and miR-449 function to stabilize a large number of mRNAs involved in cilium organization and assembly and that Tubb4b was one of their target genes. Our data demonstrate that motile cilia in the infundibulum are essential for oocyte pickup and thus, female fertility, whereas motile cilia in other parts of the oviduct facilitate gamete and embryo transport but are not absolutely required for female fertility.

Epigenetic regulations in mammalian spermatogenesis: RNA-m6A modification and beyond

Emerging evidence shows that m6A, one of the most abundant RNA modifications in mammals, is involved in the entire process of spermatogenesis, including mitosis, meiosis, and spermiogenesis. "Writers" catalyze m6A formation on stage-specific transcripts during male germline development, while "erasers" remove m6A modification to maintain a balance between methylation and demethylation. The different functions of RNA-m6A transcripts depend on their recognition by "readers". m6A modification mediates RNA metabolism, including mRNA splicing, translation, and degradation, as well as the maturity and biosynthesis of non-coding RNAs. Sperm RNA profiles are easily affected by environmental exposure and can even be inherited for several generations, similar to epigenetic inheritance. Here, we review and summarize the critical role of m6A in different developmental stages of male germ cells, to understand of the mechanisms and epigenetic regulation of m6A modifications. In addition, we also outline and discuss the important role of non-coding RNAs in spermatogenesis and RNA modifications in epigenetic inheritance.

Silica nanoparticles inducing the apoptosis via microRNA-450b-3p targeting MTCH2 in mice and spermatocyte cell

Silica nanoparticles (SiNPs) could cause reproductive toxicity. The role of miRNAs in reproductive toxicity induced by SiNPs is still ambiguous. The present study was designed to investigate the role of miRNA-450 b-3p. In vivo, 40 male mice were randomly divided into control, and 20 mg/kg SiNPs groups. The mice were administrated by tracheal perfusion for 35 days. In vitro, spermatocyte cells (GC-2spd cells) were divided into 6 groups: 0 μg/mL SiNPs groups, 5 μg/mL SiNPs groups, 5 μg/mL SiNPs + miRNA-450 b-3p mimic transfection group, 5 μg/mL SiNPs + miRNA-450 b-3p mimic negative control group, 5 μg/mL SiNPs + miRNA-450 b-3p inhibitor transfection group, and 5 μg/mL SiNPs + miRNA-450 b-3p inhibitor negative control group. The results showed that SiNPs induced the apoptosis of spermatogenic cells, decreased the quantity and quality of the sperm, reduced the expressions of miR-450 b-3p, and increased the protein expressions of the MTCH2, BID, BAX, Cytochrome C, Caspase-9, and Caspase-3 in the testis. In vitro, the mimic of miRNA-450 b-3p reversed the decrease of viability and the increase of apoptosis rate and significantly antagonized the expression enhancements of the MTCH2, BID, BAX, Cytochrome C, Caspase-9, Caspase-3 induced by SiNPs, while inhibitor of miRNA-450 b-3p further promoted the effects induced by SiNPs. The result suggested that SiNPs could inhibit the miR-450 b-3p expression resulting in activation of the mitochondrial apoptosis signaling pathways by regulating the MTCH2 in the spermatocyte cells and, thus, induce the reproductive toxicity.