Differential expression of porcine sperm microRNAs and their association with sperm morphology and motility

Genomic, transcriptomic and epigenomic analysis towards the understanding of porcine semen quality traits. Past, current and future trends

The importance of boar reproductive traits, including semen quality, in the sustainability of pig production system is increasingly being acknowledged by academic and industrial sectors. Research is needed to understand the biology and genetic components underlying these traits so that they can be incorporated into selection schemes and managerial decisions. This article reviews our current understanding of genome biology and technologies for genome, transcriptome and epigenome analysis which now facilitate the identification of causal variants affecting phenotypes more than ever before. Genetic and transcriptomic analysis of candidate genes, Genome-Wide Association Studies, expression microarrays, RNA-Seq of coding and noncoding genes and epigenomic evaluations have been conducted to profile the molecular makeups of pig sperm. These studies have provided insightful information for a several semen-related parameters. Nonetheless, this research is still incipient. The spermatozoon harbors a reduced transcriptome and highly modified epigenome, and it is assumed to be transcriptionally silent for nuclear gene expression. For this reason, the extent to which the sperm's RNA and epigenome recapitulate sperm biology and function is unclear. Hence, we anticipate that single-cell level analyses of the testicle and other male reproductive organs, which can reveal active transcription and epigenomic profiles in cells influencing sperm quality, will gain popularity and markedly advance our understanding of sperm-related traits. Future research will delve deeper into sperm fertility, boar resilience to environmental changes or harsh conditions, especially in the context of global warming, and also in transgenerational inheritance and how the environment influences the sperm transcriptome and epigenome.

Comprehensive analysis of the differential expression of mRNAs, lncRNAs, and miRNAs in Zi goose testis with high and low sperm mobility

Sperm mobility (SM) is an objective index for measuring sperm motility; however, the mechanisms underlying its regulation in geese remain unclear. The present study sought to elucidate the genetic mechanism underlying SM traits in Zi geese (Anser cygnoides L.). To this end, three successive experiments were performed. In Experiment I, SM was determined in 40 ganders; the 3 ganders with the highest mobility and three with the lowest mobility were assigned to the high and low sperm mobility rank (SMR) groups, respectively. In Experiment II, the differences in fertility between the two SMR groups were assessed within two breeding flocks comprising the selected six ganders from Experiment I and 30 females (each flock had 3 ganders and 15 females). In Experiment III, the testes of the 6 ganders were harvested for histological observation and whole-transcriptome sequencing. Results revealed better fertility, well-developed seminiferous tubules, and abundant mature sperm in the high-SMR-flock compared to those of the low-SMR-flock (89 vs. 81%) (P < 0.05). Differential expression (DE) analysis identified 76 mRNAs, 344 lncRNAs, and 17 miRNAs between the SMR groups, with LOC106049708, XPNPEP3, GNB3, ADCY8, PRKAG3, oha-miR-182-5p, and ocu-miR-10b-5p identified as key mRNAs and miRNAs contributing to SM. Enrichment analysis implicated these DE RNAs in pathways related to ATP binding, cell metabolism, apelin signaling, Wnt signaling, and Adherens junctions. Additionally, competing endogenous RNA (ceRNA) networks comprising 9 DE mRNAs, 17 DE miRNAs, and 169 DE lncRNAs were constructed. Two ceRNA network pathways (LOC106049708-oha-miR-182-5p-MSTRG.2479.6 and PRKAG3-ocu-miR-10b-5p-MSTRG.9047.14) were identified as key regulators of SM in geese. These findings offer crucial insights into the identification of key genes and ceRNA pathways influencing sperm mobility in geese.

Selection and direct biomarkers of reproductive capacity of breeding boars

Efficient management of pig reproduction is paramount for the sustainability and productivity of the global pork industry. Modern artificial insemination (AI) breeding programs have greatly benefited from the integration of advanced selection methods and biomarkers to enhance the reproductive performance of boars. While traditional selection methods have relied soley on boar phenotype, such as growth rate and conformation, modern pig breeding has shifted more and more toward molecular and genetic tools, which are still complemented by phenotypic traits. These methods encompass genomics, transcriptomics, and proteomics. Biomarkers serve as critical indicators of boar reproductive capacity. They can help to identify individuals with superior fertility and aid in the early identification of potential fertility issues, allowing for proactive management strategies. This review summarizes current knowledge of various biomarkers associated with semen quality, sperm function, and overall reproductive fitness in boars. Furthermore, we explore advanced technologies and their potential applications in uncovering novel selection methods and biomarkers for predicting boar fertility. A comprehensive understanding of selection criteria and biomarkers governing boar reproductive capacity is essential for developing effective breeding programs to enhance swine reproductive performance.

MicroRNAs in Male Fertility

Around 50% of all occurrences of infertility are attributable to the male factor, which is a significant global public health concern. There are numerous circumstances that might interfere with spermatogenesis and cause the body to produce abnormal sperm. While evaluating sperm, the count, the speed at which they migrate, and their appearance are the three primary characteristics that are analyzed. MicroRNAs, also known as miRNAs, are present in all physiological fluids and tissues. They participate in both physiological and pathological processes. Researches have demonstrated that the expression of microRNA genes differs in infertile men. These genes regulate spermatogenesis at various stages and in several male reproductive cells. Hence, microRNAs have the potential to act as useful indicators in the diagnosis and treatment of male infertility and other diseases affecting male reproduction. Despite this, additional research is necessary to determine the precise miRNA regulation mechanisms.

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).

Bifenthrin Diminishes Male Fertility Potential by Inducing Protein Defects in Mouse Sperm

A synthetic pyrethroid pesticide, bifenthrin, has been commonly used as an effective exterminator, although the rise in its usage has raised concerns regarding its effects on the environment and public health, including reproduction, globally. The current study investigated the function-related molecular disparities and mechanisms in bifenthrin-exposed sperm cells and the underlying mechanism. Therefore, epididymal spermatozoa were released, and various concentrations of bifenthrin were treated (0.1, 1, 10, and 100 μM) to evaluate their effects on sperm. The findings showed that although bifenthrin had no effect on sperm viability, various other sperm functions (e.g., motility, spontaneous acrosome reaction, and capacitation) related to male fertility were decreased, commencing at a 1 µM treatment. Molecular studies revealed nine differentially expressed sperm proteins that were implicated in motile cilium assembly, sperm structure, and metabolic processes. Furthermore, bifenthrin affected sperm functions through abnormal diminution of the expression of specific sperm proteins. Collectively, these findings provide greater insights into how bifenthrin affects male fertility at the molecular level.

Sertoli cell-derived extracellular vesicles traverse the blood-testis barrier and deliver miR-24-3p inhibitor into germ cells improving sperm mobility

Asthenozoospermia, characterized by poor sperm motility, is a common cause of male infertility. Improving energy metabolism and alleviating oxidative stress through drug regimens are potential therapeutic strategies. In this study, we observed upregulated miR-24-3p levels in asthenozoospermia spermatozoa, contributing to energy metabolism disorder and oxidative stress by reducing GSK3β expression. Thus, reducing miR-24-3p levels using drugs is expected to improve sperm motility. The blood-testis barrier (BTB) protects the testis from xenobiotics and drugs. In this study, we found that Sertoli cell-derived small extracellular vesicles (SC-sEV) can traverse the BTB and enter germ cells. We successfully loaded miR-24-3p inhibitor into SC-sEV, creating the nano-drug SC-sEV@miR-24-3p inhibitor, which effectively delivers miR-24-3p inhibitor into germ cells. In a gossypol-induced mouse asthenozoospermia model, administration of SC-sEV@miR-24-3p inhibitor significantly improved sperm motility, in vitro fertilization success, and blastocyst formation rates. As anticipated, it also improved the litter size of asthenozoospermia mice. These results suggest that SC-sEV@miR-24-3p inhibitor holds promise as a potential clinical treatment for asthenospermia.

Effect of arginine-induced motility and capacitation on RNA population in goat spermatozoa

INTRODUCTION

In vitro capacitation is essential in assisted reproductive technologies (ART) for embryo production. Recently, arginine has been proven to enhance capacitation in mammalian spermatozoa. However, the detailed mechanism of action of arginine remains elusive.

AIM

This study investigated the effect of arginine-induced capacitation and motility enhancement on the spermatozoal RNA (spRNA) population in goats.

MATERIAL AND METHODS

Goat spermatozoa were treated with arginine for up to six hours and compared with non-treated or PHE (penicillamine, hypotaurine, and epinephrine)-treated spermatozoa at different intervals (0, 1, 2, 4, and 6 hours). Sperm parameters, including viability, individual motility, capacitation, acrosome reaction, and ROS production, were evaluated. The spRNA population was analyzed by short-read RNA sequencing (RNA-seq).

RESULTS

The percentage of capacitated (73.21 ± 4.22%) and acrosome reacted (18.35 ± 0.56%) spermatozoa was highest in arginine treatment, while PHE treatment showed the highest percentage (79.82 ± 4.31%) of motile spermatozoa from 0 to 4 hours of incubation. RNA-seq analysis identified 1,321 differentially expressed genes (DEGs) in arginine-treated spermatozoa compared to the control. The PGK2, RNASE10, ODF1, and ROPN1L genes involved in sperm motility and ACR, DKKL1, KCNJ11, and PRND genes involved in the capacitation process were upregulated in arginine-treated spermatozoa. The DEGs regulate sperm capacitation-related cAMP-PKA, PI3-Akt, calcium, and MAPK signaling pathways.

CONCLUSION

The arginine-induced capacitation and enhanced sperm motility were associated with the upregulation of several genes involved in sperm motility and capacitation pathways. The comparative study also suggests that arginine may be used in lieu of PHE for motility enhancement and in vitro capacitation of goat spermatozoa.

Sperm Cryopreservation Today: Approaches, Efficiency, and Pitfalls

The cryopreservation of human spermatozoa has been an option for patients undergoing chemo or radiotherapies since the late 1950s. Presently, there are different techniques for the cryopreservation of spermatozoa. The most commonly used techniques are programmable slow freezing and freezing on liquid nitrogen vapors, while the use of vitrification is still not accepted as clinically relevant. Although there have been many improvements, the ideal technique for achieving better post-thaw sperm quality continues to be a mystery. A major obstacle during cryopreservation is the formation of intracellular ice crystals. Cryodamage generated by cryopreservation causes structural and molecular alterations in spermatozoa. Injuries can happen because of oxidative stress, temperature stress, and osmotic stress, which then result in changes in the plasma membrane fluidity, motility, viability, and DNA integrity of the spermatozoa. To prevent cryodamage as much as possible, cryoprotectants are added, and in some clinical trial cases, even antioxidants that may improve post-thaw sperm quality are added. This review discusses cryopreservation techniques, cryodamage on molecular and structural levels, and cryoprotectants. It provides a comparison of cryopreservation techniques and describes recent advances in those techniques.

Comparative analysis of microRNA and messengerRNA expression profiles in plateau zokor testicular cells under reproductive suppression

Introduction

Reproductive suppression is an adaptive strategy that affects the success rate and reproductive efficiency in animals, which in turn affects population continuation and evolution. However, no studies on the miRNAs in testicular development and spermatogenesis regulatory mechanisms under reproductive suppression have been reported.

Methods

In this study, the differentially expressed (DE) miRNAs, miRNA-mRNA interaction network and function of the plateau zokor testicular cells of non-breeders and breeders during the breeding season were comprehensively analyzed by transcriptomics.

Results

In total, 381 known and 94 novel miRNAs were determined. Compared with that in the breeders, 70 downregulated and 68 upregulated DE miRNAs were identified in the non-breeders. We predicted 1670 significant target mRNAs by analyzing the miRNA and mRNA expression profiles. According to the miRNA-mRNA interaction network, the target mRNAs of the DE miRNAs were related to testicular development and spermatogenesis. GO indicate that the target mRNAs were related to testicular development and spermatogenesis. KEGG indicate that pathways of target mRNAs enrichment related to testicular development, spermatogenesis, and energy metabolism. PROK2 was determined as the target mRNA of rno-miR-143-3p.

Discussion

Our study offers a basis for the regulatory mechanisms of miRNAs in testicular development and spermatogenesis in plateau zokor under reproductive suppression and offers a reference for reproductive regulation.

Integrated miRNA Changes in Canine Testis and Epididymis According to Age and Presence of Cryptorchidism

In the present study, we aimed to investigate age-, cryptorchidism-, and testicular tumor-related changes in miRNAs in the testis and epididymis of dogs. Twelve healthy male dogs were divided into two groups: young (<1 year, n = 8) and old (>3 years, n = 4). Five dogs with unilateral cryptorchidism, one with a Sertoli cell tumor, and one with seminoma were referred to a veterinary hospital. After surgery, the testes and epididymis tails were collected. A high-throughput miRNA array analysis was performed to identify miRNAs affected by age, cryptorchidism, and testicular tumors. The expression of only cfa-miR-503 was downregulated in the epididymis of younger dogs, whereas the expression of 64 miRNAs was upregulated. Among them, the top five miRNAs were cfa-miR-26a, cfa-miR-200c, cfa-let-7c, cfa-let-7b, and cfa-let-7a. The expression of cfa-miR-148a and cfa-miR-497 was considerably lower in cryptorchid testis than in healthy dog testis. In the epididymis, the cfa-miR-1841 level was significantly decreased. We observed a significant difference in the expression of 26 cfa-miRNAs between testicular tumors and normal tissues. This study demonstrated that aging and cryptorchidism have a causal relationship with miRNA expression. The identified miRNAs may be candidate genes for male reproductive traits and could be applied in molecular breeding programs.

Towards a Multi-Omics of Male Infertility

Infertility is a common problem affecting one in six couples and in 30% of infertile couples, the male factor is a major cause. A large number of genes are involved in spermatogenesis and a significant proportion of male infertility phenotypes are of genetic origin. Studies on infertility have so far primarily focused on chromosomal abnormalities and sequence variants in protein-coding genes and have identified a large number of disease-associated genes. However, it has been shown that a multitude of factors across various omics levels also contribute to infertility phenotypes. The complexity of male infertility has led to the understanding that an integrated, multi-omics analysis may be optimal for unravelling this disease. While there is a vast array of different factors across omics levels associated with infertility, the present review focuses on known factors from the genomics, epigenomics, transcriptomics, proteomics, metabolomics, glycomics, lipidomics, miRNomics, and integrated omics levels. These include: repeat expansions in AR, POLG, ATXN1, DMPK, and SHBG, multiple SNPs, copy number variants in the AZF region, disregulated miRNAs, altered H3K9 methylation, differential MTHFR, MEG3, PEG1, and LIT1 methylation, altered protamine ratios and protein hypo/hyperphosphorylation. This integrative review presents a step towards a multi-omics approach to understanding the complex etiology of male infertility. Currently only a few genetic factors, namely chromosomal abnormalities and Y chromosome microdeletions, are routinely tested in infertile men undergoing intracytoplasmic sperm injection. A multi-omics approach to understanding infertility phenotypes may yield a more holistic view of the disease and contribute to the development of improved screening methods and treatment options. Therefore, beside discovering as of yet unknown genetic causes of infertility, integrating multiple fields of study could yield valuable contributions to the understanding of disease development. Future multi-omics studies will enable to synthesise fragmented information and facilitate biomarker discovery and treatments in male infertility.

Expression of SPAG7 and its regulatory microRNAs in seminal plasma and seminal plasma-derived extracellular vesicles of patients with subfertility

Seminal plasma contains a variety of extracellular vesicles (EVs) that deliver RNAs including microRNAs (miRNAs) molecules. However, the roles of these EVs along with their delivered RNAs and their interactions with male infertility are not clear. Sperm-associated antigen 7 (SPAG 7) is expressed in male germ cells and plays a crucial role in several biological functions associated with sperm production and maturation. In this study, we aimed to identify the post-transcriptional regulation of SPAG7 in seminal plasma (SF-Native) and seminal plasma-derived extracellular vesicles (SF-EVs) collected from 87 men undergoing infertility treatment. Among the multiple binding sites for miRNAs within its 3'UTR of SPAG7, we identified the binding of four miRNAs (miR-15b-5p, miR-195-5p, miR-424-5p, and miR-497-5p) to the 3'UTR of SPAG7 by the dual luciferase assays. Analyzing sperm, we found reduced mRNA expression levels of SPAG7 in SF-EVs and SF-Native samples from oligoasthenozoospermic men. By contrast, two miRNAs (miR-424-5p and miR-497-5p) form the SF-Native samples, and four miRNAs (miR-195-5p, miR-424-5p, miR-497-5p, and miR-6838-5p) from the SF-EVs samples showed significantly higher expression levels in oligoasthenozoospermic men. The expression levels of miRNAs and SPAG7 were significantly correlated with basic semen parameters. These findings contribute significantly to our understanding of regulatory pathways in male fertility by showing a direct link between upregulated miRNA, notably miR-424, and downregulated SPAG7 both in seminal plasma and in plasma-derived EVs likely contributing to oligoasthenozoospermia.

Molecular insights to the sperm-cervix interaction and the consequences for cryopreserved sperm

Cryopreserved ram spermatozoa are limited in their capacity to traverse the ovine cervix and achieve fertilization. This altered interaction may be related to modified molecular communication between frozen-thawed ram spermatozoa, seminal plasma, and the female tract. As such, this review aims to identify the biological processes which underpin sperm maturation and transport throughout the female reproductive tract to elucidate factors which may alter this natural process in cryopreserved ram spermatozoa. We also assess critical barriers to ram spermatozoa specific to the ovine cervix and the role of seminal plasma in mitigating these barriers. Transcriptomics is explored as a new approach to understand the sperm-cervix interaction. Recent studies have demonstrated that both spermatozoa and seminal plasma contain a complex profile of coding and non-coding RNAs. These molecular species have clear links with functional fertility, and mounting evidence suggests they may be altered by cryopreservation. Emerging in vitro cell culture models are also investigated as a "next step" in studying this interaction, utilizing transcriptomics to identify subtle changes in female tract gene expression in response to spermatozoa. The application of such models is proposed as an exciting opportunity to investigate the unique challenges faced by cryopreserved spermatozoa traversing the ovine cervix prior to fertilization.

Comparative proteomic analysis of seminal plasma exosomes in buffalo with high and low sperm motility

BACKGROUND

Exosomes are nanosized membranous vesicles secreted by various types of cells, which facilitate intercellular communication by transporting bioactive compounds. Exosomes are abundant in biological fluids including semen, and their protein composition and the potential of seminal plasma exosomes (SPEs) as fertility biomarkers were elucidated in humans, however, little information is available regarding buffalo (Bubalus bubalis). Here, we examined protein correlation between spermatozoa, seminal plasma (SP), and SPEs, and we compared and analyzed protein differences between high-motility (H-motility) and low-motility (L-motility) SPEs in buffalo.

RESULTS

SPEs were concentrated and purified by ultracentrifugation combined with sucrose density gradient centrifugation, followed by verification using western blotting, nanoparticle tracking analysis, and transmission electron microscopy. Protein composition in spermatozoa, SP and SPEs, and protein difference in H- and L-motility SPEs were identified by LC-MS/MS proteomic analysis and were functionally analyzed through comprehensive bioinformatics. Many SPEs proteins originated from spermatozoa and SP, and nearly one third were also present in spermatozoa and SP. A series of proteins associated with reproductive processes including sperm capacitation, spermatid differentiation, fertilization, sperm-egg recognition, membrane fusion, and acrosome reaction were integrated in a functional network. Comparative proteomic analyses showed 119 down-regulated and 41 up-regulated proteins in L-motility SPEs, compared with H-motility SPEs. Gene Ontology (GO) enrichment of differentially expressed proteins (DEPs) showed that most differential proteins were located in sperm and vesicles, with activities of hydrolase and metalloproteinase, and were involved in sperm-egg recognition, fertilization, single fertilization, and sperm-zona pellucida binding processes, etc. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differential proteins were mainly involved in the PPRP signaling pathway, calcium signaling pathway, and cAMP signaling pathway, among others. Furthermore, 6 proteins associated with reproduction were validated by parallel reaction monitoring analysis.

CONCLUSION

This study provides a comprehensive description of the seminal plasma exosome proteome and may be of use for further screening of biomarkers associated with male infertility.

A Comprehensive Sequencing Analysis of Testis-Born miRNAs in Immature and Mature Indigenous Wandong Cattle (Bos taurus)

Micro RNAs (miRNAs) have been recognized as important regulators that are indispensable for testicular development and spermatogenesis. miRNAs are endogenous transcriptomic elements and mainly regulate the gene expression at post-transcriptional levels; however, the key role of miRNA in bovine testicular growth is not clearly understood. Thus, supposing to unveil the transcriptomics expression changes in the developmental processes of bovine testes, we selected three immature calves and three sexually mature bulls of the local Wandong breed for testicular-tissue sample collection. The cDNA libraries of experimental animals were established for RNA-sequencing analysis. We detected the miRNA expression in testes by using high-throughput sequencing technology, and bioinformatics analysis followed. The differentially expressed (DE) data showed that 151 miRNAs linked genes were significantly DE between immature and mature bull testes. Further, in detail, 64 were significantly up-regulated and 87 were down-regulated in the immature vs. mature testes (p-value < 0.05). Pathway analyses for miRNA-linked genes were performed and identified JAG2, BCL6, CFAP157, PHC2, TYRO3, SEPTIN6, and BSP3; these genes were involved in biological pathways such as TNF signaling, T cell receptor, PI3KAkt signaling, and functions affecting testes development and spermatogenesis. The DE miRNAs including MIR425, MIR98, MIR34C, MIR184, MIR18A, MIR136, MIR15A, MIR1388 and MIR210 were associated with cattle-bull sexual maturation and sperm production. RT-qPCR validation analysis showed a consistent correlation to the sequencing data findings. The current study provides a good framework for understanding the mechanism of miRNAs in the development of testes and spermatogenesis.

How does the boar epididymis regulate the emission of fertile spermatozoa?

The epididymis is responsible for peripheral immune tolerance of maturing spermatozoa even though these have xeno-antigens foreign to the male and female immune system. The epididymis also produces factors required for fertilization and serves as a sperm repository until the time of ejaculation. These reproduction-relevant epididymal functions occur in the mesonephros-derived duct-system that is composed of absorptive and secretory epithelial cells with the capacity for merocrine and apocrine secretion of proteins, antioxidative- and electrolyte/pH-regulating enzymes and small, non-coding RNAs (sncRNAs), many stored in epididymosomes for sperm adhesion and long-lasting modifications of sperm functions. This paper provides a review summary of current and new knowledge of how the boar epididymis affects the quality of spermatozoa in the ejaculate of breeding boars. There is a particular focus on sperm maturation, survival, function and the role of signaling to the female immune system in fertility modulation. Furthermore, aspects related to the ductus epithelial contributions regarding electrolyte control, protein production, release of epididymosomes that contain sncRNAs are emphasized as are novel associations with fertility of the male, sperm quiescence during storage in the cauda epididymis, and on changes occurring in sperm subsequent to ejaculation.

Prmt7 Downregulation in Mouse Spermatogonia Functions through miR-877-3p/Col6a3

Protein arginine methyltransferases 7 (Prmt7) is expressed in male germ cells, including primordial germ cells, gonocytes, and spermatogonia. Our previous study demonstrated that Prmt7 downregulation reduced the proliferation of GC-1 cells (a cell line of mouse immortalized spermatogonia). However, how Prmt7 regulates spermatogonial proliferation through miRNA and the target gene remains elusive. Here, we experimentally reduced the Prmt7 expression in the GC-1 cells and subjected them to miRNA sequencing to explore the miRNA profile and its Prmt7-responsive members. In total, 48 differentially expressed miRNAs (DEmiRNAs), including 36 upregulated and 12 downregulated miRNAs, were identified. After verifying the validity of sequencing results through qRT-PCR assays in randomly selected DEmiRNAs, we predicted the target genes of these DEmiRNAs. Next, we combined DEmiRNA target genes and previously identified differentially expressed genes between Prmt7 knockdown and control groups of GC-1 cells, which resulted in seven miRNA/target gene pairs. Among these miRNA/target gene pairs, we further detected the expression of Col6a3 (collagen type VI alpha 3) as the target gene of mmu-miR-877-3p. The results suggested that Prmt7 downregulation in mouse spermatogonia might function through miR-877-3p/Col6a3. Overall, these findings provide new insights into the role of Prmt7 in male germ cell development through miRNA and target genes.

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.

Transgenerational epigenetic impacts of parental infection on offspring health and disease susceptibility

Maternal immune activation (MIA) and infection during pregnancy are known to reprogramme offspring phenotypes. However, the epigenetic effects of preconceptual paternal infection and paternal immune activation (PIA) are not currently well understood. Recent reports show that paternal infection and immune activation can affect offspring phenotypes, particularly brain function, behaviour, and immune system functioning, across multiple generations without re-exposure to infection. Evidence from other environmental exposures indicates that epigenetic inheritance also occurs in humans. Given the growing impact of the coronavirus disease 2019 (COVID-19) pandemic, it is imperative that we investigate all of the potential epigenetic mechanisms and multigenerational phenotypes that may arise from both maternal and paternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as well as associated MIA, PIA, and inflammation. This will allow us to understand and, if necessary, mitigate any potential changes in disease susceptibility in the children, and grandchildren, of affected parents.

MicroRNAs and Efferocytosis: Implications for Diagnosis and Therapy

About 10-100 billion cells are generated in the human body in a day, and accordingly, 10-100 billion cells predominantly die for maintaining homeostasis. Dead cells generated by apoptosis are also rapidly engulfed by macrophages (Mθs) to be degraded. In case of the inefficient engulfment of apoptotic cells (ACs) via Mθs, they experience secondary necrosis and thus release intracellular materials, which display damage-associated molecular patterns (DAMPs) and result in diseases. Over the last decades, researchers have also reflected on the significant contribution of microRNAs (miRNAs) to autoimmune diseases through the regulation of Mθs functions. Moreover, miRNAs have shown intricate involvement with completely adjusting basic Mθs functions, such as phagocytosis, inflammation, efferocytosis, tumor promotion, and tissue repair. In this review, the mechanism of efferocytosis containing "Find-Me", "Eat-Me", and "Digest-Me" signals is summarized and the biogenesis of miRNAs is briefly described. Finally, the role of miRNAs in efferocytosis is discussed. It is concluded that miRNAs represent promising treatments and diagnostic targets in impaired phagocytic clearance, which leads to different diseases.

miRNA-Profiling in Ejaculated and Epididymal Pig Spermatozoa and Their Relation to Fertility after Artificial Insemination

Simple Summary

The present study searched for the presence and abundance of porcine spermatozoa small RNA sequences (microRNAs) that have the potential to alter gene expression patterns. Four different sperm sources were compared: spermatozoa from three different sections of the ejaculate and from the caudal epididymis, also classed as spermatozoa from higher (HF) or lower (LF) fertility boars. Sperm miRNAs were compared using high-output small RNA sequencing. We identified five sperm miRNAs not previously reported in pigs. Differences in abundance of four miRNAs known to affect the expression of genes with key roles in fertility were related to boar fertility. These miRNAs could be used as fertility markers in artificial insemination programs.

Abstract

MicroRNAs (miRNAs) are short non-coding RNAs (20–25 nucleotides in length) capable of regulating gene expression by binding -fully or partially- to the 3’-UTR of target messenger RNA (mRNA). To date, several studies have investigated the role of sperm miRNAs in spermatogenesis and their remaining presence toward fertilization and early embryo development. However, little is known about the miRNA cargo in the different sperm sources and their possible implications in boar fertility. Here, we characterized the differential abundance of miRNAs in spermatozoa from the terminal segment of the epididymis and three different fractions of the pig ejaculate (sperm-peak, sperm-rich, and post-sperm rich) comparing breeding boars with higher (HF) and lower (LF) fertility after artificial insemination (AI) using high-output small RNA sequencing. We identified five sperm miRNAs that, to our knowledge, have not been previously reported in pigs (mir-10386, mir-10390, mir-6516, mir-9788-1, and mir-9788-2). Additionally, four miRNAs (mir-1285, mir-92a, mir-34c, mir-30), were differentially expressed among spermatozoa sourced from ejaculate fractions and the cauda epididymis, and also different abundance was found between HF and LF groups in mir-182, mir-1285, mir-191, and mir-96. These miRNAs target genes with key roles in fertility, sperm survival, immune tolerance, or cell cycle regulation, among others. Linking the current findings with the expression of specific sperm proteins would help predict fertility in future AI-sires.

Significance and Relevance of Spermatozoal RNAs to Male Fertility in Livestock

Livestock production contributes to a significant part of the economy in developing countries. Although artificial insemination techniques brought substantial improvements in reproductive efficiency, male infertility remains a leading challenge in livestock. Current strategies for the diagnosis of male infertility largely depend on the evaluation of semen parameters and fail to diagnose idiopathic infertility in most cases. Recent evidences show that spermatozoa contains a suit of RNA population whose profile differs between fertile and infertile males. Studies have also demonstrated the crucial roles of spermatozoal RNA (spRNA) in spermatogenesis, fertilization, and early embryonic development. Thus, the spRNA profile may serve as unique molecular signatures of fertile sperm and may play pivotal roles in the diagnosis and treatment of male fertility. This manuscript provides an update on various spRNA populations, including protein-coding and non-coding RNAs, in livestock species and their potential role in semen quality, particularly sperm motility, freezability, and fertility. The contribution of seminal plasma to the spRNA population is also discussed. Furthermore, we discussed the significance of rare non-coding RNAs (ncRNAs) such as long ncRNAs (lncRNAs) and circular RNAs (circRNAs) in spermatogenic events.

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.

MicroRNA-222 Transferred From Semen Extracellular Vesicles Inhibits Sperm Apoptosis by Targeting BCL2L11

Seminal plasma contains a large number of extracellular vesicles (EVs). However, the roles of these EVs and their interactions with sperm are not clear. To identify the important molecules affecting sperm motility in EVs, we analyzed RNA from seminal plasma EVs of boars with different sperm motility using whole-transcriptome sequencing and proteomic analysis. In total, 7 miRNAs, 67 lncRNAs, 126 mRNAs and 76 proteins were differentially expressed between the two groups. We observed that EV-miR-222 can obviously improve sperm motility. In addition, the results suggested that miR-222 was transferred into sperm by the EVs and that miR-222 affected sperm apoptosis by inhibiting the expression of EGFR, BCL2L11, BAX, CYCs, CASP9 and CASP3. The results of electron microscopy also showed that overexpression of miR-222 in EVs could reduce sperm apoptosis. The study of the whole transcriptomes and proteomes of EVs in boar semen revealed some miRNAs may play an important role in these EVs interactions with Duroc sperm, and the findings suggest that the release of miR-222 by semen EVs is an important mechanism by which sperm viability is maintained and sperm apoptosis is reduced. Our studies provide a new insight of miR-222 in EVs regulation for sperm motility and sperm apoptosis.

Effect of freeze-thawing process on lipid peroxidation, miRNAs, ion channels, apoptosis and global DNA methylation in ram spermatozoa

This study was carried out to investigate the effect of the semen freeze-thawing process on the functionality and molecular structure of ram spermatozoa. The temperature of pooled and diluted semen at 38°C (group 1, control) was lowered to 5°C (group 2), and it was subjected to glycerolisation-equilibration (group 3), frozen and thawed (group 4). Compared to the control, deterioration in spermatological parameters and significant increases in lipid peroxidation and global DNA methylation levels were observed in groups 3 and 4. When compared with the control, significant downregulation in the levels of miR-485 of group 2, miR-29a of group 3 and let-7a, miR-485 and miR-29a of group 4, and significant upregulation in the levels of miR-107 of group 3 and miR-127 of groups 3 and 4 were detected. In comparison to the control, significant upregulation in the levels of CatSper1, CatSper2, CatSper3, CatSper4, ANO1 and TRPM3 of group 2, CatSper4, ANO1 and TRPM3 of group 3 and KCNJ11 of group 4, and significant downregulation in the CatSper 3 level of group 4 were determined. As a result, the semen freeze-thawing process causes motility and morphological disorders in rams. This may be due to molecular changes associated with lipid peroxidation in spermatozoa.

Single-molecule long-read sequencing reveals a conserved intact long RNA profile in sperm

Sperm contributes diverse RNAs to the zygote. While sperm small RNAs have been shown to impact offspring phenotypes, our knowledge of the sperm transcriptome, especially the composition of long RNAs, has been limited by the lack of sensitive, high-throughput experimental techniques that can distinguish intact RNAs from fragmented RNAs, known to abound in sperm. Here, we integrate single-molecule long-read sequencing with short-read sequencing to detect sperm intact RNAs (spiRNAs). We identify 3440 spiRNA species in mice and 4100 in humans. The spiRNA profile consists of both mRNAs and long non-coding RNAs, is evolutionarily conserved between mice and humans, and displays an enrichment in mRNAs encoding for ribosome. In sum, we characterize the landscape of intact long RNAs in sperm, paving the way for future studies on their biogenesis and functions. Our experimental and bioinformatics approaches can be applied to other tissues and organisms to detect intact transcripts.

Decreased piRNAs in Infertile Semen Are Related to Downregulation of Sperm MitoPLD Expression

Currently, the molecular mechanisms underlining male infertility are still poorly understood. Our previous study has demonstrated that PIWI-interacting RNAs (piRNAs) are downregulated in seminal plasma of infertile patients and can serve as molecular biomarkers for male infertility. However, the source and mechanism for the dysregulation of piRNAs remain obscure. In this study, we found that exosomes are present in high concentrations in human seminal plasma and confirmed that piRNAs are predominantly present in the exosomal fraction of seminal plasma. Moreover, we showed that piRNAs were significantly decreased in exosomes of asthenozoospermia patients compared with normozoospermic men. By systematically screening piRNA profiles in sperms of normozoospermic men and asthenozoospermia patients, we found that piRNAs were parallelly reduced during infertility. At last, we investigated the expression of some proteins that are essential for piRNAs biogenesis in sperms and therefore identified a tight correlation between the levels of spermatozoa piRNA and MitoPLD protein, suggesting that the loss-of-function of MitoPLD could cause a severe defect of piRNA accumulation in sperms. In summary, this study identified a parallel reduction of piRNAs and MitoPLD protein in sperms of asthenozoospermia patients, which may provide pathophysiological clues about sperm motility.

A systems biology framework integrating GWAS and RNA-seq to shed light on the molecular basis of sperm quality in swine

BACKGROUND

Genetic pressure in animal breeding is sparking the interest of breeders for selecting elite boars with higher sperm quality to optimize ejaculate doses and fertility rates. However, the molecular basis of sperm quality is not yet fully understood. Our aim was to identify candidate genes, pathways and DNA variants associated to sperm quality in swine by analysing 25 sperm-related phenotypes and integrating genome-wide association studies (GWAS) and RNA-seq under a systems biology framework.

RESULTS

By GWAS, we identified 12 quantitative trait loci (QTL) associated to the percentage of head and neck abnormalities, abnormal acrosomes and motile spermatozoa. Candidate genes included CHD2, KATNAL2, SLC14A2 and ABCA1. By RNA-seq, we identified a wide repertoire of mRNAs (e.g. PRM1, OAZ3, DNAJB8, TPPP2 and TNP1) and miRNAs (e.g. ssc-miR-30d, ssc-miR-34c, ssc-miR-30c-5p, ssc-miR-191, members of the let-7 family and ssc-miR-425-5p) with functions related to sperm biology. We detected 6128 significant correlations (P-value ≤ 0.05) between sperm traits and mRNA abundances. By expression (e)GWAS, we identified three trans-expression QTL involving the genes IQCJ, ACTR2 and HARS. Using the GWAS and RNA-seq data, we built a gene interaction network. We considered that the genes and interactions that were present in both the GWAS and RNA-seq networks had a higher probability of being actually involved in sperm quality and used them to build a robust gene interaction network. In addition, in the final network we included genes with RNA abundances correlated with more than four semen traits and miRNAs interacting with the genes on the network. The final network was enriched for genes involved in gamete generation and development, meiotic cell cycle, DNA repair or embryo implantation. Finally, we designed a panel of 73 SNPs based on the GWAS, eGWAS and final network data, that explains between 5% (for sperm cell concentration) and 36% (for percentage of neck abnormalities) of the phenotypic variance of the sperm traits.

CONCLUSIONS

By applying a systems biology approach, we identified genes that potentially affect sperm quality and constructed a SNP panel that explains a substantial part of the phenotypic variance for semen quality in our study and that should be tested in other swine populations to evaluate its relevance for the pig breeding sector.

Altered microRNAs expression levels of sperm and seminal plasma in patients with infertile ejaculates compared with normozoospermic males

Approximately 15% of couples are unable to conceive after one year of unprotected intercourse. Because sperm can be accessed with ease, it is reasonable to search for non-invasive biomarkers in semen. MicroRNAs are a family of short single-stranded non-coding RNA molecules that are capable of regulating gene expression and causing mRNA degradation. We studied the most common 11 spermatogenesis-related microRNAs expression levels in sperm and seminal plasma from patients with oligozoospermic or asthenozoospermic ejaculates, and in men with normozoospermic ejaculates. Five of these miRNAs were significantly upregulated and three were downregulated in infertile males compared to men with normozoospermic ejaculates. A statistically significant negative correlation was found between the sperm concentration and several microRNA expression level (let-7a, miR-7-1-3p, miR-141, miR-200a, and miR-429, p < 0.0001) both in sperm and in seminal plasma. We also found positive correlation between sperm concentration and some miRNA expression levels (miR-15b, miR-34b, and miR-122, p < 0.001) in sperm and in seminal plasma. This is the first study to demonstrate differences between sperm and seminal plasma miRNA expression level and to identify a correlation between the sperm concentration and miRNAs expression level. Therefore, these MiRNAs could have the potential be used as non-invasive biomarkers to diagnose males with impaired sperm production.

Integrated analysis of miRNA and mRNA expression profiles in testes of Duroc and Meishan boars

BACKGROUND

MicroRNAs (miRNAs) are small non-coding RNAs playing vital roles in regulating posttranscriptional gene expression. Elucidating the expression regulation of miRNAs underlying pig testis development will contribute to a better understanding of boar fertility and spermatogenesis.

RESULTS

In this study, miRNA expression profile was investigated in testes of Duroc and Meishan boars at 20, 75, and 270 days of age by high-throughput sequencing. Forty-five differentially expressed miRNAs were identified from testes of Duroc and Meishan boars before and after puberty. Integrated analysis of miRNA and mRNA profiles predicted many miRNA-mRNA pairs. Gene ontology and biological pathway analyses revealed that predicted target genes of ssc-mir-423-5p, ssc-mir-34c, ssc-mir-107, ssc-mir-196b-5p, ssc-mir-92a, ssc-mir-320, ssc-mir-10a-5p, and ssc-mir-181b were involved in sexual reproduction, male gamete generation, and spermatogenesis, and GnRH, Wnt, and MAPK signaling pathway. Four significantly differentially expressed miRNAs and their predicted target genes were validated by quantitative real-time polymerase chain reaction, and phospholipase C beta 1 (PLCβ1) gene was verified to be a target of ssc-mir-423-5p.

CONCLUSIONS

This study provides an insight into the functional roles of miRNAs in testis development and spermatogenesis and offers useful resources for understanding differences in sexual function development caused by the change in miRNAs expression between Duroc and Meishan boars.

From Sperm Motility to Sperm-Borne microRNA Signatures: New Approaches to Predict Male Fertility Potential

In addition to the paternal genome, spermatozoa carry several intrinsic factors, including organelles (e.g., centrioles and mitochondria) and molecules (e.g., proteins and RNAs), which are involved in important steps of reproductive biology such as spermatogenesis, sperm maturation, oocyte fertilization and embryo development. These factors constitute potential biomarkers of "viable sperm" and male fertility status and may become major assets for diagnosing instances of idiopathic male infertility in both humans and livestock animals. A better understanding of the mechanism of action of these sperm intrinsic factors in the regulation of reproductive and developmental processes still presents a major challenge that must be addressed. This review assembles the main data regarding morpho-functional and intrinsic sperm features that are associated with male infertility, with a particular focus on microRNA (miRNA) molecules.

MiR-664-2 impacts pubertal development in a precocious-puberty rat model through targeting the NMDA receptor-1†

Precocious puberty (PP) commonly results from premature activation of the hypothalamic-pituitary-gonadal axis (HPGA). Gonadotropin-releasing hormone (GnRH) is the initial trigger for HPGA activation and plays an important role in puberty onset. N-methyl-D-aspartate (NMDA) can promote pulsatile GnRH secretion and accelerates puberty onset. However, the mechanism of N-methyl-D-aspartate receptors (NMDARs) in PP pathogenesis remains obscure. We found that serum GnRH, luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogen (E2) levels, hypothalamic NMDAR1, and GnRH mRNA expression peaked at the vaginal opening (VO) day. Next, the hypothalamic NMDAR1 mRNA and protein levels in rats treated with danazol, a chemical commonly effecting on the reproductive system, were significantly increased at the VO day (postnatal day 24) compared to controls, accompanied by enhanced serum GnRH, LH, FSH, and E2 levels. Further, microRNA-664-2 (miR-664-2) was selected after bioinformatics analysis and approved in primary hypothalamic neurons, which binds to the 3'-untranslated regions of NMDAR1. Consistently, the miR-664-2 expression in hypothalamus of the Danazol group was decreased compared to Vehicle. Our results suggested that attenuated miR-664-2 might participate in PP pathogenesis through enhancing the NMDAR1 signaling.

Survey of SNPs Associated with Total Number Born and Total Number Born Alive in Pig

Reproductive productivity depend on a complex set of characteristics. The number of piglets at birth (Total number born, Litter size, TNB) and the number of alive piglets at birth (Total number born alive, NBA) are the main indicators of the reproductive productivity of sows in pig breeding. Great hopes are pinned on GWAS (Genome-Wide Association Studies) to solve the problems associated with studying the genetic architecture of reproductive traits of pigs. This paper provides an overview of international studies on SNP (Single nucleotide polymorphism) associated with TNB and NBA in pigs presented in PigQTLdb as "Genome map association". Currently on the base of Genome map association results 306 SNPs associated with TNB (218 SNPs) and NBA (88 SNPs) have been identified and presented in the Pig QTLdb database. The results are based on research of pigs such as Large White, Yorkshire, Landrace, Berkshire, Duroc and Erhualian. The presented review shows that most SNPs found in chromosome areas where candidate genes or QTLs (Quantitative trait locus) have been identified. Further research in the given direction will allow to obtain new data that will become an impulse for creating breakthrough breeding technologies and increase the production efficiency in pig farming.

Histone Post-Translational Modifications and CircRNAs in Mouse and Human Spermatozoa: Potential Epigenetic Marks to Assess Human Sperm Quality

Spermatozoa (SPZ) are motile cells, characterized by a cargo of epigenetic information including histone post-translational modifications (histone PTMs) and non-coding RNAs. Specific histone PTMs are present in developing germ cells, with a key role in spermatogenic events such as self-renewal and commitment of spermatogonia (SPG), meiotic recombination, nuclear condensation in spermatids (SPT). Nuclear condensation is related to chromatin remodeling events and requires a massive histone-to-protamine exchange. After this event a small percentage of chromatin is condensed by histones and SPZ contain nucleoprotamines and a small fraction of nucleohistone chromatin carrying a landascape of histone PTMs. Circular RNAs (circRNAs), a new class of non-coding RNAs, characterized by a nonlinear back-spliced junction, able to play as microRNA (miRNA) sponges, protein scaffolds and translation templates, have been recently characterized in both human and mouse SPZ. Since their abundance in eukaryote tissues, it is challenging to deepen their biological function, especially in the field of reproduction. Here we review the critical role of histone PTMs in male germ cells and the profile of circRNAs in mouse and human SPZ. Furthermore, we discuss their suggested role as novel epigenetic biomarkers to assess sperm quality and improve artificial insemination procedure.

The Transcriptome of Pig Spermatozoa, and Its Role in Fertility

In the study presented here we identified transcriptomic markers for fertility in the cargo of pig ejaculated spermatozoa using porcine-specific micro-arrays (GeneChip^® miRNA 4.0 and GeneChip^® Porcine Gene 1.0 ST). We report (i) the relative abundance of the ssc-miR-1285, miR-16, miR-4332, miR-92a, miR-671-5p, miR-4334-5p, miR-425-5p, miR-191, miR-92b-5p and miR-15b miRNAs, and (ii) the presence of 347 up-regulated and 174 down-regulated RNA transcripts in high-fertility breeding boars, based on differences of farrowing rate (FS) and litter size (LS), relative to low-fertility boars in the (Artificial Insemination) AI program. An overrepresentation analysis of the protein class (PANTHER) identified significant fold-increases for C-C chemokine binding (GO:0019957): CCR7, which activates B- and T-lymphocytes, 8-fold increase), XCR1 and CXCR4 (with ubiquitin as a natural ligand, 1.24-fold increase), cytokine receptor activity (GO:0005126): IL23R receptor of the IL23 protein, associated to JAK2 and STAT3, 3.4-fold increase), the TGF-receptor (PC00035) genes ACVR1C and ACVR2B (12-fold increase). Moreover, two micro-RNAs (miR-221 and mir-621) were down- and up-regulated, respectively, in high-fertility males. In conclusion, boars with different fertility performance possess a wide variety of differentially expressed RNA present in spermatozoa that would be attractive targets as non-invasive molecular markers for predicting fertility.

The construction and application of lentiviral overexpression vector of goat miR-204 in testis

The miRNA gene in DNA is first transcribed to Pri-miRNA, and then processed to Pre-miRNA, a stem-loop RNA segment (precursor) and further to miRNA which binds to mRNA by Dicer protein complex. It was confirmed that goat miR-204 could regulate the expressions of Sirt1 and the SSCs' (Spermatogonial Stem Cells) important genes Oct4 and Plzf, and inhibit the proliferation of dairy goat SSCs in vitro in our previous work. So, the research in vivo was needed next. In this study, the recombinant lentivirus vector pCDH-CMV-mir204-EF1-GreenPuro containing a goat chi-pri-mir-204 gene DNA segment was structured, and transfected into 293 T cells for packaged lentivirus, which then were injected into mouse seminiferous tubules. After 7 days, the goat miR-204 and the related genes such as Sirt1 and Plzf were detected in the mouse testis. This work laid a good foundation for further study of miR-204 biological function in vivo.

miR-26a is Involved in Glycometabolism and Affects Boar Sperm Viability by Targeting PDHX

miR-26a is associated with sperm metabolism and can affect sperm motility and apoptosis. However, how miR-26a affects sperm motility remains largely unknown. Our previous study indicated that the PDHX gene is predicted to be a potential target of miR-26a, which is responsible for pyruvate oxidative decarboxylation which is considered as a key step for connecting glycolysis with oxidative phosphorylation. In this study, we first reported a potential relationship between miR-26a and PDHX and their expressions in fresh, frozen-thawed, and epididymal boar sperm. Then, sperm viability and survival were determined after transfection of miR-26a. mRNA and protein expression level of PDHX in the liquid-preserved boar sperm after transfection were also determined by RT-qPCR and Western Blot (WB). Our results showed that expression level of PDHX was significantly increased during sperm transit from epididymal caput to corpus and cauda. Similarly, expression of PDHX was significantly higher (P < 0.05) in fresh sperm as compared to epididymal cauda and frozen-thawed sperm. However, the expression of miR-26a in epididymal corpus sperm was significantly higher (P < 0.05) than that of caput and cauda sperm. Furthermore, after transfection of boar sperm with miR-26a mimic and inhibitor under liquid storage, the lowest and highest sperm viability was observed in miR-26a mimic and inhibitor treatment (P < 0.05), respectively. The protein levels of PDHX, after 24 and 48 h of transfection of miR-26a mimics and inhibitor, were notably decreased and increased (P < 0.05), respectively, as compared to negative control (NC) group. In conclusion, the novel and enticing findings of our study provide a reasonable evidence that miR-26a via PDHX, a link between glycolysis and oxidative phosphorylation, could regulate the glycometabolic pathway which eventually affect boar sperm viability and survival.

MicroRNA-based regulatory circuit involved in sperm infertility

miRNAs (MicroRNAs), known as noncoding and important endogenous factors regulating the expression protein-coding genes, are vital regulators in each biological process. Thus, this study aims to explore the key role of four microRNAs in regulating the spermatogenesis. To conduct this experiment, 55 infertile and fertile men provided the study with the sperm and testicular tissue samples. To study the spermatozoa in terms of the morphology, Diff-Quick was applied. Then, quantitative real-time polymerase chain reaction (RT-PCR) was conducted on samples. Our data indicated that in contrast to the miR-15b, significant increasing of miR-383 and miR-122 occurred in both severe oligoasthenoteratozoospermia (SOAT) and moderate oligoasthenoteratozoospermia (MOAT) compared to normal sperm group (N). In addition, it was observed that miR-15b and miR-122 increased in patients with nonobstructive azoospermia (NOA) compared with obstructive azoospermia (OA) group. Expression levels of target genes including P53, CASPASE-9 and CYCLIN D1 underwent principle changes according to miRNAs expression level. Our finding indicated that miRNAs had essential role in the regulation of spermatogenesis, and their expression altering was associated with sperm abnormalities. Thus, microRNAs can be introduced as useful biomarkers to determine male infertility reasons to choose the effective treatment.

Exosomes in specific fractions of the boar ejaculate contain CD44: A marker for epididymosomes?

Seminal plasma (SP) is a complex fluid containing proteins, peptides, enzymes, hormones as well as extracellular vesicles (EVs). The SP interacts with spermatozoa and the inner cell lining of the female genital tract, adsorbing proteins and exosomes that modulate sperm functions and female immune responsiveness. In the present study, boar sperm-free SP was studied using flow cytometry (FC) after membrane tetraspanins (CD9, CD63 and CD81) and membrane receptor CD44 marking of non-enriched (whole SP) or gradient fractions enriched through two-step discontinuous KBr-density-gradient ultracentrifugation, in whole ejaculate or in selected ejaculate fractions. The results, evaluated by transmission electron microscopy, confirmed the presence of exosomes in all fractions of the pig SP. Noteworthy, these pig SP-exosomes were CD44-bearing when analysed by FC, with bands detected by western blotting (WB) at the expected 85 kD size. The two-step discontinuous KBr-density-gradient ultracentrifugation enriched the population of exosomes in two specific gradient fractions, indicating exosomes (either prostasomes or epididymosomes) could be separated from low-density lipoprotein (LDL) but they co-sediment with the high-density lipoprotein (HDL)-bearing fraction. The findings pave for the selective isolation of exosomes in functional studies of their function when interacting with spermatozoa, the oocyte and/or the female genitalia, including hyaluronan-CD44 interplay.

CFTR mutation compromises spermatogenesis by enhancing miR-15b maturation and suppressing its regulatory target CDC25A†

MicroRNAs (miRNAs) have recently been shown to be important for spermatogenesis; both DROSHA and Dicer1 KO mice exhibit infertility due to abnormal miRNA expression. However, the roles of individual miRNAs in spermatogenesis remain elusive. Here we demonstrated that miR-15b, a member of the miR-15/16 family, is primarily expressed in testis. A miR-15b transgenic mouse model was constructed to investigate the role of miR-15b in spermatogenesis. Impaired spermatogenesis was observed in miR-15b transgenic mice, suggesting that appropriate expression of miR-15b is vital for spermatogenesis. Furthermore, we demonstrated that overexpression of miR-15b reduced CDC25A gene post-transcriptional activity by targeting the 3′-UTR region of CDC25A, thus regulating spermatogenesis. In vitro results further demonstrated that a mutation in CFTR could affect the interaction between Ago2 with Dicer1 and that Dicer1 activity regulates miR-15b expression. We extended our study to azoospermia patients and found that infertile patients have a significantly higher level of miR-15b in semen and plasma samples. Taken together, we propose that CFTR regulation of miR-15b could be involved in the post-transcriptional regulation of CDC25A in mammalian testis and that miR-15b is important for spermatogenesis.

Exploration of miRNA and mRNA Profiles in Fresh and Frozen-Thawed Boar Sperm by Transcriptome and Small RNA Sequencing

Due to lower farrowing rate and reduced litter size with frozen-thawed semen, over 90% of artificial insemination (AI) is conducted using liquid stored boar semen. Although substantial progress has been made towards optimizing the cryopreservation protocols for boar sperm, the influencing factors and underlying mechanisms related to cryoinjury and freeze tolerance of boar sperm remain largely unknown. In this study, we report the differential expression of mRNAs and miRNAs between fresh and frozen-thawed boar sperm using high-throughput RNA sequencing. Our results showed that 567 mRNAs and 135 miRNAs were differentially expressed (DE) in fresh and frozen-thawed boar sperm. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the majority of DE mRNAs were enriched in environmental information processing such as cytokine-cytokine receptor interactions, PI3K-Akt signaling, cell adhesion, MAPK, and calcium signaling pathways. Moreover, the targets of DE miRNAs were enriched in significant GO terms such as cell process, protein binding, and response to stimuli. In conclusion, we speculate that DE mRNAs and miRNAs are heavily involved in boar sperm response to environment stimuli, apoptosis, and metabolic activities. The differences in expression also reflect the various structural and functional changes in sperm during cryopreservation.

Epigenetics of Male Fertility: Effects on Assisted Reproductive Techniques

During the last decades the study of male infertility and the introduction of the assisted reproductive techniques (ARTs) has allowed to understand that normal sperm parameters do not always predict fertilization. Sperm genetic components could play an important role in the early stages of embryonic development. Based on these acquisitions, several epigenetic investigations have been developed on spermatozoa, with the aim of understanding the multifactorial etiology of male infertility and of showing whether embryonic development may be influenced by sperm epigenetic abnormalities. This article reviews the possible epigenetic modifications of spermatozoa and their effects on male fertility, embryonic development and ART outcome. It focuses mainly on sperm DNA methylation, chromatin remodeling, histone modifications and RNAs.

Novel and differentially abundant microRNAs in sperm cells, seminal plasma, and serum of boars due to porcine reproduction and respiratory syndrome virus infection

The objectives of this study were to identify and determine relative abundance of miRNAs in boar sperm, seminal plasma (SP), and serum pre- and post-viral infection. Functional enrichment analyses on predicted targets of miRNAs of interest were performed. Boars (n = 6) were inoculated with porcine reproductive and respiratory syndrome virus (PRRSv) strain 1-8-4 (Day 0). Semen and serum were collected on Day -2 and 6. Sperm and SP were separated and aliquots were flash frozen and stored at -80 °C. Serum was frozen and stored at -80 °C. Total RNA was isolated from sperm and SP samples and subjected to RNA sequencing. Microarray analysis was performed using the Day -2 and 6 RNA samples from serum, sperm and SP. Potential miRNA targets were predicted using miRanda 3.3a and targets were then analyzed for enrichment of Gene Ontology) and InterPro terms and were considered to be enriched if P <  0.01 using the Bonferroni correction. Microarray analyses resulted in 83, 13, and 10 miRNAs with differences in abundances in sperm, serum, and SP, respectively, when comparing Day -2 and 6. Results from enrichment analyses indicated that the predicted targets of 35, nine, and five miRNAs with differences in abundances for sperm, SP, and serum, respectively, that have functions and/or conserved protein domains that are enriched when compared to the pig genome. Enriched terms for P2X purinoceptors were identified for sperm, SP and serum. Enriched terms for cell adhesion were identified for sperm and serum transcripts. Enriched terms for cell signaling were identified for sperm and SP transcripts.

Patterns of expression of sperm and seminal plasma microRNAs in boar semen

Although sperm and seminal plasma differ in their origin, biophysical and biochemical properties of seminal plasma influence the sperm function. Seminal plasma is a fluid medium containing substances from testes, epididymides and accessory glands. Composition of seminal plasma varies among animal species and in boars, prostate and bulbourethral glands are major contributors to the volume and contents. While the origin of some components of seminal plasma are known, the source of recently discovered seminal plasma microRNAs remains unknown, in part due to the difficulty of recovering and characterizing RNA from porcine sperm and seminal plasma. To test the hypothesis that seminal plasma miRNAs interact with sperm, the first objective was to validate protocols for recovering RNAs from porcine seminal plasma and sperm, whereas the second objective was to characterize expression patterns of 84 prioritized microRNAs employing real time PCR methodology. The study identified a relationship between sperm and seminal plasma microRNAs, based on the normalized threshold cycle of amplifying cDNA in sperm and seminal plasma from the same semen of Landrace boars. Therefore, it was concluded that seminal plasma miRNAs may originate from sperm or these miRNAs may shuttle between sperm and seminal plasma in order to facilitate cell-to-cell communication.

Roles of microRNAs in mammalian reproduction: from the commitment of germ cells to peri-implantation embryos

MicroRNAs (miRNAs) are active regulators of numerous biological and physiological processes including most of the events of mammalian reproduction. Understanding the biological functions of miRNAs in the context of mammalian reproduction will allow a better and comparative understanding of fertility and sterility in male and female mammals. Herein, we summarize recent progress in miRNA‐mediated regulation of mammalian reproduction and highlight the significance of miRNAs in different aspects of mammalian reproduction including the biogenesis of germ cells, the functionality of reproductive organs, and the development of early embryos. Furthermore, we focus on the gene expression regulatory feedback loops involving hormones and miRNA expression to increase our understanding of germ cell commitment and the functioning of reproductive organs. Finally, we discuss the influence of miRNAs on male and female reproductive failure, and provide perspectives for future studies on this topic.

A technical assessment of the porcine ejaculated spermatozoa for a sperm-specific RNA-seq analysis

The study of the boar sperm transcriptome by RNA-seq can provide relevant information on sperm quality and fertility and might contribute to animal breeding strategies. However, the analysis of the spermatozoa RNA is challenging as these cells harbor very low amounts of highly fragmented RNA, and the ejaculates also contain other cell types with larger amounts of non-fragmented RNA. Here, we describe a strategy for a successful boar sperm purification, RNA extraction and RNA-seq library preparation. Using these approaches our objectives were: (i) to evaluate the sperm recovery rate (SRR) after boar spermatozoa purification by density centrifugation using the non-porcine-specific commercial reagent BoviPure^TM; (ii) to assess the correlation between SRR and sperm quality characteristics; (iii) to evaluate the relationship between sperm cell RNA load and sperm quality traits and (iv) to compare different library preparation kits for both total RNA-seq (SMARTer Universal Low Input RNA and TruSeq RNA Library Prep kit) and small RNA-seq (NEBNext Small RNA and TailorMix miRNA Sample Prep v2) for high-throughput sequencing. Our results show that pig SRR (~22%) is lower than in other mammalian species and that it is not significantly dependent of the sperm quality parameters analyzed in our study. Moreover, no relationship between the RNA yield per sperm cell and sperm phenotypes was found. We compared a RNA-seq library preparation kit optimized for low amounts of fragmented RNA with a standard kit designed for high amount and quality of input RNA and found that for sperm, a protocol designed to work on low-quality RNA is essential. We also compared two small RNA-seq kits and did not find substantial differences in their performance. We propose the methodological workflow described for the RNA-seq screening of the boar spermatozoa transcriptome.

ABBREVIATIONS

FPKM: fragments per kilobase of transcript per million mapped reads; KRT1: keratin 1; miRNA: micro-RNA; miscRNA: miscellaneous RNA; Mt rRNA: mitochondrial ribosomal RNA; Mt tRNA: mitochondrial transference RNA; OAZ3: ornithine decarboxylase antizyme 3; ORT: osmotic resistance test; piRNA: Piwi-interacting RNA; PRM1: protamine 1; PTPRC: protein tyrosine phosphatase receptor type C; rRNA: ribosomal RNA; snoRNA: small nucleolar RNA; snRNA: small nuclear RNA; SRR: sperm recovery rate; tRNA: transfer RNA.