miR-638 Inhibits immature Sertoli cell growth by indirectly inactivating PI3K/AKT pathway via SPAG1 gene

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).

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.

Bta-miR-127 inhibits secretion, proliferation and promotes apoptosis by targeting ITGA6 in bovine Sertoli cell

Sertoli cell (SC) play a critical role in the spermatogenesis process involved in male fecundity and reproductive potential. SC development is regulated by microRNAs (miRNAs). However, the effect and molecular mechanism of miRNAs and target genes on bovine immature SC remains poorly understood. In this study, bta-miR-127 overexpression in SC inhibited cell secretion, proliferation, cell viability, and S-phase cells number. However, inhibition of bta-miR-127 had the opposite effect. An over-expression of bta-miR-127 significantly promotes SC apoptosis, and bta-miR-127 inhibition can significantly inhibit this process. These results reveal that bta-miR-127 is an inhibitor of SC proliferation and secretion. A combination of transcriptome sequencing, bioinformatics analysis, and dual-luciferase reporter assay showed that ITGA6 was targeted by bta-miR-127. The small interfering RNA of ITGA6 (si-ITGA6) inhibits SC proliferation and secretion, as well as promotes apoptosis. The SC proliferation and secretion marker genes, cell viability, and S phase cell number in co-transfected si-ITGA6 + miR-127 inhibitor was significantly lower than those of the bta-miR-127 inhibitor group. These results further confirmed that bta-miR-127 targeting ITGA6 inhibits the SC proliferation and secretion, and promotes SC apoptosis. These findings proposed a novel miRNA (bta-miR-127) that impeded bovine SC proliferation and promoted SC apoptosis through downregulation of ITGA6.

The PI3K/AKT signaling pathway: How does it regulate development of Sertoli cells and spermatogenic cells?

The PI3K/AKT signaling pathway is one of the most crucial regulatory mechanisms in animal cells, which can mainly regulate proliferation, survival and anti-apoptosis in cell lines. In the seminiferous epithelium, most studies were concentrated on the role of PI3K/AKT signaling in immature Sertoli cells (SCs) and spermatogonia stem cells (SSCs). PI3K/AKT signaling can facilitate the proliferation and anti-apoptosis of immature Sertoli cells and spermatogenic cells. Besides, in mature Sertoli cells, this pathway can disintegrate the structure of the blood-testis barrier (BTB) via regulatory protein synthesis and the cytoskeleton of Sertoli cells. All of these effects can directly and indirectly maintain and promote spermatogenesis in male testis.

The role of SPAG1 in the assembly of axonemal dyneins in human airway epithelia

Mutations in SPAG1, a dynein axonemal assembly factor (DNAAF) that facilitates the assembly of dynein arms in the cytoplasm before their transport into the cilium, result in primary ciliary dyskinesia (PCD), a genetically heterogenous disorder characterized by chronic oto-sino-pulmonary disease, infertility and laterality defects. To further elucidate the role of SPAG1 in dynein assembly, we examined its expression, interactions and ciliary defects in control and PCD human airway epithelia. Immunoprecipitations showed that SPAG1 interacts with multiple DNAAFs, dynein chains and canonical components of the R2TP complex. Protein levels of dynein heavy chains (DHCs) and interactions between DHCs and dynein intermediate chains (DICs) were reduced in SPAG1 mutants. We also identified a previously uncharacterized 60 kDa SPAG1 isoform, through examination of PCD subjects with an atypical ultrastructural defect for SPAG1 variants, that can partially compensate for the absence of full-length SPAG1 to assemble a reduced number of outer dynein arms. In summary, our data show that SPAG1 is necessary for axonemal dynein arm assembly by scaffolding R2TP-like complexes composed of several DNAAFs that facilitate the folding and/or binding of the DHCs to the DIC complex.

What Does Androgen Receptor Signaling Pathway in Sertoli Cells During Normal Spermatogenesis Tell Us?

Androgen receptor signaling pathway is necessary to complete spermatogenesis in testes. Difference between androgen binding location in Sertoli cell classifies androgen receptor signaling pathway into classical signaling pathway and non-classical signaling pathway. As the only somatic cell type in seminiferous tubule, Sertoli cells are under androgen receptor signaling pathway regulation via androgen receptor located in cytoplasm and plasma membrane. Androgen receptor signaling pathway is able to regulate biological processes in Sertoli cells as well as germ cells surrounded between Sertoli cells. Our review will summarize the major discoveries of androgen receptor signaling pathway in Sertoli cells and the paracrine action on germ cells. Androgen receptor signaling pathway regulates Sertoli cell proliferation and maturation, as well as maintain the integrity of blood-testis barrier formed between Sertoli cells. Also, Spermatogonia stem cells achieve a balance between self-renewal and differentiation under androgen receptor signaling regulation. Meiotic and post-meiotic processes including Sertoli cell - Spermatid attachment and Spermatid development are guaranteed by androgen receptor signaling until the final sperm release. This review also includes one disease related to androgen receptor signaling dysfunction named as androgen insensitivity syndrome. As a step further ahead, this review may be conducive to develop therapies which can cure impaired androgen receptor signaling in Sertoli cells.

Regulation of mammalian spermatogenesis by miRNAs

Male fertility requires the continual production of sperm by the process of spermatogenesis. This process requires the correct timing of regulatory signals to germ cells during each phase of their development. MicroRNAs (miRNAs) in germ cells and supporting Sertoli cells respond to regulatory signals and cause down- or upregulation of mRNAs and proteins required to produce proteins that act in various pathways to support spermatogenesis. The targets and functional consequences of altered miRNA expression in undifferentiated and differentiating spermatogonia, spermatocytes, spermatids and Sertoli cells are discussed. Mechanisms are reviewed by which miRNAs contribute to decisions that promote spermatogonia stem cell self-renewal versus differentiation, entry into and progression through meiosis, differentiation of spermatids, as well as the regulation of Sertoli cell proliferation and differentiation. Also discussed are miRNA actions providing the very first signals for the differentiation of spermatogonia stem cells in a non-human primate model of puberty initiation.

Sperm Associated Antigens: Vigorous Influencers in Life

Sperm associated antigens (SPAGs) are specific proteins in terms of performance and evolution, that have common expressions in the testes or sperm cells. Moreover, the humoral immune response against some of SPAGs can result in immunological infertilities. On the other hand, recent studies have explored several new properties of SPAGs and shed light on sperm's function, the impact of anti-sperm antibodies (ASA) in immunological infertility, and some tumors related to SPAGs. This article presents an exhaustive review of SPAGs and their roles in the cell cycle, signaling pathways, fertility, sperm-oocyte cross-talk as well as their unfavorable positions as prognostic factors in many types of cancers.

circBTBD7 Promotes Immature Porcine Sertoli Cell Growth through Modulating miR-24-3p/MAPK7 Axis to Inactivate p38 MAPK Signaling Pathway

Sertoli cells are the crucial coordinators to guarantee normal spermatogenesis and male fertility. Although circular RNAs (circRNAs) exhibit developmental-stage-specific expression in porcine testicular tissues and have been thought of as potential regulatory molecules in spermatogenesis, their functions and mechanisms of action remain largely unknown, especially in domestic animals. A novel circBTBD7 was identified from immature porcine Sertoli cells using reverse transcription PCR, Sanger sequencing, and fluorescence in situ hybridization assays. Functional assays illustrated that circBTBD7 overexpression promoted cell cycle progression and cell proliferation, as well as inhibited cell apoptosis in immature porcine Sertoli cells. Mechanistically, circBTBD7 acted as a sponge for the miR-24-3p and further facilitated its target mitogen-activated protein kinase 7 (MAPK7) gene. Overexpression of miR-24-3p impeded cell proliferation and induced cell apoptosis, which further attenuated the effects of circBTBD7 overexpression. siRNA-induced MAPK7 deficiency resulted in a similar effect to miR-24-3p overexpression, and further offset the effects of miR-24-3p inhibition. Both miR-24-3p overexpression and MAPK7 knockdown upregulated the p38 phosphorylation activity. The SB202190 induced the inhibition of p38 MAPK pathway and caused an opposite effect to that of miR-24-3p overexpression and MAPK7 knockdown. Collectively, circBTBD7 promotes immature porcine Sertoli cell growth through modulating the miR-24-3p/MAPK7 axis to inactivate the p38 MAPK signaling pathway. This study expanded our knowledge of noncoding RNAs in porcine normal spermatogenesis through deciding the fate of Sertoli cells.

miR-126 Controls the Apoptosis and Proliferation of Immature Porcine Sertoli Cells by Targeting the PIK3R2 Gene through the PI3K/AKT Signaling Pathway

Simple Summary

MicroRNAs (miRNAs) have been reported with potential regulatory roles in spermatogenesis. In the present study, we demonstrated that miR-126 can stimulate cell proliferation and restrain the apoptosis of immature porcine Sertoli cells by targeting the PIK3R2 gene. Through this process, miR-126 further activates the PI3K/AKT signaling pathway. These results indicated that miR-126, PIK3R2, and the PI3K/AKT signaling pathway might play pivotal regulatory roles in porcine spermatogenesis by deciding the destiny of immature Sertoli cells.

Abstract

The quantity of Sertoli cells in the adult testis decides the daily gamete formation, and accumulating evidence indicates that epigenetic factors regulate the proliferation of Sertoli cells. Research on the function and regulatory mechanism of microRNAs (miRNAs) in Sertoli cells has not been comprehensive yet, especially on domestic animals. In this article, we report that miR-126 controls the proliferation and apoptosis of immature porcine Sertoli cells based on previous studies. Our results confirmed that miR-126 elevation promotes cell cycle progression, cell proliferation and represses cell apoptosis; on the contrary, the inhibitory effects of miR-126 result in the opposite. The phosphoinositide-3-kinase regulatory subunit 2 (PIK3R2) gene, a member of the PI3K family, was verified as a direct target of miR-126 using the dual-luciferase reporter analysis. miR-126 negatively regulated the mRNA and protein expression level of PIK3R2 in immature porcine Sertoli cells. siRNA-induced PIK3R2 inhibition caused similar effects as miR-126 overexpression and eliminated the influences of miR-126 knockdown in immature porcine Sertoli cells. In addition, both miR-126 overexpression and PIK3R2 inhibition elevated the phosphorylation of PI3K and AKT, whereas the miR-126 knockdown demonstrated the contrary result. In short, miR-126 controls the proliferation and apoptosis of immature porcine Sertoli cells by targeting the PIK3R2 gene through the PI3K/AKT signaling pathway. The research supplies a theoretical and practical foundation for exploring the functional parts of miR-126 in swine sperm by defining the destiny of immature Sertoli cells.

Circular RNA Protein Tyrosine Kinase 2 Promotes Cell Proliferation, Migration and Suppresses Apoptosis via Activating MicroRNA-638 Mediated MEK/ERK, WNT/β-Catenin Signaling Pathways in Multiple Myeloma

Our previous study observed that circular RNA protein tyrosine kinase 2 (circ-PTK2) was upregulated and correlated with worse clinical features and unfavorable prognosis in multiple myeloma (MM) patients. Thus, this study aimed to further characterize the regulatory function of circ-PTK2 on cell malignant activities and its target microRNA-638 (miR-638) as well as downstream MEK/ERK, WNT/β-catenin signaling pathways in MM. The effect of circ-PTK2 on MM cell proliferation, apoptosis, migration, invasion and its potential target miRNAs was assessed by transfecting circ-PTK2 overexpression plasmids into U226 cells and circ-PTK2 knock-down plasmids into LP-1 cells. Furthermore, the interaction between circ-PTK2 and miR-638 mediated MEK/ERK and WNT/β-catenin signaling pathways was validated by rescue experiments. Circ-PTK2 was overexpressed in most MM cell lines compared to normal plasma cells. Overexpressing circ-PTK2 promoted proliferation and migration, inhibited apoptosis in U266 cells, but did not affect cell invasion; knocking down circ-PTK2 achieved opposite effect in LP-1 cells. Besides, circ-PTK2 reversely regulated miR-638 expression but not miR-4690, miR-6724, miR-6749 or miR-6775. The following luciferase reporter assay illustrated the direct bind of circ-PTK2 towards miR-638. In rescue experiments, overexpressing miR-638 suppressed proliferation, migration, while promoted apoptosis in both wild U266 cells and circ-PTK2-overexpressed U266 cells; meanwhile, overexpressing miR-638 also suppressed MEK/ERK and WNT/β-catenin pathways in both wild U266 cells and circ-PTK2-overexpressed U266 cells. Knocking down miR-638 achieved opposite effect in both wild LP-1 cells and circ-PTK2-knocked-down LP-1 cells. In conclusion, circ-PTK2 promotes cell proliferation, migration, suppresses cell apoptosis via miR-638 mediated MEK&ERK and WNT&β-catenin signaling pathways in MM.

MicroRNA-125a-5p modulates the proliferation and apoptosis of TM4 Sertoli cells by targeting RAB3D and regulating the PI3K/AKT signaling pathway

Sertoli cells are cells that provide protection and nutrition for developing sperm. Each stage of sperm development occurs on the surface of Sertoli cells. MicroRNA (MiR)-125a-5p is involved in male reproduction. The current research aimed to probe the role of miR-125a-5p in Sertoli cell function. Functionally, miR-125a-5p knockdown facilitated Sertoli cell proliferation, while miR-125a-5p overexpression suppressed Sertoli cell proliferation, as evidenced by 5-ethynyl-20-deoxyuridine incorporation assay. Additionally, miR-125a-5p knockdown inhibited Sertoli cell apoptosis, while miR-125a-5p upregulation facilitated Sertoli cell apoptosis, as evidenced by flow cytometry analysis. Computationally, we identified four predicted mRNA targets of miR-125a-5p. Based on the results of luciferase reporter assay, miR-125a-5p was confirmed to bind to the predicted sequence in the Ras-related protein Rab-3D (RAB3D) 3'UTR. Rescue experiments showed that miR-125a-5p suppressed the proliferative ability of TM4 Sertoli cells and facilitated their apoptosis by targeting RAB3D. Finally, our data confirmed that miR-125a-5p and RAB3D modulated activation of the PI3K/AKT pathway. In conclusion, our data showed that miR-125a-5p regulated Sertoli cell proliferation and apoptosis by targeting RAB3D and regulating the PI3K/AKT pathway.

A network pharmacology approach to determine the underlying mechanisms of action of Yishen Tongluo formula for the treatment of oligoasthenozoospermia

Oligoasthenozoospermia is a complex disease caused by a variety of factors, and its incidence is increasing yearly worldwide. Yishen Tongluo formula (YSTLF), created by Professor Sun Zixue, has been used to treat oligoasthenozoospermia in clinical practice for several decades with a good therapeutic effect. However, the chemical and pharmacological profiles of YSTLF remain unclear and need to be elucidated. In this study, a network pharmacology approach was applied to explore the potential mechanisms of YSTLF in oligoasthenozoospermia treatment. All of the compounds in YSTLF were retrieved from the corresponding databases, and the bioactive ingredients were screened according to their oral bioavailability (OB) and drug-likeness (DL). The potential proteins of YSTLF were obtained from the traditional Chinese medicine systems pharmacology (TCMSP) database and the Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM) database, while the potential genes of oligoasthenozoospermia were obtained from the GeneCards database and the DisGeNET database. The STRING database was used to construct an interaction network according to the common targets identified by the online tool Venny for YSTLF and oligoasthenozoospermia. The topological characteristics of nodes were visualized and analyzed through Cytoscape. Biological functions and significant pathways were determined and analyzed using the Gene Ontology (GO) knowledgebase, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Metascape. Finally, the disease-formula-compound-target-pathway network was constructed by Cytoscape. A total of 106 bioactive ingredients and 134 potential targets from YSTLF were associated with oligoasthenozoospermia or considered to be therapeutically relevant. Pathway analysis indicated that the PI3K/Akt, MAPK and apoptosis signaling pathways were significant pathways involved in oligoasthenozoospermia. In conclusion, the current study expounded the pharmacological actions and molecular mechanisms of YSTLF in treating oligoasthenozoospermia from a holistic viewpoint. The potential molecular mechanisms were closely related to antioxidative stress, antiapoptosis and anti-inflammation, with TNF, CCND1, ESR1, NFKBIA, NR3C1, MAPK8, and IL6 being possible targets. This network pharmacology prediction may offer a helpful tool to illustrate the molecular mechanisms of the Chinese herbal compound YSTLF in oligoasthenozoospermia treatment.

Hsa-miR-100-3p Controls the Proliferation, DNA Synthesis, and Apoptosis of Human Sertoli Cells by Binding to SGK3

Human Sertoli cell is required for completing normal spermatogenesis, and significantly, it has important applications in reproduction and regenerative medicine because of its great plasticity. Nevertheless, the molecular mechanisms underlying the fate decisions of human Sertoli cells remain to be clarified. Here, we have demonstrated the expression, function, and mechanism of Homo sapiens-microRNA (hsa-miR)-100-3p in human Sertoli cells. We revealed that miR-100-3p was expressed at a higher level in human Sertoli cells by 10% fetal bovine serum (FBS) than 0.5% FBS. MiR-100-3p mimics enhanced the DNA synthesis and the proliferation of human Sertoli cells, as indicated by 5-ethynyl-2′-deoxyuridine (EdU) and Cell Counting Kit-8 (CCK-8) assays. Flow cytometry showed that miR-100-3p mimics reduced the apoptosis of human Sertoli cells, and notably, we predicted and further identified serum/glucocorticoid regulated kinase family member 3 (SGK3) as a direct target of MiR-100-3p. SGK3 silencing increased the proliferation and decreased the apoptosis of human Sertoli cells, while SGK3 siRNA 3 assumed a similar role to miR-100-3p mimics in human Sertoli cells. Collectively, our study indicates that miR-100-3p regulates the fate decisions of human Sertoli cells by binding to SGK3. This study is of great significance, since it provides the novel epigenetic regulator for the proliferation and apoptosis of human Sertoli cells and it may offer a new clue for gene therapy of male infertility.

Bta-miR-34b inhibits proliferation and promotes apoptosis via the MEK/ERK pathway by targeting MAP2K1 in bovine primary Sertoli cells

Immature Sertoli cell (SC) proliferation determines the final number of mature SCs and further regulates spermatogenesis. Accumulating evidence demonstrated that microRNAs (miRNAs) play an important role in SC proliferation, differentiation, and apoptosis. However, the effect and molecular mechanism of miRNA on bovine immature SC remain to be poorly understood. In this study, miRNA sequencing of testes collected in mature (24-mo old) and immature (neonatal) bulls was conducted to determine the miRNA expression profiles. MicroRNA-34b was one of the differentially expressed miRNAs and was selected for in-depth functional studies pertaining to SC growth. The results showed that miR-34b mimic transfection in primary Sertoli cells (PSC) inhibited cell proliferation and induced cell cycle arrested at G2 phase and decreased the expression of cell cycle-related genes such as CCNB1, CDK1, CDC25C, and C-MYC. MicroRNA-34b overexpression also leads to increased cell apoptosis, with proapoptotic genes P53 and BAX upregulated, while antiapoptotic gene BCL2 decreased. However, miR-34b knockdown had the opposite effects. Through a combination of transcriptome sequencing, bioinformatics analysis, dual-luciferase reporter assay, and Western blotting, mitogen-activated protein kinase kinase1 (MAP2K1), also known as MEK1, was identified as a target of miR-34b. In addition, PSC proliferation inhibition was mediated by cell cycle arrest and apoptosis with MAP2K1 interference. Overexpression of MAP2K1 effectively reversed the miR-34b-repressed PSC cell growth. Moreover, both miR-34b overexpression and MAP2K1 knockdown decreased the protein levels of P-ERK1/2, while MAP2K1 overexpression showed opposite effects. In summary, data suggest that miR-34b regulates PSC proliferation and apoptosis through the MEK/ERK signaling pathway. These data provide a theoretical and experimental framework for further clarifying the regulation of cell growth in PSC of bovine.

AR regulates porcine immature Sertoli cell growth via binding to RNF4 and miR-124a

Sertoli cells are the only somatic cells in the seminiferous epithelium which directly contact with germ cells. Sertoli cells exhibit polarized alignment at the basal membrane of seminiferous tubules to maintain the microenvironment for growth and development of germ cells, and therefore play a crucial role in spermatogenesis. Androgens exert their action through androgen receptor (AR) and AR signalling in the testis is essential for maintenance of spermatogonial numbers, blood-testis barrier integrity, completion of meiosis, adhesion of spermatids and spermiation. In the present study, we demonstrated that AR gene could promote the proliferation of immature porcine Sertoli cells (ST cells) and the cell cycle procession, and accelerate the transition from G1 phase into S phase in ST cells. Meanwhile, miR-124a could affect the proliferation and cell cycle procession of ST cells by targeting 3'-UTR of AR gene. Furthermore, AR bound to the RNF4 via AR DNA-binding domain (DBD) and we verified that RNF4 was necessary for AR to regulate the growth of ST cells. Above all, this study suggests that AR regulates ST cell growth via binding to RNF4 and miR-124a, which may help us to further understand the function of AR in spermatogenesis.

miR-222 Suppresses Immature Porcine Sertoli Cell Growth by Targeting the GRB10 Gene Through Inactivating the PI3K/AKT Signaling Pathway

Sertoli cells are central and essential coordinators of spermatogenesis. Accumulating evidence has demonstrated that miRNAs participate in the regulation of Sertoli cell growth. However, the functions and the regulatory mechanisms of miRNAs in Sertoli cells of domestic animals remain largely unknown. Here we report that miR-222 overexpression repressed cell cycle progression and proliferation and promoted the apoptosis of immature porcine Sertoli cells, whereas miR-222 inhibition resulted in the opposite result. miR-222 directly targeted the 3′-UTR of the GRB10 gene and inhibited its mRNA abundance. An siRNA-induced GRB10 knockdown showed similar effects as did miR-222 overexpression on cell proliferation and apoptosis and further attenuated the role of miR-222 inhibition. Furthermore, both miR-222 overexpression and GRB10 inhibition repressed the phosphorylation of PI3K and AKT, the key elements of the PI3K/AKT signaling pathway, whereas GRB10 inhibition offsets the effects of the miR-222 knockdown. Overall, we concluded that miR-222 suppresses immature porcine Sertoli cell growth by targeting the GRB10 gene through inactivation of the PI3K/AKT signaling pathway. This study provides novel insights into the epigenetic regulation of porcine spermatogenesis by determining the fate of Sertoli cells.

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.

miR-4270 regulates cell proliferation and apoptosis in patients with Sertoli cell-only syndrome by targeting GADD45A and inactivating the NOTCH signaling pathway

In recent decades, growing data has suggested that microRNAs (miRNAs, miRs) play a critical role in the development of Sertoli cells (SC), including regulating SC maturation, synthesis, proliferation, and apoptosis. Previous reports of miRNA microarray have identified aberrant miR-4270 expression in patients with Sertoli-cell-only syndrome (SCOS). However, it is not known whether miR-4270 is associated with the pathogenesis of SCOS. In this study, we aimed to further investigate the roles and potential mechanisms of miR-4270 on SC proliferation and apoptosis. Our data confirmed that miR-4270 was significantly upregulated in SC of SCOS patients compared with healthy controls. EdU and CCK-8 assays showed silencing of miR-4270 by specific inhibitor significantly enhanced human SC and TM4 cells proliferation. ELISA and flow cytometry assays indicated that miR-4270 knockdown prominently suppressed the apoptosis of human SC and TM4 cells. Furthermore, expression of cell cycle genes, including CCNE1 (cyclin E1), CCND1 (cyclin D1) and CDK4 (cyclin dependent kinase 4), were obviously upregulated in human SC and TM4 cells by qRT-PCR assay after knockdown of miR-4270, while expression of cell apoptotic factors, including CASP3 (caspase 3), CASP6 (caspase 6) and CASP7 (caspase 7), were all markedly decreased. Notably, GADD45A (growth arrest and DNA damage inducible alpha) mRNA was downregulated in SC of SCOS patients, and negatively corrected with miR-4270 expression. Moreover, bioinformatics tools and dual-luciferase reporter assay identified that miR-4270 directly bound the 3'-UTR of GADD45A mRNA to inhibit GADD45A expression. Meanwhile, Western blots analysis validated that the protein expression levels of NOTCH1 (notch receptor 1) and HES1 (hes family bHLH transcription factor 1) were significantly increased in SC and TM4 cells after miR-4270 silencing or GADD45A overexpression. Taken together, our data demonstrated that miR-4270 regulates proliferation and apoptosis in SC of SCOS patients by inactivating NOTCH signaling pathway via GADD45A gene, which may offer a new insight into the development of human SC and provide a promising biomarker for the treatment of SCOS.

miR-130a promotes immature porcine Sertoli cell growth by activating SMAD5 through the TGF-β-PI3K/AKT signaling pathway

Sertoli cells play vital roles in normal spermatogenesis, and microRNAs (miRNAs) participate in regulating Sertoli cell development. However, the functions and mechanisms of action of most identified miRNAs in porcine Sertoli cells remain largely unknown. Herein, we primarily explored the regulatory roles of miR-130a in immature porcine Sertoli cells using EdU-based high-content screening assay. The results demonstrated that 27 miRNAs have potential roles in the promotion of immature porcine Sertoli cell proliferation, and miR-130a was identified as a promising candidate. miR-130a promoted cell cycle progression and cell proliferation, whereas it impeded cell apoptosis in immature porcine Sertoli cells. It also contributed to Sertoli cell proliferation and testis development in vivo. A TMT-based proteomics approach revealed that miR-130a regulated the expression of 91 proteins and multiple pathways, including the TGF-β and PI3K/AKT signaling. miR-130a did not directly target the 3'-UTR of SMAD5; however, it increased SMAD5 phosphorylation. Moreover, miR-130a enhanced TGF-β signaling by activating SMAD5 protein, and TGF-β signaling further activated the PI3K/AKT signaling pathway to promote cell proliferation and inhibit cell apoptosis in porcine immature Sertoli cells. Collectively, miR-130a promoted immature porcine Sertoli cell growth by activating SMAD5 through the TGF-β-PI3K/AKT signaling pathway. This study, therefore, provides novel insights into the effects of miR-130a on porcine spermatogenesis through the regulation of immature Sertoli cell proliferation and apoptosis.

Profiling of miRNAs in porcine Sertoli cells

Background

Sertoli cells (SCs) create a specialized environment to support and dictate spermatogenesis. MicroRNAs (miRNAs), a kind of ~ 22 nt small noncoding RNAs, have been reported to be highly abundant in mouse SCs and play critical roles in spermatogenesis. However, the miRNAs of porcine SCs remain largely unknown.

Methods

We isolated porcine SCs and conducted small RNA sequencing. By comparing miRNAs in germ cells, we systematically analyzed the miRNA expression pattern of porcine SCs. We screened the highly enriched SC miRNAs and predicted their functions by Gene Ontology analysis. The dual luciferase assay was used to elucidate the regulation of tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) by ssc-miR-149.

Results

The analysis showed that 18 miRNAs were highly expressed in SCs and 15 miRNAs were highly expressed in germ cells. These miRNAs were predicted to mediate SC and germ cell functions. In addition, ssc-miR-149 played critical roles in SCs by targeting TRAF3.

Conclusion

Our findings provide novel insights into the miRNA expression pattern and their regulatory roles of porcine SCs.

miR-362 knock-down promotes proliferation and inhibits apoptosis in porcine immature Sertoli cells by targeting the RMI1 gene

Immature Sertoli cell proliferation determines the total number of mature Sertoli cells and further regulates normal spermatogenesis. Accumulating evidence demonstrates that microRNAs (miRNAs) play regulatory roles in immature Sertoli cell proliferation, while the functions and mechanisms of the Sertoli cells of domestic animals are poorly understood. In the present study, we aimed to investigate the roles of miR-362 in cell proliferation and apoptosis of porcine immature Sertoli cells. The results showed that miR-362 inhibition promoted the entrance of cells into the S phase and increased the expressions of cell cycle-related genes c-MYC, CNNE1, CCND1 and CDK4. Knock-down of miR-362 also promoted cell proliferation and inhibited apoptosis, which was demonstrated by the results from cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) and Annexin V-FITC/PI staining assays. The recQ-mediated genome instability protein 1 (RMI1) gene was identified as a potential target gene of miR-362 via luciferase reporter assay, and miR-362 repressed the protein expression of RMI1 in porcine immature Sertoli cells. siRNA-induced RMI1 knock-down further abolished the effects of miR-362 inhibition on porcine immature Sertoli cells. Collectively, we concluded that miR-362 knock-down promotes proliferation and inhibits apoptosis in porcine immature Sertoli cells by targeting the RMI1 gene, which indicates that miR-362 determines the fate of immature Sertoli cells.

The Role of MicroRNAs in Mammalian Fertility: From Gametogenesis to Embryo Implantation

The genetic codes inscribed during two key developmental processes, namely gametogenesis and embryogenesis, are believed to determine subsequent development and survival of adult life. Once the embryo is formed, its further development mainly depends on its intrinsic characteristics, maternal environment (the endometrial receptivity), and the embryo–maternal interactions established during each phase of development. These developmental processes are under strict genetic regulation that could be manifested temporally and spatially depending on the physiological and developmental status of the cell. MicroRNAs (miRNAs), one of the small non-coding classes of RNAs, approximately 19–22 nucleotides in length, are one of the candidates for post-transcriptional developmental regulators. These tiny non-coding RNAs are expressed in ovarian tissue, granulosa cells, testis, oocytes, follicular fluid, and embryos and are implicated in diverse biological processes such as cell-to-cell communication. Moreover, accumulated evidences have also highlighted that miRNAs can be released into the extracellular environment through different mechanisms facilitating intercellular communication. Therefore, understanding miRNAs mediated regulatory mechanisms during gametogenesis and embryogenesis provides further insights about the molecular mechanisms underlying oocyte/sperm formation, early embryo development, and implantation. Thus, this review highlights the role of miRNAs in mammalian gametogenesis and embryogenesis and summarizes recent findings about miRNA-mediated post-transcriptional regulatory mechanisms occurring during early mammalian development.