Potential regulatory functions of microRNAs in the ovary

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Altered Differential Expression of Genes and microRNAs Related to Adhesion and Apoptosis Pathways in Patients with Different Phenotypes of Endometriosis

We aim to investigate the expression of genes (MAPK1 and CAPN2) and microRNAs (miR-30a-5p, miR-7-5p, miR-143-3p, and miR-93-5p) involved in adhesion and apoptosis pathways in superficial peritoneal endometriosis (SE), deep infiltrating endometriosis (DE), and ovarian endometrioma (OE), and to evaluate whether these lesions share the same pathophysiological mechanisms. We used samples of SE (n = 10), DE (n = 10), and OE (n = 10), and endometrial biopsies of these respective patients affected with endometriosis under treatment at a tertiary University Hospital. Endometrial biopsies collected in the tubal ligation procedure from women without endometriosis comprised the control group (n = 10). Quantitative real-time polymerase chain reaction was performed. The expression of MAPK1 (p < 0.0001), miR-93-5p (p = 0.0168), and miR-7-5p (p = 0.0006) was significantly lower in the SE group than in the DE and OE groups. The expression of miR-30a (p = 0.0018) and miR-93 (p = 0.0052) was significantly upregulated in the eutopic endometrium of women with endometriosis compared to the controls. MiR-143 (p = 0.0225) expression also showed a statistical difference between the eutopic endometrium of women with endometriosis and the control group. In summary, SE showed lower pro-survival gene expression and miRNAs involved in this pathway, indicating that this phenotype has a different pathophysiological mechanism compared to DE and OE.

Role of miRNAs interference on ovarian functions and premature ovarian failure

Premature ovarian failure is a to some extent unknown and intricate problem with diverse causes and clinical manifestations. The lack of ovarian sex hormones presumably is effective in the occurrence of ovarian failure. Our progress in this field has been very little despite undertaken scientific research endeavors; scholars still are trying to understand the explanation of this dilemmatic medical condition. In contrast, the practice of clinical medicine has made meaningful strides in providing assurance to the women with premature ovarian insufficiency that their quality of life as well as long-term health can be optimized through timely intervention. Very recently Scientists have investigated the regulating effects of small RNA molecules on steroidogenesis apoptosis, ovulation, gonadal, and corpus luteum development of ovaries. In this literature review, we tried to talk over the mechanisms of miRNAs in regulating gene expression after transcription in the ovary. Video abstract.

Genetic Variations miR-10aA>T, miR-30cA>G, miR-181aT>C, and miR-499bA>G and the Risk of Recurrent Pregnancy Loss in Korean Women

This study investigated the genetic association between recurrent pregnancy loss (RPL) and microRNA (miRNA) polymorphisms in miR-10aA>T, miR-30cA>G, miR-181aT>C, and miR-499bA>G in Korean women. Blood samples were collected from 381 RPL patients and 281 control participants, and genotyping of miR-10aA>T, miR-30cA>G, miR-181aT>C, and miR-499bA>G was carried out by TaqMan miRNA RT-Real Time polymerase chain reaction (PCR). Four polymorphisms were identified, including miR-10aA>T, miR-30cA>G, miR-181aT>C, and miR-499bA>G. MiR-10a dominant model (AA vs. AT + TT) and miR-499bGG genotypes were associated with increased RPL risk (adjusted odds ratio [AOR] = 1.520, 95% confidence interval [CI] = 1.038−2.227, p = 0.032; AOR = 2.956, 95% CI = 1.168−7.482, p = 0.022, respectively). Additionally, both miR-499 dominant (AA vs. AG + GG) and recessive (AA + AG vs. GG) models were significantly associated with increased RPL risk (AOR = 1.465, 95% CI = 1.062−2.020, p = 0.020; AOR = 2.677, 95% CI = 1.066−6.725, p = 0.036, respectively). We further propose that miR-10aA>T, miR-30cA>G, and miR-499bA>G polymorphisms effects could contribute to RPL and should be considered during RPL patient evaluation.

The Potential Role of Circulating MicroRNAs in Male Rat Infertility Treated with Kaempferia parviflora

BACKGROUND

Therapeutic strategies based on herbal plants and diets containing sufficient amounts of antioxidants and essential vitamins are very important factors in treating reproduction and male infertility worldwide. Thus, the aim of this study was to investigate the potential effects of Kaempferia parviflora (KP) on the role of some microRNAs in treated and nontreated infertile rats. In addition, the correlation of expressed microRNAs with sperm count, sperm motility, and sperm viability was identified. The probable use of these microRNAs as a diagnostic marker for predicting the clinical response of infertility to the treatment with KP was also achieved.

METHODS

In the present study, the potential effects of Kaempferia parviflora (KP) at different doses (140, 280, and 420 mg/kg) for six weeks on male rats with subinfertility were explored. In addition, the effect of KP on the expression of circulating microRNAs and its correlation with the parameters of sexual infertility was identified by performing both in vitro and in vivo assays. In vitro antioxidant activity, sperm functional analysis, serum testosterone, and expression of circulating microRNAs were conducted using colorimetric, ELISA, and real-time RT-PCR analysis, respectively.

RESULTS

Kaempferia parviflora (KP) at nontoxic doses of 140-420 mg/kg/day for six weeks significantly improved serum testosterone and epididymal sperm parameters (sperm count, motility, and sperm viability), increased testicular weight, and provided a reduction in the percentage of abnormal spermatozoon in infertile male rats. The expression of miR-328 and miR-19b significantly decreased, and miR-34 significantly increased in infertile rats treated with KP compared to infertile nontreated rats. After six weeks of KP therapy, the change in the expression levels of miRNAs was correlated positively with higher levels of serum testosterone and the measures of epididymal sperm parameters. The respective area under the receiver operating characteristic curve (AUC-ROC) was applied to predict the potential use of miR-328, miR-19b, and miR-34 in the diagnosis of male infertility in treated and nontreated infertile male rats. The data showed that AUC cutoff values of 0.91 for miR-328, 0.89 for miR-19b, and 0.86 for miR34 were the best estimated values for the clinical diagnosis of male rats with infertility. In rats treated with KP for six weeks, AUC cutoff values of 0.76 for miR-328, 0.79 for miR-19b, and 0.81 for miR-34 were the best cutoff values reported for the clinical response of infertility to KP therapy after six weeks.

CONCLUSIONS

In this study, the improvement of male infertility might proceed via antioxidant and antiapoptotic pathways, which significantly improve spermatogenesis and aphrodisiac properties of males. In addition, the expression of miRNAs, miR-328, miR-34, and miR-19b, in KP-treated and nontreated infertile rats significantly correlated with increased serum testosterone levels and epididymal sperm parameters as well. MicroRNAs, miR-328, miR-34, and miR-19b, might be related to oxidative and apoptotic pathways that proceeded in spermatogenesis. Thus, the use of miRNAs could have a role as diagnostic, therapeutic, and predictive markers for assessing the clinical response of Kaempferia parviflora treatment for six weeks. This may have potential applications in the therapeutic strategies based on herbal plants for male infertility. However, in subsequent studies, the genetic regulatory mechanisms of the expressed miRNAs should be fully characterized.

Regulation of granulosa cell functions through NRP-1 mediated internalization of follicular fluid non-exosomal miR-210

Crosstalk between follicular fluid (FF) and granulosa cells (GCs) plays a vital role in the regulation of folliculogenesis, ensuring regular reproductive cycle in mammals. This crosstalk is primarily mediated by hormones and signaling molecules, such as cytokines and chemokines. Recently, extracellular microRNAs (miRNAs) have gained a lot of attention in cell-to-cell communication. Extracellular miRNA transportation occurs through exosomes, a kind of micro-vesicles produced from almost all cells. However, the mode of non-exosomal miRNA internalization is not much studied. In the present study, we explored the role of neuropilin-1 (NRP-1) as a receptor in internalizing FF non-exosomal miRNAs in GCs. We first confirmed the expression of NRP-1 in GCs during follicular development followed by its role in the internalization of miR-210, a non-exosomal miRNA. This study showed that incubation of GCs with a non-exosomal fraction of FF increased the content of miR-210 in GCs as compared to their control. To illustrate the role of NRP-1 as a receptor, NRP-1 was knockdown using siRNA. Silencing experimental results showed a significant decrease in uptake of miR-210 in NRP-1 knockdown GCs. Furthermore, downstream expression analysis of miR-210 target genes (CYP19A1, PCNA, and EFNA3) also confirmed the NRP-1 mediated miR-210 internalization. Results of the present study clearly demonstrated that FF non-exosomal miR-210 can be internalized through the NRP-1 receptor. Furthermore, differential expression of NRP-1 in GCs suggests its role in follicular development. Overall, these findings suggest that FF non-exosomal miRNA plays an important role in GC functions and female reproduction.

Effects of neonatal exposure to methoxychlor on corpus luteum in gilts: A transcriptomic analysis

This study investigated the effects of neonatal exposure to methoxychlor (MXC), a synthetic organochlorine used as an insecticide with estrogenic, antiestrogenic, and antiandrogenic activities, on luteal function in pigs. Piglets were injected subcutaneously with MXC (20 μg/kg body weight) or corn oil (control) between postnatal Days 1 and 10 (N = 5/group). Corpora lutea from sexually mature gilts were examined for luteal steroid and prostaglandin concentrations and processed for total RNA isolation and subsequent RNA sequencing. Intra-luteal concentrations of androstenedione and prostaglandin E₂ were greater, while that of estrone was lower when compared to control. Fifty-three differentially expressed (DE) microRNAS (miRNAs) (p-adjusted <.05 and log2(fold change) ≥.5) and 359 DE genes (p-adjusted <.05 and log2(fold change) ≥1) were identified in luteal tissue in response to neonatal MXC treatment. MXC was found to affect the expression of genes related to lipogenesis, steroidogenesis, membrane transport, immune response, cell signaling and adhesion. These results suggest an earlier onset of structural luteolysis in pigs caused by MXC actions in neonates. Since negative correlation analysis showed the potential interactions of miRNAs with specific messenger RNAs, we propose that these miRNAs are potential mediators of the long-term MXC effect on the CL function in pigs.

Overexpression of miR-144-3p alleviates polycystic ovaries syndrome through targeting expression of HSP-70

Increasing microRNAs are shown to be participate in polycystic ovarian syndrome (PCOS) pathogenesis. Nevertheless, the biological effects of miR-144-3p and its detailed mechanisms in PCOS are to be investigated. The purpose of our work was to study the function of miR-144-3p in PCOS. Currently, Expression of miR-144-3p was greatly reduced in PCOS patients and PCOS rat models. In addition, HSP-70 expression was greatly elevated PCOS. Cell proliferation assays and flow cytometry assay were carried out following the overexpression of miR-144-3p in ovarian granulosa cells from PCOS rat models. We observed that miR-144-3p overexpression induced the proliferation and repressed cell apoptosis while loss of miR-144-3p demonstrated an opposite process. Then, PCOS rat models were classified to four groups: LV-NC group, LV-miR-144-3p group, Anti-control group, and Anti-miR-144-3p group. In response to loss of miR-144-3p, we found E2, T, and LH serum levels were elevated and FSH serum level was inhibited. Upregulation of miR-144-3p exhibited an opposite process. Moreover, HSP-70 was a direct target of miR-144-3p. Furthermore, increased expression of HSP-70 rescued the effects of miR-144-3p on ovarian granulosa cell growth and apoptosis. In addition, knockdown of HSP-70 alleviated endocrine disorders and abnormal ovarian weight in vivo. To sum up, miR-144-3p might function as a novel target for PCOS treatment via targeting HSP-70.

The association of miR-25T>C, miR-32C>A, miR-125C>T, and miR-222G>T polymorphisms with a risk of primary ovarian insufficiency in Korean women

OBJECTIVE

The purpose of this study was to investigate the association of microRNA polymorphisms (miR-25T>C, miR-32C>A, miR-125C>T, and miR-222G>T) with primary ovarian insufficiency (POI) in Korean women.

METHODS

We conducted a case-control study of Korean women: 142 participants with POI and 266 controls with at least 1 live birth and no history of pregnancy loss.

RESULTS

The haplotype-based multifactor dimensionality reduction analysis revealed that the T-C-T-G (miR-25/-32/-125/-222), T-A-C-G (miR-25/-32/-125/-222), C-T-G (miR-32/-125/-222), A-C-G (miR-32/-125/-222), T-G (miR-122/-222), C-T (miR-32/-125), and C-C (miR-25/-32) inferred haplotypes were significantly less frequent in POI (P < 0.05), which suggested potential protective effects. Participants with POI had significantly increased luteinizing hormone levels (P < 0.05), but hormonal levels, including luteinizing hormone, were not significantly different between POI women and control women with miR-32/-125/-222.

CONCLUSIONS

After considering multiple comparisons, we concluded that miR-25T>C, miR-32C>A, miR-125C>T, and miR-222G>T had no relation with POI.

The Expression of miRNAs in Human Ovaries, Oocytes, Extracellular Vesicles, and Early Embryos: A Systematic Review

The recent discovery of microRNAs (miRNAs) in human reproductive tissues and cells indicates a possible functional role in reproductive function. However, the studies published to date in female reproductive tissues/cells and embryos are inconclusive and sometimes controversial. In order to update the knowledge of this field, the present study aimed to discuss, through a systematic review, the role of miRNAs in female human reproduction and early embryogenesis. We conducted a systematic review of the published literature in MEDLINE and EMBASE databases through June 2018 (plus a complementary search until July 2019), in accordance with the PRISMA guidelines. We have included descriptive and observational studies, in which fertile/infertile women were well-defined. The primary outcome was the miRNA expression in ovaries, oocytes, extracellular vesicles, and embryos. We identified 25,204 articles, of which 28 were selected for qualitative analysis: 18 in ovaries and extracellular vesicles, three in oocytes, and seven in embryos. The present systematic review of descriptive and observational studies demonstrates that aberrant miRNA expression in female reproductive tissues/cells and embryos is related with infertility and embryogenesis errors. The expression of specific miRNAs, particularly in extracellular vesicles, may be used in the future as biomarkers of infertility and prognostic tools of embryo development.

Answer to Controversy: miR-10a Replacement Approaches Do Not Offer Protection against Chemotherapy-Induced Gonadotoxicity in Mouse Model

It is well known that chemotherapeutic agents may lead to premature ovarian failure and infertility. Therefore, fertility preservation is highly recommended for female cancer survivors. Despite the currently available techniques, new, non-invasive methods need to be developed to protect the ovarian follicles during oncological treatments. MicroRNAs can be effective tools in this field, as they alter their expression during chemotherapy exposure, and hence they can be useful to minimize the off-target toxicity. Previously, we identified several miRNAs with an important role in newborn mouse ovaries exposed to chemotherapy; among them, the miR-10a was one of the most downregulated miRNAs. Given the controversial role of miR-10a in the ovarian function, we decided to investigate its implication in chemotherapy-induced gonadotoxicity. The downregulated levels of miR-10a were restored by a liposome system conjugated with a mimic miR-10a, and the overexpressed miR-10a prevented the upregulation of the targeted gene, phosphatase and tensin homolog (Pten). The apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) Assay and Bax expression quantification, while histological studies were also performed to evaluate the follicle count and development. Our results showed that the miR-10a replacement could not protect the ovaries from chemotherapy-induced apoptosis, whereas the targeting of Pten may affect the follicle activation via the phosphoinositide 3-kinase (PI3K)/PTEN/protein kinase B (AKT) pathway. Consequently, the application of miR-10a in fertility preservation is not recommended, and the role of miR-10a needs to be further elucidated.

MicroRNA-9 affects isolated ovarian granulosa cells proliferation and apoptosis via targeting vitamin D receptor

MicroRNAs (miRNAs or miRs)-9 expression was reported to be upregulated in the follicular fluid of patients with polycystic ovary syndrome (PCOS). However, whether miR-9 affects ovarian dysfunction of PCOS and the related mechanisms are still unclear. Here we detected miR-9 and vitamin D receptor (VDR) expression in women with PCOS and controls, and investigated whether miR-9 affects ovarian granulosa cells (GCs) proliferation and apoptosis by targeting VDR. We found increased miR-9 and decreased VDR in the blood and isolated ovarian GCs of women with PCOS compared with the controls. MiR-9 promoted GCs proliferation and inhibited GCs apoptosis in vitro, and these effects were attenuated by its target VDR. High concentrations of insulin upregulated miR-9 expression in GCs. In conclusion this study firstly proved miR-9 affects ovarian GCs proliferation and apoptosis through targeting VDR. MiR-9 might be a potential molecular target for improving the dysfunction of GCs in PCOS.

Steroids and miRNAs in assessment of ovarian tissue damage following cryopreservation

Ovarian cortical tissue cryopreservation is a relatively novel approach to preserving fertility in women diagnosed with cancer. However, the effects of freezing-thawing are not fully understood, mainly due to the lack of suitable methods to assess tissue's survival after thawing. Disparities in steroid production have been associated with ovarian failure by disrupting folliculogenesis, ovulation and oocyte apoptosis. Moreover, specific microRNAs, identified in human ovarian follicles, are thought to play a fundamental role in folliculogenesis. In this study, we investigated the possible interplay between the ovarian steroidal production and microRNA expression patterns in spent culture media, as potential non-invasive markers for ovarian tissue damage after cryopreservation. Cryopreservation of ovarian cortical tissue decreased (P<0.05) both steroid production (oestradiol and progesterone) and expression of microRNA-193b and 320A in spent culture media over 5 days, however, expression of microRNA-24 increased (P<0.05). The number of primordial follicles were also reduced (P<0.05) in fresh-cultured and cryopreserved-cultured cortical tissues when compared with fresh tissues. Downregulation of microRNA-193b and microRNA-320A together with upregulation of microRNA-24 could have a synergistic role in cell apoptosis, and consequently leading to reduced oestradiol and progesterone production. Thus, there appears to be an interplay between these microRNAs, ovarian steroid production and cell damage, which can be further explored as novel non-invasive markers of cell damage following cryopreservation.

Clustered miRNAs and their role in biological functions and diseases

MicroRNAs (miRNAs) are endogenous, small non-coding RNAs known to regulate expression of protein-coding genes. A large proportion of miRNAs are highly conserved, localized as clusters in the genome, transcribed together from physically adjacent miRNAs and show similar expression profiles. Since a single miRNA can target multiple genes and miRNA clusters contain multiple miRNAs, it is important to understand their regulation, effects and various biological functions. Like protein-coding genes, miRNA clusters are also regulated by genetic and epigenetic events. These clusters can potentially regulate every aspect of cellular function including growth, proliferation, differentiation, development, metabolism, infection, immunity, cell death, organellar biogenesis, messenger signalling, DNA repair and self-renewal, among others. Dysregulation of miRNA clusters leading to altered biological functions is key to the pathogenesis of many diseases including carcinogenesis. Here, we review recent advances in miRNA cluster research and discuss their regulation and biological functions in pathological conditions.

Genome -wide transcriptome profiling in ovaries of small-tail Han sheep during the follicular and luteal phases of the oestrous cycle

Ovarian function, the control of which is predominantly integrated by the hypothalamic-pituitary-ovarian axis, is pivotal for maintaining reproductive efficiency in sheep. To understand the regulatory mechanism of the follicular-luteal phase transition in prolific sheep, the genome-wide expression patterns of microRNAs and genes in ovarian tissue of Small Tail Han sheep were examined during the follicular and luteal phases of the oestrous cycle. Differentially expressed genes (n = 450) were identified and a total of 139 known and 72 novel miRNAs were identified in the two libraries. It is suggested that differential abundance of miR-200a, 200b and 200c may have an important role in the follicular-luteal transition. A miRNA-regulated gene expression network was created for exploring the regulation of the follicular-luteal transition and quantitative real-time PCR verified the reliability of the RNA-seq data.

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.

Identification of microRNAs as potential markers of ovarian toxicity

Exposure to environmental toxicants has been associated with ovarian dysfunction yet sensitive biomarkers of adverse effect are lacking. We previously demonstrated that cigarette smoke exposure induced decreased relative ovarian weight, increased follicle loss and granulosa cell autophagy in mice. We postulate that cigarette smoke exposure will induce changes in the epigenome that can be used to reveal potential sensitive biomarkers of ovarian toxicity. Therefore, we evaluated differences in expression of 940 microRNAs (miRNAs), environmentally responsive small non-coding genes that regulate expression of genes at the post-transcriptional level, in ovarian tissue from 8-week-old female C57BL/6 mice exposed to room air or cigarette smoke 5 days per week for 8 weeks. A total of 152 miRNAs were dysregulated in expression, 17 of which were examined with quantitative polymerase chain reaction analysis. Using an online miRNA database tool, complete lists of predicted miRNA gene targets were generated, 12 of which were measured for their expression levels with quantitative polymerase chain reaction. An online bioinformatics resource database, DAVID generated functional classification lists of the target genes and their associated biological pathways. Results of the present pilot study suggest that miR-379, miR-15b, miR-691, miR-872 and miR-1897-5p are potentially useful markers of ovarian toxicity and dysfunction. Examination of the expression pattern of the target mRNA for these miRNA species demonstrated that cigarette smoke exposure induced significant changes that affect mitogen-activated protein kinase signaling pathways. We therefore suggest that miRNAs could serve as sensitive markers of ovarian toxicity and elucidate affected pathways.

MicroRNA Signaling in Embryo Development

Expression of microRNAs (miRNAs) is essential for embryonic development and serves important roles in gametogenesis. miRNAs are secreted into the extracellular environment by the embryo during the preimplantation stage of development. Several cell types secrete miRNAs into biological fluids in the extracellular environment. These fluid-derived miRNAs have been shown to circulate the body. Stable transport is dependent on proper packaging of the miRNAs into extracellular vesicles (EVs), including exosomes. These vesicles, which also contain RNA, DNA and proteins, are on the forefront of research on cell-to-cell communication. Interestingly, EVs have been identified in many reproductive fluids, such as uterine fluid, where their miRNA content is proposed to serve as a mechanism of crosstalk between the mother and conceptus. Here, we review the role of miRNAs in molecular signaling and discuss their transport during early embryo development and implantation.

miR-26a-5p Regulates TNRC6A Expression and Facilitates Theca Cell Proliferation in Chicken Ovarian Follicles

Ovarian theca cells play an indispensable role in ovarian follicular development and hormone secretion. miR-26a-5p was reported to be differentially expressed in mature and immature chicken ovaries in our previous study; however, the role of miR-26a-5p in regulating ovarian follicle function is still unclear. In this study, we demonstrated that the expression dynamics of TNRC6A mRNA in either chicken ovaries or follicles showed an opposite trend compared with that of chicken miR-26a-5p expression. miR-26a-5p inhibited TNRC6A mRNA expression by directly targeting its 3'-untranslated region in cultured chicken theca cells. Overexpression of miR-26a-5p promoted chicken follicular theca cell proliferation in vitro. Furthermore, overexpression of miR-26a-5p and knockdown of TNRC6A significantly upregulated the antiapoptotic BCL-2 gene. Taken together, this study revealed the expression dynamics of miR-26a-5p and TNRC6A in chicken ovaries and ovarian follicles and the relationship between the expression of miR-26a-5p and TNRC6A in chicken ovarian theca cells. These results suggest that miR-26a-5p facilitates chicken ovarian theca cell proliferation by targeting the TNRC6A gene.

Single nucleotide polymorphisms at miR-146a/196a2 and their primary ovarian insufficiency-related target gene regulation in granulosa cells

MicroRNAs post-transcriptionally regulate gene expression in animals and plants. The aim of this study was to identify new target genes for microRNA polymorphisms (miR-146aC>G and miR-196a2T>C) in primary ovarian insufficiency (POI). We cloned and transfected miR-146aC>G and miR-196a2T>C into human granulosa cells and used microarrays and qPCR-arrays to examine the changes in the messenger RNA expression profile. We show miR-146aC>G and miR-196a2T>C change the mRNA expression patterns in granulosa cell. In each case, mRNAs were up or down-regulated after treatments with miR-146a C or G and miR-196a2 T or C. We found that miR-146a led to a significantly altered regulation of the mRNA levels of FOXO3, FOXL2 and CCND2 compared to controls. We also found that the polymorphisms of miR-146a led to a significantly altered regulation of CCND2 and FOXO3. Our results suggest that miR-146aC>G and miR-196a2T>C can regulate the levels of many of their target transcripts. In addition, specific target genes of miR-146aC>G polymorphisms may be involved in granulosa cell regulation.

Association of miR-938G>A Polymorphisms with Primary Ovarian Insufficiency (POI)-Related Gene Expression

MicroRNAs (miRNAs) post-transcriptionally regulate gene expression in animals and plants. The aim of this study was to investigate whether polymorphisms in miR-938 are associated with the risk of primary ovarian insufficiency (POI) and POI-related target gene regulation. We identified the miR-938G>A polymorphisms within the seed sequence of mature miRNA and aligned the seed sequence with the 3′ untranslated region (UTR) of the gonadotropin-releasing hormone receptor (GnRHR) mRNA, a miR-938 target gene. We found that the binding of miR-938 to the 3′-UTR of GnRHR mRNA was significantly different between normal and variant alleles. Our data suggests that the dysregulation of miR-938G>A influences the binding to GnRHR and that miR-938G>A polymorphisms might contribute to regulation of POI-related target genes.

Circulatory microRNA 23a and microRNA 23b and polycystic ovary syndrome (PCOS): the effects of body mass index and sex hormones in an Eastern Han Chinese population

Background

MicroRNAs (miRNAs) regulate the expression of genes involved in various cellular functions related to metabolism, inflammation, and reproduction. This study evaluated the effects of sex hormones and obesity on the expression of circulating miR-23a and miR-23b in women with polycystic ovary syndrome (PCOS) and healthy women.

Methods

Serum sex hormones concentrations and body mass index (BMI) were measured in 18 women with PCOS and in 30 healthy women from the East China area and these measurements were correlated with serum miR-23a/b levels. The effect of miR-23a and miR-23b risk factors on occurrence of PCOS and predisposing factors of PCOS on these miRNA expressions were evaluated.

Results

The expressions of miR-23a/b were significantly lower in the women with PCOS than the normal women, and the expression levels of miR-23a/b were positively correlated with each other in the normal women (p = 0.001) but not in the women with PCOS (p > 0.05). In the women with PCOS, miR-23a was positively correlated with BMI (p = 0.03). However, no correlations were found between the levels of miR-23a/b and the sex hormones in the normal and PCOS women. On the other hand, without considering the presence or absence of PCOS, increase in BMI had a positive effect on the levels of circulating miR-23b; while testosterone had negative effects on the levels of circulating miR-23a. Furthermore, the likelihood of women with PCOS decreased by 0.01-fold for every 1 fold increase of miR-23a expression.

Conclusions

Both reduced levels and discordance between the expressions of miR-23a/b were observed in the women with PCOS and miR-23a/b were affected from testosterone and BMI, reversely. Therefore, miR-23a alteration in contrast with miR-23b is a better indicator for evaluation of PCOS than the miR-23b.

The Role of Serum MicroRNA-6767-5p as a Biomarker for the Diagnosis of Polycystic Ovary Syndrome

Background

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder, and the underlying molecular mechanisms are not clear. To date, few studies have been conducted on the altered expression of serum microRNAs (miRNAs) in women with PCOS. The present study was performed to examine the role of the serum miRNA as a biomarker for the diagnosis of PCOS and its relationship with metabolic and reproductive traits.

Methods

A cross-sectional comparison was made in 21 women with PCOS and age- and body mass index (BMI)- matched 21 healthy women in an academic center laboratory between December 2008 and October 2010. We selected miRNAs that were more than 1.5-fold up-regulated or less than 0.67-fold down-regulated in women with PCOS compared with controls using the SurePrint G3 Human miRNA Microarray. Subsequently, we validated the relative expression of the miRNAs using TaqMan quantitative real-time polymerase chain reaction (RT-qPCR) assays.

Results

Serum miRNA-4522, miRNA-324-3p, and miRNA-6767-5p were down-regulated in women with PCOS compared with controls in the microarray analysis. Among these miRNAs, serum miRNA-6767-5p was validated (fold change in women with PCOS/controls = 0.39, P-value<0.05) by RT-qPCR. The miRNA-6767-5p was negatively associated with fasting glucose (β = -0.370) and positively associated with the number of menses per year (β = 0.383) after adjustment for age and BMI (Ps<0.05). Genes targeted by miRNA-6767-5p were involved in the cell cycle and the immune system.

Conclusions

Serum miRNA-6767-5p may be a novel candidate as a molecular biomarker in the diagnosis of PCOS and may participate in the development of the metabolic and reproductive traits of PCOS.

Association of breast cancer-related microRNA polymorphisms with idiopathic primary ovarian insufficiency

OBJECTIVE

The aim of our study was to investigate whether breast cancer-related microRNA polymorphisms are associated with primary ovarian insufficiency (POI) risk.

METHODS

Four breast cancer-related microRNA polymorphisms (miR-27aA > G [rs895819], miR-135bC > T [rs74141216], miR-423C > A [rs6505162], and miR-608G > C [rs4919510]) were genotyped in 136 women with idiopathic POI and 224 controls of Korean ethnicity using polymerase chain reaction-restriction fragment length polymorphism analysis. Differences in genotype frequencies between cases and controls were compared. Odds ratios and 95% CIs were determined as measures of the strength of association between genotype and POI.

RESULTS

Two haplotypes (G-C-A-G and A-T-C-C) of miR-27a/miR-135b/miR-423/miR-608 were associated with increased POI risk. The haplotypes G-A-G of miR-27a/miR-423/miR-608 and A-T-C of miR-27a/miR-135b/miR-608 were associated with higher POI risk, whereas the G-T haplotype of miR-27a/miR-135b was associated with decreased POI risk. The association between POI risk and the G-A-G haplotype of miR-27a/miR-423/miR-608 remained significant after false discovery rate correction for multiple comparisons. The combined genotypes AA/CT/CC/CC, AG/CC/CA/GC, GG/CC/CC/CC, and GG/CC/CA/GG of miR-27a/miR-135b/miR-423/miR-608 were also associated with higher POI risk. Increased POI risk was observed in combined genotypes GG/CC/GG of miR-27a/miR-135b/miR-608; AA/CC/GC, AG/CA/GC, GG/CC/GG, GG/CC/CC, and GG/CA/GG of miR-27a/miR-423/miR-608; and GG/GG of miR-27a/miR-608; however, these associations were not significant after false discovery rate correction. None of the four microRNA polymorphisms alone was associated with POI risk.

CONCLUSIONS

Our data suggest that breast cancer-related microRNA polymorphisms, including miR-27aA > G, miR-423C > A, and miR-608G > C, are associated with increased POI risk via interactions between miR-27aG, miR-423A, and miR-608G variants. However, our results should be interpreted cautiously because of our small sample size and the low statistical power of our study design.

Controlled ovarian hyperstimulation induced changes in the expression of circulatory miRNA in bovine follicular fluid and blood plasma

Background

Despite its role in increasing the number of offspring during the lifetime of an individual animal, controlled ovarian hyperstimulation (COH) may have detrimental effects on oocyte development, embryo quality and endometrial receptivity. Circulating miRNAs in bio-fluids have been shown to be associated with various pathological conditions including cancers. Here we aimed to investigate the effect of COH on the level of extracellular miRNAs in bovine follicular fluid and blood plasma and elucidate their mode of circulation and potential molecular mechanisms to be affected in the reproductive tract.

Method

Twelve simmental heifers were estrous synchronized and six of them were hyperstimulated using FSH. Follicular fluid samples from experimental animals were collected using ovum pick up technique at day 0 of the estrous cycle and blood samples were collected at day 0, 3 and 7 of post ovulation. The expression profile of circulatory miRNAs in follicular fluid and blood plasma were performed using the human miRCURY LNA™ Universal RT miRNA PCR array system. A comparative threshold cycle method was used to determine the relative abundance of the miRNAs.

Results

A total of 504 and 402 miRNAs were detected in both bovine follicular fluid and blood plasma, respectively. Of these 57 and 21 miRNAs were found to be differentially expressed in follicular fluid and blood plasma, respectively derived from hyperstimulated versus unstimulated heifers. Bioinformatics analysis of those circulating miRNAs indicated that their potential target genes are involved in several pathways including TGF-beta signaling pathway, MAPK signaling pathway, pathways in cancer and Oocyte meiosis.

Moreover, detail analysis of the mode of circulation of some candidates showed that most of the miRNA were found to be detected in both exosomal and Ago2 protein complex fraction of both follicular fluid and blood plasma.

Conclusion

Our data provide the consequence of hyperstimulation induced changes of extracellular miRNAs in bovine follicular fluid and blood plasma, which may have a potential role in regulating genes associated not only with bovine ovarian function but also involved in altering various physiological in bovine oocytes, embryos and modulating reproductive tract environment.

Physiologic Course of Female Reproductive Function: A Molecular Look into the Prologue of Life

The genetic, endocrine, and metabolic mechanisms underlying female reproduction are numerous and sophisticated, displaying complex functional evolution throughout a woman's lifetime. This vital course may be systematized in three subsequent stages: prenatal development of ovaries and germ cells up until in utero arrest of follicular growth and the ensuing interim suspension of gonadal function; onset of reproductive maturity through puberty, with reinitiation of both gonadal and adrenal activity; and adult functionality of the ovarian cycle which permits ovulation, a key event in female fertility, and dictates concurrent modifications in the endometrium and other ovarian hormone-sensitive tissues. Indeed, the ultimate goal of this physiologic progression is to achieve ovulation and offer an adequate environment for the installation of gestation, the consummation of female fertility. Strict regulation of these processes is important, as disruptions at any point in this evolution may equate a myriad of endocrine-metabolic disturbances for women and adverse consequences on offspring both during pregnancy and postpartum. This review offers a summary of pivotal aspects concerning the physiologic course of female reproductive function.

MicroRNA in ovarian function

The mammalian ovary is a dynamic organ. The coordination of follicle recruitment, selection, and ovulation and the timely development and regression of the corpus luteum are essential for a functional ovary and fertility. Deregulation of any of these processes results in ovarian dysfunction and potential infertility. MicroRNA (miRNA) are short noncoding RNA that regulate developmental processes and time-sensitive functions. The expression of miRNA in the ovary varies with cell type, function, and stage of the estrous cycle. miRNA are involved in the formation of primordial follicles, follicular recruitment and selection, follicular atresia, oocyte-cumulus cell interaction, granulosal cell function, and luteinization. miRNA are differentially expressed in luteal cells at the various stages of the estrous cycle and during maternal recognition of pregnancy, suggesting a role in luteal development, maintenance, and regression. An understanding of the patterns of expression and functions of miRNA in the ovary will lead to novel therapeutics to treat ovarian dysfunction and improve fertility and, potentially, to the development of better contraceptives.

Identification of differentially expressed microRNAs in the ovary of polycystic ovary syndrome with hyperandrogenism and insulin resistance

BACKGROUND

Polycystic ovary syndrome (PCOS) is the commonest endocrinopathy in women of reproductive age. The patients often develop insulin resistance (IR) or hyperinsulinemia despite manifesting anovulation and signs of hyperandrogenism. The cause and effect relationship of hyperinsulinemia and hyperandrogenemia (HA) is still debated. Micro-ribonucleic acids (miRNAs) have recently been shown to play a role in regulation of ovarian function. Our current study focused on the altered expression of miRNAs with PCOS.

METHODS

Ovarian theca interna tissues were obtained from 10 PCOS patients and 8 controls that were non-PCOS and had normal insulin sensitivity undergoing laparoscopy and/or ovarian wedge resection. Total RNA of all samples was extracted. We studied the repertoire of miRNAs in both PCOS and non-PCOS women by microarray hybridization. Bioinformatic analysis was performed for predicting targets of the differentially expressed miRNAs. Furthermore, selected miRNAs were validated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

RESULTS

A total of 27 miRNAs were differentially expressed in PCOS patients with respect to the controls in our discovery evaluationand two (miR-92a and miR-92b) of them were significantly downregulated in PCOS women in followed validation (P < 0.05). Targets prediction revealed that miR-92a targeted both GATA family of zinc finger transcription factor GATA-binding factor 6 (GATA6) and insulin receptor substrate proteins 2 (IRS-2).

CONCLUSIONS

MiRNAs are differentially expressed between PCOS patients and controls. We identified and validated two miRNAs-miR-92a and miR-92b. They are significantly downregulated and may be involved in the pathogenesis of PCOS.

MicroRNAs in ovarian function and disorders

MicroRNAs (miRNAs) are endogenous, small, noncoding single-stranded RNA molecules approximately 22 nucleotides in length. miRNAs are involved in the post-transcriptional regulation of various important cellular physiological and pathological processes, including cell proliferation, differentiation, apoptosis, and hormone biosynthesis and secretion. Ovarian follicles are the key functional units of female reproduction, and the development of these follicles is a complex and precise process accompanied by oocyte maturation as well as surrounding granulosa cell proliferation and differentiation. Numerous miRNAs expressed in the ovary regulate ovarian follicle growth, atresia, ovulation and steroidogenesis and play an important role in ovarian disorders. This review considers recent advances in the identification of miRNAs involved in the regulation of ovarian function as well as the possible influence of miRNAs on ovarian-derived disorders, such as ovarian cancer, polycystic ovarian syndrome and premature ovarian failure. An improved understanding of the regulation of ovarian function by miRNAs may shed light on new strategies for ovarian biology and ovarian disorders.

Circulating microRNAs in patients with polycystic ovary syndrome

AIM

To explore the pattern of expression of circulating miRNAs in patients with polycystic ovary syndrome (PCOS).

MATERIALS AND METHODS

Microarray and qRT-PCR were used to investigate circulating miRNAs in PCOS during clinical diagnosis. The targets of dys-regulated miRNAs were predicted using bioinformatics, followed by function and pathway analysis using the databases of Gene Ontology and the KEGG pathway.

RESULTS

BMI, triglyceride, HOMA-IR, Testosterone and CRP levels were significantly higher, while estradiol was significantly lower in PCOS than in control groups. After SAM analysis, 5 circulating miRNAs were significantly up-regulated (let-7i-3pm, miR-5706, miR-4463, miR-3665, miR-638) and 4 (miR-124-3p, miR-128, miR-29a-3p, let-7c) were down-regulated in PCOS patients. Hierarchical clustering showed a general distinction between PCOS and control samples in a heat map. After joint prediction by different statistical methods, 34 and 41 genes targeted were up-and down-regulated miRNAs, in PCOS and controls, respectively. Further, GO and KEGG analyses revealed the involvement of the immune system, ATP binding, MAPK signaling, apoptosis, angiogenesis, response to reactive oxygen species and p53 signaling pathways in PCOS.

CONCLUSIONS

We report a novel non-invasive miRNA profile which distinguishes PCOS patients from healthy controls. The miRNA-target database may provide a novel understanding of PCOS and potential therapeutic targets.

The expression pattern of microRNAs in granulosa cells of subordinate and dominant follicles during the early luteal phase of the bovine estrous cycle

This study aimed to investigate the miRNA expression patterns in granulosa cells of subordinate (SF) and dominant follicle (DF) during the early luteal phase of the bovine estrous cycle. For this, miRNA enriched total RNA isolated from granulosa cells of SF and DF obtained from heifers slaughtered at day 3 and day 7 of the estrous cycle was used for miRNAs deep sequencing. The results revealed that including 17 candidate novel miRNAs, several known miRNAs (n = 291-318) were detected in SF and DF at days 3 and 7 of the estrous cycle of which 244 miRNAs were common to all follicle groups. The let-7 families, bta-miR-10b, bta-miR-26a, bta-miR-99b and bta-miR-27b were among abundantly expressed miRNAs in both SF and DF at both days of the estrous cycle. Further analysis revealed that the expression patterns of 16 miRNAs including bta-miR-449a, bta-miR-449c and bta-miR-222 were differentially expressed between the granulosa cells of SF and DF at day 3 of the estrous cycle. However, at day 7 of the estrous cycle, 108 miRNAs including bta-miR-409a, bta-miR-383 and bta-miR-184 were differentially expressed between the two groups of granulosa cell revealing the presence of distinct miRNA expression profile changes between the two follicular stages at day 7 than day 3 of the estrous cycle. In addition, unlike the SF, marked temporal miRNA expression dynamics was observed in DF groups between day 3 and 7 of the estrous cycle. Target gene prediction and pathway analysis revealed that major signaling associated with follicular development including Wnt signaling, TGF-beta signaling, oocyte meiosis and GnRH signaling were affected by differentially expressed miRNAs. Thus, this study highlights the miRNA expression patterns of granulosa cells in subordinate and dominant follicles that could be associated with follicular recruitment, selection and dominance during the early luteal phase of the bovine estrous cycle.

Application of microRNA in diagnosis and treatment of ovarian cancer

Ovarian cancer has a poor prognosis because early detection is difficult and recurrent ovarian cancer is usually drug-resistant. The morbidity and mortality of ovarian cancer are high worldwide and new methods of diagnosis and therapy are needed. MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression that are involved in carcinogenesis, metastasis, and invasion. Thus, miRNAs are likely to be useful as diagnostic and prognostic biomarkers and for cancer therapy. Many miRNAs have altered expression in ovarian cancer compared to normal ovarian tissues and these changes may be useful for diagnosis and treatment. For example, deficiencies of enzymes including Dicer and Drosha that are required for miRNA biogenesis may be adverse prognostic factors; miRNAs such as miR-214 and miR-31, which are involved in drug resistance, and the miR-200 family, which is implicated in metastasis, may serve as biomarkers; and transfection of downregulated miRNAs and inhibition of upregulated miRNAs may be effective for treatment of ovarian cancer. Chemotherapy targeting epigenetic mechanisms associated with miRNAs may also be effective to reverse gene silencing.

microRNA biomarkers in cystic diseases

microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by targeting the 3’-untranslated region of multiple target genes. Pathogenesis results from defects in several gene sets; therefore, disease progression could be prevented using miRNAs targeting multiple genes. Moreover, recent studies suggest that miRNAs reflect the stage of the specific disease, such as carcinogenesis. Cystic diseases, including polycystic kidney disease, polycystic liver disease, pancreatic cystic disease, and ovarian cystic disease, have common processes of cyst formation in the specific organ. Specifically, epithelial cells initiate abnormal cell proliferation and apoptosis as a result of alterations to key genes. Cysts are caused by fluid accumulation in the lumen. However, the molecular mechanisms underlying cyst formation and progression remain unclear. This review aims to introduce the key miRNAs related to cyst formation, and we suggest that miRNAs could be useful biomarkers and potential therapeutic targets in several cystic diseases. [BMB Reports 2013; 46(7):338-345]

Altered expression of miRNAs in a dihydrotestosterone-induced rat PCOS model

Background

The polycystic ovary syndrome (PCOS) is a complex and heterogeneous endocrine condition characterized by hyperandrogenism, hyperinsulinemia, insulin resistance and chronic anovulation. Regulation and interaction of a multitude of genes required for follicular development are found to be altered in PCOS. MicroRNAs (miRNAs) mediate posttranscriptional gene regulation by binding to the 3´ untranslated region of mRNAs to either inhibit or enhance translation. However, the extent and regulation of miRNA expression in PCOS is poorly understood and the current study is the first to describe altered expression of miRNAs in PCOS.

Methods

A chronically androgenized [5α-dihydrotestosterone (DHT)-treated] rat model which recapitulates many of the phenotypes of human PCOS, and miRNA PCR array was used to investigate the expression of 349 miRNAs in DHT treated rat ovaries. The ovarian expression of several selected miRNAs was also analyzed by in situ localization experiment.

Results

DHT-treated rats exhibit increased body weight, disrupted estrus cyclicity, decreased insulin sensitivity and decreased ovarian weight, with the latter phenomenon readily rescued by gonadotropin treatment in vivo. In general, 24% of the 349 miRNAs investigated were found to be differentially expressed between DHT-treated and control rats. Most of the differentially expressed miRNAs were found to be predominantly localized in the theca cells of the follicles. In silico analysis of the potential target genes of dysregulated miRNAs revealed their possible involvement in various pathways in the regulation of ovarian function.

Conclusion

Our current findings suggest that miRNAs are differentially regulated in hyperandrogenism, a condition possibly involved in the dysregulation of steroid hormone receptors and intra-ovarian factors, and that miRNAs may be involved in the etiology of PCOS.

MicroRNA-145 suppresses mouse granulosa cell proliferation by targeting activin receptor IB

MicroRNAs (miRNAs) are a class of 21- to 25-nucleotide non-coding RNAs, some of which are important gene regulators involved in folliculogenesis. In this study, we used CCK-8, real-time PCR and Western blot assays to demonstrate that miR-145 inhibits mouse granulosa cell (mGC) proliferation. Combined with the results of luciferase reporter assays that studied the 3'-untranslated region of ACVRIB mRNA, these assays identified ACVRIB as a direct target of miR-145. The ectopic expression of miR-145 reduced the levels of both ACVRIB mRNA and protein and also interfered with activin-induced Smad2 phosphorylation. Altogether, this study revealed that miR-145 suppresses mGC proliferation by targeting ACVRIB.

Association of miR-146aC>G, miR-196a2T>C, and miR-499A>G polymorphisms with risk of premature ovarian failure in Korean women

We investigated whether microRNA (miRNA) polymorphisms (miR-146aC>G, miR-196a2T>C, and miR-499A>G) confer risk of premature ovarian failure (POF) in Korean women. DNA samples from 136 patients with POF and 234 controls were genotyped for the 3 miRNA single-nucleotide polymorphisms by polymerase chain reaction-restriction fragment length polymorphism. The miR-146aCG/miR-196a2TC combined genotype was less frequent in patients than in controls (P < .05), conferring less susceptibility. Using haplotype-based multifactor dimensionality reduction analysis, the C-C-A and G-T-A inferred haplotypes (miR-146a/miR-196a2/miR-499) were less frequent in patients, suggesting protective effects (P < .05 for each), whereas the C-T-A and G-C-A haplotypes were more frequent in patients (P < .05 for each). The C-T and G-C haplotypes (miR-146a/miR-196a2) were more frequent in patients, whereas the C-C and G-T haplotypes were less frequent in patients (P < .05 for each). However, none of the 3 miRNA polymorphisms alone was associated with POF risk. Our findings suggest that putative gene-gene interaction between miR-146 and miR-196a2 may be involved in POF development.

The potential role of microRNAs in regulating gonadal sex differentiation in the chicken embryo

Differential gene expression regulates tissue morphogenesis. The embryonic gonad is a good example, where the developmental decision to become an ovary or testis is governed by female- or male-specific gene expression. A number of genes have now been identified that control gonadal sex differentiation. However, the potential role of microRNAs (miRNAs) in ovarian and testicular pathways is unknown. In this review, we summarise our current understanding of gonadal differentiation and the possible involvement of miRNAs, using the chicken embryo as a model system. Chickens and other birds have a ZZ/ZW sex chromosome system, in which the female, ZW, is the heterogametic sex, and the male, ZZ, is homogametic (opposite to mammals). The Z-linked DMRT1 gene is thought to direct testis differentiation during embryonic life via a dosage-based mechanism. The conserved SOX9 gene is also likely to play a key role in testis formation. No master ovary determinant has yet been defined, but the autosomal FOXL2 and Aromatase genes are considered central. No miRNAs have been definitively shown to play a role in embryonic gonadal development in chickens or any other vertebrate species. Using next generation sequencing, we carried out an expression-based screen for miRNAs expressed in embryonic chicken gonads at the time of sexual differentiation. A number of miRNAs were identified, including several that showed sexually dimorphic expression. We validated a subset of miRNAs by qRT-PCR, and prediction algorithms were used to identify potential targets. We discuss the possible roles for these miRNAs in gonadal development and how these roles might be tested in the avian model.

RNA interference and ovarian functions

RNA interference, a recently discovered new mechanism controlling gene expression via small RNAs, was shown to be involved in characterization and control of basic ovarian cell functions. The main classes of small RNAs, as well as their expression in ovaries have been described. Furthermore, the successful application of RNA interference for study and control of basic ovarian functions (proliferation, apoptosis, secretory activity, luteogenesis, oocyte maturation, and related ovarian cell malignant transformation) and production of recombinant proteins have been demonstrated. Application of RNA interference in reproductive biology and medicine can be successful in two main areas: (1) characterization and prediction of physiological and pathological state (association between particular small RNA and physiological or pathological processes), (2) application of small RNAs for regulation of reproductive processes and treatment of reproductive disorders or their particular indexes. Problems of improvement of small RNA delivery to target ovarian cells and potent RNA interference-related approaches for treatment of ovarian disorders (especially of ovarian cancer) have been discussed.

MicroRNAs in cholangiociliopathies

This review is focused on current findings implicating miRNAs in the polycystic liver diseases, which we categorized as cholangiociliopathies. Our recent data suggest that deregulation of miRNA pathways is emerging as a novel mechanism in the development of cholangiociliopathies. Experimental evidence demonstrates that miRNAs (i.e., miR-15a) influence hepatic cyst growth by affecting the expression of the cell cycle regulator, Cdc25A. Given that abnormalities in many cellular processes (i.e., cell cycle regulation, cell proliferation, cAMP and calcium signaling, the EGF-stimulated mitogen-activated protein kinase (MAPK) pathway and fluid secretion) contribute to the hepatic cystogenesis, the potential role of miRNAs in regulation of these processes is discussed.