Effect of vitrification on biogenesis pathway and expression of development-related microRNAs in preimplantation mouse embryos

Vitrification of embryos has been known as the most efficient cryopreservation method in assisted reproductive technology clinics. Vitrification of preimplantation embryo might be associated with altered gene expression profile and biochemical changes of vitrified embryos. Stringent regulation of gene expression in early embryonic stages is very critical for normal development. In the present study, we investigated the effect of vitrification on the canonical miRNA biogenesis pathway, and also the expression of developmental related miRNAs, in 8-cell and blastocyst mouse embryos. Although the expression pattern of the miRNA biogenesis pathway genes differed between 8-cell and blastocyst mouse embryos, vitrification did not affect the expression level of these genes in preimplantation embryos. The expression levels of miR-21 and let-7a were significantly decreased in vitrified 8-cell embryos and fresh blastocysts when compared with fresh 8-cell embryos. The expression of Stat3 was significantly reduced in blastocysts after vitrification. The alteration in the expression pattern of miRNAs, due to their mode of action, can affect broad downstream key developmental signaling pathways. Therefore, the blastocyst stage is the preferred point for embryo vitrification as they are less susceptible to cryo-damages regarding the stability of miRNAs related to the developmental and implantation competence of embryo.

The association of AGO1 (rs595961G>A, rs636832A>G) and AGO2 (rs11996715C>A, rs2292779C>G, rs4961280C>A) polymorphisms and risk of recurrent implantation failure

Recurrent implantation failure (RIF) is a common reproductive clinical condition treated by fertility specialists at in vitro fertilization (IVF) clinics. Several factors affect embryo implantation including the age of the female, the quality of embryos and the sperm, genetics, immunologic factors. Here, we investigated the association of Argonaute 1 (AGO1) and Argonaute 2 (AGO2) polymorphisms and RIF. We collected blood samples from 167 patients with RIF and 211 controls. Genetic polymorphisms were detected by polymerase chain reaction (PCR) – restriction fragment length polymorphism analysis and real-time PCR. We found that the AGO2 rs4961280C>A polymorphism (adjusted odds ratio [AOR] = 1.984; P = 0.023) was significantly associated with RIF. Furthermore, in RIF patients with three or more consecutive implantation failure, the AGO2 rs4961280C>A CA genotype (AOR = 2.133; P = 0.013) and dominant model (AOR = 2.272; P = 0.006) were both significantly associated with prevalence of RIF. An analysis of variance revealed that patients with the AGO2 rs2292779C>G genotypes (CC: 6.52 ± 2.55; CG: 7.46 ± 3.02; GG: 8.42 ± 2.74; P = 0.044) and the dominant model (CC: 6.52 ± 2.55; CG+GG: 7.70 ± 2.97; P = 0.029) exhibited significantly increased white blood cell levels. Furthermore, patients with the AGO1 rs595961G>A dominant model (GG: 36.81 ± 8.69; GA+AA: 31.58 ± 9.17; P = 0.006) and the AGO2 rs4961280C>A recessive model (CC+CA: 35.42 ± 8.77; AA: 22.00 ± 4.24; P = 0.035) exhibited a significantly decreased number of CD4⁺ helper T cells. Our study showed that AGO1 and AGO2 polymorphisms are associated with the prevalence of RIF. Hence, the results suggest that variations in AGO1 and AGO2 genotypes may be useful clinical biomarkers for the development and prognosis of RIF.

Association study of AGO1 and AGO2 genes polymorphisms with recurrent pregnancy loss

An Argonaute (AGO) protein within the RNA-induced silencing complex binds a microRNA, permitting the target mRNA to be silenced. We hypothesized that variations in AGO genes had the possibility including affected the miRNA function and associated with recurrent pregnancy loss (RPL) susceptibility. Especially, we were chosen the AGO1 (rs595961, rs636832) and AGO2 (rs2292779, rs4961280) polymorphisms because of those polymorphisms have already reported in other diseases excluding the RPL. Here, we conducted a case-control study (385 RPL patients and 246 controls) to evaluate the association of four polymorphisms with RPL. We found that the AGO1 rs595961 AA genotype, recessive model (P = 0.039; P = 0.043, respectively), the AGO1 rs636832 GG genotype, and recessive model (P = 0.037; P = 0.016, respectively) were associated with RPL in women who had had four or more consecutive pregnancy losses. The patients with the AGO1 rs636832 GG genotypes had greater platelet counts (P = 0.023), while the patients with the AGO2 rs4961280 CA genotypes had less homocysteine (P = 0.027). Based on these results, we propose that genetic variations with respect to the AGO1 and AGO2 genotypes are associated with risk for RPL, and might serve as useful biomarkers for the prognosis of RPL.

Differential microRNA expression between decidual and peripheral blood natural killer cells in early pregnancy

STUDY QUESTION

Have decidual natural killer (dNK) cells a different microRNA (miRNA or miR) expression pattern compared to NK cells circulating in the peripheral blood (pb) of healthy pregnant women in the first trimester of gestation?

SUMMARY ANSWER

dNK cells have a unique miRNA profile, showing exclusive expression of a set of miRNAs and significant up- or down-regulation of most of the miRNAs shared with pbNK cells.

WHAT IS KNOWN ALREADY

dNK cells differ from pbNK cells both phenotypically and functionally, and their origin is still debated. Many studies have indicated that miRNAs regulate several important aspects of NK cell biology, such as development, activation and effector functions.

STUDY DESIGN, SIZE, DURATION

Decidua basalis and peripheral blood specimens were collected from women (n = 7) undergoing voluntary termination of gestation in the first trimester of pregnancy. dNK and pbNK cells were then highly purified by cell sorting.

PARTICIPANTS/MATERIALS, SETTING, METHODS

miRNAs expression was analysed by quantitative RT-PCR (qRT-PCR)-based arrays using RNA purified from freshly isolated and highly purified pbNK and dNK cells. Results from arrays were validated by qRT-PCR assays. The bioinformatics tool ingenuity pathway analysis (IPA) was applied to determine the cellular network targeted by validated miRNAs and the correlated biological functions.

MAIN RESULTS AND THE ROLE OF CHANCE

Herein, we identified the most differentially expressed miRNAs in NK cells isolated from peripheral blood and uterine decidua of pregnant women. We found that 36 miRNAs were expressed only in dNK cells and two miRNAs only in pbNK cells. Moreover, 48 miRNAs were commonly expressed by both NK cell preparations although at different levels: 28 were upregulated in dNK cells, while 15 were downregulated compared to pbNK cells. Validation of a selected set (n = 11) of these miRNAs confirmed the differential expression of nine miRNAs: miR-10b and miR-214 expressed only in dNK cells and miR-200a-3p expressed only in pbNK cells; miR-130b-3p, miR-125a-5p, miR-212-3p and miR-454 were upregulated while miR-210-3p and miR-132 were downregulated in dNK cells compared to pbNK cells. IPA network analysis identified a single network connecting all the miRNAs as well as their significant involvement in several classes of functions: 'Organismal injury, Reproductive system disease, Inflammatory disease' and 'Cellular development'. These miRNAs target molecules such as argonaute 2, tumour protein p53, insulin and other genes that belong to the same network and significantly influence cell differentiation and pregnancy.

LIMITATIONS, REASONS FOR CAUTION

In the present study, the cellular network and biological functions modulated by miRNAs differentially expressed in dNK and pbNK cells were identified by IPA considering only molecules and relationships that were with confidence 'experimentally observed' in leucocytes. The decidual and pbNK cells that were analysed here are a heterogeneous population and further study will help to disentangle whether there are differences in miRNA production by the different subsets of NK cells.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study describing a different miRNA expression profile in dNK cells compared to matched pbNK cells during the first trimester of pregnancy. Our findings improved the body of knowledge on dNK cell biology and strongly suggest further investigation into the roles of miRNAs that are differentially expressed in human dNK compared to pbNK cells. Our results suggest that specific miRNAs can modulate dNK cell origin and functions, highlighting a potential role of this miRNA signature in human development and diseases.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the Istituto Pasteur, Fondazione Cenci Bolognetti, the European NoE EMBIC within FP6 (Contract number LSHN-CT-2004-512040), Istituto Italiano di Tecnologia, and Ministero dell'Istruzione, dell'Università e della Ricerca (Ricerche Universitarie), and from Università Politecnica delle Marche. There are no conflicts of interest to declare.

MicroRNA expression profile in RAW264·7 macrophage cells exposed to Echinococcus multilocularis metacestodes

MicroRNAs (miRNAs) are short noncoding RNAs, involved in the regulation of parasite diseases. However, a role of miRNAs in Echinococcus multilocularis infection remains largely unknown. In this study, we first found the expression levels of key genes involved in miRNA biogenesis and function, including Ago2, Xpo5, Tarbp2 and DgcR8, were obviously altered in the macrophage RAW264·7 cells exposed to E. multilocularis metacestodes. Compared with the control, 18 and 32 known miRNAs were found to be differentially expressed (P 2) in the macrophages exposed to E. multilocularis metacestodes for 6 and 12 h, respectively. Among these, several are known to be involved in regulating cytokine activities and immune responses. Quantitative real-time polymerase chain reaction results showed that the expression of nine selected miRNAs was consistent with the sequencing data at each treatment time points. Moreover, there were statistically significant correlations between the expression levels of miRNAs and their corresponding targeted genes. Our data give us some clues to pinpoint a role of miRNAs in the course of infection and immunity of E. multilocularis.

Global characterization and target identification of piRNAs and endo-siRNAs in mouse gametes and zygotes

A set of small RNAs known as rasRNAs (repeat-associated small RNAs) have been related to the down-regulation of Transposable Elements (TEs) to safeguard genome integrity. Two key members of the rasRNAs group are piRNAs and endo-siRNAs. We have performed a comparative analysis of piRNAs and endo-siRNAs present in mouse oocytes, spermatozoa and zygotes, identified by deep sequencing and bioinformatic analysis. The detection of piRNAs and endo-siRNAs in the spermatozoa and revealed also in zygotes, hints to their potential delivery to oocytes during fertilization. However, a comparative assessment of the three cell types indicates that both piRNAs and endo-siRNAs are mainly maternally inherited. Finally, we have assessed the role of the different rasRNA molecules in connection with amplification processes by way of the "ping-pong cycle". Our results suggest that the ping-pong cycle can act on other rasRNAs, such as tRNA- and rRNA-derived fragments, thus not only being restricted to TEs during gametogenesis.

Overexpression of human Argonaute2 inhibits cell and tumor growth

BACKGROUND

Argonaute (Ago) proteins are essential for the biogenesis and function of -20-30 nucleotide long RNAs such as microRNAs (miRNAs). Ago expression increases or decreases under various physiological conditions, although the functional consequences are unknown. In addition, while reduced global miRNA production was shown to enhance cellular transformation and tumorigenesis, how Ago proteins contribute to human diseases has not been reported.

METHOD

Ago2, an essential Ago isoform in mammals, was stably expressed in 293 T, the human embryonic kidney cell line, and H1299, the human lung adenocarcinoma cell line. miRNA and mRNA expression was investigated by quantitative PCR and microarray profiling. Cell proliferation and migration was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and scratch assay in the cell cultures, respectively. How Ago2 affected cell growth in vivo was determined by H1299 xenograft tumor growth in mice. Changes in Ago2 expression in human lung cancer samples were investigated by quantitative PCR and immunohistochemistry.

RESULTS

Stable Ago2 overexpression elicited specific changes in miRNA and mRNA expression in both 293 T and H1299 cells. It also inhibited cell proliferation and migration in cell cultures as well as xenograft tumor growth in nude mice. Ago2 expression was lower in human lung adenocarcinomas than in the paired, non-cancerous tissues.

GENERAL SIGNIFICANCE

We concluded that changes in Ago2 expression might have significant physiological and pathological consequences in vivo.

Genome-wide small RNA sequencing and gene expression analysis reveals a microRNA profile of cancer susceptibility in ATM-deficient human mammary epithelial cells

Deficiencies in the ATM gene are the underlying cause for ataxia telangiectasia, a syndrome characterized by neurological, motor and immunological defects, and a predisposition to cancer. MicroRNAs (miRNAs) are useful tools for cancer profiling and prediction of therapeutic responses to clinical regimens. We investigated the consequences of ATM deficiency on miRNA expression and associated gene expression in normal human mammary epithelial cells (HME-CCs). We identified 81 significantly differentially expressed miRNAs in ATM-deficient HME-CCs using small RNA sequencing. Many of these have been implicated in tumorigenesis and proliferation and include down-regulated tumor suppressor miRNAs, such as hsa-miR-29c and hsa-miR-16, as well as over-expressed pro-oncogenic miRNAs, such as hsa-miR-93 and hsa-miR-221. MicroRNA changes were integrated with genome wide gene expression profiles to investigate possible miRNA targets. Predicted mRNA targets of the miRNAs significantly regulated after ATM depletion included many genes associated with cancer formation and progression, such as SOCS1 and the proto-oncogene MAF. While a number of miRNAs have been reported as altered in cancerous cells, there is little understanding as to how these small RNAs might be driving cancer formation or how they might be used as biomarkers for cancer susceptibility. This study provides preliminary data for defining miRNA profiles that may be used as prognostic or predictive biomarkers for breast cancer. Our integrated analysis of miRNA and mRNA expression allows us to gain a better understanding of the signaling involved in breast cancer predisposition and suggests a mechanism for the breast cancer-prone phenotype seen in ATM-deficient patients.

New advances of microRNAs in the pathogenesis of rheumatoid arthritis, with a focus on the crosstalk between DNA methylation and the microRNA machinery

Rheumatoid arthritis (RA) is a symmetrical polyarticular disease of unknown aetiology that affects primarily the articular cartilage and bone. Characteristic features of RA pathogenesis are persistent inflammation, synovium hyperplasia and cartilage erosion accompanied by joint swelling and joint destruction. Several lines of evidence have showed a crucial role of activated fibroblast-like synoviocytes (FLS) in the pathogenesis of RA. MicroRNAs (miRNAs) are endogenous, single-stranded, non-coding RNAs with about 21 nucleotides in length and have been detected in a variety of sources, including tissues, serum, and other body fluids, such as saliva. In light of key roles of miRNAs in the regulation of gene expression, miRNAs influence a wide range of physiological and pathological processes. For example, miRNAs are evident in various malignant and nonmalignant diseases, and accumulating evidence also shows that miRNAs have important roles in the pathogenesis of RA. It has been demonstrated that miRNAs can be aberrantly expressed even in the different stages of RA progression, allowing miRNAs to help understand the pathogenesis of the disease, to act as important biomarkers, and to monitor the disease severity and the effects of drug treatment. In addition, miRNAs are emerging as potential targets for new therapeutic strategies of this kind of autoimmune disorders. The ultimate goal is the identification of miRNA targets that could be manipulated through specific therapies, aiming at activation or inhibition of specific miRNAs responsible for the RA development. In this review, the importance of miRNAs in the pathogenesis of RA is discussed systematically, with particular emphasis on the role of the crosstalk between DNA methylation and the microRNA machinery.