MicroRNAs are small non-coding RNAs that modulate gene expression at post-transcriptional level, playing a crucial role in cell differentiation and development. Recently, some reports have shown that a limited number of mammalian microRNAs are also involved in anti-viral defense. In this study, the analysis of the hepatitis B virus (HBV) genome by the computer program MiRanda led to the identification of seven sites that are potential targets for human liver microRNAs. These sites were found to be clustered in a 995-bp segment within the viral polymerase ORF and the overlapping surface antigen ORF, and conserved among the most common HBV subtypes. The HBV genomic targets were then subjected to a validation test based on cultured hepatic cells (HepG2, HuH-7 and PLC/PRF/5) and luciferase reporter genes. In this test, one of the selected microRNAs, hsa-miR-125a-5p, was found to interact with the viral sequence and to suppress the reporter activity markedly. The microRNA was then shown to interfere with the viral translation, down-regulating the expression of the surface antigen. Overall, these results support the emerging concept that some mammalian microRNAs play a role in virus-host interaction. Furthermore, they provide the basis for the development of new strategies for anti-HBV intervention.

Aims MicroRNAs (miRNAs) play an important role in the pathogenesis of structural alterations of the failing heart through their ability to regulate negatively the expression levels of genes that govern the process of adaptive and maladaptive cardiac remodelling. We studied whether LV reverse remodelling after CRT was associated with changes of circulating miRNAs in patients with heart failure (HF) and dyssynchrony. Methods and results A prospective, non‐randomized self‐control trial was performed in 81 patients with HF eligible for CRT. At baseline, to select the HF miRNA profile, we evaluated the expression of 84 miRNAs (implicated in the pathogenesis of structural alterations of the failing heart) in three groups of patients: healthy subjects (healthy group, n = 15); patients with HF (HF group, n = 81); and patients without HF matched for age, sex, and concomitant disease with HF patients (control group, n = 60). At 12 months, the selected miRNA profile was evaluated in plasma from responder (n = 55) and non‐responder HF patients (n = 26) to CRT. In the test cohort, the HF patients were characterized by lower expression of 48 miRNAs (all P < 0.04) as compared with healthy subjects. In the validation cohort, the HF patients were characterized by lower expression of 24 miRNAs (all P < 0.03) as compared with control patients. At 12 months, 55 patients (68%) were considered responders and 26 non‐responders to CRT (32%). Responders showed an increase in expression of 19 miRNAs (all P < 0.03) compared with baseline expression, whereas in the non‐responders we observed an increase of six miRNAs (all P < 0.05) compared with baseline expression. At follow‐up, miRNAs were differentially expressed between responders and non‐responders. The responders were characterized by higher expression of five miRNAs (miRNA‐26b‐5p, miRNA‐145‐5p, miRNA‐92a‐3p, miRNA‐30e‐5p, and miRNA‐29a‐3p; P < 0.01 for all) as compared with non‐responders. Conclusions In responders, reverse remodelling is associated with favourable changes in miRNAs that regulate cardiac fibrosis, apoptosis, and hypertrophy.

To study in HBsAg chronic carriers the expression of liver hsa-miR-125a-5p and its correlation with liver HBV-DNA values and clinical presentation, 27 consecutive Caucasian, HBsAg/anti-HBe/HBV-DNA-positive patients who were naive to nucleos(t)ide analogues and interferon therapy and had no marker of HCV, HDV or HIV infection and no history of alcohol intake were enrolled. For each patient, liver HBV DNA and liver hsa-miR-125a-5p were quantified by real-time PCR in relation to β-globin DNA or RNU6B, respectively. Liver fibrosis and necroinflammation were graded by applying Ishak's scoring system. Liver hsa-miR-125a-5p was detected in all patients enrolled and a correlation between its concentration and liver HBV DNA was demonstrated (p10³ IU/ml (p6 (p = 0.02) and those with fibrosis score >2 (p2 (p = 0.02) than in patients with a lower load. By multivariate logistic regression analysis, liver hsa-miR-125a-5p was identified as an independent predictor of disease progression: O.R. = 4.21, C.I. 95% = 1.08–16.43, p6; O.R. = 3.12, C.I. 95% = 1.17–8.27, p2. In conclusion, in HBsAg/anti-HBe-positive patients, the liver hsa-miR-125a-5p level correlated with liver and plasma HBV-DNA values and was associated to a more severe disease progression.

MicroRNAs (miRNA) are small-non coding RNAs endowed with great regulatory power, thus playing key roles not only in almost all physiological pathways, but also in the pathogenesis of several diseases. Surprisingly, genomic distribution analysis revealed the highest density of miRNA sequences on the X chromosome; this evolutionary conserved mammalian feature equips females with a larger miRNA machinery than males. However, miRNAs contribution to some X-related conditions, properties or functions is still poorly explored. With the aim to support and focus research in the field, this review analyzes the literature and databases about X-linked miRNAs, trying to understand how miRNAs could contribute to emerging gender-biased functions and pathological mechanisms, such as immunity and cancer. A fine map of miRNA sequences on the X chromosome is reported, and their known functions are discussed; in addition, bioinformatics functional analyses of the whole X-linked miRNA targetome (predicted and validated) were performed. The emerging scenario points to different gaps in the knowledge that should be filled with future experimental investigations, also in terms of possible implications and pathological perspectives for X chromosome aneuploidy syndromes, such as Turner and Klinefelter syndromes.

MicroRNAs are small non-coding RNAs that modulate gene expression at post-transcriptional level, playing a crucial role in cell differentiation and development. Recently, some reports have shown that a limited number of mammalian microRNAs also display antiviral effects. This article summarizes the data in the field paying a special attention to the conservation of the microRNA target sequences in the viral populations. This issue is relevant both for the evaluation of the biological significance of the antiviral effects and for the development of microRNA-based strategies for antiviral intervention.