MicroRNA expression and its association with DNA repair in preimplantation embryos

Active DNA repair pathways are crucial for preserving genomic integrity and are likely among the complex mechanisms involved in the normal development of preimplantation embryos. MicroRNAs (miRNA), short non-coding RNAs, are key regulators of gene expression through the post-transcriptional and post-translational modification of mRNA. The association of miRNA expression with infertility or polycystic ovarian syndrome has been widely investigated; however, there are limited data regarding the importance of miRNA regulation in DNA repair during preimplantation embryo development. In this article, we review normal miRNA biogenesis and consequences of aberrant miRNA expression in the regulation of DNA repair in gametes and preimplantation embryos.

The Role of MicroRNA in Hepatitis C Virus Replication

Hepatitis C virus (HCV) infection is a major global health problem. There is no effective vaccine and the current treatment regimen with pegylated interferon α and ribavirin is associated with significant adverse events. Therefore, there is an urgent need to identify new antiviral targets for HCV therapy. In recent years, a growing number of microRNAs (miRNAs) have been reported to be able to regulate HCV replication and infection by interacting with the HCV genome directly or by regulating host innate immunity to build a nonspecific antiviral state within cells. In this review, we discuss HCV virology and standard of care followed by miRNA in general, and then give a brief overview of miRNAs involved in HCV infection and discuss their potential application as a therapeutic option for the treatment of HCV infection.

Role of stromal-epithelial interaction in the formation and development of cancer cells

Identification of gene expression mechanisms began with works on embryonic induction. The same mechanism of cell-cell interactions also contributes to the process of oncogenesis. Damage to epithelial cells' genetic apparatus turns them into precancerous stem cells that are not yet capable of tumor growth. They can be transformed into cancer stem cells and undergo further progression as a result of epigenetic effects of apocrine secretion by surrounding activated stromal cells (mostly myofibroblasts). These factors may activate the damaged genetic information. On the contrary, the level of malignancy can be decreased by adding culture medium from non-activated stromal cells. One must not exclude the possibility that in a number of cases genetically altered bone marrow may migrate to damaged or inflamed tissues and become there a source of stromal cells, as well as of parenchymal stem cells in a damaged organ, where they may give rise to changed epithelial (precancerous) stem cells or to activated stromal cells, thus leading to malignant tumor growth. Cancer treatment should also affect activated stromal cells. It may prevent emergence and progression of cancerous stem cells.

Hypomethylation of repeated DNA sequences in cancer

An important feature of cancer development and progression is the change in DNA methylation patterns, characterized by the hypermethylation of specific genes concurrently with an overall decrease in the level of 5-methylcytosine. Hypomethylation of the genome can affect both single-copy genes, repeat DNA sequences and transposable elements, and is highly variable among and within cancer types. Here, we review our current understanding of genome hypomethylation in cancer, with a particular focus on hypomethylation of the different classes and families of repeat sequences. The emerging data provide insights into the importance of methylation of different repeat families in the maintenance of chromosome structural integrity and the fidelity of normal transcriptional regulation. We also consider the events underlying cancer-associated hypomethylation and the potential for the clinical use of characteristic DNA methylation changes in diagnosis, prognosis or classification of tumors.

MicroRNAs in cancer management and their modulation by dietary agents

MicroRNAs (miRNAs) represent a class of small (21-23 nucleotides) non-coding RNAs that emerged as key post-transcriptional gene regulators, implicated in numerous physiological and pathological processes. Currently, a main focus of miRNA research is related to the roles of miRNAs in cancer development. The biogenesis and modes of action of miRNAs have not been completely elucidated; however, miRNA-mediated translational repression is involved in the regulation of almost every cellular process. Thus, pathological alterations in miRNA expression signatures are commonly associated with disease development. This review specifically focuses on miRNAs in cancer, with an emphasis on their use as potential biomarkers for cancer diagnosis and prognosis. Then, we discuss the potential use of synthetic antisense or miRNA mimetic oligonucleotides and dietary agents to modulate miRNA expression for chemotherapy and chemoprevention of cancer, respectively.

MicroRNA signatures in liver diseases

MicroRNAs (miRNAs) are an emerging class of highly conserved non-coding small RNAs that regulate gene expression at the post-transcriptional level. It is now clear that miRNAs can potentially regulate every aspect of cellular activity, including differentiation and development, metabolism, proliferation, apoptotic cell death, viral infection and tumorigenesis. Recent studies provide clear evidence that miRNAs are abundant in the liver and modulate a diverse spectrum of liver functions. Deregulation of miRNA expression may be a key pathogenetic factor in many liver diseases including viral hepatitis, hepatocellular cancer and polycystic liver diseases. A clearer understanding of the mechanisms involved in miRNA deregulation will offer new diagnostic and therapeutic strategies to treat liver diseases. Moreover, better understanding of miRNA regulation and identification of tissue-specific miRNA targets employing transgenic/knockout models and/or modulating oligonucleotides will improve our knowledge of liver physiology and diseases.

MicroRNA signatures in liver diseases

MicroRNAs (miRNAs) are an emerging class of highly conserved non-coding small RNAs that regulate gene expression at the post-transcriptional level. It is now clear that miRNAs can potentially regulate every aspect of cellular activity, including differentiation and development, metabolism, proliferation, apoptotic cell death, viral infection and tumorigenesis. Recent studies provide clear evidence that miRNAs are abundant in the liver and modulate a diverse spectrum of liver functions. Deregulation of miRNA expression may be a key pathogenetic factor in many liver diseases including viral hepatitis, hepatocellular cancer and polycystic liver diseases. A clearer understanding of the mechanisms involved in miRNA deregulation will offer new diagnostic and therapeutic strategies to treat liver diseases. Moreover, better understanding of miRNA regulation and identification of tissue-specific miRNA targets employing transgenic/knockout models and/or modulating oligonucleotides will improve our knowledge of liver physiology and diseases.