A study of microRNAsin silicoandin vivo: emerging regulators of embryonic stem cells

miR-373 suppresses gastric cancer metastasis by downregulating vimentin

MicroRNA-373 (miR-373) has been reported to be an oncogene in a number of solid human tumors. However, the role of miR‑373 in gastric cancer has not been completely elucidated and the mechanisms remain unclear. In the present study, we compared miR‑373 expression between clinical gastric cancer tissues and paired non‑tumorous tissues by reverse transcription‑quantitative polymerase chain reaction. The impact of miR‑373 on proliferation, migration and invasion in gastric cancer cells was additionally investigated. Hsa‑miR‑373 mimics were applied to mimic the function of endogenous miR‑373. A colony formation assay and flow cytometry were performed to analyze the proliferation of gastric cancer cells. Wound healing and Transwell invasion assays were employed to detect the migratory and invasive abilities of gastric cancer cells. Western blotting was used to test the expression of epithelial‑mesenchymal transition‑associated proteins. The results demonstrated that the level of miR‑373 in gastric cancer was upregulated compared with paired non‑tumorous tissues. It was confirmed that miR‑373 inhibited the migration and invasion of the gastric cancer cell lines SGC‑7901 and HGC‑27 by downregulating vimentin expression. The results of the present study demonstrated an oncogenic role of miR‑373 in the metastasis of human gastric cancer, and may provide a novel therapeutic strategy for gastric cancer.

Exosome miR-371b-5p promotes proliferation of lung alveolar progenitor type II cells by using PTEN to orchestrate the PI3K/Akt signaling

Background

Pathways directing endogenous stem/progenitor cells to restore normal architecture and function of damaged/diseased lungs remain underexplored. Published data have revealed that alveolar progenitor type II cell (ATIIC)-derived signaling promotes re-epithelialization of injured alveoli, yet the underlying mechanism is unknown. Here we aim to define the role of ATIIC-derived exosome miRNA signaling in controlling ATIIC-specific proliferation or differentiation in response to injury.

Methods

Pluripotent stem cell-derived cultures, which contain early lung stem/progenitor populations that can subsequently differentiate into ATIICs, were used as a model for unbiased screening and identification of ATIIC phenotype-specific exosome miRNA signaling, and human induced pluripotent stem cell-derived ATIICs (hiPSC-ATIICs) were employed to examine the molecular basis of key exosome miRNA signaling in promoting ATIIC-specific proliferation. QRT-PCR was performed to examine expression pattern of ATIIC-derived key exosome miRNA in an alveolar injury model and in injured human lungs.

Results

We show that human ATIIC line (A549)-derived exosome miR-371b-5p promotes ATIIC-specific proliferation, but not differentiation, in differentiating cultures of pluripotent stem cells. Using 3′UTR-driven luciferase reporters, we identified PTEN as a direct target of miR-371b-5p. Transfection of miR-371b-5p mimic into hiPSC-ATIICs leads to significantly decreased expression of endogenous PTEN, which stimulates phosphorylation of Akt and its downstream substrates, GSK3β and FOXOs, promoting cell proliferation. While not expressed in normal ATIIC phenotypes, the exosome miR-371b-5p expression is significantly induced after hiPSC-ATIICs or hATIICs (human primary ATIICs) are subjected to bleomycin-induced injury. To rule out that the ATIIC-derived exosome-miRNAs are merely a cell culture phenomenon, we transplanted hiPSC-ATIICs into bleomycin-challenged lungs of mice, and found that the transplanted hiPSC-ATIICs engraft and express exosome miR-371b-5p, along with additional survival of numerous mouse ATIICs in bleomycin-injured lungs. Consistent with these findings, significant levels of exosome miR-371b-5p were also detected in lavage samples of patients with acute pneumonia, but not in those from patients without pulmonary disorders.

Conclusions

Collectively, our data strongly suggest that ATIIC-derived exosome miR-371b-5p may serve as a niche signaling to augment ATIIC survival/proliferation, promoting re-epithelialization of injured alveoli, and thus provide a promising novel target to develop treatment for currently incurable lung diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0586-2) contains supplementary material, which is available to authorized users.

Regulation of Embryonic Stem Cell Self-Renewal and Differentiation by MicroRNAs

MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression. They play an important role in various cellular processes such as apoptosis, differentiation, secretion, and proliferation. Embryonic stem cells (ESCs) are derived from the inner cell mass of the blastocyst stage of the embryo. miRNAs are critical factors for the self-renewal and differentiation of ESCs. In this review, we will focus on the role of miRNAs in the self-renewal and directional differentiation of ESCs. We will present the current knowledge on key points related to miRNA biogenesis and their function in ESCs.

miR-335 correlates with senescence/aging in human mesenchymal stem cells and inhibits their therapeutic actions through inhibition of AP-1 activity

MicroRNAs, small noncoding RNAs, regulate gene expression primarily at the posttranscriptional level. We previously found that miR-335 is critically involved in the regulation and differentiation capacity of human mesenchymal stem cells (hMSCs) in vitro. In this study, we investigated the significance of miR-335 for the therapeutic potential of hMSCs. Analysis of hMSCs in ex vivo culture demonstrated a significant and progressive increase in miR-335 that is prevented by telomerase. Expression levels of miR-335 were also positively correlated with donor age of hMSCs, and were increased by stimuli that induce cell senescence, such as γ-irradiation and standard O2 concentration. Forced expression of miR-335 resulted in early senescence-like alterations in hMSCs, including: increased SA-β-gal activity and cell size, reduced cell proliferation capacity, augmented levels of p16 protein, and the development of a senescence-associated secretory phenotype. Furthermore, overexpression of miR-335 abolished the in vivo chondro-osseous potential of hMSCs, and disabled their immunomodulatory capacity in a murine experimental model of lethal endotoxemia. These effects were accompanied by a severely reduced capacity for cell migration in response to proinflammatory signals and a marked reduction in Protein Kinase D1 phosphorylation, resulting in a pronounced decrease of AP-1 activity. Our results demonstrate that miR-335 plays a key role in the regulation of reparative activities of hMSCs and suggests that it might be considered a marker for the therapeutic potency of these cells in clinical applications.

MicroRNA-29a inhibits mesenchymal stem cell viability and proliferation by targeting Roundabout 1

Secreted Slit glycoproteins and their Roundabout (Robo) receptors have been identified as important axon guidance molecules. The pivotal role of Slit‑Robo signaling is in regulating cell proliferation. MicroRNAs (miRNAs), a class of small non‑coding RNAs, function as critical regulators of gene expression by binding to the 3'‑untranslated region of mRNAs and causing mRNA degradation or translational repression. The present study demonstrated that downregulation of Robo1 using small interfering RNA inhibited mesenchymal stem cell (MSC) proliferation. Additionally, four miRNAs (miR), including miR‑218, miR‑29a, miR‑146 and miR‑148, inhibited the protein expression of Robo1 in the MSCs, with miR‑29 having the most marked effect. A luciferase reporter assay identified Robo1 as a novel target of miR‑29a. Overexpression of miR‑29a suppressed the protein expression levels of Robo1 and Slit2 and inhibited the viability and proliferation of the MSCs. By contrast, overexpression of Robo1 partly rescued these inhibitory effects of miR‑29a on the MSCs confirming that miR‑29a inhibited MSC viability and proliferation, at least partially, by directly targeting Robo1. These results indicated that the miR‑29a/Robo1 axis is crucial for the regulation of MSC viability and proliferation, suggesting that miR‑29a may serve as a potential clinical target for MSC expansion and stem cell transplantation.

Regulation of Fanconi anemia protein FANCD2 monoubiquitination by miR-302

Fanconi anemia (FA) is a recessively inherited multigene disease characterized by congenital defects, progressive bone marrow failure, and heightened cancer susceptibility. Monoubiquitination of the FA pathway member FANCD2 contributes to the repair of replication stalling DNA lesions. However, cellular regulation of FANCD2 monoubiquitination remains poorly understood. In the present study, we identified the miR-302 cluster as a potential regulator of FANCD2 by bioinformatics analysis. MicroRNAs (miRNAs) are the major posttranscriptional regulators of a wide variety of biological processes, and have been implicated in a number of diseases. Expression of the exogenous miR-302 cluster (without miR-367) reduced FANCD2 monoubiquitination and nuclear foci formation. Furthermore, miR-302 cells showed extensive chromosomal breakage upon MMC treatment when compared to mock control cells. Taken together, our results suggest that overexpression of miR-302 plays a critical role in the regulation of FANCD2 monoubiquitination, resulting in characteristic defects in DNA repair within cells.

Low expression of miR-449 in gynecologic clear cell carcinoma

Clinical detection of ovarian clear cell carcinomas is important because of the poor prognosis. To identify microRNA profiles specific for clear cell carcinomas, microRNA expression profiles were compared between clear cell carcinomas and serous carcinomas of the ovary using microRNA microarray. In parallel, clear cell carcinomas were compared with germ cell tumors of the ovary. Six microRNAs differentially expressed between ovarian clear cell and serous carcinomas distinguished uterine clear cell carcinomas from endometrioid carcinomas. MiR-449 was underexpressed in both ovarian and uterine clear cell carcinomas. When germ cell tumors were compared with clear cell carcinomas of the ovary, miR-302d was the most significantly overexpressed microRNA in germ cell tumors. Thus, here we describe microRNA profiles characteristic for clear cell carcinomas of the ovary and uterus.

Temporal and Spatial Expression Patterns of miR-302 and miR-367 During Early Embryonic Chick Development

The microRNAs (miRNAs) are small, non-coding RNAs that modulate protein expression by interfering with target mRNA translation or stability. miRNAs play crucial roles in various functions such as cellular, developmental, and physiological processes. The spatial expression patterns of miRNAs are very essential for identifying their functions. The expressions of miR-302 and miR-367 are critical in maintaining stemness of pluripotent stem cells, including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) but their functions in early development are not fully elucidated. So, we used Locked Nucleic Acid (LNA) probes to perform in situ hybridization and confirmed the temporal and spatial distribution patterns during early chick development. As a result, we found that miR-302 and miR-367 were expressed in various tissues such as primitive steak, neural ectoderm, neural plate, neural fold, neural tube, notochord, and oral cavity. Specially, we confirmed that miR-302 and miR-367 were strongly expressed in neural folds in HH8 to HH10. miR-302 was expressed on dorsal part of the neural tube but miR-367 was expressed on lateral and ventral parts of the neural tube. And also we performed quantitative stem-loop real-time PCR to analyze global expression level of miR-302 and miR-367. miR-302 and miR-367 expression was sustained before Hamburger and Hamilton stage (HH) 14. Thus, the temporal and spatial expression patterns of miR-302 and miR-367 may provide us information of the role of these miRNAs on tissue formation during early chick development.

Chitosan combined with molecular beacon for mir-155 detection and imaging in lung cancer

Lung cancer is the major cause of cancer-related deaths worldwide, thus developing effective methods for its early diagnosis is urgently needed. In recent years, microRNAs (miRNAs, miR) have been reported to play important roles in carcinogenesis and have become potential biomarkers for cancer diagnosis and treatment. Molecular beacon (MB) technology is a universal technology to detect DNA/RNA expression in living cells. As a natural polymers, chitosan (CS) nanoparticles could be used as a carrier for safe delivery of nucleic acid. In this study, we developed a probe using nanoparticles of miR-155 MB self assembled with CS (CS-miR-155 MB) to image the expression of miR-155 in cancer cells. Hybridization assay showed that the locked nucleic acid (LAN) modified miR-155 MB could target miR-155 effectively and sensitively. The miR-155 MB self-assembly with CS nanoparticles formed stable complexes at the proper weight ratio. The CS nanoparticles showed higher fluorescence intensity and transfection efficiency than the lipid-based formulation transfection agent by confocal microscopy and flow cytometry analysis. The CS-MB complexes were found to be easily synthesized and exhibited strong enzymatic stability, efficient cellular uptake, high target selectivity and biocompatibility. The CS-MB complexes can also be applied in other cancers just by simply changing for a targeted miRNA highly expressed in those cancer cells. Therefore, it is a promising vehicle used for detecting miRNA expression in living cells.

PAX6 downregulates miR-124 expression to promote cell migration during embryonic stem cell differentiation

PAX6-null mice exhibit defects in multiple organs leading to neonatal lethality, but the mechanism by which this occurs has not yet fully elucidated. In this study, we generated induced pluripotent stem cells (iPSCs) from Pax6-mutant mice and investigated the effect of PAX6 on cell fate during embryoid body (EB) formation. We found that PAX6 promotes cell migration by directly downregulating miR-124, which is important for the fate transition of migratory cells during gastrulation of embryonic stem (ES) cells. Although several downstream targets of miR-124 have been reported, little is known regarding the upstream regulation of miR-124. When we observed EB formation of iPSCs from Pax6-mutant mice, we found that higher levels of miR-124 in Pax6 homozygous EBs (Homo-EBs) inhibited cell migration, whereas inhibition of miR-124 in Homo-EBs rescued the migratory phenotypes associated with PAX6 deficiency. Further, we found that PAX6 binds to the promoter regions of the miR-124-3 gene and directly represses its expression. Therefore, we propose a novel PAX6-miR-124 pathway that controls ES cell migration. Our findings may provide important information for studies on ES cell differentiation and embryonic development.

Profiling of microRNA in human and mouse ES and iPS cells reveals overlapping but distinct microRNA expression patterns

Using quantitative PCR-based miRNA arrays, we comprehensively analyzed the expression profiles of miRNAs in human and mouse embryonic stem (ES), induced pluripotent stem (iPS), and somatic cells. Immature pluripotent cells were purified using SSEA-1 or SSEA-4 and were used for miRNA profiling. Hierarchical clustering and consensus clustering by nonnegative matrix factorization showed two major clusters, human ES/iPS cells and other cell groups, as previously reported. Principal components analysis (PCA) to identify miRNAs that segregate in these two groups identified miR-187, 299-3p, 499-5p, 628-5p, and 888 as new miRNAs that specifically characterize human ES/iPS cells. Detailed direct comparisons of miRNA expression levels in human ES and iPS cells showed that several miRNAs included in the chromosome 19 miRNA cluster were more strongly expressed in iPS cells than in ES cells. Similar analysis was conducted with mouse ES/iPS cells and somatic cells, and several miRNAs that had not been reported to be expressed in mouse ES/iPS cells were suggested to be ES/iPS cell-specific miRNAs by PCA. Comparison of the average expression levels of miRNAs in ES/iPS cells in humans and mice showed quite similar expression patterns of human/mouse miRNAs. However, several mouse- or human-specific miRNAs are ranked as high expressers. Time course tracing of miRNA levels during embryoid body formation revealed drastic and different patterns of changes in their levels. In summary, our miRNA expression profiling encompassing human and mouse ES and iPS cells gave various perspectives in understanding the miRNA core regulatory networks regulating pluripotent cells characteristics.

A Single Nucleotide Polymorphism within the Interferon Gamma Receptor 2 Gene Perfectly Coincides with Polledness in Holstein Cattle

Polledness is a high impact trait in modern milk and beef production to meet the demands of animal welfare and work safety. Previous studies have mapped the polled-locus to the proximal region of the bovine chromosome 1 (BTA1) and narrowed it down to approximately 1 Mb. Sequencing of the positional candidate genes within the 1 Mb polled region and whole genome sequencing of Holsteins revealed a single nucleotide polymorphism (SNP) AC000158: g.1390292G>A within intron 3 of the interferon gamma receptor 2 gene (IFNGR2) in perfect co-segregation with polledness in Holsteins. This complete association was validated in 443 animals of the same breed. This SNP allows reliable genotyping of horned, heterozygous and homozygous polled Holsteins, even in animals that could not be resolved using the previously published haplotype for Holstein.

Epigenetic signatures in stem cells and cancer stem cells

The physiological properties of pluripotency in stem cells and the processes of cell specialization are governed by epigenetic mechanisms, as they are inheritable but not dependent on the cell genotype. There is cumulating evidence demonstrating the presence of cells with stem cell properties within tumors, suggesting that these cells are responsible for tumor growth and heterogeneity. As epigenetic control of self-renewal and pluripotency is a hallmark of stem cells, there is increased interest in studying similar epigenetic mechanisms governing these stemness properties in cancer stem cells. Here we will review the evidence supporting a role for epigenetic mechanisms in the induction of cancer stem cells, with an emphasis on the epigenetic regulatory networks involved in the establishment of normal self-renewal and pluripotency, and their potential deregulation in cancer. We will also discuss the data supporting the plasticity of these mechanisms and its potential therapeutic implications.

Developing assays to address identity, potency, purity and safety: cell characterization in cell therapy process development

A major challenge to commercializing cell-based therapies is developing scalable manufacturing processes while maintaining the critical quality parameters (identity, potency, purity, safety) of the final live cell product. Process development activities such as extended passaging and serum reduction/elimination can facilitate the streamlining of cell manufacturing process as long as the biological functions of the product remain intact. Best practices in process development will be dependent on cell characterization; a thorough understanding of the cell-based product. Unique biological properties associated with different types of cell-based products are discussed. Cell characterization may be used as a tool for successful process development activities, which can promote a candidate cell therapy product through clinical development and ultimately to a commercialized product.

Integrating post-transcriptional regulation into the embryonic stem cell gene regulatory network

Stem cell behavior is orchestrated as a multilayered, concert of gene regulatory mechanisms collectively referred to as the gene regulatory network (GRN). Via cooperative mechanisms, transcriptional, epigenetic, and post-transcriptional regulators activate and repress gene expression to finely regulate stem cell self-renewal and commitment. Due to their tractability, embryonic stem cells (ESCs) serve as the model stem cell to dissect the complexities of the GRN, and discern its relation to stem cell fate. By way of high-throughput genomic analysis, targets of individual gene regulators have been established in ESCs. The compilation of these discrete networks has revealed convergent, multi-dimensional gene regulatory mechanisms involving transcription factors, epigenetic modifiers, non-coding RNA (ncRNA), and RNA-binding proteins. Here we highlight the seminal genomic studies that have shaped our understanding of the ESC GRN and describe alternate post-transcriptional gene regulatory mechanisms that require in depth analyses to draft networks that fully model ESC behavior.

MicroRNAs regulating cell pluripotency and vascular differentiation

Human embryonic stem cells (hESC) offer broad potential for regenerative medicine owing to their capacity for self renewal, exponential scale up and differentiation into any cell type in the adult body. hESC have been proposed as a potentially unlimited source for the generation of transplantable, healthy, functional vascular cells for repair of ischemic tissues. To optimally harness this potential necessitates precise control over biological processes that govern maintenance, pluripotency and cell differentiation including signalling cascades, gene expression profiles and epigenetic modification. Such control may be elicited by microRNAs, which are powerful negative regulators of gene expression. Here, we review the role for miRNAs in both the maintenance of pluripotency and differentiation of cells to a cardiovascular lineage including endothelial cells, vascular smooth muscle cells and cardiomyocytes and put this into context for regenerative medicine in the cardiovascular system.

The function of e-cadherin in stem cell pluripotency and self-renewal

Embryonic stem (ES) and induced-pluripotent stem (iPS) cells can be grown indefinitely under appropriate conditions whilst retaining the ability to differentiate to cells representative of the three primary germ layers. Such cells have the potential to revolutionize medicine by offering treatment options for a wide range of diseases and disorders as well as providing a model system for elucidating mechanisms involved in development and disease. In recent years, evidence for the function of E-cadherin in regulating pluripotent and self-renewal signaling pathways in ES and iPS cells has emerged. In this review, we discuss the function of E-cadherin and its interacting partners in the context of development and disease. We then describe relevant literature highlighting the function of E-cadherin in establishing and maintaining pluripotent and self-renewal properties of ES and iPS cells. In addition, we present experimental data demonstrating that exposure of human ES cells to the E-cadherin neutralizing antibody SHE78.7 allows culture of these cells in the absence of FGF2-supplemented medium.

miR-124a is important for migratory cell fate transition during gastrulation of human embryonic stem cells

Precise control of gene expression is of paramount importance for proper embryonic development. Although a number of microRNAs (miRNAs) has been implicated in fine-tuning mRNA translation during development, their exact roles for gastrulation, particularly in connection with functional targets, have yet to be clarified, with regard to stage-specific cell migration to form three embryonic germ layers. We found that miR-124a is expressed in human embryonic stem cells (hESC), but is gradually downregulated during embryoid body (EB) formation in vitro. We also provide evidence that SLUG and IQGAP1, which modulates rearrangement of the migratory cytoskeleton, are specific targets for miR-124a during EB formation. Furthermore, we show that the beginning of cell migration, a hallmark event in gastrulation, is tightly coupled with downregulation of miR-124a during EB formation and induction of SLUG and IQGAP1. Overexpressed miR-124a in hESC reduced expression of SLUG and IQGAP1 and blocked migratory cell behavior in EB. An expression level of MIXL1, associated with gastulation process, was also inversely correlated with expression of miR-124a. Taken together, our results strongly suggest that miR-124a may play an active role in inhibiting hESCs from differentiation into EB by downregulating expression of SLUG and IQGAP1, thereby maintaining stemness.

Emerging roles of microRNAs in the control of embryonic stem cells and the generation of induced pluripotent stem cells

MicroRNAs (miRNAs) have emerged as critical regulators of gene expression. These small, non-coding RNAs are believed to regulate more than a third of all protein coding genes, and they have been implicated in the control of virtually all biological processes, including the biology of stem cells. The essential roles of miRNAs in the control of pluripotent stem cells were clearly established by the finding that embryonic stem (ES) cells lacking proteins required for miRNA biogenesis exhibit defects in proliferation and differentiation. Subsequently, the function of numerous miRNAs has been shown to control the fate of ES cells and to directly influence critical gene regulatory networks controlled by pluripotency factors Sox2, Oct4, and Nanog. Moreover, a growing list of tissue-specific miRNAs, which are silenced or not processed fully in ES cells, has been found to promote differentiation upon their expression and proper processing. The importance of miRNAs for ES cells is further indicated by the exciting discovery that specific miRNA mimics or miRNA inhibitors promote the reprogramming of somatic cells into induced pluripotent stem (iPS) cells. Although some progress has been made during the past two years in our understanding of the contribution of specific miRNAs during reprogramming, further progress is needed since it is highly likely that miRNAs play even wider roles in the generation of iPS cells than currently appreciated. This review examines recent developments related to the roles of miRNAs in the biology of pluripotent stem cells. In addition, we posit that more than a dozen additional miRNAs are excellent candidates for influencing the generation of iPS cells as well as for providing new insights into the process of reprogramming.

Identification of an intermediate state as spermatogonial stem cells reprogram to multipotent cells

The aim of this study was to understand the mechanisms that allow mSSC lines to be established from SSCs. Small, multilayer clumps of SSCs formed during two to four weeks of in vitro culture and were then transferred to MEF feeders. Small, round, monolayer colonies containing cells destined to convert to mSSCs, designated as intermediate state SSCs (iSSCs), first appeared after two to three passages. During an additional nine passages (47-54 days) under the same culture conditions, iSSCs slowly proliferated and maintained their morphology. Ultimately, a cell type with an ES-like morphology (mSSC) appeared from the iSSC colonies, and two mSSC cell lines were established. The mSSCs had a high proliferative potential in serum-free ES culture medium and have been successfully maintained since their first establishment (> 12 months). We also compared the specific characteristics of iSSCs with those of SSCs and mSSCs using immunocytochemistry, FACS, RT-PCR, DNA methylation, and miRNA analyses. The results suggest that iSSCs represent a morphologically distinct intermediate state with characteristic expression patterns of pluripotency-related genes and miRNAs that arise during the conversion of SSCs into mSSCs. Our results suggest that iSSCs could be a useful model for evaluating and understanding the initiation mechanisms of cell reprogramming.

Function of microRNA-375 and microRNA-124a in pancreas and brain

In recent years, our understanding of how gene regulatory networks control cell physiology has improved dramatically. Studies have demonstrated that transcription is regulated not only by protein factors, but also by small RNA molecules, microRNAs (miRNAs). The first miRNA was discovered in 1993 as a result of a genetic screen for mutations in Caenorhabditis elegans. Since then, the use of sophisticated techniques and screening tools has promoted a more definitive understanding of the role of miRNAs in mammalian development and diseases. miRNAs have emerged as important regulators of genes involved in many biological processes, including development, cell proliferation and differentiation, apoptosis and metabolism. Over the last few years, the number of reviews dealing with miRNAs has increased at an impressive pace. In this review, we present general information on miRNA biology and focus more closely on comparing the expression, regulation and molecular functions of the two miRNAs, miR-375 and miR-124a. miR-375 and miR-124a share similar features; they are both specifically expressed in the pancreas and brain and directly bind a common target gene transcript encoding myotrophin, which regulates exocytosis and hormone release. Here, we summarize the available data obtained by our group and other laboratories and provide an overview of the specific molecular function of miR-375 and miR-124a in the pancreas and the brain, revealing a potential functional overlap for these two miRNAs and the emerging therapeutic potential of miRNAs in the treatment of human metabolic diseases.

Concerted stimuli regulating osteo-chondral differentiation from stem cells: phenotype acquisition regulated by microRNAs

Bone and cartilage are being generated de novo through concerted actions of a plethora of signals. These act on stem cells (SCs) recruited for lineage-specific differentiation, with cellular phenotypes representing various functions throughout their life span. The signals are rendered by hormones and growth factors (GFs) and mechanical forces ensuring proper modelling and remodelling of bone and cartilage, due to indigenous and programmed metabolism in SCs, osteoblasts, chondrocytes, as well as osteoclasts and other cell types (eg T helper cells).This review focuses on the concerted action of such signals, as well as the regulatory and/or stabilizing control circuits rendered by a class of small RNAs, designated microRNAs. The impact on cell functions evoked by transcription factors (TFs) via various signalling molecules, also encompassing mechanical stimulation, will be discussed featuring microRNAs as important members of an integrative system. The present approach to cell differentiation in vitro may vastly influence cell engineering for in vivo tissue repair.

MicroRNAs in normal and malignant myelopoiesis

MicroRNAs (miRNAs) are a class of non-coding protein, single-stranded RNA of 18-22 nucleotides, that exert their actions at post-transcriptional level, mostly through base pairing with the 3'-untranslated region of the target mRNA, thus leading to its translational repression and/or degradation. Recent studies have shown that miRNAs play a crucial role in normal hematopoiesis through the control of the expression of key regulators of hematopoiesis (i.e., transcription factors, growth factor receptors, chemokine receptors), involving regulatory loops that selectively operate in the various hematopoietic lineages. Extensive miRNA deregulation has been observed in leukemia and functional studies support a role for miRNAs in the pathogenesis of these disorders.