Notch-dependent repression of miR-155 in the bone marrow niche regulates hematopoiesis in an NF-κB-dependent manner

Surgical preparation of rats and mice for intravital microscopic imaging of abdominal organs

Intravital microscopy is a powerful research tool that can provide insight into cellular and subcellular events that take place in organs in the body. However, meaningful results can only be obtained from animals whose physiology is preserved during the process of microscopy. Here I discuss the importance of preserving the overall state of health of the animal, methods of anesthesia, surgical techniques for intravital microscopy of various abdominal organs, methods to maintain and monitor the physiology of the animal during microscopy and associated peri- and post-operative recovery considerations.

Context-dependent function of ROS in the vascular endothelium: The role of the Notch pathway and shear stress

Reactive oxygen species (ROS) act as signal molecules in several biological processes whereas excessive, unregulated, ROS production contributes to the development of pathological conditions including endothelial dysfunction and atherosclerosis. The maintenance of a healthy endothelium depends on many factors and on their reciprocal interactions; in this framework, the Notch pathway and shear stress (SS) play two lead roles. Recently, evidence of a crosstalk between ROS, Notch, and SS, is emerging. The aim of this review is to describe the way ROS interact with the Notch pathway and SS protecting from-or promoting-the development of endothelial dysfunction. © 2017 BioFactors, 43(4):475-485, 2017.

MicroRNAs as regulatory elements in immune system logic

MicroRNAs (miRNAs) are crucial post-transcriptional regulators of haematopoietic cell fate decisions. They act by negatively regulating the expression of key immune development genes, thus contributing important logic elements to the regulatory circuitry. Deletion studies have made it increasingly apparent that they confer robustness to immune cell development, especially under conditions of environmental stress such as infectious challenge and ageing. Aberrant expression of certain miRNAs can lead to pathological consequences, such as autoimmunity and haematological cancers. In this Review, we discuss the mechanisms by which several miRNAs influence immune development and buffer normal haematopoietic output, first at the level of haematopoietic stem cells, then in innate and adaptive immune cells. We then discuss the pathological consequences of dysregulation of these miRNAs.

Adult haematopoietic stem cell niches

Stem cell niches are specialized microenvironments that promote the maintenance of stem cells and regulate their function. Recent advances have improved our understanding of the niches that maintain adult haematopoietic stem cells (HSCs). These advances include new markers for HSCs and niche cells, systematic analyses of the expression patterns of niche factors, genetic tools for functionally identifying niche cells in vivo, and improved imaging techniques. Together, they have shown that HSC niches are perivascular in the bone marrow and spleen. Endothelial cells and mesenchymal stromal cells secrete factors that promote HSC maintenance in these niches, but other cell types also directly or indirectly regulate HSC niches.

Notch Represses Transcription by PRC2 Recruitment to the Ternary Complex

It is well established that Notch functions as a transcriptional activator through the formation of a ternary complex that comprises Notch, Maml, and CSL. This ternary complex then serves to recruit additional transcriptional cofactors that link to higher order transcriptional complexes. The mechanistic details of these events remain unclear. This report reveals that the Notch ternary complex can direct the formation of a repressor complex to terminate gene expression of select target genes. Herein, it is demonstrated that p19^Arf and Klf4 are transcriptionally repressed in a Notch-dependent manner. Furthermore, results indicate that Notch recruits Polycomb Repressor Complex 2 (PRC2) and Lysine Demethylase 1 (KDM1A/LSD1) to these promoters, which leads to changes in the epigenetic landscape and repression of transcription. The demethylase activity of LSD1 is a prerequisite for Notch-mediated transcriptional repression. In addition, a stable Notch transcriptional repressor complex was identified containing LSD1, PRC2, and the Notch ternary complex. These findings demonstrate a novel function of Notch and provide further insight into the mechanisms of Notch-mediated tumorigenesis.Implications: This study provides rationale for the targeting of epigenetic enzymes to inhibit Notch activity or use in combinatorial therapy to provide a more profound therapeutic response. Mol Cancer Res; 15(9); 1173-83. ©2017 AACR.

Extrinsic regulation of hematopoietic stem cells in development, homeostasis and diseases

Lifelong generation of blood and immune cells depends on hematopoietic stem cells (HSCs). Their function is precisely regulated by complex molecular networks that integrate and respond to ever changing physiological demands of the body. Over the past several years, significant advances have been made in understanding the extrinsic regulation of HSCs during development and in homeostasis. Propelled by technical advances in the field, the cellular and molecular components of the microenvironment that support HSCs in vivo are emerging. In addition, the interaction of HSCs with their niches is appreciated as a critical contributor to the pathogenesis of a number of hematologic disorders. Here, we review these advances in detail and highlight the extrinsic regulation of HSCs in the context of development, homeostasis, and diseases. WIREs Dev Biol 2017, 6:e279. doi: 10.1002/wdev.279 For further resources related to this article, please visit the WIREs website.

Tuning of major signaling networks (TGF-β, Wnt, Notch and Hedgehog) by miRNAs in human stem cells commitment to different lineages: Possible clinical application

Two distinguishing characteristics of stem cells, their continuous division in the undifferentiated state and growth into any cell types, are orchestrated by a number of cell signaling pathways. These pathways act as a niche factor in controlling variety of stem cells. The core stem cell signaling pathways include Wingless-type (Wnt), Hedgehog (HH), and Notch. Additionally, they critically regulate the self-renewal and survival of cancer stem cells. Conversely, stem cells' main properties, lineage commitment and stemness, are tightly controlled by epigenetic mechanisms such as DNA methylation, histone modifications and non-coding RNA-mediated regulatory events. MicroRNAs (miRNAs) are cellular switches that modulate stem cells outcomes in response to diverse extracellular signals. Numerous scientific evidences implicating miRNAs in major signal transduction pathways highlight new crosstalks of cellular processes. Aberrant signaling pathways and miRNAs levels result in developmental defects and diverse human pathologies. This review discusses the crosstalk between the components of main signaling networks and the miRNA machinery, which plays a role in the context of stem cells development and provides a set of examples to illustrate the extensive relevance of potential novel therapeutic targets.

Distinct gene expression profiles associated with Notch ligands Delta-like 4 and Jagged1 in plaque material from peripheral artery disease patients: a pilot study

Background

The lack of early diagnosis, progression markers and effective pharmacological treatment has dramatic unfavourable effects on clinical outcomes in patients with peripheral artery disease (PAD). Addressing these issues will require dissecting the molecular mechanisms underlying this disease. We sought to characterize the Notch signaling and atherosclerosis relevant markers in lesions from femoral arteries of symptomatic PAD patients.

Methods

Plaque material from the common femoral, superficial femoral or popliteal arteries of 20 patients was removed by directional atherectomy. RNA was obtained from 9 out of 20 samples and analysed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR).

Results

We detected expression of Notch ligands Delta-like 4 (Dll4) and Jagged1 (Jag1), of Notch target genes Hes1, Hey1, Hey2, HeyL and of markers of plaque inflammation and stability such as vascular cell adhesion molecule 1 (VCAM1), smooth muscle 22 (SM22), cyclooxygenase 2 (COX2), Bcl2, CD68 and miRNAs 21-5p, 125a-5p, 126-5p,146-5p, 155-5p, 424-5p. We found an “inflamed plaque” gene expression profile characterized by high Dll4 associated to medium/high CD68, COX2, VCAM1, Hes1, miR126-5p, miR146a-5p, miR155-5p, miR424-5p and low Jag1, SM22, Bcl2, Hey2, HeyL, miR125a-5p (2/9 patients) and a “stable plaque” profile characterized by high Jag1 associated to medium/high Hey2, HeyL, SM22, Bcl2, miR125a and low Dll4, CD68, COX2, VCAM1, miR126-5p, miR146a-5p, miR155-5p, miR424-5p (3/9 patients). The remaining patients (4/9) showed a plaque profile with intermediate characteristics.

Conclusions

This study reveals the existence of a gene signature associated to Notch activation by specific ligands that could be predictive of PAD progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1199-3) contains supplementary material, which is available to authorized users.

MicroRNA-155-5p promotes hepatocellular carcinoma progression by suppressing PTEN through the PI3K/Akt pathway

MicroRNA‐155‐5p (miR‐155‐5p) has been reported to play an oncogenic role in different human malignancies; however, its role in hepatocellular carcinoma (HCC) progression is not clearly understood. In this study, we used real‐time PCR in 20 rats with chemically‐induced HCC, 28 human HCC tissues, and the matched paracarcinoma tissues, and HCC cell lines to determine the expression patterns of miR‐155‐5p and PTEN mRNA. Algorithm‐based and experimental strategies, such as dual luciferase gene reporter assays, real‐time PCR and western blots were used to identify PTEN as a candidate miR‐155‐5p target. Gain‐ and loss‐of‐function experiments and administration of a PI3K/Akt pathway inhibitor (wortmannin) were used to identify the effects of miR‐155‐5p and PTEN in MTT assays, flow cytometric analysis, wound healing assays and transwell assays. The results showed that miR‐155‐5p was highly overexpressed; however, PTEN was underexpressed in the HCC rat models, human HCC tissues and cell lines. In addition, miR‐155‐5p upregulation and PTEN downregulation were significantly associated with TNM stage (P < 0.05). Through in vitro experiments, we found that miR‐155‐5p promoted proliferation, invasion and migration, but inhibited apoptosis in HCC by directly targeting the 3′‐UTR of PTEN. Western blots showed that miR‐155‐5p inactivated Bax and caspase‐9, but activated Bcl‐2 to inhibit apoptosis, and it activated MMP to promote migration and invasion via the PI3K/Akt pathway. A xenograft tumor model was used to demonstrate that miR‐155‐5p targets PTEN and activates the PI3K/Akt pathway in vivo as well. Our study highlighted the importance of miR‐155‐5p and PTEN associated with aggressive HCC both in vitro and in vivo.

miR-155 Inhibits Mouse Osteoblast Differentiation by Suppressing SMAD5 Expression

Osteogenesis from preosteoblasts is important for bone tissue engineering. MicroRNAs are a class of endogenous small RNA molecules that potentially modulate osteogenesis. In this study, we found that miR-155 expression was downregulated in a time-dependent manner in cells of the preosteoblast cell line MC3T3-E1 after osteogenic induction using bone morphogenetic protein 2 (BMP2). Transfection with miR-155 decreased alkaline phosphatase (ALP) activity, ALP expression, and the staining intensity of Alizarin Red in MC3T3-E1 cells treated with BMP2, whereas treatment with miR-155 inhibitor promoted BMP2-induced osteoblast differentiation. The luciferase assay confirmed that miR-155 can bind to the 3′ untranslated region of SMAD5 mRNA. miR-155 transfection significantly decreased the expression of SMAD5 protein and mRNA in MC3T3-E1 cells under control media and the p-SMAD5 protein level during osteogenesis. After transfecting cells with the SMAD5 overexpression plasmids, the inhibitory effect of miR-155 on osteogenesis was significantly attenuated. In conclusion, miR-155 inhibited osteoblast differentiation by downregulating the translation of SMAD5 in mouse preosteoblast cells. Inhibition of miR-155 promoted osteogenic potential and thus it can be used as a potential target in the treatment of bone defects.

Combining Intravital Fluorescent Microscopy (IVFM) with Genetic Models to Study Engraftment Dynamics of Hematopoietic Cells to Bone Marrow Niches

Increasing evidence indicates that normal hematopoiesis is regulated by distinct microenvironmental cues in the BM, which include specialized cellular niches modulating critical hematopoietic stem cell (HSC) functions^1,2. Indeed, a more detailed picture of the hematopoietic microenvironment is now emerging, in which the endosteal and the endothelial niches form functional units for the regulation of normal HSC and their progeny^3,4,5. New studies have revealed the importance of perivascular cells, adipocytes and neuronal cells in maintaining and regulating HSC function^6,7,8. Furthermore, there is evidence that cells from different lineages, i.e. myeloid and lymphoid cells, home and reside in specific niches within the BM microenvironment. However, a complete mapping of the BM microenvironment and its occupants is still in progress. Transgenic mouse strains expressing lineage specific fluorescent markers or mice genetically engineered to lack selected molecules in specific cells of the BM niche are now available. Knock-out and lineage tracking models, in combination with transplantation approaches, provide the opportunity to refine the knowledge on the role of specific "niche" cells for defined hematopoietic populations, such as HSC, B-cells, T-cells, myeloid cells and erythroid cells. This strategy can be further potentiated by merging the use of two-photon microscopy of the calvarium. By providing in vivo high resolution imaging and 3-D rendering of the BM calvarium, we can now determine precisely the location where specific hematopoietic subsets home in the BM and evaluate the kinetics of their expansion over time. Here, Lys-GFP transgenic mice (marking myeloid cells)⁹ and RBPJ knock-out mice (lacking canonical Notch signaling)¹⁰ are used in combination with IVFM to determine the engraftment of myeloid cells to a Notch defective BM microenvironment.

Myeloproliferative neoplasm stem cells

Myeloproliferative neoplasms (MPNs) arise in the hematopoietic stem cell (HSC) compartment as a result of the acquisition of somatic mutations in a single HSC that provides a selective advantage to mutant HSC over normal HSC and promotes myeloid differentiation to engender a myeloproliferative phenotype. This population of somatically mutated HSC, which initiates and sustains MPNs, is termed MPN stem cells. In >95% of cases, mutations that drive the development of an MPN phenotype occur in a mutually exclusive manner in 1 of 3 genes: JAK2, CALR, or MPL The thrombopoietin receptor, MPL, is the key cytokine receptor in MPN development, and these mutations all activate MPL-JAK-STAT signaling in MPN stem cells. Despite common biological features, MPNs display diverse disease phenotypes as a result of both constitutional and acquired factors that influence MPN stem cells, and likely also as a result of heterogeneity in the HSC in which MPN-initiating mutations arise. As the MPN clone expands, it exerts cell-extrinsic effects on components of the bone marrow niche that can favor the survival and expansion of MPN stem cells over normal HSC, further sustaining and driving malignant hematopoiesis. Although developed as targeted therapies for MPNs, current JAK2 inhibitors do not preferentially target MPN stem cells, and as a result, rarely induce molecular remissions in MPN patients. As the understanding of the molecular mechanisms underlying the clonal dominance of MPN stem cells advances, this will help facilitate the development of therapies that preferentially target MPN stem cells over normal HSC.

The microenvironment in human myeloid malignancies: emerging concepts and therapeutic implications

Similar to their healthy counterpart, malignant hematopoietic stem cells in myeloid malignancies, such as myeloproliferative neoplasms, myelodysplastic syndromes, and acute myeloid leukemia, reside in a highly complex and dynamic cellular microenvironment in the bone marrow. This environment provides key regulatory signals for and tightly controls cardinal features of hematopoietic stem cells (HSCs), including self-renewal, quiescence, differentiation, and migration. These features are essential to maintaining cellular homeostasis and blood regeneration throughout life. A large number of studies have extensively addressed the composition of the bone marrow niche in mouse models, as well as the cellular and molecular communication modalities at play under both normal and pathogenic situations. Although instrumental to interrogating the complex composition of the HSC niche and dissecting the niche remodeling processes that appear to actively contribute to leukemogenesis, these models may not fully recapitulate the human system due to immunophenotypic, architectural, and functional inter-species variability. This review summarizes several aspects related to the human hematopoietic niche: (1) its anatomical structure, composition, and function in normal hematopoiesis; (2) its alteration and functional relevance in the context of chronic and acute myeloid malignancies; (3) age-related niche changes and their suspected impact on hematopoiesis; (4) ongoing efforts to develop new models to study niche-leukemic cell interaction in human myeloid malignancies; and finally, (5) how the knowledge gained into leukemic stem cell (LSC) niche dependencies might be exploited to devise novel therapeutic strategies that aim at disrupting essential niche-LSC interactions or improve the regenerative ability of the disease-associated hematopoietic niche.

Protein Tyrosine Phosphatase PRL2 Mediates Notch and Kit Signals in Early T Cell Progenitors

The molecular pathways regulating lymphoid priming, fate, and development of multipotent bone marrow hematopoietic stem and progenitor cells (HSPCs) that continuously feed thymic progenitors remain largely unknown. While Notch signal is indispensable for T cell specification and differentiation, the downstream effectors are not well understood. PRL2, a protein tyrosine phosphatase that regulates hematopoietic stem cell proliferation and self-renewal, is highly expressed in murine thymocyte progenitors. Here we demonstrate that protein tyrosine phosphatase PRL2 and receptor tyrosine kinase c-Kit are critical downstream targets and effectors of the canonical Notch/RBPJ pathway in early T cell progenitors. While PRL2 deficiency resulted in moderate defects of thymopoiesis in the steady state, de novo generation of T cells from Prl2 null hematopoietic stem cells was significantly reduced following transplantation. Prl2 null HSPCs also showed impaired T cell differentiation in vitro. We found that Notch/RBPJ signaling upregulated PRL2 as well as c-Kit expression in T cell progenitors. Further, PRL2 sustains Notch-mediated c-Kit expression and enhances stem cell factor/c-Kit signaling in T cell progenitors, promoting effective DN1-DN2 transition. Thus, we have identified a critical role for PRL2 phosphatase in mediating Notch and c-Kit signals in early T cell progenitors. Stem Cells 2017;35:1053-1064.

Association between NF-κB Pathway Gene Variants and sICAM1 Levels in Taiwanese

Intercellular adhesion molecule–1 (ICAM1) is crucial to the development and progression of atherosclerosis. Recent genome-wide association studies (GWAS) have revealed that single nucleotide polymorphisms (SNPs) in two of the nuclear factor-κB (NF-κB) pathway genes, NFKBIK and RELA, are associated with soluble ICAM1 (sICAM1) levels. However, neither of these two gene variants is found in the Asian populations. This study aimed to elucidate whether other candidate gene variants involved in the NF-κB pathway may be associated with sICAM1 levels in Taiwanese. After excluding carriers of the ICAM1 rs5491-T allele, three SNPs in the ICAM1 gene and eight SNPs in six of the NF-κB pathway genes (NFKB1, PDCD11, TNFAIP3, NKAPL, IKBKE, and PRKCB) were analyzed for their association with sICAM1 levels in 480 individuals. Our data showed that two SNPs, rs5498 of ICAM1 and rs1635 of NKAPL, were significantly associated with sICAM1 levels (P = 0.002 and 0.004, respectively) in the Taiwanese population. Using a multivariate analysis, rs5498 and rs1635 as well as the previously reported ABO genotypes and rs12051272 of the CDH13 gene were independently associated with sICAM1 levels (P = 0.001, 0.001, 0.006 and 0.031, respectively). An analysis with combined risk alleles of four candidate SNPs in the ICAM1, NKAPL, ABO, and CDH13 genes showed an increase in sICAM1 levels with added numbers of risk alleles and weighted genetic risk score. Our findings thus expanded the repertoire of gene variants responsible for the regulation of sICAM1 levels in the Asian populations.

Endothelial-specific inhibition of NF-κB enhances functional haematopoiesis

Haematopoietic stem cells (HSCs) reside in distinct niches within the bone marrow (BM) microenvironment, comprised of endothelial cells (ECs) and tightly associated perivascular constituents that regulate haematopoiesis through the expression of paracrine factors. Here we report that the canonical NF-κB pathway in the BM vascular niche is a critical signalling axis that regulates HSC function at steady state and following myelosuppressive insult, in which inhibition of EC NF-κB promotes improved HSC function and pan-haematopoietic recovery. Mice expressing an endothelial-specific dominant negative IκBα cassette under the Tie2 promoter display a marked increase in HSC activity and self-renewal, while promoting the accelerated recovery of haematopoiesis following myelosuppression, in part through protection of the BM microenvironment following radiation and chemotherapeutic-induced insult. Moreover, transplantation of NF-κB-inhibited BM ECs enhanced haematopoietic recovery and protected mice from pancytopenia-induced death. These findings pave the way for development of niche-specific cellular approaches for the treatment of haematological disorders requiring myelosuppressive regimens.

The complex microenvironmental signalling pathways that govern haematopoietic stem cell (HSC) activity remain poorly defined. Here, the authors identify endothelial NF-κB signalling as regulating regenerative HSC function, accelerating haematopoietic recovery following myelosuppressive injury in mice.

Myeloid malignancies and the microenvironment

Research in the last few years has revealed a sophisticated interaction network between multiple bone marrow cells that regulate different hematopoietic stem cell (HSC) properties such as proliferation, differentiation, localization, and self-renewal during homeostasis. These mechanisms are essential to keep the physiological HSC numbers in check and interfere with malignant progression. In addition to the identification of multiple mutations and chromosomal aberrations driving the progression of myeloid malignancies, alterations in the niche compartment recently gained attention for contributing to disease progression. Leukemic cells can remodel the niche into a permissive environment favoring leukemic stem cell expansion over normal HSC maintenance, and evidence is accumulating that certain niche alterations can even induce leukemic transformation. Relapse after chemotherapy is still a major challenge during treatment of myeloid malignancies, and cure is only rarely achieved. Recent progress in understanding the niche-imposed chemoresistance mechanisms will likely contribute to the improvement of current therapeutic strategies. This article discusses the role of different niche cells and their stage- and disease-specific roles during progression of myeloid malignancies and in response to chemotherapy.

Leukaemogenic effects of Ptpn11 activating mutations in the stem cell microenvironment

Germline activating mutations of the protein tyrosine phosphatase SHP2 (encoded by PTPN11), a positive regulator of the RAS signalling pathway, are found in 50% of patients with Noonan syndrome. These patients have an increased risk of developing leukaemia, especially juvenile myelomonocytic leukaemia (JMML), a childhood myeloproliferative neoplasm (MPN). Previous studies have demonstrated that mutations in Ptpn11 induce a JMML-like MPN through cell-autonomous mechanisms that are dependent on Shp2 catalytic activity. However, the effect of these mutations in the bone marrow microenvironment remains unclear. Here we report that Ptpn11 activating mutations in the mouse bone marrow microenvironment promote the development and progression of MPN through profound detrimental effects on haematopoietic stem cells (HSCs). Ptpn11 mutations in mesenchymal stem/progenitor cells and osteoprogenitors, but not in differentiated osteoblasts or endothelial cells, cause excessive production of the CC chemokine CCL3 (also known as MIP-1α), which recruits monocytes to the area in which HSCs also reside. Consequently, HSCs are hyperactivated by interleukin-1β and possibly other proinflammatory cytokines produced by monocytes, leading to exacerbated MPN and to donor-cell-derived MPN following stem cell transplantation. Remarkably, administration of CCL3 receptor antagonists effectively reverses MPN development induced by the Ptpn11-mutated bone marrow microenvironment. This study reveals the critical contribution of Ptpn11 mutations in the bone marrow microenvironment to leukaemogenesis and identifies CCL3 as a potential therapeutic target for controlling leukaemic progression in Noonan syndrome and for improving stem cell transplantation therapy in Noonan-syndrome-associated leukaemias.

Notch, lipids, and endothelial cells

PURPOSE OF REVIEW

Notch signaling is an evolutionary conserved pathway critical for cardiovascular development and angiogenesis. More recently, the contribution of Notch signaling to the homeostasis of the adult vasculature has emerged as an important novel paradigm, but much remains to be understood.

RECENT FINDINGS

Recent findings shed light on the impact of Notch in vascular and immune responses to microenvironmental signals as well as on the onset of atherosclerosis. In the past year, studies in human and mice explored the role of Notch in the maintenance of a nonactivated endothelium. Novel pieces of evidence suggest that this pathway is sensitive to environmental factors, including inflammatory mediators and diet-derived by-products.

SUMMARY

An emerging theme is the ability of Notch to respond to changes in the microenvironment, including glucose and lipid metabolites. In turn, alterations in Notch enable an important link between metabolism and transcriptional changes, thus this receptor appears to function as a metabolic sensor with direct implications to gene expression.

Concise Review: The Malignant Hematopoietic Stem Cell Niche

Hematopoietic stem cell (HSC) proliferation, self-renewal, and trafficking are dependent, in part, upon signals generated by stromal cells in the bone marrow. Stromal cells are organized into niches that support specific subsets of hematopoietic progenitors. There is emerging evidence that malignant hematopoietic cells may generate signals that alter the number and/or function of specific stromal cell populations in the bone marrow. At least in some cases, the resulting alterations in the bone marrow microenvironment confer a competitive advantage to the malignant HSC and progenitor cells and/or render them less sensitive to chemotherapy. Targeting these signals represents a promising therapeutic strategy for selected hematopoietic malignancies. In this review, we focus on two questions. How do alterations in bone marrow stromal cells arise in hematopoietic malignancies, and how do they contribute to disease pathogenesis? Stem Cells 2017;35:3-8.

Aldehyde dehydrogenases inhibition eradicates leukemia stem cells while sparing normal progenitors

The vast majority of patients with acute myeloid leukemia (AML) achieve complete remission (CR) after standard induction chemotherapy. However, the majority subsequently relapse and die of the disease. A leukemia stem cell (LSC) paradigm has been invoked to explain this failure of CR to reliably translate into cure. Indeed, LSCs are highly enriched in CD34+CD38− leukemic cells that exhibit positive aldehyde dehydrogenase activity (ALDH+) on flow cytometry, these LSCs are resistant to currently existing treatments in AML such as cytarabine and anthracycline that, at the cost of great toxicity on normal cells, are highly active against the leukemic bulk, but spare the LSCs responsible for relapse. To try to combat the LSC population selectively, a well-characterized ALDH inhibitor by the trivial name of dimethyl ampal thiolester (DIMATE) was assessed on sorted CD34+CD38− subpopulations from AML patients and healthy patients. ALDH activity and cell viability were monitored by flow cytometry. From enzyme kinetic studies DIMATE is an active enzyme-dependent, competitive, irreversible inhibitor of ALDH1. On cells in culture, DIMATE is a powerful inhibitor of ALDHs 1 and 3, has a major cytotoxic activity on human AML cell lines. Moreover, DIMATE is highly active against leukemic populations enriched in LSCs, but, unlike conventional chemotherapy, DIMATE is not toxic for healthy hematopoietic stem cells which retained, after treatment, their self-renewing and multi-lineage differentiation capacity in immunodeficient mice, xenografted with human leukemic cells. DIMATE eradicates specifically human AML cells and spares healthy mouse hematologic cells.

MicroRNAs in Control of Stem Cells in Normal and Malignant Hematopoiesis

Studies on hematopoietic stem cells (HSCs) and leukemia stem cells (LSCs) have helped to establish the paradigms of normal and cancer stem cell concepts. For both HSCs and LSCs, specific gene expression programs endowed by their epigenome functionally distinguish them from their differentiated progenies. MicroRNAs (miRNAs), as a class of small non-coding RNAs, act to control post-transcriptional gene expression. Research in the past decade has yielded exciting findings elucidating the roles of miRNAs in control of multiple facets of HSC and LSC biology. Here we review recent progresses on the functions of miRNAs in HSC emergence during development, HSC switch from a fetal/neonatal program to an adult program, HSC self-renewal and quiescence, HSC aging, HSC niche, and malignant stem cells. While multiple different miRNAs regulate a diverse array of targets, two common themes emerge in HSC and LSC biology: miRNA mediated regulation of epigenetic machinery and cell signaling pathways. In addition, we propose that miRNAs themselves behave like epigenetic regulators, as they possess key biochemical and biological properties that can provide both stability and alterability to the epigenetic program. Overall, the studies of miRNAs in stem cells in the hematologic contexts not only provide key understandings to post-transcriptional gene regulation mechanisms in HSCs and LSCs, but also will lend key insights for other stem cell fields.

miR-9 and miR-124 synergistically affect regulation of dendritic branching via the AKT/GSK3β pathway by targeting Rap2a

A single microRNA (miRNA) can regulate expression of multiple proteins, and expression of an individual protein may be controlled by numerous miRNAs. This regulatory pattern strongly suggests that synergistic effects of miRNAs play critical roles in regulating biological processes. miR-9 and miR-124, two of the most abundant miRNAs in the mammalian nervous system, have important functions in neuronal development. In this study, we identified the small GTP-binding protein Rap2a as a common target of both miR-9 and miR-124. miR-9 and miR-124 together, but neither miRNA alone, strongly suppressed Rap2a, thereby promoting neuronal differentiation of neural stem cells (NSCs) and dendritic branching of differentiated neurons. Rap2a also diminished the dendritic complexity of mature neurons by decreasing the levels of pAKT and pGSK3β. Our results reveal a novel pathway in which miR-9 and miR-124 synergistically repress expression of Rap2a to sustain homeostatic dendritic complexity during neuronal development and maturation.

Forced Activation of Notch in Macrophages Represses Tumor Growth by Upregulating miR-125a and Disabling Tumor-Associated Macrophages

Tumor-associated macrophages (TAM) contribute greatly to hallmarks of cancer. Notch blockade was shown to arrest TAM differentiation, but the precise role and underlying mechanisms require elucidation. In this study, we employed a transgenic mouse model in which the Notch1 intracellular domain (NIC) is activated conditionally to define the effects of active Notch1 signaling in macrophages. NIC overexpression had no effect on TAM differentiation, but it abrogated TAM function, leading to repressed growth of transplanted tumors. Macrophage miRNA profiling identified a novel downstream mediator of Notch signaling, miR-125a, which was upregulated through an RBP-J-binding site at the first intronic enhancer of the host gene Spaca6A. miR-125a functioned downstream of Notch signaling to reciprocally influence polarization of M1 and M2 macrophages by regulating factor inhibiting hypoxia inducible factor-1α and IRF4, respectively. Notably, macrophages transfected with miR-125a mimetics increased phagocytic activity and repressed tumor growth by remodeling the immune microenvironment. We also identified a positive feedback loop for miR-125a expression mediated by RYBP and YY1. Taken together, our results showed that Notch signaling not only supported the differentiation of TAM but also antagonized their protumorigenic function through miR-125a. Targeting this miRNA may reprogram macrophages in the tumor microenvironment and restore their antitumor potential.

Normal and leukemic stem cell niches: insights and therapeutic opportunities

Hematopoietic stem cells (HSCs) rely on instructive cues from the bone marrow (BM) niche to maintain their quiescence and adapt blood production to the organism's needs. Alterations in the BM niche are commonly observed in blood malignancies and directly contribute to the aberrant function of disease-initiating leukemic stem cells (LSCs). Here, we review recent insights into the cellular and molecular determinants of the normal HSC niche and describe how genetic changes in stromal cells and leukemia-induced BM niche remodeling contribute to blood malignancies. Moreover, we discuss how these findings can be applied to non-cell-autonomous therapies targeting the LSC niche.

The hematopoietic stem cell niche in homeostasis and disease

The bone marrow microenvironment contains a heterogeneous population of stromal cells organized into niches that support hematopoietic stem cells (HSCs) and other lineage-committed hematopoietic progenitors. The stem cell niche generates signals that regulate HSC self-renewal, quiescence, and differentiation. Here, we review recent studies that highlight the heterogeneity of the stromal cells that comprise stem cell niches and the complexity of the signals that they generate. We highlight emerging data that stem cell niches in the bone marrow are not static but instead are responsive to environmental stimuli. Finally, we review recent data showing that hematopoietic niches are altered in certain hematopoietic malignancies, and we discuss how these alterations might contribute to disease pathogenesis.

Endothelial NOTCH1 is suppressed by circulating lipids and antagonizes inflammation during atherosclerosis

Briot et al. show that inflammatory lipids deriving from a high-fat diet suppress NOTCH1 expression and signaling in adult arterial endothelium and propose that reduction of endothelial NOTCH1 is a predisposing factor in the onset of atherosclerosis.

Although much progress has been made in identifying the mechanisms that trigger endothelial activation and inflammatory cell recruitment during atherosclerosis, less is known about the intrinsic pathways that counteract these events. Here we identified NOTCH1 as an antagonist of endothelial cell (EC) activation. NOTCH1 was constitutively expressed by adult arterial endothelium, but levels were significantly reduced by high-fat diet. Furthermore, treatment of human aortic ECs (HAECs) with inflammatory lipids (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine [Ox-PAPC]) and proinflammatory cytokines (TNF and IL1β) decreased Notch1 expression and signaling in vitro through a mechanism that requires STAT3 activation. Reduction of NOTCH1 in HAECs by siRNA, in the absence of inflammatory lipids or cytokines, increased inflammatory molecules and binding of monocytes. Conversely, some of the effects mediated by Ox-PAPC were reversed by increased NOTCH1 signaling, suggesting a link between lipid-mediated inflammation and Notch1. Interestingly, reduction of NOTCH1 by Ox-PAPC in HAECs was associated with a genetic variant previously correlated to high-density lipoprotein in a human genome-wide association study. Finally, endothelial Notch1 heterozygous mice showed higher diet-induced atherosclerosis. Based on these findings, we propose that reduction of endothelial NOTCH1 is a predisposing factor in the onset of vascular inflammation and initiation of atherosclerosis.

Three-Dimensionally Controllable Synthesis of Multichannel Silica Nanotubes and Their Application as Dual Drug Carriers

Three-dimensionally controllable multichannel silica nanotubes (MC-SNTs) have been constructed. Quaternary ammonium type (C_n H_2n+1 (CH₃ )₃ N⁺ ) surfactants were used as structure-directing agents (SDAs) in basic ammonia. A low concentration of block copolymer HO(CH₂ CH₂ O)₂₀ [CH₂ CH(CH₃ )O]₇₀ (CH₂ CH₂ O)₂₀ H (P123) was employed as an additive. The length, diameter, and pore size of MC-SNTs can be finely controlled in the range of 50 nm to 5 μm, 50 nm to 350 nm, and 2 nm to 3 nm by changing the molar ratio of P123 and SDA, the concentration of ammonia, and the length of carbon chain of SDAs, respectively. Observations based on transmission electron microscopy confirmed the role of P123 and ammonia in the self-assembly of micelles of SDA. Compared with the one-pot method reported previously, the aspect ratios (ARs; length/diameter) of obtained MC-SNTs were tunable in a wide range of approximately 1 to 100. The tunable MC-SNTs were used as dual drug-delivery carriers for anticancer drug doxorubicin (Dox) and anti-inflammatory drug ibuprofen (Ibu). Results of release behavior and toxicity to cancer cells of Dox-Ibu-loaded MC-SNTs with different ARs revealed that Dox and Ibu were successfully codelivered and did not interfere with each other. The produced MC-SNTs with larger AR values of showed advantages in the amount of accumulated dual drugs, the duration time of release, and inhibition of the growth of HeLa cells.

An Exploration of the Role of MicroRNAs in Psoriasis: A Systematic Review of the Literature

Psoriasis is recently characterized by a specific microRNAs (miRNAs) expression profile, which guides the researchers' efforts to explore the therapeutic targets and objective biomarkers that reflect the diagnosis and disease activity in clinical use for psoriasis.The paper presents a state-of-the-art review of expression and function of miRNAs in psoriasis along with its clinical implications.We analyzed all literature searched by keywords "microRNA" and "psoriasis" in PubMed (Medline) from inception up to July 2015, and the references in the literature searched were also considered.Relevant literature was chosen according to the objective of this review. Relevant literature was searched by 3 independent investigators, and experts in the field of miRNAs and psoriasis were involved in analyzing process.We included any study in which role of miRNAs in psoriasis was examined in relation to disease pathogenesis, diagnosis, and treatment.The specific miRNAs profile has been identified from human psoriatic skin, blood, and hair samples. It is found that genetic polymorphisms related to some of specific miRNAs, miR-146a for example, are associated with psoriasis susceptibility. Key roles of several unique miRNAs, such as miR-203 and miR-125b, in inflammatory responses and immune dysfunction, as well as hyperproliferative disorders of psoriatic lesions have been revealed. Moreover, circulating miRNAs detected from blood samples have a potential of clinic application to be the biomarkers of diagnosis, prognosis, and treatment responses. Additionally, a new layer of regulatory mechanisms mediated by miRNAs is to some extent revealed in pathogenesis of psoriasis.The dramatically altered mRNA expression profiles are displayed in psoriasis, and some of these may become disease markers and therapeutic targets. Herein, this work underscores the potential importance of miRNAs to diagnosis, prognosis, and treatment of psoriasis. However, further study in this field is worth doing in the future, as the exact roles of miRNAs in psoriasis have not been fully elucidated.Systematic review registration number is not registered.

Impact of Notch1 Deletion in Macrophages on Proinflammatory Cytokine Production and the Outcome of Experimental Autoimmune Encephalomyelitis

Notch signaling is involved in regulating TLR-mediated responses in activated macrophages. In this study, we investigated the impact of Notch signaling in macrophages in an experimental autoimmune encephalomyelitis (EAE) model. To examine the impact of deficiency in Notch signaling in activated macrophages in EAE, an adoptive transfer of activated macrophages derived from Notch1(fl/fl) × Mx1cre(+/-) (Notch1 knockout [N1KO]) or CSL/Rbp-jκ(fl/fl) × Mx1cre(+/-) (CSL/RBP-Jκ KO) mice was performed prior to induction of EAE. Mice receiving activated N1KO macrophages showed decreased severity of EAE compared with mice receiving wild-type or CSL/RBP-Jκ KO macrophages. In vitro restimulation of splenocytes by myelin oligodendrocyte glycoprotein 35-55 peptide from these mice revealed that cells from mice receiving N1KO macrophages produced significantly less IL-17 compared with the control mice, whereas IFN-γ production was similar in both groups. We found that activated N1KO, but not CSL/RBP-Jκ KO, macrophages produced less IL-6 and had lower CD80 expression compared with wild-type and did not exhibit any defect in IL-12p40/70 production, whereas activated macrophages from CSL/RBP-Jκ KO mice phenocopied γ-secretase inhibitor treatment for reduced IL-12p40/70 production. Furthermore, the nuclear translocation of the NF-κB subunit c-Rel was compromised in γ-secretase inhibitor-treated and CSL/RBP-Jκ KO but not N1KO macrophages. These results suggest that Notch1 and CSL/RBP-Jκ in macrophages may affect the severity of EAE differently, possibly through modulating IL-6 and CD80 expression, which is involved in the Th17 but not Th1 response.

Single and Compound Knock-outs of MicroRNA (miRNA)-155 and Its Angiogenic Gene Target CCN1 in Mice Alter Vascular and Neovascular Growth in the Retina via Resident Microglia

The response of the retina to ischemic insult typically leads to aberrant retinal neovascularization, a major cause of blindness. The epigenetic regulation of angiogenic gene expression by miRNAs provides new prospects for their therapeutic utility in retinal neovascularization. Here, we focus on miR-155, a microRNA functionally important in inflammation, which is of paramount importance in the pathogenesis of retinal neovascularization. Whereas constitutive miR-155-deficiency in mice results in mild vascular defects, forced expression of miR-155 causes endothelial hyperplasia and increases microglia count and activation. The mouse model of oxygen-induced retinopathy, which recapitulates ischemia-induced aberrant neovessel growth, is characterized by increased expression of miR-155 and localized areas of microglia activation. Interestingly, miR-155 deficiency in mice reduces microglial activation, curtails abnormal vessel growth, and allows for rapid normalization of the retinal vasculature following ischemic insult. miR-155 binds to the 3'-UTR and represses the expression of the CCN1 gene, which encodes an extracellular matrix-associated integrin-binding protein that both promotes physiological angiogenesis and harnesses growth factor-induced abnormal angiogenic responses. Single CCN1 deficiency or double CCN1 and miR-155 knock-out in mice causes retinal vascular malformations typical of faulty maturation, mimicking the vascular alterations of miR-155 gain of function. During development, the miR-155/CCN1 regulatory axis balances the proangiogenic and proinflammatory activities of microglia to allow for their function as guideposts for sprout fusion and anastomosis. Under ischemic conditions, dysregulated miR-155 and CCN1 expression increases the inflammatory load and microglial activation, prompting aberrant angiogenic responses. Thus, miR-155 functions in tandem with CCN1 to modulate inflammation-induced vascular homeostasis and repair.

Leukemic marrow infiltration reveals a novel role for Egr3 as a potent inhibitor of normal hematopoietic stem cell proliferation

Cytopenias resulting from the impaired generation of normal blood cells from hematopoietic precursors are important contributors to morbidity and mortality in patients with leukemia. However, the process by which normal hematopoietic cells are overtaken by emerging leukemia cells and how different subsets of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) are distinctly influenced during leukemic cell infiltration is poorly understood. To investigate these important questions, we used a robust nonirradiated mouse model of human MLL-AF9 leukemia to examine the suppression of HSCs and HPCs during leukemia cell expansion in vivo. Among all the hematopoietic subsets, long-term repopulating HSCs were the least reduced, whereas megakaryocytic-erythroid progenitors were the most significantly suppressed. Notably, nearly all of the HSCs were forced into a noncycling state in leukemic marrow at late stages, but their reconstitution potential appeared to be intact upon transplantation into nonleukemic hosts. Gene expression profiling and further functional validation revealed that Egr3 was a strong limiting factor for the proliferative potential of HSCs. Therefore, this study provides not only a molecular basis for the more tightened quiescence of HSCs in leukemia, but also a novel approach for defining functional regulators of HSCs in disease.

Physiological roles of miR-155

miR-155 is involved in non-coding microRNAs found in humans, mice and chickens of which the sequence is conserved. Historically, miR-155 was identified as a B-cell integration cluster (bic), which induces B-cell leucosis in chickens, by its activation through viral promoter insertion. Subsequent studies have shown that transgenic mice expressing miR-155 in B cells generated lymphoma, showing that miR-155 is oncogenic. Biochemical investigation identifies many substrates of miR-155, and one of them in B cells and macrophages is the SH2-domain containing inositol-5'-phosphatase 1. A deficiency of miR-155 in the immune system causes attenuated immune functions. Clinically, several types of malignancy including diffuse large B-cell lymphoma have high miR-155 expression levels.

Pharmacological targeting of miR-155 via the NEDD8-activating enzyme inhibitor MLN4924 (Pevonedistat) in FLT3-ITD acute myeloid leukemia

High levels of microRNA-155 (miR-155) are associated with poor outcome in acute myeloid leukemia (AML). In AML, miR-155 is regulated by NF-κB, the activity of which is, in part, controlled by the NEDD8-dependent ubiquitin ligases. We demonstrate that MLN4924, an inhibitor of NEDD8-activating enzyme presently being evaluated in clinical trials, decreases binding of NF-κB to the miR-155 promoter and downregulates miR-155 in AML cells. This results in the upregulation of the miR-155 targets SHIP1, an inhibitor of the PI3K/Akt pathway, and PU.1, a transcription factor important for myeloid differentiation, leading to monocytic differentiation and apoptosis. Consistent with these results, overexpression of miR-155 diminishes MLN4924-induced antileukemic effects. In vivo, MLN4924 reduces miR-155 expression and prolongs the survival of mice engrafted with leukemic cells. Our study demonstrates the potential of miR-155 as a novel therapeutic target in AML via pharmacologic interference with NF-κB-dependent regulatory mechanisms. We show the targeting of this oncogenic microRNA with MLN4924, a compound presently being evaluated in clinical trials in AML. As high miR-155 levels have been consistently associated with aggressive clinical phenotypes, our work opens new avenues for microRNA-targeting therapeutic approaches to leukemia and cancer patients.

Notch Receptor-Ligand Engagement Maintains Hematopoietic Stem Cell Quiescence and Niche Retention

Notch is long recognized as a signaling molecule important for stem cell self-renewal and fate determination. Here, we reveal a novel adhesive role of Notch-ligand engagement in hematopoietic stem and progenitor cells (HSPCs). Using mice with conditional loss of O-fucosylglycans on Notch EGF-like repeats important for the binding of Notch ligands, we report that HSPCs with faulty ligand binding ability display enhanced cycling accompanied by increased egress from the marrow, a phenotype mainly attributed to their reduced adhesion to Notch ligand-expressing stromal cells and osteoblastic cells and their altered occupation in osteoblastic niches. Adhesion to Notch ligand-bearing osteoblastic or stromal cells inhibits wild type but not O-fucosylglycan-deficient HSPC cycling, independent of RBP-JK -mediated canonical Notch signaling. Furthermore, Notch-ligand neutralizing antibodies induce RBP-JK -independent HSPC egress and enhanced HSPC mobilization. We, therefore, conclude that Notch receptor-ligand engagement controls HSPC quiescence and retention in the marrow niche that is dependent on O-fucosylglycans on Notch.

Notch one up to stroma: endothelial notch prevents inflammation and myeloproliferation

In this issue of Cell Stem Cell, Wang et al. (2014) describe a signaling axis present in bone marrow stromal cells that suppresses inflammation and myeloid expansions. Loss of endothelial Notch signaling leads to deregulation of miR-155 expression, activation of NF-kB, and increased proinflammatory cytokine production, which promotes a myeloproliferative phenotype.

Sca-1+Lin-CD117- mesenchymal stem/stromal cells induce the generation of novel IRF8-controlled regulatory dendritic cells through Notch-RBP-J signaling

Mesenchymal stem/stromal cells (MSCs) can influence the destiny of hematopoietic stem/progenitor cells (HSCs) and exert broadly immunomodulatory effects on immune cells. However, how MSCs regulate the differentiation of regulatory dendritic cells (regDCs) from HSCs remains incompletely understood. In this study, we show that mouse bone marrow-derived Sca-1(+)Lin(-)CD117(-) MSCs can drive HSCs to differentiate into a novel IFN regulatory factor (IRF)8-controlled regDC population (Sca(+) BM-MSC-driven DC [sBM-DCs]) when cocultured without exogenous cytokines. The Notch pathway plays a critical role in the generation of the sBM-DCs by controlling IRF8 expression in an RBP-J-dependent way. We observed a high level of H3K27me3 methylation and a low level of H3K4me3 methylation at the Irf8 promoter during sBM-DC induction. Importantly, infusion of sBM-DCs could alleviate colitis in mice with inflammatory bowel disease by inhibiting lymphocyte proliferation and increasing the numbers of CD4(+)CD25(+) regulatory T cells. Thus, these data infer a possible mechanism for the development of regDCs and further support the role of MSCs in treating immune disorders.

Inflammatory signaling regulates hematopoietic stem and progenitor cell emergence in vertebrates

TLR4–MyD88–NF-κB is required for HSPC emergence in zebrafish and mouse embryos. Notch functions downstream of inflammatory signaling to regulate HSPC emergence.

MicroRNAs expressed in hematopoietic stem/progenitor cells are deregulated in acute myeloid leukemias

MicroRNAs are key regulators of hematopoiesis, specifically involved in regulating the maintenance of stemness of primitive hematopoietic progenitor cells (HPCs) and the early and late stages of hematopoietic differentiation. Some microRNAs have been found to be expressed in hematopoietic stem cells (HSCs) and primitive HPCs, and play a relevant role in regulation of the early steps of hematopoietic cell differentiation. Notable examples of these microRNAs are given by miR-22, miR-29, miR-125 and miR-126. These HSC/HPC-regulating microRNAs are often deregulated in some subsets of acute myeloid leukemia (AML), with pathogenic, diagnostic and prognostic implications. Therefore, elucidation of the pattern of microRNA expression at the level of the early stages of hematopoietic cell differentiation has essential implications, not only for elucidation of the molecular bases of the early stages of hematopoietic differentiation, but also for a better understanding of the pathogenic mechanisms underlying AML.

The role of notch in the cardiovascular system: potential adverse effects of investigational notch inhibitors

Targeting the Notch pathway is a new promising therapeutic approach for cancer patients. Inhibition of Notch is effective in the oncology setting because it causes a reduction of highly proliferative tumor cells and it inhibits survival of cancer stem cells, which are considered responsible for tumor recurrence and metastasis. Additionally, since Delta-like ligand 4 (Dll4)-activated Notch signaling is a major modulator of angiogenesis, anti-Dll4 agents are being investigated to reduce vascularization of the tumor. Notch plays a major role in the heart during the development and, after birth, in response to cardiac damage. Therefore, agents used to inhibit Notch in the tumors (gamma secretase inhibitors and anti-Dll4 agents) could potentially affect myocardial repair. The past experience with trastuzumab and other tyrosine kinase inhibitors used for cancer therapy demonstrates that the possible cardiotoxicity of agents targeting shared pathways between cancer and heart and the vasculature should be considered. To date, Notch inhibition in cancer patients has resulted only in mild gastrointestinal toxicity. Little is known about the potential long-term cardiotoxicity associated to Notch inhibition in cancer patients. In this review, we will focus on mechanisms through which inhibition of Notch signaling could lead to cardiomyocytes and endothelial dysfunctions. These adverse effects could contrast with the benefits of therapeutic responses in cancer cells during times of increased cardiac stress and/or in the presence of cardiovascular risk factor.

MicroRNA Expression Analysis in Patients with Primary Myelofibrosis, Polycythemia vera and Essential Thrombocythemia

MicroRNAs (miRNA) are small non-coding RNA molecules that play critical roles in cell differentiation, proliferation and apoptosis and thus regulate haematopoietic stem cells and committed progenitor cells. We analyzed expressions of miRNAs associated with hematopoietic transformation of myeloid, erythroid and megakaryocytic progenitor cells during haematopoiesis (mir155, mir181a, mir221, mir222, mir223, mir451), in patients with primary myelofibrosis (PMF) (n = 22), polycythemia vera (PV) (n = 33), essential thrombocythemia (ET) (n = 49) and in healthy controls (n = 40) by quantitate/real time polymerase chain reaction. RT-PCR testing was negative for BCR-ABL1 fusion gene in all the patients. Mir155 was expressed in higher levels in all 3 disorders (p < 0.05). Mir221 was higher especially in ET and PMF group (p < 0.05). Mir222 expression was lower in PV patients (p < 0.05) and higher in ET and PMF patients compared to control group. Mir223 expression was higher in ET and PMF group than control group (p > 0.05). Mir451 levels were lower in all three groups compared to control group (p < 0.05). There was no difference in expression levels of mir181a between groups. JAK2V617F positivity, co-morbidities, drugs, and gender did not affect miRNA expressions. This study holds promise for the future application of these molecules for differential diagnosis and as therapeutic targets in Philadelphia chromosome negative myeloproliferative neoplasms.

Noncoding RNAs regulate NF-κB signaling to modulate blood vessel inflammation

Cardiovascular diseases such as atherosclerosis are one of the leading causes of morbidity and mortality worldwide. The clinical manifestations of atherosclerosis, which include heart attack and stroke, occur several decades after initiation of the disease and become more severe with age. Inflammation of blood vessels plays a prominent role in atherogenesis. Activation of the endothelium by inflammatory mediators leads to the recruitment of circulating inflammatory cells, which drives atherosclerotic plaque formation and progression. Inflammatory signaling within the endothelium is driven predominantly by the pro-inflammatory transcription factor, NF-κB. Interestingly, activation of NF-κB is enhanced during the normal aging process and this may contribute to the development of cardiovascular disease. Importantly, studies utilizing mouse models of vascular inflammation and atherosclerosis are uncovering a network of noncoding RNAs, particularly microRNAs, which impinge on the NF-κB signaling pathway. Here we summarize the literature regarding the control of vascular inflammation by microRNAs, and provide insight into how these microRNA-based pathways might be harnessed for therapeutic treatment of disease. We also discuss emerging areas of endothelial cell biology, including the involvement of long noncoding RNAs and circulating microRNAs in the control of vascular inflammation.

Notch signal integration in the vasculature during remodeling

Notch signaling plays many important roles in homeostasis and remodeling in the vessel wall, and serves a critical role in the communication between endothelial cells and smooth muscle cells. Within blood vessels, Notch signaling integrates with multiple pathways by mechanisms including direct protein–protein interaction, cooperative or synergistic regulation of signal cascades, and co-regulation of transcriptional targets. After establishment of the mature blood vessel, the spectrum and intensity of Notch signaling change during phases of active remodeling or disease progression. These changes can be mediated by regulation via microRNAs and protein stability or signaling, and corresponding changes in complementary signaling pathways. Notch also affects endothelial cells on a system level by regulating key metabolic components. This review will outline the most recent findings of Notch activity in blood vessels, with a focus on how Notch signals integrate with other molecular signaling pathways controlling vascular phenotype.