Evidence for the involvement of miRNA in redox regulated angiogenic response of human microvascular endothelial cells

Suppression of Induced microRNA-15b Prevents Rapid Loss of Cardiac Function in a Dicer Depleted Model of Cardiac Dysfunction

Background

Dicer endonuclease, critical for maturation of miRNAs, is depleted in certain forms of cardiomyopathy which results in differential expression of certain microRNAs. We sought to elucidate the mechanisms underlying the rapid loss of cardiac function following cardiac-specific Dicer depletion in adult mice.

Results

Conditional Dicer deletion in the adult murine myocardium demonstrated compromised heart function, mitochondrial dysfunction and oxidant stress. Elevated miR-15b was observed as an early response to Dicer depletion and was found to silence Pim-1 kinase, a protein responsible for maintaining mitochondrial integrity and function. Anti-miRNA based suppression of induced miRNA-15b rescued the function of Dicer-depleted adult heart and attenuated hypertrophy.

Conclusions

Anti-miRNA based suppression of inducible miRNA-15b can prevent rapid loss of cardiac function in a Dicer-depleted adult heart and can be a key approach worthy of therapeutic consideration.

The role of redox signaling in epigenetics and cardiovascular disease

SIGNIFICANCE

The term epigenetics refers to the changes in the phenotype and gene expression that occur without alterations in the DNA sequence. There is a rapidly growing body of evidence that epigenetic modifications are involved in the pathological mechanisms of many cardiovascular diseases (CVDs), which intersect with many of the pathways involved in oxidative stress.

RECENT ADVANCES

Most studies relating epigenetics and human pathologies have focused on cancer. There has been a limited study of epigenetic mechanisms in CVDs. Although CVDs have multiple established genetic and environmental risk factors, these explain only a portion of the total CVD risk. The epigenetic perspective is beginning to shed new light on how the environment influences gene expression and disease susceptibility in CVDs. Known epigenetic changes contributing to CVD include hypomethylation in proliferating vascular smooth muscle cells in atherosclerosis, changes in estrogen receptor-α (ER-α) and ER-β methylation in vascular disease, decreased superoxide dismutase 2 expression in pulmonary hypertension (PH), as well as trimethylation of histones H3K4 and H3K9 in congestive heart failure.

CRITICAL ISSUES

In this review, we discuss the epigenetic modifications in CVDs, including atherosclerosis, congestive heart failure, hypertension, and PH, with a focus on altered redox signaling.

FUTURE DIRECTIONS

As advances in both the methodology and technology accelerate the study of epigenetic modifications, the critical role they play in CVD is beginning to emerge. A fundamental question in the field of epigenetics is to understand the biochemical mechanisms underlying reactive oxygen species-dependent regulation of epigenetic modification.

MicroRNAs and tumor vasculature normalization: impact on anti-tumor immune response

Inefficient immune response is a major glitch during tumor growth and progression. Chaotic and leaky blood vessels created in the process of angiogenesis allow tumor cells to escape and extricate anti-cancer immunity. Proangiogenic characteristics of hypoxic tumor microenvironment maintained by low oxygen tension attract endothelial progenitor cells, drive expansion of cancer stem cells, and deviantly differentiate monocyte descendants. Such cellular milieu further boosts immune tolerance and eventually appoint immunity for cancer advantage. Blood vessel normalization strategies that equilibrate oxygen levels within tumor and fix abnormal vasculature bring exciting promises to future anticancer therapies especially when combined with conventional chemotherapy. Recently, a new group of microRNAs (miRs) engaged in angiogenesis, called angiomiRs and hypoxamiRs, emerged as new therapeutic targets in cancer. Some of those miRs were found to efficiently regulate cancer immunity and their dysregulation efficiently programs aberrant angiogenesis and cancer metastasis. The present review highlights new findings in the field of miRs proficiency to normalize aberrant angiogenesis and to restore anti-tumor immune responses.

MiR-29a modulates the angiogenic properties of human endothelial cells

Although extensive investigation has been made on miR-29a in relation to malignancies, only a little information has been provided about the angiogenic property of this miRNA so far. Herein, we sought to investigate the role of miR-29a in regulating cell cycle and angiogenic phenotype of endothelial cells. The results showed that miR-29a is highly expressed and upregulated by hypoxia-mimicking reagents in human umbilical vein endothelial cells (HUVEC). Consistent with this preliminary finding, introduction of exogenous agomiR-29a, or Antagomir-29a altered cell cycle progression and promoted, or repressed the proliferation and tube formation of HUVEC, respectively. Furthermore, by using luciferase reporter assay, the expression of HBP1, a suppressor transcription factor was directly regulated by miR-29a through 3'-UTR. Increased or decreased HBP1 protein level was associated with the inhibition or overexpression of miR-29a, respectively. We conclude that miR-29a has a significant role in regulating cell cycle, proliferation and angiogenic properties of HUVEC, and this function is likely mediated through HBP1 protein at the post-transcriptional level. As a novel molecular target, miR-29a may have a potential value for the treatment of angiogenesis-associated diseases such as cardiovascular diseases and cancers.

MicroRNAs in skin and wound healing

MicroRNAs (miRNAs) are small noncoding RNA molecules ∼22 nucleotides in length that can post-transcriptionally repress gene expression. MiRNAs bind to their target messenger RNAs (mRNAs), leading to mRNA degradation or suppression of translation. miRNAs have recently been shown to play pivotal roles in skin development and are linked to various skin pathologies, cancer, and wound healing. Chronic wounds represent a major health burden and drain on resources and developing more effective treatments is therefore a necessity. Increase in the understanding of the regulation of chronic wound biology is therefore required to develop newer therapies. This review focuses on the role of miRNAs in cutaneous biology, the various methods of miRNA modulation, and the therapeutic opportunities in treatment of skin diseases and wound healing.

Dicer and Drosha expression and response to Bevacizumab-based therapy in advanced colorectal cancer patients

PURPOSE

The miRNA-regulating enzymes Dicer and Drosha exhibit aberrant expression in several cancer types. Dicer and Drosha play a crucial role during the angiogenetic process in vitro and, for Dicer, in vivo. We aimed to investigate the potential role of Dicer and Drosha in predicting response to Bevacizumab-based therapy in advanced colorectal cancer (CRC) patients.

METHODS

Dicer and Drosha mRNA levels were analysed in formalin-fixed paraffin-embedded specimens from patients affected by advanced CRC treated with or without Bevacizumab-containing regimens (n=116 and n=50, respectively) and from patients with diverticulosis as control group (n=20). The experimental data were obtained using qRT-PCR, analysed comparing Dicer and Drosha expression levels in tumour samples versus normal mucosa and then compared to clinical outcome.

RESULTS

The tumour samples from Bevacizumab-treated patients showed a significantly higher Drosha expression (P<.001) versus normal mucosa, while Dicer levels did not differ. Intriguingly, we found that low Dicer levels predicted a longer progression-free survival (PFS) (P<.0001) and overall survival (OS) (P=.009). In addition, low Dicer levels were associated with better response to Bevacizumab-based treatments versus high Dicer levels (1.7% complete responses and 53.4% partial responses versus 0% and 32.7%, respectively; P=.0067). Multivariate analysis identified three independent predictors of improved OS: high performance status (PS) (relative risk (RR) 1.45; P=.011), lower organs involvement (RR 0.79; P=.034) and low Dicer expression (RR 0.71; P=.008). Conversely, Drosha levels were not associated with prognosis and outcome associated with treatment. In non-Bevacizumab-treated patients, Dicer and Drosha expression did not correlate with outcome.

CONCLUSION

These findings suggest that low Dicer mRNA levels seem to be independent predictors of favourable outcome and response in patients affected by advanced CRCs treated with Bevacizumab-based therapy.

Aging-induced dysregulation of dicer1-dependent microRNA expression impairs angiogenic capacity of rat cerebromicrovascular endothelial cells

Age-related impairment of angiogenesis is likely to play a central role in cerebromicrovascular rarefaction and development of vascular cognitive impairment, but the underlying mechanisms remain elusive. To test the hypothesis that dysregulation of Dicer1 (ribonuclease III, a key enzyme of the microRNA [miRNA] machinery) impairs endothelial angiogenic capacity in aging, primary cerebromicrovascular endothelial cells (CMVECs) were isolated from young (3 months old) and aged (24 months old) Fischer 344 × Brown Norway rats. We found an age-related downregulation of Dicer1 expression both in CMVECs and in small cerebral vessels isolated from aged rats. In aged CMVECs, Dicer1 expression was increased by treatment with polyethylene glycol-catalase. Compared with young cells, aged CMVECs exhibited altered miRNA expression profile, which was associated with impaired proliferation, adhesion to vitronectin, collagen and fibronectin, cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing technology), and impaired ability to form capillary-like structures. Overexpression of Dicer1 in aged CMVECs partially restored miRNA expression profile and significantly improved angiogenic processes. In young CMVECs, downregulation of Dicer1 (siRNA) resulted in altered miRNA expression profile associated with impaired proliferation, adhesion, migration, and tube formation, mimicking the aging phenotype. Collectively, we found that Dicer1 is essential for normal endothelial angiogenic processes, suggesting that age-related dysregulation of Dicer1-dependent miRNA expression may be a potential mechanism underlying impaired angiogenesis and cerebromicrovascular rarefaction in aging.

Epigenetic mechanisms in the pathogenesis of diabetic foot ulcers

The incidence of diabetes mellitus, a chronic metabolic disease associated with both predisposing genetic and environmental factors, is increasing globally. As a result, it is expected that there will also be an increasing incidence of diabetic complications which arise as a result of poor glycemic control. Complications include cardiovascular diseases, nephropathy, retinopathy and diabetic foot ulcers. The findings of several major clinical trials have identified that diabetic complications may arise even after many years of proper glycemic control. This has led to the concept of persistent epigenetic changes. Various epigenetic mechanisms have been identified as important contributors to the pathogenesis of diabetes and diabetic complications. The aim of this review is to provide an overview of the pathobiology of type 2 diabetes with an emphasis on complications, particularly diabetic foot ulcers. An overview of epigenetic mechanisms is provided and the focus is on the emerging evidence for aberrant epigenetic mechanisms in diabetic foot ulcers.

The microRNA miR-199a-5p down-regulation switches on wound angiogenesis by derepressing the v-ets erythroblastosis virus E26 oncogene homolog 1-matrix metalloproteinase-1 pathway

miR-199a-5p plays a critical role in controlling cardiomyocyte survival. However, its significance in endothelial cell biology remains ambiguous. Here, we report the first evidence that miR-199a-5p negatively regulates angiogenic responses by directly targeting v-ets erythroblastosis virus E26 oncogene homolog 1 (Ets-1). Induction of miR-199a-5p in human dermal microvascular endothelial cells (HMECs) blocked angiogenic response in Matrigel® culture, whereas miR-199a-5p-deprived cells exhibited enhanced angiogenesis in vitro. Bioinformatics prediction and miR target reporter assay recognized Ets-1 as a novel direct target of miR-199a-5p. Delivery of miR-199a-5p blocked Ets-1 expression in HMECs, whereas knockdown endogenous miR-199a-5p induced Ets-1 expression. Matrix metalloproteinase 1 (MMP-1), one of the Ets-1 downstream mediators, was negatively regulated by miR-199a-5p. Overexpression of Ets-1 not only rescued miR-199a-5p-dependent anti-angiogenic effects but also reversed miR-199a-5p-induced loss of MMP-1 expression. Similarly, Ets-1 knockdown blunted angiogenic response and induction of MMP-1 in miR-199a-5p-deprived HMECs. Examination of cutaneous wound dermal tissue revealed a significant down-regulation of miR-199a-5p expression, which was associated with induction of Ets-1 and MMP-1. Mice carrying homozygous deletions in the Ets-1 gene exhibited blunted wound blood flow and reduced abundance of endothelial cells. Impaired wound angiogenesis was associated with compromised wound closure, insufficient granulation tissue formation, and blunted induction of MMP-1. Thus, down-regulation of miR-199a-5p is involved in the induction of wound angiogenesis through derepressing of the Ets-1-MMP1 pathway.

miRNA in wound inflammation and angiogenesis

Chronic wounds represent a rising health and economic burden to our society. Emerging studies indicate that miRNAs play a key role in regulating several hubs that orchestrate the wound inflammation and angiogenesis processes. Of interest to wound inflammation are the regulatory loops where inflammatory mediators elicited following injury are regulated by miRNAs, as well as regulate miRNA expression. Adequate angiogenesis is a key determinant of success in ischemic wound repair. Hypoxia and cellular redox state are among the key factors that drive wound angiogenesis. We provided first evidence demonstrating that miRNAs regulate cellular redox environment via a NADPH oxidase-dependent mechanism in human microvascular endothelial cells (HMECs). We further demonstrated that hypoxia-sensitive miR-200b is involved in induction of angiogenesis by directly targeting Ets-1 in HMECs. These studies point toward a potential role of miRNA in wound angiogenesis. miRNA-based therapeutics represent one of the major commercial hot spots in today's biotechnology market space. Understanding the significance of miRs in wound inflammation and angiogenesis may help design therapeutic strategies for management of chronic nonhealing wounds.

miR-210: the master hypoxamir

MicroRNAs are small non-coding RNAs implicated mainly in post-transcriptional gene silencing by interacting with the untranslated region of the transcript. miR-210 represents major hypoxia-inducible miRs, also known as hypoxamirs, which is ubiquitously expressed in a wide range of cells, serving versatile functions. This review article summarizes the current progress on biogenesis of miR-210 and its physiological roles including arrest of cell proliferation, repression of mitochondrial respiration, arrest of DNA repair, vascular biology, and angiogenesis. Given the fact that miR-210 is aberrantly expressed in a number of diseases such as tumor progression, myocardial infarction and cutaneous ischemic wounds, miR-210 could serve as an excellent candidate for prognostic purposes and therapeutic intervention. With the advancement of computational prediction, high-throughput target validation methodology, sequencing, proteomic analysis, and microarray, it is anticipated that more down-stream targets of miR-210 and its associated biological consequences under hypoxia will be unveiled establishing miR-210 as a major hub in the biology of hypoxia-response.

Permissive role of miR-663 in induction of VEGF and activation of the ATF4 branch of unfolded protein response in endothelial cells by oxidized phospholipids

OBJECTIVE

Atherosclerotic lesions contain high concentrations of oxidized phospholipids (OxPLs) known to induce VEGF via the ATF4 arm of unfolded protein response (UPR), and to promote angiogenic reactions thus potentially contributing to the progression and destabilization of atherosclerotic plaques. In order to get further insights into the mechanisms of cellular stress-induced angiogenesis we studied the role of a specific microRNA (miR-663) in the mechanisms of VEGF induction by OxPLs and inducers of UPR.

METHODS

miRNA and mRNA levels were determined using microarray profiling and qRT-PCR methods. Proteins were analyzed by Western blotting. miR-663 levels were changed by transfecting cells with synthetic oligonucleotides.

RESULTS

OxPAPC elevated miR-663 in two types of human endothelial cells (ECs). Knockdown of miR-663 inhibited upregulation of VEGF mRNA in ECs treated by OxPAPC, OxPAPS or OxPAPA. In addition, silencing of miR-663 suppressed upregulation by OxPAPC of ATF4 mRNA and protein, as well as a downstream gene TRIB. Similarly to the inhibition of OxPAPC effects, knockdown of miR-663 suppressed elevation of ATF4, VEGF and TRIB in response to another inducer of UPR, tunicamycin. Overexpression of miR-663 reversed the inhibition of VEGF induction by miR-663 inhibitor.

CONCLUSION

miR-663 is critically important for 2 key events induced in ECs by stress agents and oxidized lipids, namely induction of transcription factor ATF4 and its downstream gene VEGF. These findings allow hypothesizing that miR-663 plays a general role in control of the ATF4 branch of UPR induced by different agents.

Reciprocal induction of human dermal microvascular endothelial cells and human mesenchymal stem cells: time-dependent profile in a co-culture system

OBJECTIVES

Angiogenesis is closely associated with osteogenesis where reciprocal interactions between endothelial and osteoblast cells play an important role in bone regeneration. For these reasons, the aim of this work was to develop a co-culture system to study in detail any time-dependent interactions between human mesenchymal stem cells (HMSC) and human dermal microvascular endothelial cells (HDMEC), co-cultured in a 2D system, for 35 days.

MATERIALS AND METHODS

HMSC and HDMEC were co-cultured at a ratio of 1:4, respectively. Single-cell cultures were used as controls. Cell viability/proliferation was assessed using MTT, DNA quantification and calcein-AM assays. Cell morphology was monitored using confocal microscopy, and real time PCR was performed. Alkaline phosphatase activity and histochemical staining were evaluated. Matrix mineralization assays were also performed.

RESULTS

Cells were able to grow in characteristic patterns maintaining their viability and phenotype expression throughout culture time, compared to HMSC and HDMEC monocultures. HMSC differentiation seemed to be enhanced in the co-culture conditions, since it was observed an over expression of osteogenesis-related genes, and of ALP activity. Furthermore, presence of calcium phosphate deposits was also confirmed.

CONCLUSIONS

This work reports in detail the interactions between HMSC and HDMEC in a long-term co-culture 2D system. Endothelial and mesenchymal stem cells cultured in the present co-culture conditions ensured proliferation and phenotype differentiation of cell types, osteogenesis stimulation and over-expression of angiogenesis-related genes, in the same culture system. It is believed that the present work can lead to significant developments for bone tissue regeneration and cell biology studies.

MicroRNAs in hypertension: mechanisms and therapeutic targets

Hypertension is a complex, multifactorial disease, and its development is determined by a combination of genetic susceptibility and environmental factors. Several mechanisms have been implicated in the pathogenesis of hypertension: increased activity of the sympathetic nervous system, overactivation of the renin-angiotensin aldosterone system (RAAS), dysfunction of vascular endothelium, impaired platelet function, thrombogenesis, vascular smooth muscle and cardiac hypertrophy, and altered angiogenesis. MicroRNAs are short, noncoding nucleotides regulating target messenger RNAs at the post-transcriptional level. MicroRNAs are involved in virtually all biologic processes, including cellular proliferation, apoptosis, and differentiation. Thus, microRNA deregulation often results in impaired cellular function and disease development, so microRNAs have potential therapeutic relevance. Many aspects of the development of essential hypertension at the molecular level are still unknown. The elucidation of these processes regulated by microRNAs and the identification of novel microRNA targets in the pathogenesis of hypertension is a highly valuable and exciting strategy that may eventually led to the development of novel treatment approaches for hypertension. This article reviews the potential role of microRNAs in the mechanisms associated with the development and consequences of hypertension and discusses advances in microRNA-based approaches that may be important in treating hypertension.

Downregulation of endothelial microRNA-200b supports cutaneous wound angiogenesis by desilencing GATA binding protein 2 and vascular endothelial growth factor receptor 2

OBJECTIVE

MicroRNAs (miRs) regulate angiogenesis by posttranscriptional silencing of target genes. The significance of angiostatic miR-200b in switching on skin wound angiogenesis was tested.

METHODS AND RESULTS

Wounding caused imminent and transient downregulation of miR-200b in dermal wound-edge endothelial cells. Derailing this injury response by lentiviral delivery of miR-200b in vivo impaired wound angiogenesis. Computational prediction, target reporter luciferase assay, and Western blot analysis provided first evidence that miR-200b targets globin transcription factor binding protein 2 (GATA2) and vascular endothelial growth factor receptor 2 (VEGFR2). Overexpression of GATA2 or VEGFR2 in endothelial cells rescued the angiostatic effect of miR-200b in vitro. Downregulation of miR-200b derepressed GATA2 and VEGFR2 expression to switch on wound angiogenesis, which was disrupted in diabetic wounds. Treatment of endothelial cells with tumor necrosis factor-α, a proinflammatory cytokine abundant in diabetic wounds, induced miR-200b expression, silenced GATA2 and VEGFR2, and suppressed angiogenesis. These outcomes were attenuated using anti-miR-200b strategy. Neutralization of tumor necrosis factor-α in the diabetic wounds improved wound angiogenesis and closure, which was accompanied by downregulation of miR-200b expression and desilencing of GATA2 and VEGFR2.

CONCLUSIONS

Injury-induced repression of miR-200b turned on wound angiogenesis. In mice with diabetes mellitus,excessive tumor necrosis factor-α induced miR-200b blunting proangiogenic functions of GATA2 and VEGFR2.

MicroRNAs mediate metabolic stresses and angiogenesis

MicroRNAs are short endogenous RNA molecules that are able to regulate (mainly inhibiting) gene expression at the post-transcriptional level. The MicroRNA expression profile is cell-specific, but it is sensitive to perturbations produced by stresses and diseases. Endothelial cells subjected to metabolic stresses, such as calorie restriction, nutrients excess (glucose, cholesterol, lipids) and hypoxia may alter their functionality. This is predictive for the development of pathologies like atherosclerosis, diabetes, and hypertension. Moreover, cancer cells can activate a resting endothelium by secreting pro-angiogenic factors, in order to promote neoangiogenesis, which is essential for tumor growth. Endothelial altered phenotype is mirrored by altered mRNA, microRNA, and protein expression, with a microRNA being able to control pathways by regulating the expression of multiple mRNAs. In this review we will consider the involvement of microRNAs in modulating the response of endothelial cells to metabolic stresses and their role in promoting or halting angiogenesis.

A New Level of Complexity

The discovery of the regulatory role of noncoding RNAs, and micro (mi)RNAs in particular, has added a new layer of complexity to our understanding of cardiovascular development. miRNAs regulate and modulate various steps of cardiovascular morphogenesis, cell proliferation, differentiation, and phenotype modulation. miRNAs simultaneously regulate multiple targets, and many miRNAs can bind to the same target, allowing for a complex pattern of regulation of gene expression. miRNA families are continuously added during evolution paralleling the increased complexity of the cardiovascular system in vertebrates compared with invertebrates. Several lines of evidence suggest that the appearance of miRNAs is at least in part responsible for the formation of complex organ systems and stable regulatory mechanisms in vertebrates. We review the current understanding of miRNAs during cardiovascular development. Further progress in this area will help to decipher quantitative changes in gene expression that provide robustness to cellular phenotypes and regulatory options to diseases processes. miRNAs might also provide clues to better understand congenital heart defects, which are the most common birth defects in human newborns.

Arterial remodeling and atherosclerosis: miRNAs involvement

Cardiometabolic diseases (CMD) (such as atherosclerosis, diabetes, and hypertension) are the primary cause of death and disability in the Western world. Although lifestyle programs and therapeutic approaches have significantly reduced the socio-economic burden of CMD, a large number of events still cannot be avoided (the so called residual risk). Recent developments in genetics and genomics provide a platform for investigating further this area with the aim of deepening our understanding of the atherosclerotic phenomena underlying CMD, for instance by providing better information on the type of subjects who would benefit the most from therapeutic interventions, or by discovering new genetic and metabolic derangements that may be targeted for the development of new interventions. MicroRNAs (miRNA) are short, non-coding RNAs that negatively regulate the expression of proteins by binding to specific sequences on the 3' region of target mRNAs. Bioinformatics analysis predicts that each miRNA may regulate hundreds of targets, suggesting that miRNAs may play roles in almost every biological pathway and process, including those of the cardiovascular system. Studies are beginning to unravel their fundamental importance in vessel biology. Here, we review recent advance regarding the involvement of miRNAs in arterial remodeling and atherosclerosis.

Expression of let-7i is associated with Toll-like receptor 4 signal in coronary artery disease: effect of statins on let-7i and Toll-like receptor 4 signal

Toll-like receptor (TLR) 4 signal plays an important role in immunity in coronary artery disease (CAD). A recent report has demonstrated that one of the let-7 family microRNAs, let-7i, directly regulates Toll-like receptor 4 (TLR4) expression and contributes to immune response. The aim of this study was to determine whether let-7i is expressed with TLR4 in patients with CAD, and whether statins (atorvastatin or rosuvastatin) might affect these levels. To determine the effects of let-7i on TLR4 expression, human THP-1 cells transfected with let-7i were analyzed for TLR4 levels. This study included 98 patients with CAD and 48 subjects without CAD (non-CAD). Patients with CAD were randomized to 12 months of treatment with atorvastatin or rosuvastatin. Monocytes were obtained from peripheral blood at baseline and after 12 months of each type of therapy. Levels of let-7i and TLR4 were measured by real-time RT-PCR and FACS. Functional approaches to let-7i showed that transfection of let-7i into human THP-1 cells resulted in regulation of TLR4 expression. Levels of let-7i were lower in the CAD group than in the non-CAD group (0.98±0.42 vs. 4.65±1.21, P<0.01). There was a negative correlation between let-7i and TLR4 levels in patients with CAD (let-7i vs. TLR4 mRNA: r=-0.60, P<0.01; let-7i vs. TLR4 MFI: r=-0.32, P<0.01). The atorvastatin group had markedly increased let-7i levels and diminished TLR4 levels (all P<0.01), whereas the rosuvastatin group showed no change in these levels. This study suggests that atorvastatin down-regulates TLR4 signal via let-7i expression in CAD patients, possibly contributing to the beneficial effects of atorvastatin on let-7i-mediated TLR4 signal in this disorder.

MicroRNAs as new maestro conducting the expanding symphony orchestra of regenerative and reparative medicine

The human genome encodes 1,048 microRNAs (miRNAs). These miRNAs regulate virtually all biological processes. Leaving ignominy on the significance miRNAs behind we are approaching a new era in tissue repair where an ever expanding orchestra of events that enable tissue repair and regeneration seems to be conducted by miRNAs as the maestro. microRNAs are emerging as molecular rheostats that fine-tune and switch regulatory circuits governing tissue repair. Key elements of tissue repair such as stem cell biology, inflammation, hypoxia-response, and angiogenesis are all under the sophisticated control of a network of specific mRNAs. Embryonic stem cells lacking miRNAs lose their "stemness." Manipulation of specific cellular miRNAs helps enhance reprogramming of somatic cells to an embryonic stem cell-like phenotype helping generate inducible pluripotent stem cells. Expression of miRNAs is subject to control by epigenetic factors. Such control influences the balance between proliferation and differentiation of stem cells. Angiomirs regulate various aspects of angiogenesis, such as proliferation, migration, and morphogenesis of endothelial cells. MiRNAs play a key role in resolution of inflammation. Hypoxia-inducible mRNAs or hypoxamirs suppress mitochondrial respiration, cause cell cycle arrest, and interfere with growth factor signaling. miRNA-210 is a good example in this category that impairs wound closure. As fine tools enabling specific and temporally controlled manipulation of cell-specific miRNAs emerge, miRNA-based therapies hold promise in facilitating tissue repair. Treatment of skin wounds has lower barriers because it lends itself to local delivery of miRNA mimics and antagonizing agents minimizing risks associated with systemic off-target toxicity.

MicroRNA epigenetics: a new avenue for wound healing research

A group of small non-coding RNA molecules, termed microRNAs (miRNAs), have generated considerable interest in recent years due to their central role in a growing number of biologic processes. Serving as post-transcriptional regulators of gene expression, miRNAs have also emerged as critical factors in the pathogenesis of many diseases. As a result, they show great potential as accurate diagnostic and prognostic markers, as well as viable therapeutic targets for treating disease. It has been proposed that miRNAs play a significant role in cutaneous wound repair and that aberrant miRNA expression may result in disorganized or poor healing. Specific patterns of miRNA expression have been identified in wound healing models. miRNAs are important regulators of leucocyte function and the cytokine network, and are necessary for endothelial cell migration and capillary formation. These molecules also control proliferation and differentiation of wound-specific cells and can determine extracellular matrix composition. This article reviews the evidence for miRNA regulation of inflammation, angiogenesis, fibroblast function, keratinocyte function, and apoptosis, which are essential components for effective wound repair. The future potential for improving wound healing outcomes using miRNA-based therapies is also discussed.

MiRNA in innate immune responses: novel players in wound inflammation

Chronic wounds represent a major and rising socioeconomic threat affecting over 6.5 million people in the United States costing in excess of US $25 billion annually. Wound healing is a physiological response to injury that is conserved across tissue systems. In humans, wounding is followed by instant response aimed at hemostasis, which in turn provides the foundation for inflammatory processes that closely follow. Inflammation is helpful and a prerequisite for healing as long as it is mounted and resolved in a timely manner. Chronic inflammation derails the healing cascade resulting in impaired wound closure. Disruption of Dicer, the RNase III enzyme that generates functional miRNAs, has a major impact on the overall immune system. Emerging studies indicate that miRNAs, especially miR-21, miR-146a/b, and miR-155, play a key role in regulating several hubs that orchestrate the inflammatory process. Direct evidence from studies addressing wound inflammation being limited, the current work represents a digest of the relevant literature that is aimed at unveiling the potential significance of miRNAs in the regulation of wound inflammation. Such treatment would help establish new paradigms highlighting a central role of miRs in the understanding and management of dysregulated inflammation as noted in conjunction with chronic wounds.

miR-200b targets Ets-1 and is down-regulated by hypoxia to induce angiogenic response of endothelial cells

The miR-200 family plays a crucial role in epithelial to mesenchymal transition via controlling cell migration and polarity. We hypothesized that miR-200b, one miR-200 family member, could regulate angiogenic responses via modulating endothelial cell migration. Delivery of the miR-200b mimic in human microvascular endothelial cells (HMECs) suppressed the angiogenic response, whereas miR-200b-depleted HMECs exhibited elevated angiogenesis in vitro, as evidenced by Matrigel® tube formation and cell migration. Using in silico studies, miR target reporter assay, and Western blot analysis revealed that v-ets erythroblastosis virus E26 oncogene homolog 1 (Ets-1), a crucial angiogenesis-related transcription factor, serves as a novel direct target of miR-200b. Knocking down endogenous Ets-1 simulated an anti-angiogenic response of the miR-200b mimic-transfected cells. Certain Ets-1-associated genes, namely matrix metalloproteinase 1 and vascular endothelial growth factor receptor 2, were negatively regulated by miR-200b. Overexpression of Ets-1 rescued miR-200b-dependent impairment in angiogenic response and suppression of Ets-1-associated gene expression. Both hypoxia as well as HIF-1α stabilization inhibited miR-200b expression and elevated Ets-1 expression. Experiments to identify how miR-200b modulates angiogenesis under a low oxygen environment illustrated that hypoxia-induced miR-200b down-regulation de-repressed Ets-1 expression to promote angiogenesis. This study provides the first evidence that hypoxia-sensitive miR-200b is involved in induction of angiogenesis via directly targeting Ets-1 in HMECs.

Metastamirs: a stepping stone towards improved cancer management

MicroRNAs (miRNAs) are non-coding RNAs that regulate protein expression. Aberrant miRNA expression in cancer has been well documented; miRNAs can act as oncogenes or tumor-suppressor genes, depending on the cellular context and target genes that they regulate, and are involved in tumor progression and metastasis. The potential mechanisms by which miRNAs are involved in tumor aggressiveness include migration, invasion, cell proliferation, epithelial-to-mesenchymal transition, angiogenesis and apoptosis. MiRNAs are involved in various cellular pathways and an miRNA can elicit more than one biological effect in a given cell. Existing data show the potential clinical utility of miRNAs as prognostic and predictive markers for aggressive and metastatic cancers. The stability of miRNAs in formalin-fixed, paraffin-embedded tissues and body fluids is advantageous for biomarker discovery and validation. In addition, miRNAs can be extracted from small biopsy specimens, which is a further advantage. Finally, miRNAs are potential therapeutic agents for personalized cancer management.

microRNA: a master regulator of cellular processes for bioengineering systems

microRNAs (miRNAs) are small RNAs 18 to 24 nucleotides in length that serve the pivotal function of regulating gene expression. Instead of being translated into proteins, the mature single-stranded miRNA binds to messenger RNAs (mRNAs) to interfere with the translational process. It is estimated that whereas only 1% of the genomic transcripts in mammalian cells encode miRNA, nearly one-third of the encoded genes are regulated by miRNA. Various bioinformatics databases, tools, and algorithms have been developed to predict the sequences of miRNAs and their target genes. In combination with the in silico approaches in systems biology, experimental studies on miRNA provide a new bioengineering approach for understanding the mechanism of fine-tuning gene regulation. This review aims to provide state-of-the-art information on this important mechanism of gene regulation for researchers working in biomedical engineering and related fields. Particular emphases are placed on summarizing the current tools and strategies for miRNA study from a bioengineering perspective and the possible applications of miRNAs (such as antagomirs and miRNA sponges) in biomedical engineering research.

MicroRNAs in skin and wound healing

MicroRNAs (miRNAs) are small endogenous RNA molecules ∼22 nt in length. miRNAs are capable of posttranscriptional gene regulation by binding to their target messenger RNAs (mRNAs), leading to mRNA degradation or suppression of translation. miRNAs have recently been shown to play pivotal roles in skin development and are linked to various skin pathologies, cancer, and wound healing. This review focuses on the role of miRNAs in cutaneous biology, the various methods of miRNA modulation, and the therapeutic opportunities in treatment of skin diseases and wound healing.

Improved function of diabetic wound-site macrophages and accelerated wound closure in response to oral supplementation of a fermented papaya preparation

Carica papaya Linn is widely known as a medicinal fruit. We sought to study a standardized fermented papaya preparation (FPP) for its effects on wound healing in adult obese diabetic (db/db) mice. FPP blunted the gain in blood glucose and improved the lipid profile after 8 weeks of oral supplementation. However, FPP did not influence weight gain during the supplementation period. FPP (0.2 g/kg body weight) supplementation for 8 weeks before wounding was effective in correcting wound closure. Studies on viable macrophages isolated from the wound site demonstrated that FPP supplementation improved respiratory-burst function as well as inducible NO production. Reactive oxygen species support numerous aspects of wound healing; NO availability in diabetic wounds is known to be compromised. Diabetic mice supplemented with FPP showed a higher abundance of CD68 as well as CD31 at the wound site, suggesting effective recruitment of monocytes and an improved proangiogenic response. This work provides the first evidence that diabetic-wound outcomes may benefit from FPP supplementation by specifically influencing the response of wound-site macrophages and the subsequent angiogenic response. Given that FPP has a long track record of safe human consumption, testing of the beneficial effects of FPP on diabetic wound-related outcomes in a clinical setting is warranted.

microRNAs and lung cancer: tumors and 22-mers

Work over the last decade has revealed novel regulatory mechanisms in pathological disease states that are mediated by microRNAs and has inspired researchers to begin elucidating the specific roles of miRNAs in the regulation of genes involved in cancer development and progression. Recently, miRNAs have been explored as therapeutic targets and diagnostic markers of cancer. In this paper, we review recent advances in the study of miRNAs involved in tumorigenesis, focusing on miRNA regulation of genes that have been demonstrated to play critical roles in lung cancer development. We discuss miRNA regulation of genes that play critical roles in the process of malignant transformation, angiogenesis and tumor metastasis, the dysregulation of miRNA expression in cancer development, and the development of miRNA-based diagnostics and therapeutics.

Hypoxia inducible microRNA 210 attenuates keratinocyte proliferation and impairs closure in a murine model of ischemic wounds

Ischemia complicates wound closure. Here, we are unique in presenting a murine ischemic wound model that is based on bipedicle flap approach. Using this model of ischemic wounds we have sought to elucidate how microRNAs may be implicated in limiting wound re-epithelialization under hypoxia, a major component of ischemia. Ischemia, evaluated by laser Doppler as well as hyperspectral imaging, limited blood flow and lowered tissue oxygen saturation. EPR oximetry demonstrated that the ischemic wound tissue had pO(2) <10 mm Hg. Ischemic wounds suffered from compromised macrophage recruitment and delayed wound epithelialization. Specifically, epithelial proliferation, as determined by Ki67 staining, was compromised. In vivo imaging showed massive hypoxia inducible factor-1alpha (HIF-1alpha) stabilization in ischemic wounds, where HIF-1alpha induced miR-210 expression that, in turn, silenced its target E2F3, which was markedly down-regulated in the wound-edge tissue of ischemic wounds. E2F3 was recognized as a key facilitator of cell proliferation. In keratinocytes, knock-down of E2F3 limited cell proliferation. Forced stabilization of HIF-1alpha using Ad-VP16- HIF-1alpha under normoxic conditions up-regulated miR-210 expression, down-regulated E2F3, and limited cell proliferation. Studies using cellular delivery of miR-210 antagomir and mimic demonstrated a key role of miR-210 in limiting keratinocyte proliferation. In summary, these results are unique in presenting evidence demonstrating that the hypoxia component of ischemia may limit wound re-epithelialization by stabilizing HIF-1alpha, which induces miR-210 expression, resulting in the down-regulation of the cell-cycle regulatory protein E2F3.

MicroRNAs in cardiovascular diseases: biology and potential clinical applications

Cardiovascular diseases represent one of the major causes for increasing rates of human morbidity and mortality across the world. This reinforces the necessity for the development of novel diagnostics and therapies for the early identification and cure of heart diseases. MicroRNAs are evolutionarily conserved small regulatory non-coding RNAs that regulate the expression of large number of genes. They are involved in several cellular pathophysiological pathways and have been shown to play a significant role in the pathogenesis of many disease states. Recent studies have correlated dysregulated miRNA expressions to diseased hearts and also shown the relevance of miRNA in growth, development, function, and stress responsiveness of the heart. The possibility of exploiting miRNAs to develop diagnostic markers or manipulating them to obtain therapeutic effects is very attractive since they have very specific targets in a particular cellular pathway. In this review we will summarize the role played by miRNAs in the heart and discuss the scope of utilizing miRNA-based strategies in the clinics for the benefit of mankind.

Role of microRNA-23b in flow-regulation of Rb phosphorylation and endothelial cell growth

MicroRNAs (miRs) can regulate many cellular functions, but their roles in regulating responses of vascular endothelial cells (ECs) to mechanical stimuli remain unexplored. We hypothesize that the physiological responses of ECs are regulated by not only mRNA and protein signaling networks, but also expression of the corresponding miRs. EC growth arrest induced by pulsatile shear (PS) flow is an important feature for flow regulation of ECs. miR profiling showed that 21 miRs are differentially expressed (8 up- and 13 downregulated) in response to 24-h PS as compared to static condition (ST). The mRNA expression profile indicates EC growth arrest under 24-h PS. Analysis of differentially expressed miRs yielded 68 predicted mRNA targets that overlapped with results of microarray mRNA profiling. Functional analysis of miR profile indicates that the cell cycle network is highly regulated. The upregulation of miR-23b and miR-27b was found to correlate with the PS-induced EC growth arrest. Inhibition of miR-23b using antagomir-23b oligonucleotide (AM23b) reversed the PS-induced E2F1 reduction and retinoblastoma (Rb) hypophosphorylation and attenuated the PS-induced G1/G0 arrest. Antagomir AM27b regulated E2F1 expression, but did not affect Rb and growth arrest. Our findings indicate that PS suppresses EC proliferation through the regulation of miR-23b and provide insights into the role of miRs in mechanotransduction.

Residual microvascular risk in diabetes: unmet needs and future directions

The burden of microvascular disease in patients with type 2 diabetes mellitus continues to escalate worldwide. Current standards of care reduce but do not eliminate the risk of diabetic retinopathy, nephropathy or neuropathy in these patients. Correction of atherogenic dyslipidemia, which is characterized by elevated triglyceride levels and low levels of HDL cholesterol, might provide additional benefit. Whereas promising data have been published with respect to fibrate therapy for maculopathy, fenofibrate for diabetic retinopathy, and statin or fibrate therapy for diabetic nephropathy, further studies are warranted to define optimal management strategies for reducing the residual microvascular risk. Such strategies are especially relevant in cases of diabetic peripheral neuropathy, where even optimal care fails to affect disease progression. Identification of those factors that are most relevant to residual diabetes-related microvascular risk is a priority of an ongoing multinational epidemiological study. In this Review, we highlight an urgent need to address the issue of microvascular residual risk in patients with or at risk of type 2 diabetes mellitus.

microRNAs in gliomas: small regulators of a big problem

Gliomas are the most common form of primary brain tumors and are associated with a poor clinical outcome. The molecular mechanisms that contribute to gliomagenesis have become increasingly clear in recent years, yet much remains to be learned. This is particularly true for the role of microRNAs in gliomagenesis, as an appreciation for the significance of aberrant miRNA expression in human cancer has only emerged in the last 5 years. It is now evident that microRNAs regulate a wide variety of tumorigenic processes including cellular proliferation, differentiation, angiogenesis, invasion, and apoptosis. Here we review the current state of knowledge related to the role of microRNAs in glial tumor development. This is a rapidly evolving field and it is likely that we have only begun to appreciate the involvement of microRNAs in relation to glioma formation, and the therapeutic potential of microRNAs to improve outcome for glioma patients.

Role of specific microRNAs for endothelial function and angiogenesis

Accumulating evidence indicates that various aspects of angiogenesis, such as proliferation, migration, and morphogenesis of endothelial cells, can be regulated by specific miRNAs in an endothelial-specific manner. As novel molecular targets, miRNAs have a potential value for treatment of angiogenesis-associated diseases such as cancers, inflammation, and vascular diseases. In this article, we review the latest advances in the identification and validation of angiogenesis-regulatory miRNAs and their targets, and discuss their roles and mechanisms in regulating endothelial cell function and angiogenesis.

Micromanaging vascular biology: tiny microRNAs play big band

Micro-RNAs (miRNAs) are estimated to regulate 30% of the human genome primarily through translational repression. In 2005-2008, the first series of observations establishing the key significance of miRNAs in the regulation of vascular biology came from experimental studies involved in arresting miRNA biogenesis to deplete the miRNA pools of vascular tissues and cells. Dicer-dependent biogenesis of miRNA is required for blood vessel development during embryogenesis and wound healing. miRNAs regulate redox signaling in endothelial cells, a key regulator of vascular cell biology. miRNAs that regulate angiogenesis include miRNA 17-5p, cluster 17-92, 21, 27a&b, 126, 130a, 210, 221, 222, 378 and the let7 family. miRNAs also represent a new therapeutic target for the treatment of proliferative vascular diseases as well as hypertension. Evidence supporting the regulation of inducible adhesion molecules by miRNA supports a role of miRNAs in regulating vascular inflammation. Productive strategies to safely up-regulate as well as down-regulate miRNAs in vivo are in place and being tested for their value in disease intervention. Prudent targeting of non-coding genes such as miRNAs, which in turn regulates large sets of coding genes, holds promise in gene therapy. Recent developments in miRNA biology offer lucrative opportunities to manage vascular health.

AngiomiRs--key regulators of angiogenesis

The formation of new blood vessels through the process of angiogenesis is critical in vascular development and homeostasis. Aberrant angiogenesis leads to a variety of diseases, such as ischemia and cancer. Recent studies have revealed important roles for miRNAs in regulating endothelial cell (EC) function, especially angiogenesis. Mice with EC-specific deletion of Dicer, a key enzyme for generating miRNAs, display defective postnatal angiogenesis. Specific miRNAs (angiomiRs) have recently been shown to regulate angiogenesis in vivo. miRNA-126, an EC-restricted miRNA, regulates vascular integrity and developmental angiogenesis. miR-378, miR-296, and the miR-17-92 cluster contribute to tumor angiogenesis. Manipulating angiomiRs in the settings of pathological vascularization represents a new therapeutic approach.

Effect of atorvastatin on microRNA 221 / 222 expression in endothelial progenitor cells obtained from patients with coronary artery disease

BACKGROUND

Endothelial progenitor cells (EPCs) play an important role in the maintenance of vascular integrity. Lipid lowering therapy (LLT) with statins may contribute to biologically relevant activities including the proliferation of endothelial cells. The physiological role of microRNA (miR)-221/222, a newly discovered class of small RNA, is closely linked to the proliferation of endothelial cells. We therefore investigated whether LLT with statins might affect miR-221/222 expression in EPCs obtained from patients with coronary artery disease (CAD).

MATERIALS AND METHODS

This study included 44 patients with stable CAD and 22 subjects without CAD (non-CAD). Patients with CAD were randomized to 12 months of LLT with atorvastatin (10 mg day(-1)) or pravastatin (10 mg day(-1)). EPCs were obtained from peripheral blood at baseline and after 12 months of statin therapy. Levels of miR-221/222 in EPCs were measured by real-time RT-PCR.

RESULTS

Levels of miR-221/222 were significantly higher in the CAD group than in the non-CAD group (P < 0.01). Levels of miR-221/222 were weakly negatively correlated with EPC number in the CAD group. After 12 months of therapy, changes in lipid profiles were greater in the atorvastatin group than in the pravastatin group. LLT with atorvastatin markedly increased EPC numbers and decreased miR-221/222 levels (all P < 0.05), whereas LLT with pravastatin did not change EPC numbers or miR-221/222 levels.

CONCLUSIONS

This study demonstrates that LLT with atorvastatin increases EPC numbers and decreases miR-221/222 levels in patients with CAD, possibly contributing to the beneficial effects of LLT with atorvastatin in this disorder.

MicroRNAs: control and loss of control in human physiology and disease

Analysis of the human genome indicates that a large fraction of the genome sequences are RNAs that do not encode any proteins, also known as non-coding RNAs. MicroRNAs (miRNAs) are a group of small non-coding RNA molecules 20-22 nucleotides (nt) in length that are predicted to control the activity of approximately 30% of all protein-coding genes in mammals. miRNAs play important roles in many diseases, including cancer, cardiovascular disease, and immune disorders. The expression of miRNAs can be regulated by epigenetic modification, DNA copy number change, and genetic mutations. miRNAs can serve as a valuable therapeutic target for a large number of diseases. For miRNAs with oncogenic capabilities, potential therapies include miRNA silencing, antisense blocking, and miRNA modifications. For miRNAs with tumor suppression functions, overexpression of those miRNAs might be a useful strategy to inhibit tumor growth. In this review, we discuss the current progress of miRNA research, regulation of miRNA expression, prediction of miRNA targets, and regulatory role of miRNAs in human physiology and diseases, with a specific focus on miRNAs in pancreatic cancer, liver cancer, colorectal cancer, cardiovascular disease, the immune system, and infectious disease. This review provides valuable information for clinicians and researchers who want to recognize the newest advances in this new field and identify possible lines of investigation in miRNAs as important mediators in human physiology and diseases.

Regulation of angiogenesis by oxygen and metabolism

Blood vessels form an important interface between the environment and the organism by carrying oxygen and nutrients to all cells and thus determining cellular metabolism. It is therefore not surprising that oxygen and metabolism influence the development of the vascular network. Here, we discuss recent insights regarding the emerging crosstalk between angiogenesis and metabolism. We will highlight advances in how oxygen and metabolism regulate angiogenesis as well as how angiogenic factors in turn also regulate metabolism.

MicroRNAs as novel regulators of angiogenesis

MicroRNAs are short noncoding RNAs that function as negative regulators of gene expression. Posttranscriptional regulation by miRNAs is important for many aspects of development, homeostasis, and disease. Endothelial cells are key regulators of different aspects of vascular biology, including the formation of new blood vessels (angiogenesis). Here, we review the approaches and current experimental evidence for the involvement of miRNAs in the regulation of the angiogenic process and their potential therapeutic applications for vascular diseases associated with abnormal angiogenesis.

MicroRNA expression in response to murine myocardial infarction: miR-21 regulates fibroblast metalloprotease-2 via phosphatase and tensin homologue

AIMS

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level by either degradation or translational repression of a target mRNA. Encoded in the genome of most eukaryotes, miRNAs have been proposed to regulate specifically up to 90% of human genes through a process known as miRNA-guided RNA silencing. For the first time, we sought to test how myocardial ischaemia-reperfusion (IR) changes miR expression.

METHODS AND RESULTS

Following 2 and 7 h of IR or sham operation, myocardial tissue was collected and subjected to miRNA expression profiling and quantification using a Bioarray system that screens for human-, mice-, rat-, and Ambi-miR. Data mining and differential analyses resulted in 13 miRs that were up-regulated on day 2, 9 miRs that were up-regulated on day 7, and 6 miRs that were down-regulated on day 7 post-IR. Results randomly selected from expression profiling were validated using real-time PCR. Tissue elements laser-captured from the infarct site showed marked induction of miR-21. In situ hybridization studies using locked nucleic acid miR-21-specific probe identified that IR-inducible miR-21 was specifically localized in the infarct region of the IR heart. Immunohistochemistry data show that cardiac fibroblasts (CFs) are the major cell type in the infarct zone. Studies with isolated CFs demonstrated that phosphatase and tensin homologue (PTEN) is a direct target of miR-21. Modulation of miR-21 regulated expression of matrix metalloprotease-2 (MMP-2) via a PTEN pathway. Finally, we noted a marked decrease in PTEN expression in the infarct zone. This decrease was associated with increased MMP-2 expression in the infarct area.

CONCLUSION

This work constitutes the first report describing changes in miR expression in response to IR in the mouse heart, showing that miR-21 regulates MMP-2 expression in CFs of the infarct zone via a PTEN pathway.

MicroRNAs: opening a new vein in angiogenesis research

Activation of the angiogenic program in endothelial cells is vital for normal embryonic development and for physiological angiogenesis in the adult. In addition, angiogenesis is an important therapeutic target: Formation of new blood vessels is desirable for regenerative purposes, such as during tissue healing or transplantation, but can be pathological, as in diabetic retinopathy and cancer. The response of the vascular endothelium to angiogenic stimuli is modulated by noncoding RNAs called microRNAs. The endothelial cell-specific microRNA microRNA-126 (miR-126) promotes angiogenesis in response to angiogenic growth factors, such as vascular endothelial growth factor or basic fibroblast growth factor, by repressing negative regulators of signal transduction pathways. Additional microRNAs have been implicated in the regulation of various aspects of angiogenesis. Thus, targeting the expression of microRNAs may be a novel therapeutic approach for diseases involving excess or insufficient vasculature.

Redox control of endothelial function and dysfunction: molecular mechanisms and therapeutic opportunities

The endothelium is essential for the maintenance of vascular homeostasis. Central to this role is the production of endothelium-derived nitric oxide (EDNO), synthesized by the endothelial isoform of nitric oxide synthase (eNOS). Endothelial dysfunction, manifested as impaired EDNO bioactivity, is an important early event in the development of various vascular diseases, including hypertension, diabetes, and atherosclerosis. The degree of impairment of EDNO bioactivity is a determinant of future vascular complications. Accordingly, growing interest exists in defining the pathologic mechanisms involved. Considerable evidence supports a causal role for the enhanced production of reactive oxygen species (ROS) by vascular cells. ROS directly inactivate EDNO, act as cell-signaling molecules, and promote protein dysfunction, events that contribute to the initiation and progression of endothelial dysfunction. Increasing data indicate that strategies designed to limit vascular ROS production can restore endothelial function in humans with vascular complications. The purpose of this review is to outline the various ways in which ROS can influence endothelial function and dysfunction, describe the redox mechanisms involved, and discuss approaches for preventing endothelial dysfunction that may highlight future therapeutic opportunities in the treatment of cardiovascular disease.

Role of microRNAs in vascular diseases, inflammation, and angiogenesis

The integrity of the endothelial monolayer is fundamental for the homoeostasis of the vascular system. Functional endothelial cells are also required for the growth of new blood vessels during neovascularization. Although multiple growth factors have been shown to regulate angiogenesis and vascular development, little is known about the complex upstream regulation of gene expression and translation. MicroRNAs (miRNAs) are an emerging class of highly conserved, non-coding small RNAs that regulate gene expression on the post-transcriptional level by inhibiting the translation of protein from mRNA or by promoting the degradation of mRNA. More than 500 human miRNAs have been identified so far, and increasing evidence indicates that miRNAs have distinct expression profiles and play crucial roles in various physiological and pathological processes such as cardiogenesis, haematopoietic lineage differentiation, and oncogenesis. Meanwhile, a few specific miRNAs that regulate endothelial cell functions and angiogenesis have been described. Let7-f, miR-27b, and mir-130a were identified as pro-angiogenic miRNAs. In contrast, miR-221 and miR-222 inhibit endothelial cell migration, proliferation, and angiogenesis in vitro by targeting the stem cell factor receptor c-kit and indirectly regulating endothelial nitric oxide synthase expression. Moreover, some miRNAs are involved in tumour angiogenesis such as the miR-17-92 cluster and miR-378. Early studies also indicate the contribution of specific miRNAs (e.g. miR-155, miR-21, and miR-126) to vascular inflammation and diseases. Thus, the identification of miRNAs and their respective targets may offer new therapeutic strategies to treat vascular diseases such as atherosclerosis, to improve neovascularization after ischaemia, or to prevent tumour progression.

Characterization of the acute temporal changes in excisional murine cutaneous wound inflammation by screening of the wound-edge transcriptome

This work represents a maiden effort to systematically screen the transcriptome of the healing wound-edge tissue temporally using high-density GeneChips. Changes during the acute inflammatory phase of murine excisional wounds were characterized histologically. Sets of genes that significantly changed in expression during healing could be segregated into the following five sets: up-early (6-24 h; cytokine-cytokine receptor interaction pathway), up-intermediary (12-96 h; leukocyte-endothelial interaction pathway), up-late (48-96 h; cell-cycle pathway), down-early (6-12 h; purine metabolism) and down-intermediary (12-96 h; oxidative phosphorylation pathway). Results from microarray and real-time PCR analyses were consistent. Results listing all genes that were significantly changed at any specific time point were further mined for cell-type (neutrophils, macrophages, endothelial, fibroblasts, and pluripotent stem cells) specificity. Candidate genes were also clustered on the basis of their functional annotation, linking them to inflammation, angiogenesis, reactive oxygen species (ROS), or extracellular matrix (ECM) categories. Rapid induction of genes encoding NADPH oxidase subunits and downregulation of catalase in response to wounding is consistent with the fact that low levels of endogenous H2O2 is required for wound healing. Angiogenic genes, previously not connected to cutaneous wound healing, that were induced in the healing wound-edge included adiponectin, epiregulin, angiomotin, Nogo, and VEGF-B. This study provides a digested database that may serve as a valuable reference tool to develop novel hypotheses aiming to elucidate the biology of cutaneous wound healing comprehensively.