MicroRNA-21 regulates vascular smooth muscle cell function via targeting tropomyosin 1 in arteriosclerosis obliterans of lower extremities

The Role of MicroRNAs in Arterial Stiffness and Arterial Calcification. An Update and Review of the Literature

Arterial stiffness is an independent risk factor for fatal and non-fatal cardiovascular events, such as systolic hypertension, coronary artery disease, stroke, and heart failure. Moreover it reflects arterial aging which in many cases does not coincide with chronological aging, a fact that is in large attributed to genetic factors. In addition to genetic factors, microRNAs (miRNAs) seem to largely affect arterial aging either by advancing or by regressing arterial stiffness. MiRNAs are small RNA molecules, ~22 nucleotides long that can negatively control their target gene expression posttranscriptionally. Pathways that affect main components of stiffness such as fibrosis and calcification seem to be influenced by up or downregulation of specific miRNAs. Identification of this aberrant production of miRNAs can help identify epigenetic changes that can be therapeutic targets for prevention and treatment of vascular diseases. The present review summarizes the specific role of the so far discovered miRNAs that are involved in pathways of arterial stiffness.

Mitoxantrone suppresses vascular smooth muscle cell (VSMC) proliferation and balloon injury-induced neointima formation: An in vitro and in vivo study

Neointima formation, which occurs after vascular injury due to vascular disease or interventions such as angioplasty and stent placement, is a complex process that involves multiple molecular and cellular mechanisms. The inhibition of neointima formation is vital to prevent restenosis of blood vessels. In the present study, we investigated whether the systemic administration of mitoxantrone can inhibit neointima formation, and evaluated the underlying mechanisms under in vitro and in vivo experimental conditions. In vitro, rat and human vascular smooth muscle cells (RVSMCs and HVSMCs) were stimulated with platelet-derived growth factor-BB (PDGF-BB) and treated with mitoxantrone or DMSO as a control. In vivo, 54 male Sprague-Dawley rats were subjected to carotid artery balloon injury and then intravenously administered with mitoxantrone. Cell proliferation was determined using the CCK-8 assay. Cell cycle analysis was performed using flow cytometry, and protein expression was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. We used monoclonal mouse anti-bromodeoxyuridine (BrdU) antibody for the detection of BrdU and anti-Topoisomerase II antibody for staining Type II topoisomerase (Topo II), one week after the ballon injury. In both RVSMCs and HVSMCs, mitoxantrone treatment induced Topo II degradation, as well as suppressed DNA replication, cell cycle progression, and VSMC proliferation. A reduction in intimal hyperplasia, intimal-to-medial area ratio, and Topo II level was observed in mitoxantrone-treated rats, as compared to the control (saline) group. Overall, our results indicate that systemic administration of mitoxantrone can reduce neointimal hyperplasia and, thus, represents a suitable option for restenosis treatment.

MicroRNA-31 promotes arterial smooth muscle cell proliferation and migration by targeting mitofusin-2 in arteriosclerosis obliterans of the lower extremitie

MicroRNA (miR)-31 serves a key role in various biological processes, including tumor development, angiogenesis and inflammation. Whether miR-31 is involved in the pathological processes of arteriosclerosis obliterans (ASO) remains to be elucidated, as does the mechanism of miR-31 regulation of arterial smooth muscle cells (ASMCs). In the present study, miR-31 expression was detected by reverse transcription-quantitative polymerase chain reaction and in situ hybridization, and was significantly upregulated in human ASO arterial walls compared with normal arterial walls (P<0.001). In addition, miR-31 proliferation was detected by Cell Counting Kit-8 and EdU assays; proliferation was significantly promoted in platelet-derived growth factor (PDGF)-BB-induced human ASMCs (HASMCs) (P<0.001). miR-31 migration was detected by transwell and wound closure assays, and was revealed to be promoted in PDGF-BB-induced HASMCs (P<0.001). Lastly, HASMCs were transfected with miR-31 mimics and inhibitors, and negative controls. A dual-luciferase reporter assay was performed to verify that mitofusin-2 (MFN2) was a direct target of miR-31 and that MFN2 expression was significantly downregulated by miR-31 at a post-transcriptional level in HASMCs as detected by western blotting (P<0.01). These findings suggest that miR-31 is able to promote the proliferation and migration of HASMCs, at least in part, by targeting MFN2. The results of the present study provide novel insight into the underlying mechanisms and roles of miR-31/MFN2 in the pathology of ASO, which may offer a potential therapeutic target for the treatment of ASO.

Association of miR-21, miR-126 and miR-605 gene polymorphisms with ischemic stroke risk

We investigated whether three common microRNA polymorphisms (miR-21T>C [rs1292037], miR-126G>A [rs4636297] and miR-605T>C [rs2043556]) were associated with ischemic stroke (IS) risk in a Chinese population. The study population comprised 592 ischemic stroke patients and 456 normal controls. The polymorphisms were measured using Snapshot SNP genotyping assays and confirmed by sequencing. Relative expressions of miR-21, miR-126 and miR-605 were measured by quantitative real-time PCR. We found that miR-126 gene rs4636297 polymorphism was associated with decreased ischemic stroke risk (GA vs. GG: AOR=0.64, adjust P=0.025; AA vs. GG: AOR=0.32, adjust P=0.007; dominant model: AOR=0.58, adjust P=0.004). MiR-21 gene rs1292037 and miR-605 gene rs2043556 polymorphisms were not associated with ischemic stroke risk. In addition, compared with normal controls, serum miR-126 level was significantly decreased in ischemic stroke patients, while the miR-21 level was significantly increased. Importantly, patients carrying rs4636297 GA/AA genotypes had higher serum miR-126 level (P<0.05). MiR-126 gene rs4636297 polymorphism and serum miR-126/-21 levels are associated with ischemic stroke risk. Our data indicates that miR-126 and miR-21 play roles in the development of ischemic stroke.

MicroRNA-124 controls human vascular smooth muscle cell phenotypic switch via Sp1

Phenotypic switch of vascular smooth muscle cells (VSMCs) plays an important role in the pathogenesis of atherosclerosis and aortic dissection. However, the mechanisms of phenotypic modulation are still unclear. MicroRNAs have emerged as important regulators of VSMC function. We recently found that microRNA-124 (miR-124) was downregulated in proliferative vascular diseases that were characterized by a VSMC phenotypic switch. Therefore, we speculated that the aberrant expression of miR-124 might play a critical role in human aortic VSMC phenotypic switch. Using quantitative RT-PCR, we found that miR-124 was dramatically downregulated in the aortic media of clinical specimens of the dissected aorta and correlated with molecular markers of the contractile VSMC phenotype. Overexpression of miR-124 by mimicking transfection significantly attenuated platelet-derived growth factor-BB-induced human aortic VSMC proliferation and phenotypic switch. Furthermore, we identified specificity protein 1 (Sp1) as the downstream target of miR-124. A luciferase reporter assay was used to confirm direct miR-124 targeting of the 3'-untranslated region of the Sp1 gene and repression of Sp1 expression in human aortic VSMCs. Furthermore, constitutively active Sp1 in miR-124-overexpressing VSMCs reversed the antiproliferative effects of miR-124. These results demonstrated a novel mechanism of miR-124 modulation of VSMC phenotypic switch by targeting Sp1 expression.NEW & NOTEWORTHY Previous studies have demonstrated that miR-124 is involved in the proliferation of a variety of cell types. However, miRNAs are expressed in a tissue-specific manner. We first identified miR-124 as a critical regulator in human aortic vascular smooth muscle cell differentiation, proliferation, and phenotype switch by targeting the 3'-untranslated region of specificity protein 1.

Natural antisense transcript TPM1-AS regulates the alternative splicing of tropomyosin I through an interaction with RNA-binding motif protein 4

LncRNAs play a vital role in alternative splicing of target genes. However, the mechanisms underlying lncRNAs involvement in splicing are poorly understood. In the present study, we identified a previously uncharacterized lncRNA, which is denoted as TPM1-AS, is reverse-transcribed from the fourth intronic region of the tropomyosin I (TPM1). In situ hybridization and RNA immunoprecipitation assays demonstrated that TPM1-AS was located in the nucleus and interacted with RNA-binding motif protein 4 (RBM4) in human esophageal cancer cells. TPM1-AS overexpression or RBM4 knockdown decreased endogenous exon 2a expression of TPM1, resulting in specifically down-regulation of TPM1variant V2 and V7 in human esophageal cancer cells. Mechanismly, the interaction of TPM1-AS with RBM4 hindered binding of RBM4 to TPM1 pre-mRNA and inhibited RBM4 to promote endogenous exon 2a inclusion of TPM1. Importantly, overexpression of TPM1-AS inhibited migration and filopodium formation, whereas TPM1variant V2 and V7 promoted these behaviors of human esophageal cancer cells. Taken together, the results suggest that a natural antisense TPM1-AS regulates the alternative splicing of TPM1 through an interaction with RBM4 and involves in TPM1-mediated filopodium formation and migration of cancer cells.

MicroRNAs在结直肠癌中的研究进展

结直肠癌在我国恶性肿瘤中的发病率较高, 且其死亡率居高不下. 目前, 越来越多的学者十分关注微小RNAs(microRNAs, miRNAs)与结直肠癌的关系. miRNAs是普遍存在于生物体内的一类小分子非编码RNA, miRNAs的异常表达与结直肠癌的发生和进展密切相关. miRNAs可以通过转录后基因调控的方式, 来影响肿瘤细胞的增殖、调亡以及对化疗的敏感性等. 在这里, 我们回顾了近年来关于miRNAs与结直肠癌的相关文献, 了解miRNAs在结直肠癌中的表达、结直肠癌化疗耐药以及其与预后的关系, 从而更好的了解结直肠癌进展的生物学过程, 有助于结直肠癌的诊断与治疗, 提高结直肠癌患者的预后.

Gene expression profiles and signaling mechanisms in α2B-adrenoceptor-evoked proliferation of vascular smooth muscle cells

BACKGROUND

α2-adrenoceptors are important regulators of vascular tone and blood pressure. Regulation of cell proliferation is a less well investigated consequence of α2-adrenoceptor activation. We have previously shown that α2B-adrenoceptor activation stimulates proliferation of vascular smooth muscle cells (VSMCs). This may be important for blood vessel development and plasticity and for the pathology and therapeutics of cardiovascular disorders. The underlying cellular mechanisms have remained mostly unknown. This study explored pathways of regulation of gene expression and intracellular signaling related to α2B-adrenoceptor-evoked VSMC proliferation.

RESULTS

The cellular mechanisms and signaling pathways of α2B-adrenoceptor-evoked proliferation of VSMCs are complex and include redundancy. Functional enrichment analysis and pathway analysis identified differentially expressed genes associated with α2B-adrenoceptor-regulated VSMC proliferation. They included the upregulated genes Egr1, F3, Ptgs2 and Serpine1 and the downregulated genes Cx3cl1, Cav1, Rhoa, Nppb and Prrx1. The most highly upregulated gene, Lypd8, represents a novel finding in the VSMC context. Inhibitor library screening and kinase activity profiling were applied to identify kinases in the involved signaling pathways. Putative upstream kinases identified by two different screens included PKC, Raf-1, Src, the MAP kinases p38 and JNK and the receptor tyrosine kinases EGFR and HGF/HGFR. As a novel finding, the Src family kinase Lyn was also identified as a putative upstream kinase.

CONCLUSIONS

α2B-adrenoceptors may mediate their pro-proliferative effects in VSMCs by promoting the activity of bFGF and PDGF and the growth factor receptors EGFR, HGFR and VEGFR-1/2. The Src family kinase Lyn was also identified as a putative upstream kinase. Lyn is known to be expressed in VSMCs and has been identified as an important regulator of GPCR trafficking and GPCR effects on cell proliferation. Identified Ser/Thr kinases included several PKC isoforms and the β-adrenoceptor kinases 1 and 2. Cross-talk between the signaling mechanisms involved in α2B-adrenoceptor-evoked VSMC proliferation thus appears to involve PKC activation, subsequent changes in gene expression, transactivation of EGFR, and modulation of kinase activities and growth factor-mediated signaling. While many of the identified individual signals were relatively small in terms of effect size, many of them were validated by combining pathway analysis and our integrated screening approach.

Epigenetics and Vascular Diseases: Influence of Non-coding RNAs and Their Clinical Implications

Epigenetics refers to heritable mechanisms able to modulate gene expression that do not involve alteration of the genomic DNA sequence. Classically, mechanisms such as DNA methylation and histone modifications were part of this classification. Today, this field of study has been expanded and includes also the large class of non-coding RNAs (ncRNAs). Indeed, with the extraordinary possibilities introduced by the next-generation sequencing approaches, our knowledge of the mammalian transcriptome has greatly improved. Today, we have identifying thousands of ncRNAs, and unsurprisingly, a direct association between ncRNA dysregulation and development of cardiovascular pathologies has been identified. This class of gene modulators is further divided into short-ncRNAs and long-non-coding RNAs (lncRNAs). Among the short-ncRNA sub-group, the best-characterized players are represented by highly conserved RNAs named microRNAs (miRNAs). miRNAs principally inhibit gene expression, and their involvement in cardiovascular diseases has been largely studied. On the other hand, due to the different roles played by lncRNAs, their involvement in cardiovascular pathology development is still limited, and further studies are needed. For instance, in order to define their roles in the cellular processes associated with the development of diseases, we need to better characterize the details of their mechanisms of action; only then might we be able to develop innovative therapeutic strategies. In this review, we would like to give an overview of the current knowledge on the function of ncRNAs and their involvement in the development of vascular diseases.

MicroRNA-98 rescues proliferation and alleviates ox-LDL-induced apoptosis in HUVECs by targeting LOX-1

Oxidized low-density lipoprotein (ox-LDL) is a major and critical mediator of atherosclerosis, and the underlying mechanism is thought to involve the ox-LDL-induced dysfunction of endothelial cells (ECs). MicroRNAs (miRNAs), which are a group of small non-coding RNA molecules that post-transcriptionally regulate the expression of target genes, have been associated with diverse cellular functions and the pathogenesis of various diseases, including atherosclerosis. miRNA-98 (miR-98) has been demonstrated to be involved in the regulation of cellular apoptosis; however, the role of miR-98 in ox-LDL-induced dysfunction of ECs and atherosclerosis has yet to be elucidated. Therefore, the present study aimed to investigate the role of miR-98 in ox-LDL-induced dysfunction of ECs and the underlying mechanism. It was demonstrated that miR-98 expression was markedly downregulated in ox-LDL-treated human umbilical vein ECs (HUVECs) and that miR-98 promoted the proliferation and alleviated apoptosis of HUVECs exposed to ox-LDL. In addition, the results demonstrated that lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) was a direct target of miR-98 in HUVECs, as indicated by a luciferase assay. The results of the present study suggested that miR-98 may inhibit the uptake of toxic ox-LDL, maintain HUVEC proliferation and protect HUVECs against apoptosis via the suppression of LOX-1.

Co-Targeting IGF-1R and Autophagy Enhances the Effects of Cell Growth Suppression and Apoptosis Induced by the IGF-1R Inhibitor NVP-AEW541 in Triple-Negative Breast Cancer Cells

BACKGROUND

Triple-negative breast cancer (TNBC) is the most intractable type of breast cancer, and there is a lack of effective targeted therapy. Insulin-like growth factor-1 receptor (IGF-1R) is reportedly a potential target for TNBC treatment. However, satisfying treatment outcomes in breast cancer patients have yet to be achieved with IGF-1R-targeted agents.

METHODS

To confirm whether inhibiting IGF-1R could induce autophagy, we detected autophagy-related proteins by western blotting and immunofluorescence staining of LC3-II. The IGF-1R inhibitor NVP-AEW541, autophagy inhibitor 3-methyladenine (3-MA) and Atg7 small interfering RNA (siRNA) were used to further investigate the effects of autophagy induced by IGF-1R inhibition in TNBC cells. The CCK8 assay, EdU assay, apoptosis and cell cycle analyses were applied to test cell function after treatment.

RESULTS

NVP-AEW541 markedly induced autophagy in TNBC cells by increasing the levels of the autophagy-related protein Beclin-1 and the LC3-II/LC-I ratio and reducing the selective autophagy substrate p62. Joint application of 3-MA or Atg7 siRNA enhanced the cell growth inhibition and apoptosis effects of NVP-AEW541 by arresting cells at G1/G0 phase and increasing Bax expression and decreasing that of Bcl-2.

CONCLUSION

Targeting IGF-1R in TNBC induces cell-protective autophagy, thereby weakening the therapeutic effect of agents directed toward IGF-1R. Our findings reveal that combined use autophagy-disrupting agents can enhance the therapeutic efficacy of IGF-1R inhibitors in TNBC cells and may provide a valuable treatment strategy for IGF-1R inhibitor-based therapies for TNBC and other IGF-1 signaling-associated tumors.

Function, Role, and Clinical Application of MicroRNAs in Vascular Aging

Vascular aging, a specific type of organic aging, is related to age-dependent changes in the vasculature, including atherosclerotic plaques, arterial stiffness, fibrosis, and increased intimal thickening. Vascular aging could influence the threshold, process, and severity of various cardiovascular diseases, thus making it one of the most important risk factors in the high mortality of cardiovascular diseases. As endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are the main cell biological basis of these pathology changes of the vasculature, the structure and function of ECs and VSMCs play a key role in vascular aging. MicroRNAs (miRNAs), small noncoding RNAs, have been shown to regulate the expression of multiple messenger RNAs (mRNAs) posttranscriptionally, contributing to many crucial aspects of cell biology. Recently, miRNAs with functions associated with aging or aging-related diseases have been studied. In this review, we will summarize the reported role of miRNAs in the process of vascular aging with special emphasis on EC and VSMC functions. In addition, the potential application of miRNAs to clinical practice for the diagnosis and treatment of cardiovascular diseases will also be discussed.

NCK Associated Protein 1 Modulated by miRNA-214 Determines Vascular Smooth Muscle Cell Migration, Proliferation, and Neointima Hyperplasia

BACKGROUND

MicroRNA miR-214 has been implicated in many biological cellular functions, but the impact of miR-214 and its target genes on vascular smooth muscle cell (VSMC) proliferation, migration, and neointima smooth muscle cell hyperplasia is unknown.

METHODS AND RESULTS

Expression of miR-214 was closely regulated by different pathogenic stimuli in VSMCs through a transcriptional mechanism and decreased in response to vascular injury. Overexpression of miR-214 in serum-starved VSMCs significantly decreased VSMC proliferation and migration, whereas knockdown of miR-214 dramatically increased VSMC proliferation and migration. Gene and protein biochemical assays, including proteomic analyses, showed that NCK associated protein 1 (NCKAP1)-a major component of the WAVE complex that regulates lamellipodia formation and cell motility-was negatively regulated by miR-214 in VSMCs. Luciferase assays showed that miR-214 substantially repressed wild-type but not the miR-214 binding site mutated version of NCKAP1 3' untranslated region luciferase activity in VSMCs. This result confirmed that NCKAP1 is the functional target of miR-214 in VSMCs. NCKAP1 knockdown in VSMCs recapitulates the inhibitory effects of miR-214 overexpression on actin polymerization, cell migration, and proliferation. Data from cotransfection experiments also revealed that inhibition of NCKAP1 is required for miR-214-mediated lamellipodia formation, cell motility, and growth. Importantly, locally enforced expression of miR-214 in the injured vessels significantly reduced NCKAP1 expression levels, inhibited VSMC proliferation, and prevented neointima smooth muscle cell hyperplasia after injury.

CONCLUSIONS

We uncovered an important role of miR-214 and its target gene NCKAP1 in modulating VSMC functions and neointima hyperplasia. Our findings suggest that miR-214 represents a potential therapeutic target for vascular diseases.

MicroRNA-497 Induces Apoptosis and Suppresses Proliferation via the Bcl-2/Bax-Caspase9-Caspase3 Pathway and Cyclin D2 Protein in HUVECs

INTRODUCTION

MicroRNAs play crucial roles in various types of diseases. However, to date, no information about the role of miR-497 in the development of atherosclerosis has been reported. This study investigated the possible role of miR-497 in vascular endothelial cell injury during the early stage of atherosclerosis.

MATERIALS AND METHODS

The expression level of miR-497 in human umbilical vein endothelial cells (HUVECs) exposed to ox-LDL was detected using qRT-PCR. To perform gain of function and loss of function analyses, miR-497 mimics were transfected into HUVECs, and miR-497 inhibitors were transfected into HUVECs stimulated with ox-LDL. Flow cytometry was used to analyze cell cycle progression and apoptosis. EdU and CCK-8 assays were employed to detect DNA synthesis and cell proliferation, respectively. After bioinformatics prediction, a dual Luciferase Reporter assay was used to analyze the direct target genes of miR-497. The mRNA and protein levels of the target genes were detected using qRT-PCR and western blot analyses, respectively. Caspase-9/3 activity was analyzed to determine the mechanism of endothelial dysfunction.

RESULTS

We showed that miR-497 was significantly upregulated in HUVECs stimulated with ox-LDL. Ectopic expression of miR-497 suppressed cell proliferation, induced apoptosis and increased the activity of caspase-9/3. After verification, Bcl2 and CCND2 were shown to be direct target genes of miR-497 in HUVECs. MiR-497 significantly suppressed cell proliferation by arresting the cell cycle through the CCND2 protein and induced apoptosis through the Bcl2/Bax-caspase9-caspase3 pathway.

CONCLUSION

Overall, our study shows that miR-497 might play a role in the development of atherosclerosis by inducing apoptosis and suppressing the proliferation of vascular endothelial cells. Therefore, miR-497 could be a potential therapeutic target for the treatment of atherosclerosis.

Hyperglycaemia-induced reciprocal changes in miR-30c and PAI-1 expression in platelets

Type 2 diabetic mellitus (DM2) is associated with accelerated thrombotic complications and is characterized by high levels of plasminogen activator inhibitor-1 (PAI-1). Recent studies show that human platelets have high levels of miR-30c and synthesize considerable active PAI-1. The underlying mechanism of how PAI-1 expression is upregulated in DM2 is poorly understood. We now report that hyperglycaemia-induced repression of miR-30c increases PAI-1 expression and thrombus formation in DM2. Bioinformatic analysis and identification of miRNA targets were assessed using luciferase assays, quantitative real-time PCR and western blots invitro and in vivo. The changes in miR-30c and PAI-1 levels were identified in platelets from healthy and diabetic individuals. We found that miR-30c directly targeted the 3′ UTR of PAI-1 and negatively regulated its expression. miR-30c was negatively correlated with glucose and HbA1c levels in DM2. In HFD-fed diabetic mice, increasing miR-30c expression by lenti-miR-30c significantly decreased the PAI-1 expression and prolonged the time to occlusion in an arterial thrombosis model. Platelet depletion/reinfusion experiments generating mice with selective ablation of PAI-1 demonstrate a major contribution by platelet-derived PAI-1 in the treatment of lenti-miR-30c to thrombus formation. These results provide important implications regarding the regulation of fibrinolysis by platelet miRNA under diabetic mellitus.

Role of noncoding RNA in vascular remodelling

PURPOSE OF REVIEW

Noncoding RNAs (ncRNAs), such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are becoming fundamentally important in the pathophysiology relating to injury-induced vascular remodelling. We highlight recent studies that demonstrate the involvement of ncRNAs in vein graft disease, in in-stent restenosis and in pulmonary arterial hypertension, with a particular focus on endothelial cell and vascular smooth muscle cell function. We also briefly discuss the emerging role of exosomal-derived ncRNAs and how this mechanism impacts on vascular function.

RECENT FINDINGS

ncRNAs have been described as novel regulators in the pathophysiology of vascular injury, inflammation, and vessel wall remodelling. In particular, several studies have demonstrated that manipulation of miRNAs can reduce the burden of pathological vascular remodelling. Such studies have also shown that exosomal miRNA-mediated, cell-to-cell communication between endothelial cells and vascular smooth muscle cells is critical in the disease process. In addition to miRNAs, lncRNAs are emerging as regulators of vascular function in health and disease. Although lncRNAs are complex in both their sheer numbers and mechanisms of action, identifying their contribution to vascular disease is essential.

SUMMARY

Given the important roles of ncRNAs in vascular injury and remodelling together will their capacity for cell-to-cell communication, manipulating ncRNA might provide novel therapeutic interventions.

Nanomedicine Meets microRNA: Current Advances in RNA-Based Nanotherapies for Atherosclerosis

Cardiovascular disease (CVD) accounts for almost half of all deaths worldwide and has now surpassed infectious disease as the leading cause of death and disability in developing countries. At present, therapies such as low-density lipoprotein-lowering statins and antihypertensive drugs have begun to bend the morality curve for coronary artery disease (CAD); yet, as we come to appreciate the more complex pathophysiological processes in the vessel wall, there is an opportunity to fine-tune therapies to more directly target mechanisms that drive CAD. MicroRNAs (miRNAs) have been identified that control vascular cell homeostasis,(1-3) lipoprotein metabolism,(4-9) and inflammatory cell function.(10) Despite the importance of these miRNAs in driving atherosclerosis and vascular dysfunction, therapeutic modulation of miRNAs in a cell- and context-specific manner has been a challenge. In this review, we summarize the emergence of miRNA-based therapies as an approach to treat CAD by specifically targeting the pathways leading to the disease. We focus on the latest development of nanoparticles (NPs) as a means to specifically target the vessel wall and what the future of these nanomedicines may hold for the treatment of CAD.

Thyroid Hormone and Vascular Remodeling

Both hyperthyroidism and hypothyroidism affect the cardiovascular system. Hypothyroidism is known to be associated with enhanced atherosclerosis and ischemic heart diseases. The accelerated atherosclerosis in the hypothyroid state has been traditionally ascribed to atherogenic lipid profile, diastolic hypertension, and impaired endothelial function. However, recent studies indicate that thyroid hormone has direct anti-atherosclerotic effects, such as production of nitric oxide and suppression of smooth muscle cell proliferation. These data suggest that thyroid hormone inhibits atherogenesis through direct effects on the vasculature as well as modification of risk factors for atherosclerosis. This review summarizes the basic and clinical studies on the role of thyroid hormone in vascular remodeling. The possible application of thyroid hormone mimetics to the therapy of hypercholesterolemia and atherosclerosis is also discussed.

miRNA-34a reduces neointima formation through inhibiting smooth muscle cell proliferation and migration

AIMS

We have recently reported that microRNA-34a (miR-34a) regulates vascular smooth muscle cell (VSMC) differentiation from stem cells in vitro and in vivo. However, little is known about the functional involvements of miR-34a in VSMC functions and vessel injury-induced neointima formation. In the current study, we aimed to establish the causal role of miR-34a and its target genes in VSMC proliferation, migration and neointima lesion formation.

METHODS AND RESULTS

Various pathological stimuli regulate miR-34a expression in VSMCs through a transcriptional mechanism, and the P53 binding site is required for miR-34a gene regulation by these stimuli. miR-34a over-expression in serum-starved VSMCs significantly inhibited VSMC proliferation and migration, while knockdown of miR-34a dramatically promoted VSMC proliferation and migration, respectively. Notch homolog 1 (Notch1), a well-reported regulator in VSMC functions and arterial remodeling, was predicted as one of the top targets of miR-34a by using several computational miRNA target prediction tools, and was negatively regulated by miR-34a in VSMCs. Luciferase assay showed miR-34a substantially repressed wild type Notch1-3'-UTR-luciferase activity in VSMCs, but not mutant Notch1-3'-UTR-luciferease reporter, confirming the Notch1 is the functional target of miR-34a in VSMCs. Data from co-transfection experiments also revealed that miR-34a inhibited VSMC proliferation and migration through modulating Notch gene expression levels. Importantly, the expression level of miR-34a was significantly down-regulated in injured arteries, and miR-34a perivascular over-expression significantly reduced Notch1 expression levels, decreased VSMC proliferation, and inhibited neointima formation in wire-injured femoral arteries.

CONCLUSION

Our data have demonstrated that miR-34a is an important regulator in VSMC functions and neointima hyperplasia, suggesting its potential therapeutic application for vascular diseases.

Vascular Smooth Muscle as a Target for Novel Therapeutics

Cardiovascular disease is the principal cause of death in patients with type 2 diabetes (T2DM). Exposure of the vasculature to metabolic disturbances leaves a persistent imprint on vascular walls, and specifically on smooth muscle cells (SMC) that favours their dysfunction and potentially underlies macrovascular complications of T2DM. Current diabetes therapies and continued development of newer treatments has led to the ability to achieve more efficient glycaemic control. There is also some evidence to suggest that some of these treatments may exert favourable pleiotropic effects, some of which may be at the level of SMC. However, emerging interest in epigenetic markers as determinants of vascular disease, and a putative link with diabetes, opens the possibility for new avenues to develop robust and specific new therapies. These will likely need to target cell-specific epigenetic changes such as effectors of DNA histone modifications that promote or inhibit gene transcription, and/or microRNAs capable of regulating entire cellular pathways through target gene repression. The growing epidemic of T2DM worldwide, and its attendant cardiovascular mortality, dictates a need for novel therapies and personalised approaches to ameliorate vascular complications in this vulnerable population.

Altered Plasma MicroRNAs as Novel Biomarkers for Arteriosclerosis Obliterans

AIM

Arteriosclerosis obliterans (ASO) of the lower extremities is a major cause of adult limb loss worldwide. A timely diagnosis in the early stages of the disease determines the clinical outcomes, however lacking of palpable symptoms remains the biggest obstacle. This study aimed to screen a cluster of microRNAs (miRNAs) that can be used as biomarker for the ASO in the earlier stages.

METHODS

Plasma from 3 patients with ASO and 3 healthy controls were profiled to screen altered miRNAs by microarray, then Real time PCR was further used to confirm the changes in 55 ASO patients and 54 controls.We also analyzed the correlation of miRNAs level with Fontaine stages and the influence of T2DM which is a common complication with ASO on the level of miRNAs.

RESULT

Twenty-four aberrantly expressed miRNAs were screened in the plasma of ASO patients. Real time PCR verified that the level of miR-4284 was significantly increased, while levels of miR-4463, miR-4306 and miR-221-3p were significantly decreased both in the plasma and in the sclerotic samples compared with the controls. Interestingly, we revealed a time and stage specific expression manner, as shown that expression of miR-4284 increased at the stage I of ASO and maintained the tendency to stage IV, while miR-4463 expression decreased at every stage of ASO; however, the expression of miR-4463 showed opposite changes in ASO patients with or without T2DM.

CONCLUSION

Altered expressions of miR-4284 and miR-4463 are novel characteristics and may serve as potential biomarkers for the early diagnosis of ASO.

Reducing In-Stent Restenosis: Therapeutic Manipulation of miRNA in Vascular Remodeling and Inflammation

Background

Drug-eluting stents reduce the incidence of in-stent restenosis, but they result in delayed arterial healing and are associated with a chronic inflammatory response and hypersensitivity reactions. Identifying novel interventions to enhance wound healing and reduce the inflammatory response may improve long-term clinical outcomes. Micro–ribonucleic acids (miRNAs) are noncoding small ribonucleic acids that play a prominent role in the initiation and resolution of inflammation after vascular injury.

Objectives

This study sought to identify miRNA regulation and function after implantation of bare-metal and drug-eluting stents.

Methods

Pig, mouse, and in vitro models were used to investigate the role of miRNA in in-stent restenosis.

Results

We documented a subset of inflammatory miRNAs activated after stenting in pigs, including the miR-21 stem loop miRNAs. Genetic ablation of the miR-21 stem loop attenuated neointimal formation in mice post-stenting. This occurred via enhanced levels of anti-inflammatory M2 macrophages coupled with an impaired sensitivity of smooth muscle cells to respond to vascular activation.

Conclusions

MiR-21 plays a prominent role in promoting vascular inflammation and remodeling after stent injury. MiRNA-mediated modulation of the inflammatory response post-stenting may have therapeutic potential to accelerate wound healing and enhance the clinical efficacy of stenting.

KSHV MicroRNAs Repress Tropomyosin 1 and Increase Anchorage-Independent Growth and Endothelial Tube Formation

Kaposi’s sarcoma (KS) is characterized by highly vascularized spindle-cell tumors induced after infection of endothelial cells by Kaposi’s sarcoma-associated herpesvirus (KSHV). In KS tumors, KSHV expresses only a few latent proteins together with 12 pre-microRNAs. Previous microarray and proteomic studies predicted that multiple splice variants of the tumor suppressor protein tropomyosin 1 (TPM1) were targets of KSHV microRNAs. Here we show that at least two microRNAs of KSHV, miR-K2 and miR-K5, repress protein levels of specific isoforms of TPM1. We identified a functional miR-K5 binding site in the 3’ untranslated region (UTR) of one TPM1 isoform. Furthermore, the inhibition or loss of miR-K2 or miR-K5 restores expression of TPM1 in KSHV-infected cells. TPM1 protein levels were also repressed in KSHV-infected clinical samples compared to uninfected samples. Functionally, miR-K2 increases viability of unanchored human umbilical vein endothelial cells (HUVEC) by inhibiting anoikis (apoptosis after cell detachment), enhances tube formation of HUVECs, and enhances VEGFA expression. Taken together, KSHV miR-K2 and miR-K5 may facilitate KSHV pathogenesis.

Local MicroRNA Modulation Using a Novel Anti-miR-21-Eluting Stent Effectively Prevents Experimental In-Stent Restenosis

OBJECTIVE

Despite advances in stent technology for vascular interventions, in-stent restenosis (ISR) because of myointimal hyperplasia remains a major complication.

APPROACH AND RESULTS

We investigated the regulatory role of microRNAs in myointimal hyperplasia/ISR, using a humanized animal model in which balloon-injured human internal mammary arteries with or without stenting were transplanted into Rowett nude rats, followed by microRNA profiling. miR-21 was the only significantly upregulated candidate. In addition, miR-21 expression was increased in human tissue samples from patients with ISR compared with coronary artery disease specimen. We systemically repressed miR-21 via intravenous fluorescein-tagged-locked nucleic acid-anti-miR-21 (anti-21) in our humanized myointimal hyperplasia model. As expected, suppression of vascular miR-21 correlated dose dependently with reduced luminal obliteration. Furthermore, anti-21 did not impede reendothelialization. However, systemic anti-miR-21 had substantial off-target effects, lowering miR-21 expression in liver, heart, lung, and kidney with concomitant increase in serum creatinine levels. We therefore assessed the feasibility of local miR-21 suppression using anti-21-coated stents. Compared with bare-metal stents, anti-21-coated stents effectively reduced ISR, whereas no significant off-target effects could be observed.

CONCLUSION

This study demonstrates the efficacy of an anti-miR-coated stent for the reduction of ISR.

[Epigenetics in atherosclerosis]

The association studies based on candidate genes carried on for decades have helped in visualizing the influence of the genetic component in complex diseases such as atherosclerosis, also showing the interaction between different genes and environmental factors. Even with all the knowledge accumulated, there is still some way to go to decipher the individual predisposition to disease, and if we consider the great influence that environmental factors play in the development and progression of atherosclerosis, epigenetics is presented as a key element in trying to expand our knowledge on individual predisposition to atherosclerosis and cardiovascular disease. Epigenetics can be described as the discipline that studies the mechanisms of transcriptional regulation, independent of changes in the sequence of DNA, and mostly induced by environmental factors. This review aims to describe what epigenetics is and how epigenetic mechanisms are involved in atherosclerosis.

MicroRNA-1298 is regulated by DNA methylation and affects vascular smooth muscle cell function by targeting connexin 43

AIMS

Growing evidence links microRNA to the process of peripheral vascular disease. Recently, we have found that microRNA-1298(miR-1298) is one of the most significantly down-regulated microRNAs in human arteries with arteriosclerosis obliterans (ASO) of the lower extremities. However, little is known regarding its role in the process of ASO. The present study aimed to investigate the expression, regulatory mechanisms, and functions of miR-1298 in the process of ASO.

METHODS AND RESULTS

Using quantitative reverse-transcription PCR and in situ hybridization assays, miR-1298 was observed predominantly expressed in the vascular smooth muscle cells (VSMCs) and was significantly down-regulated in ASO compared with normal arteries. Pyrosequencing analysis revealed that the miR-1298 DNA upstream of CpG sites were hypermethylated in ASO compared with normal arteries. Next, the luciferase reporter assay revealed that miR-1298 down-regulation is related with upstream DNA CpG site hypermethylation. Introducing a miR-1298 mimic into cultured VSMCs significantly attenuated cell proliferation and migration. Connexin 43 (Cx43) was validated to be a functional target of miR-1298 that was involved in the miR-1298-mediated cellular effects. Finally, lentivirus-mediated delivery of miR-1298 and its target Cx43 into a rat carotid balloon injury model indicated that re-overexpression of miR-1298 significantly decreased neointimal formation by targeting connexin 43.

CONCLUSION

Our data demonstrate a specific role of the upstream DNA methylation/miR-1298/Cx43 pathway in regulating VSMC function and suggest that modulation of miR-1298 levels may offer a novel therapeutic approach for ASO.

MicroRNA-155 modulates the proliferation of vascular smooth muscle cells by targeting endothelial nitric oxide synthase

A variety of microRNAs (miRNAs) have been reported to be significantly be involved in the regulation of vascular smooth muscle cell (VSMC) proliferation, which is an essential process for the formation of atherosclerotic plaque. The objective of the present study was to explore the role of microRNA-155 (miR-155) in the regulation of VSMC growth and migration. A total of 12 atherosclerotic plaque samples and 9 control samples were collected, and the expression levels of miR-155/endothelial nitric oxide synthase (eNOS) were determined in those samples by RT-qPCR and western blot analysis. The results revealed that the relative expression levels of miR-155 in the atherosclerotic plaque samples were significantly upregulated compared with those in the normal control samples. We further found eNOS to be an effective target of miR-155 in the VSMCs by luciferase assay, which was confirmed by the observation that VSMCs transfected with miR-155 mimics exhibited a significantly lower protein expression level of eNOS. We also demonstrated that the exogenous overexpression of miR-155 significantly enhanced cell proliferation by inhibiting apoptosis in human aortic SMCs (HASMCs), and it also promoted the migratory ability of the cells. In conclusion, our data demonstrate that miR-155 is significantly upregulated in atherosclerotic plaque, functioning to accelerate the proliferation and migration of VSMCs by targeting eNOS.

Epigenetic reprogramming in atherosclerosis

Recent data support the involvement of epigenetic alterations in the pathogenesis of atherosclerosis. The most widely investigated epigenetic mechanism is DNA methylation although also histone code changes occur during the diverse steps of atherosclerosis, such as endothelial cell proliferation, vascular smooth muscle cell (SMC) differentiation, and inflammatory pathway activation. In this review, we focus on the main genes that are epigenetically modified during the atherogenic process, particularly nitric oxide synthase (NOS), estrogen receptors (ERs), collagen type XV alpha 1 (COL15A1), vascular endothelial growth factor receptor (VEGFR), and ten-eleven translocation (TET), which are involved in endothelial dysfunction; gamma interferon (IFN-γ), forkhead box p3 (FOXP3), and tumor necrosis factor-α (TNF-α), associated with atherosclerotic inflammatory process; and p66shc, lectin-like oxLDL receptor (LOX1), and apolipoprotein E (APOE) genes, which are regulated by high cholesterol and homocysteine (Hcy) levels. Furthermore, we also discuss the role of non-coding RNAs (ncRNA) in atherosclerosis. NcRNAs are involved in epigenetic regulation of endothelial function, SMC proliferation, cholesterol synthesis, lipid metabolism, and inflammatory response.

Therapeutic Potential of Modulating MicroRNA in Peripheral Artery Disease

Peripheral artery disease (PAD) produces significant disability attributable to lower extremity ischemia. Limited treatment modalities exist to ameliorate clinical symptoms in patients with PAD. Growing evidence links microRNAs to key processes that govern disease expression in PAD including angiogenesis, endothelial function, inflammation, vascular regeneration, vascular smooth muscle cell function, restenosis, and mitochondrial function. MicroRNAs have been identified in circulation and may serve as novel biomarkers in PAD. This article reviews the potential contribution of microRNA to key pathways of disease development in PAD that may lead to microRNA-based diagnostic and therapeutic approaches.

Prediction of long-term outcome after acute myocardial infarction using circulating miR-145

BACKGROUND

Recent reports have shown that miR-145 concentration correlates with infarct size. In this paper, we attempt to predict heart failure and cardiovascular death after acute myocardial infarction using circulating miR-145 concentration.

METHODS

We assessed 246 patients with first ST-segment-elevation myocardial infarction who underwent successful percutaneous coronary intervention. We measured circulating miR-145, N-terminal fragment of the precursor B-type natriuretic peptide, myocardial-band creatine kinase, and cardiac troponin-I concentrations on day 5 after primary percutaneous coronary intervention and assessed their correlations with long-term clinical outcome.

RESULTS

During the one-year follow-up period, 72 patients experienced primary composite cardiac events (cardiac death or hospitalization for worsening heart failure). Multivariable Cox proportional hazards analysis indicated that circulating miR-145 (hazard ratio 7.174, 95% confidence interval 4.208-12.229); p < 0.0001) was a significant independent predictor of cardiac events after adjustment for multiple confounders.

CONCLUSION

Circulating miR-145 may be a novel biomarker for predicting long-term outcome after acute myocardial infarction.

Involvement of MicroRNA-133a in the Development of Arteriosclerosis Obliterans of the Lower Extremities via RhoA Targeting

AIM

RhoA is a critical factor in regulating the proliferation and migration of arterial smooth muscle cells (ASMCs) in patients with arteriosclerosis obliterans (ASO). RhoA is modulated by microRNA-133a (miR-133a) in cardiac myocytes and bronchial smooth muscle cells. However, the relationship between miR-133a and RhoA with respect to the onset of ASO in the lower extremities is uncertain.

METHODS

We employed in situ hybridization (ISH) and immunohistochemistry (IHC) to detect the location of miR-133a and RhoA in ASO clinical samples, respectively. 5-ethynyl-2'-deoxyuridine (EdU), cell counting kit-8 (CCK-8), Transwell and wound closure assays were utilized to determine the features of human ASMC (HASMC) proliferation and migration. The expression of miR-133a in the HASMCs was assessed using quantitative real-time PCR (qRT-PCR), while that of RhoA was examined via qRT-PCR and Western blotting.

RESULTS

We found miR-133a and RhoA to be primarily located in the ASMCs of ASO. miR-133a was significantly downregulated in the ASO tissues and proliferating HASMCs. In contrast, RhoA was upregulated in the ASO samples. The proliferation and migration of HASMCs was markedly promoted by the downregulation of miR-133a and inhibited by the upregulation of miR-133a. The Luciferase assay confirmed that RhoA was a direct target of miR-133a. The upregulation of miR-133a in the HASMCs decreased the RhoA expression at the protein level. Inversely, the downregulation of miR-133a increased the RhoA protein expression. Of note, the overexpression of RhoA in the HASMCs attenuated the anti-proliferative and anti-migratory effects of miR-133a.

CONCLUSIONS

Our data indicate that miR-133a regulates the functions of HASMCs by targeting RhoA and may be involved in the pathogenesis of ASO. These findings may lead to the development of potential therapeutic targets for ASO of the lower extremities.

Upregulation of let-7a inhibits vascular smooth muscle cell proliferation in vitro and in vein graft intimal hyperplasia in rats

BACKGROUND

Proliferation of vascular smooth muscle cells (VSMCs) is a crucial event in the pathogenesis of intimal hyperplasia, which is the main cause of restenosis after vascular reconstruction. In this study, we assessed the impact of let-7a microRNA (miRNA) on the proliferation of VSMCs.

METHODS

Using miRNA microarrays analysis for miRNA expression in the vein graft model. Lentiviral vector-mediated let-7a was transfected into the vein grafts. In situ hybridization was performed to detect let-7a. Cultured rat VSMCs were transfected with let-7a mimics for different periods of time. Cell proliferation, migration and cell cycle activity were monitored following transfection of the let-7a mimics. Immunohistochemical and Western blotting analysis the expression levels of c-myc and K-ras.

RESULTS

We found that let-7a was the most downregulated miRNA in the vein graft model. In vivo proliferation of VSMCs was assessed in a rat model of venous graft intimal hyperplasia. Let-7a was found to localize mainly to the VSMCs. Let-7a miRNA expression was increased in VSMCs in the neointima of the let-7a treated group. Intimal hyperplasia was suppressed by upregulation of let-7a via lentiviral vector-mediated mimics. In cultured VSMCs, the expression of let-7a increased upon starving, and the upregulation of let-7a miRNA significantly decreased cell proliferation and migration. Immunohistochemical and Western blotting analysis demonstrated that treatment with let-7a mimics resulted in decreased expression levels of c-myc and K-ras.

CONCLUSIONS

The results indicate that let-7a miRNA is a novel regulator of VSMC proliferation in intimal hyperplasia. These findings suggest that let-7a miRNA is a promising therapeutic target for the prevention of intimal hyperplasia.

Noncoding RNAs and atherosclerosis

Noncoding RNAs (ncRNAs) represent a class of RNA molecules that typically do not code for proteins. Emerging data suggest that ncRNAs play an important role in several physiological and pathological conditions such as cancer and cardiovascular diseases, including atherosclerosis. The best-characterized ncRNAs are the microRNAs which are small, approximately 22-nucleotide sequences of RNA that regulate gene expression at the posttranscriptional level through transcript degradation or translational repression. MicroRNAs control several aspects of atherosclerosis, including endothelial cell, vascular smooth cell, and macrophage functions as well as lipoprotein metabolism. Apart from microRNAs, recently ncRNAs, especially long ncRNAs, have emerged as important potential regulators of the progression of atherosclerosis. However, the molecular mechanism of their regulation and function as well as the significance of other ncRNAs such as small nucleolar RNAs during atherogenesis is largely unknown. In this review, we summarize the recent findings in the field, highlighting the importance of ncRNAs in atherosclerosis and discuss their potential use as therapeutic targets in cardiovascular diseases.

MiR-142-3p attenuates the migration of CD4⁺ T cells through regulating actin cytoskeleton via RAC1 and ROCK2 in arteriosclerosis obliterans

The migration of CD4⁺ T cells plays an important role in arteriosclerosis obliterans (ASO). However, the molecular mechanisms involved in CD4⁺ T cell migration are still unclear. The current study is aimed to determine the expression change of miR-142-3p in CD4⁺ T cells from patients with ASO and investigate its role in CD4⁺ T cell migration as well the potential mechanisms involved. We identified by qRT-PCR and in situ hybridization that the expression of miR-142-3p in CD4⁺ T cells was significantly down-regulated in patients with ASO. Chemokine (C-X-C motif) ligand 12 (CXCL12), a common inflammatory chemokine under the ASO condition, was able to down-regulate the expression of miR-142-3p in cultured CD4⁺ T cells. Up-regulation of miR-142-3p by lentivirus-mediated gene transfer had a strong inhibitory effect on CD4⁺ T cell migration both in cultured human cells in vitro and in mouse aortas and spleens in vivo. RAC1 and ROCK2 were identified to be the direct target genes in human CD4⁺ T cells, which are further confirmed by dual luciferase assay. MiR-142-3p had strong regulatory effects on actin cytoskeleton as shown by the actin staining in CD4⁺ T cells. The results suggest that the expression of miR-142-3p is down-regulated in CD4⁺ T cells from patients with ASO. The down-regulation of miR-142-3p could increase the migration of CD4⁺ T cells to the vascular walls by regulation of actin cytoskeleton via its target genes, RAC1 and ROCK2.

Circulating microRNA: a novel potential biomarker for early diagnosis of intracranial aneurysm rupture a case control study

Objective

To investigate warning effect of serum miRNA for intracranial aneurysm rupture through microarray hybridization.

Methods

24 were selected from 560 patients in our department and divided into group A, B, C and D. They are aneurysms with daughter aneurysms group, aneurysm without daughter aneurysms group, ruptured aneurysms group and angiography negative group. Then a microarray study was carried out using serum miRNA. Differentially expressed miRNAs were identified. Cluster analysis was performed in order to make the results looks more intuitive and potential gene targets were retrieved from miRNA target prediction databases.

Results

Microarray study identified 86 miRNAs with significantly different (p < 0.05) expression levels between three experimental groups and control group. Among them 69 are up-regulated and 17 are down-regulated. All miRNAs in group A are up-regulated, while there are up and down-regulated in group B and C. A total of 8291 predicted target genes are related to these miRNAs. Bioinformatic analysis revealed that several target genes are involved in apoptosis and activation of cells associated with function of vascular wall.

Conclusion

Our gene level approach reveals several different serum miRNAs between normal people and aneurysm patients, as well as among different phases of aneurysm, suggesting that miRNA may participate in the regulation of the occurrence and development of intracranial aneurysm, and also have warning effect for intracranial aneurysm rupture. All differently expressed miRNA in group A are up-regulated, which may suggesting protective function of miRNA for intracranial vascular wall.

MicroRNA-663 regulates human vascular smooth muscle cell phenotypic switch and vascular neointimal formation

RATIONALE

Abnormal phenotypic switch of vascular smooth muscle cell (VSMC) is a hallmark of vascular disorders such as atherosclerosis and restenosis after angioplasty. MicroRNAs (miRNAs) have emerged as important regulators for VSMC function, and we recently identified miR-663 as critical for controlling human aortic smooth muscle cell proliferation.

OBJECTIVE

To investigate whether miR-663 plays a role in human VSMC phenotypic switch and the development of neointima formation.

METHODS AND RESULTS

By using quantitative reverse-transcription polymerase chain reaction, we found that miR-663 was significantly downregulated in human aortic VSMCs on platelet-derived growth factor treatment, whereas expression was markedly increased during VSMC differentiation. Furthermore, we demonstrated that overexpression of miR-663 increased expression of VSMC differentiation marker genes, such as smooth muscle 22α, smooth muscle α-actin, calponin, and smooth muscle myosin heavy chain, and potently inhibited platelet-derived growth factor-induced VSMC proliferation and migration. We identified the transcription factor JunB and myosin light chain 9 as downstream targets of miR-663 in human VSMCs, because overexpression of miR-663 markedly inhibited expression of JunB and its downstream molecules, such as myosin light chain 9 and matrix metalloproteinase 9. Finally, we showed that adeno-miR-663 markedly suppressed the neointimal lesion formation by ≈50% in mice after vascular injury induced by carotid artery ligation, specifically via decreased JunB expression.

CONCLUSIONS

These results indicate that miR-663 is a novel modulator of human VSMC phenotypic switch by targeting JunB/myosin light chain 9 expression. These findings suggest that targeting miR-663 or its specific downstream targets in human VSMCs may represent an attractive approach for the treatment of proliferative vascular diseases.

Non-coding RNAs: the "dark matter" of cardiovascular pathophysiology

Large-scale analyses of mammalian transcriptomes have identified a significant number of different RNA molecules that are not translated into protein. In fact, the use of new sequencing technologies has identified that most of the genome is transcribed, producing a heterogeneous population of RNAs which do not encode for proteins (ncRNAs). Emerging data suggest that these transcripts influence the development of cardiovascular disease. The best characterized non-coding RNA family is represented by short highly conserved RNA molecules, termed microRNAs (miRNAs), which mediate a process of mRNA silencing through transcript degradation or translational repression. These microRNAs (miRNAs) are expressed in cardiovascular tissues and play key roles in many cardiovascular pathologies, such as coronary artery disease (CAD) and heart failure (HF). Potential links between other ncRNAs, like long non-coding RNA, and cardiovascular disease are intriguing but the functions of these transcripts are largely unknown. Thus, the functional characterization of ncRNAs is essential to improve the overall understanding of cellular processes involved in cardiovascular diseases in order to define new therapeutic strategies. This review outlines the current knowledge of the different ncRNA classes and summarizes their role in cardiovascular development and disease.

Perivascular cells in blood vessel regeneration

Vascular engineering seeks to design and construct functional blood vessels comprising endothelial cells (ECs) and perivascular cells (PCs), with the ultimate goal of clinical translation. While EC behavior has been extensively investigated, PCs play an equally significant role in the development of novel regenerative strategies, providing functionality and stability to vessels. The two major classes of PCs are vascular smooth muscle cells (vSMCs) and pericytes; vSMCs can be further sub-classified as either contractile or synthetic. The inclusion of these cell types is crucial for successful regeneration of blood vessels. Furthermore, understanding distinctions between vSMCs and pericytes will enable improved therapeutics in a tissue-specific manner. Here we focus on the approaches and challenges facing the use of PCs in vascular regeneration, including their characteristics, stem cell sources, and interactions with ECs. Finally, we discuss biochemical and microRNA (miR) regulators of PC behavior and engineering approaches that mimic various cues affecting PC function.

Micromanaging abdominal aortic aneurysms

The contribution of abdominal aortic aneurysm (AAA) disease to human morbidity and mortality has increased in the aging, industrialized world. In response, extraordinary efforts have been launched to determine the molecular and pathophysiological characteristics of the diseased aorta. This work aims to develop novel diagnostic and therapeutic strategies to limit AAA expansion and, ultimately, rupture. Contributions from multiple research groups have uncovered a complex transcriptional and post-transcriptional regulatory milieu, which is believed to be essential for maintaining aortic vascular homeostasis. Recently, novel small noncoding RNAs, called microRNAs, have been identified as important transcriptional and post-transcriptional inhibitors of gene expression. MicroRNAs are thought to "fine tune" the translational output of their target messenger RNAs (mRNAs) by promoting mRNA degradation or inhibiting translation. With the discovery that microRNAs act as powerful regulators in the context of a wide variety of diseases, it is only logical that microRNAs be thoroughly explored as potential therapeutic entities. This current review summarizes interesting findings regarding the intriguing roles and benefits of microRNA expression modulation during AAA initiation and propagation. These studies utilize disease-relevant murine models, as well as human tissue from patients undergoing surgical aortic aneurysm repair. Furthermore, we critically examine future therapeutic strategies with regard to their clinical and translational feasibility.

The vascular smooth muscle cell: a therapeutic target in Type 2 diabetes?

The rising epidemic of T2DM (Type 2 diabetes mellitus) worldwide is of significant concern. The inherently silent nature of the disease in its early stages precludes early detection; hence cardiovascular disease is often established by the time diabetes is diagnosed. This increased cardiovascular risk leads to significant morbidity and mortality in these individuals. Progressive development of complications as a result of previous exposure to metabolic disturbances appears to leave a long-lasting impression on cells of the vasculature that is not easily reversed and is termed 'metabolic memory'. SMCs (smooth muscle cells) of blood vessel walls, through their inherent ability to switch between a contractile quiescent phenotype and an active secretory state, maintain vascular homoeostasis in health and development. This plasticity also confers SMCs with the essential capacity to adapt and remodel in pathological states. Emerging clinical and experimental studies propose that SMCs in diabetes may be functionally impaired and thus contribute to the increased incidence of macrovascular complications. Although this idea has general support, the underlying molecular mechanisms are currently unknown and hence are the subject of intense research. The aim of the present review is to explore and evaluate the current literature relating to the problem of vascular disease in T2DM and to discuss the critical role of SMCs in vascular remodelling. Possibilities for therapeutic strategies specifically at the level of T2DM SMCs, including recent novel advances in the areas of microRNAs and epigenetics, will be evaluated. Since restoring glucose control in diabetic patients has limited effect in ameliorating their cardiovascular risk, discovering alternative strategies that restrict or reverse disease progression is vital. Current research in this area will be discussed.

Targeting smooth muscle microRNAs for therapeutic benefit in vascular disease

In view of the bioinformatic projection that a third of all protein coding genes and essentially all biological pathways are under control of microRNAs (miRNAs), it is not surprising that this class of small RNAs plays roles in vascular disease progression. MiRNAs have been shown to be involved in cholesterol turnover, thrombosis, glucose homeostasis and vascular function. Some miRNAs appear to be specific for certain cells, and the role that such cell-specific miRNAs play in vascular disease is only beginning to be appreciated. A notable example is the miR-143/145 cluster which is enriched in mature and highly differentiated smooth muscle cells (SMCs). Here we outline and discuss the recent literature on SMC-expressed miRNAs in major vascular diseases, including atherosclerosis, neointima formation, aortic aneurysm formation, and pulmonary arterial hypertension. Forced expression of miR-145 emerges as a promising strategy for reduction and stabilization of atherosclerotic plaques as well as for reducing neointimal hyperplasia. It is concluded that if obstacles in the form of delivery and untoward effects of antimirs and mimics can be overcome, the outlook for targeting of SMC-specific miRNAs for therapeutic benefit in vascular disease is bright.

MicroRNA-638 is highly expressed in human vascular smooth muscle cells and inhibits PDGF-BB-induced cell proliferation and migration through targeting orphan nuclear receptor NOR1

AIMS

Aberrant vascular smooth muscle cell (VSMC) proliferation and migration contribute significantly to the development of vascular pathologies, such as atherosclerosis and restenosis. MicroRNAs have recently emerged as critical modulators in cellular processes and the purpose of this study is to identify novel miRNA regulators implicated in human aortic VSMC proliferation and migration.

METHODS AND RESULTS

To identify miRNAs that are differentially expressed in human VSMCs, we performed miRNA microarray analysis in human aortic smooth muscle cells (SMCs) at different time points after platelet-derived growth factor (PDGF) stimulation. Here, we identified microRNA-638 (miR-638) as a transcript that was one of the most significantly down-regulated in human VSMCs after PDGF stimulation. Furthermore, we confirmed, by Quantitative RT-PCR, that miR-638 is highly expressed in human VSMCs, and its expression is markedly down-regulated in a dose- and time-dependent manner upon PDGF treatment. Consistent with a critical role in SMC proliferation, we found that miR-638 expression was significantly up-regulated in human VSMCs cultured in differentiation medium, a condition that inhibits SMC proliferation. Furthermore, we identified the orphan nuclear receptor NOR1 as a downstream target gene product of miR-638 and down-regulation of NOR1 is critical for miR-638-mediated inhibitory effects on PDGF-induced cyclin D1 expression, cell proliferation, and migration in human aortic SMCs.

CONCLUSION

These results indicate that miR-638 is a key molecule in regulating human VSMC proliferation and migration by targeting the NOR1/cyclin D pathway and suggest that specific modulation of miR-638 in human VSMCs may represent an attractive approach for the treatment of proliferative vascular diseases.

MicroRNA-21 is induced by rapamycin in a model of tuberous sclerosis (TSC) and lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis (LAM), a multisystem disease of women, is manifest by the proliferation of smooth muscle-like cells in the lung resulting in cystic lung destruction. Women with LAM can also develop renal angiomyolipomas. LAM is caused by mutations in the tuberous sclerosis complex genes (TSC1 or TSC2), resulting in hyperactive mammalian Target of Rapamycin (mTOR) signaling. The mTOR inhibitor, Rapamycin, stabilizes lung function in LAM and decreases the volume of renal angiomyolipomas, but lung function declines and angiomyolipomas regrow when treatment is discontinued, suggesting that factors induced by mTORC1 inhibition may promote the survival of TSC2-deficient cells. Whether microRNA (miRNA, miR) signaling is involved in the response of LAM to mTORC1 inhibition is unknown. We identified Rapamycin-dependent miRNA in LAM patient angiomyolipoma-derived cells using two separate screens. First, we assayed 132 miRNA of known significance to tumor biology. Using a cut-off of >1.5-fold change, 48 microRNA were Rapamycin-induced, while 4 miRs were downregulated. In a second screen encompassing 946 miRNA, 18 miRs were upregulated by Rapamycin, while eight were downregulated. Dysregulation of miRs 29b, 21, 24, 221, 106a and 199a were common to both platforms and were classified as candidate “RapamiRs.” Validation by qRT-PCR confirmed that these microRNA were increased. miR-21, a pro-survival miR, was the most significantly increased by mTOR-inhibition (p<0.01). The regulation of miR-21 by Rapamycin is cell type independent. mTOR inhibition promotes the processing of the miR-21 transcript (pri-miR-21) to a premature form (pre-miR-21). In conclusion, our findings demonstrate that Rapamycin upregulates multiple miRs, including pro-survival miRs, in TSC2-deficient patient-derived cells. The induction of miRs may contribute to the response of LAM and TSC patients to Rapamycin therapy.

miRNA-21 is dysregulated in response to vein grafting in multiple models and genetic ablation in mice attenuates neointima formation

Aims

The long-term failure of autologous saphenous vein bypass grafts due to neointimal thickening is a major clinical burden. Identifying novel strategies to prevent neointimal thickening is important. Thus, this study aimed to identify microRNAs (miRNAs) that are dysregulated during neointimal formation and determine their pathophysiological relevance following miRNA manipulation.

Methods and results

We undertook a microarray approach to identify dysregulated miRNAs following engraftment in an interpositional porcine graft model. These profiling experiments identified a number of miRNAs which were dysregulated following engraftment. miR-21 levels were substantially elevated following engraftment and these results were confirmed by quantitative real-time PCR in mouse, pig, and human models of vein graft neointimal formation. Genetic ablation of miR-21 in mice or grafted veins dramatically reduced neointimal formation in a mouse model of vein grafting. Furthermore, pharmacological knockdown of miR-21 in human veins resulted in target gene de-repression and a significant reduction in neointimal formation.

Conclusion

This is the first report demonstrating that miR-21 plays a pathological role in vein graft failure. Furthermore, we also provided evidence that knockdown of miR-21 has therapeutic potential for the prevention of pathological vein graft remodelling.

Respiratory complex I is essential to induce a Warburg profile in mitochondria-defective tumor cells

Background

Aerobic glycolysis, namely the Warburg effect, is the main hallmark of cancer cells. Mitochondrial respiratory dysfunction has been proposed to be one of the major causes for such glycolytic shift. This hypothesis has been revisited as tumors appear to undergo waves of gene regulation during progression, some of which rely on functional mitochondria. In this framework, the role of mitochondrial complex I is still debated, in particular with respect to the effect of mitochondrial DNA mutations in cancer metabolism. The aim of this work is to provide the proof of concept that functional complex I is necessary to sustain tumor progression.

Methods

Complex I-null osteosarcoma cells were complemented with allotopically expressed complex I subunit 1 (MT-ND1). Complex I re-assembly and function recovery, also in terms of NADH consumption, were assessed. Clones were tested for their ability to grow in soft agar and to generate tumor masses in nude mice. Hypoxia levels were evaluated via pimonidazole staining and hypoxia-inducible factor-1α (HIF-1α) immunoblotting and histochemical staining. 454-pyrosequencing was implemented to obtain global transcriptomic profiling of allotopic and non-allotopic xenografts.

Results

Complementation of a truncative mutation in the gene encoding MT-ND1, showed that a functional enzyme was required to perform the glycolytic shift during the hypoxia response and to induce a Warburg profile in vitro and in vivo, fostering cancer progression. Such trigger was mediated by HIF-1α, whose stabilization was regulated after recovery of the balance between α-ketoglutarate and succinate due to a recuperation of NADH consumption that followed complex I rescue.

Conclusion

Respiratory complex I is essential for the induction of Warburg effect and adaptation to hypoxia of cancer cells, allowing them to sustain tumor growth. Differently from other mitochondrial tumor suppressor genes, therefore, a complex I severe mutation such as the one here reported may confer anti-tumorigenic properties, highlighting the prognostic values of such genetic markers in cancer.

MicroRNAs and Cardiovascular Disease

MicroRNAs (miRNAs) regulate gene expression by binding to their targets and promoting RNA degradation and/or inhibiting protein translation. In recent years, miRNAs have revolutionized our understanding of gene regulatory networks, providing new prospective tools to manage disease. Atherosclerosis and other cardiovascular diseases are a leading cause of disability and death in the US and in other western populations and pose an enormous burden on our healthcare system. Altered lipid homeostasis in liver or in the artery wall, and disruption of endothelial and smooth muscle cell function have been shown to contribute to the onset and progression of cardiovascular disease. This review focuses on recent advances in the field of vascular biology- and lipid metabolism-related miRNomics.