MicroRNAs are essential for stretch-induced vascular smooth muscle contractile differentiation via microRNA (miR)-145-dependent expression of L-type calcium channels

YAP and TAZ in Vascular Smooth Muscle Confer Protection Against Hypertensive Vasculopathy

BACKGROUND

Hypertension remains a major risk factor for cardiovascular diseases, but the underlying mechanisms are not well understood. We hypothesize that appropriate mechanotransduction and contractile function in vascular smooth muscle cells are crucial to maintain vascular wall integrity. The Hippo pathway effectors YAP (yes-associated protein 1) and TAZ (WW domain containing transcription regulator 1) have been identified as mechanosensitive transcriptional coactivators. However, their role in vascular smooth muscle cell mechanotransduction has not been investigated in vivo.

METHODS

We performed physiological and molecular analyses utilizing an inducible smooth muscle-specific YAP/TAZ knockout mouse model.

RESULTS

Arteries lacking YAP/TAZ have reduced agonist-mediated contraction, decreased myogenic response, and attenuated stretch-induced transcriptional regulation of smooth muscle markers. Moreover, in established hypertension, YAP/TAZ knockout results in severe vascular lesions in small mesenteric arteries characterized by neointimal hyperplasia, elastin degradation, and adventitial thickening.

CONCLUSIONS

This study demonstrates a protective role of YAP/TAZ against hypertensive vasculopathy.

Degradation of Premature-miR-181b by the Translin/Trax RNase Increases Vascular Smooth Muscle Cell Stiffness

[Figure: see text].

Expression and Change of miRs 145, 221 and 222 in Hypertensive Subjects Treated with Enalapril, Losartan or Olmesartan

miR profile could be associated to CV risk, and also to prognosis/outcome in response to therapeutic approach. We aimed to evaluate if anti-hypertensive drugs enalapril, losartan or olmesartan have effects on monocyte miR profile in essential hypertensives without target organ involvement. For this purpose, 82 hypertensives and 49 controls were included; we evaluated SBP/DBP, lipid profile, glucose, CRP, fibrinogen, arterial stiffness indices (PWV; AIx), and cIMT at baseline (T0) and after 24 weeks of treatment (T1). Subjects with LDL-C ≥ 160 mg/dL, TG ≥ 200 mg/dL, BMI ≥ 30, and other additional CV risk factors were excluded. Patients who were prescribed to receive once-a-day enalapril 20 mg, losartan 100 mg or olmesartan 20 mg were eligible for the study. At T1, we found a significant improvement of SBP (-18.5%), DBP (-18%), HDL-C and LDL-C (+3% and -5.42%), glucose (-2.15%), BMI (-3.23%), fibrinogen (-11%), CRP (-17.5%,), AIx (-49.1%) PWV (-32.2%), and monocyte miR expression (miR-221: -28.4%; miR-222: -36%; miR-145: +41.7%) with respect to baseline. miR profile was compared to control subjects at baseline and at T1. We found some little difference in the behaviour of the three treatments on some variables: olmesartan was the most effective in reducing fibrinogen, DBP, CRP, and AIx (-13.1%, -19.3%, -21.4%, and -56.8%, respectively). Enalapril was the drug more significantly increasing the expression of miR-145. In conclusion, enalapril, losartan and olmesartan are effective in improving mechanical and humoral factors associated to AS and atherogenesis. These drugs appear to be able to modify miRs 221/222 and miR-145 expression in drug-naïve hypertensives, making it closer to that of control subjects; additionally, this provides a good blood pressure compensation, contributing to slow the progression of vascular damage.

microRNA-mRNA Profile of Skeletal Muscle Differentiation and Relevance to Congenital Myotonic Dystrophy

microRNAs (miRNAs) regulate messenger RNA (mRNA) abundance and translation during key developmental processes including muscle differentiation. Assessment of miRNA targets can provide insight into muscle biology and gene expression profiles altered by disease. mRNA and miRNA libraries were generated from C2C12 myoblasts during differentiation, and predicted miRNA targets were identified based on presence of miRNA binding sites and reciprocal expression. Seventeen miRNAs were differentially expressed at all time intervals (comparing days 0, 2, and 5) of differentiation. mRNA targets of differentially expressed miRNAs were enriched for functions related to calcium signaling and sarcomere formation. To evaluate this relationship in a disease state, we evaluated the miRNAs differentially expressed in human congenital myotonic dystrophy (CMD) myoblasts and compared with normal control. Seventy-four miRNAs were differentially expressed during healthy human myocyte maturation, of which only 12 were also up- or downregulated in CMD patient cells. The 62 miRNAs that were only differentially expressed in healthy cells were compared with differentiating C2C12 cells. Eighteen of the 62 were conserved in mouse and up- or down-regulated during mouse myoblast differentiation, and their C2C12 targets were enriched for functions related to muscle differentiation and contraction.

Diverse roles of microRNA-145 in regulating smooth muscle (dys)function in health and disease

MicroRNAs are short, non-coding RNAs that target messenger RNAs for degradation. miR-145 is a vascular-enriched microRNA that is important for smooth muscle cell (SMC) differentiation. Under healthy circumstances, SMC exist in a contractile, differentiated phenotype promoted by miR-145. In cases of disease or injury, SMC can undergo reversible dedifferentiation into a synthetic phenotype, accompanied by inhibition of miR-145 expression. Vascular disorders such as atherosclerosis and neointimal hyperplasia are characterised by aberrant phenotypic switching in SMC. This review will summarise the physiological roles of miR-145 in vascular SMC, including the molecular regulation of differentiation, proliferation and migration. Furthermore, it will discuss the different ways in which miR-145 can be dysregulated and the downstream impact this has on the progression of vascular pathologies. Finally, it will discuss whether miR-145 may be suitable for use as a biomarker of vascular disease.

Cellular and molecular effects of hyperglycemia on ion channels in vascular smooth muscle

Diabetes affects millions of people worldwide. This devastating disease dramatically increases the risk of developing cardiovascular disorders. A hallmark metabolic abnormality in diabetes is hyperglycemia, which contributes to the pathogenesis of cardiovascular complications. These cardiovascular complications are, at least in part, related to hyperglycemia-induced molecular and cellular changes in the cells making up blood vessels. Whereas the mechanisms mediating endothelial dysfunction during hyperglycemia have been extensively examined, much less is known about how hyperglycemia impacts vascular smooth muscle function. Vascular smooth muscle function is exquisitely regulated by many ion channels, including several members of the potassium (K+) channel superfamily and voltage-gated L-type Ca2+ channels. Modulation of vascular smooth muscle ion channels function by hyperglycemia is emerging as a key contributor to vascular dysfunction in diabetes. In this review, we summarize the current understanding of how diabetic hyperglycemia modulates the activity of these ion channels in vascular smooth muscle. We examine underlying mechanisms, general properties, and physiological relevance in the context of myogenic tone and vascular reactivity.

Cell signaling model for arterial mechanobiology

Arterial growth and remodeling at the tissue level is driven by mechanobiological processes at cellular and sub-cellular levels. Although it is widely accepted that cells seek to promote tissue homeostasis in response to biochemical and biomechanical cues—such as increased wall stress in hypertension—the ways by which these cues translate into tissue maintenance, adaptation, or maladaptation are far from understood. In this paper, we present a logic-based computational model for cell signaling within the arterial wall, aiming to predict changes in extracellular matrix turnover and cell phenotype in response to pressure-induced wall stress, flow-induced wall shear stress, and exogenous sources of angiotensin II, with particular interest in mouse models of hypertension. We simulate a number of experiments from the literature at both the cell and tissue level, involving single or combined inputs, and achieve high qualitative agreement in most cases. Additionally, we demonstrate the utility of this modeling approach for simulating alterations (in this case knockdowns) of individual nodes within the signaling network. Continued modeling of cellular signaling will enable improved mechanistic understanding of arterial growth and remodeling in health and disease, and will be crucial when considering potential pharmacological interventions.

Biological soft tissues are characterized by continuous production and removal of material, which endows them with a remarkable ability to adapt to changes in their biochemical and biomechanical environments. For arteries, mechanical stimuli result primarily from changes in blood pressure or flow, and biochemical changes are induced by multiple factors, including pharmacological intervention. In order to understand how arterial properties are maintained in health, or how they adapt or fail to adapt in disease, we must understand better how these diverse stimuli affect material turnover. Extracellular matrix is tightly regulated by mechano-sensing and mechano-regulation, and therefore cell signaling, thus we present a computational model of relevant signaling pathways within the vascular wall, with the aim of predicting changes in wall composition and function in response to three main inputs: pressure-induced wall stress, flow-induced wall shear stress, and exogenous angiotensin II. We obtain qualitative agreement with a range of experimental studies from the literature, and provide illustrative examples demonstrating how such models can be used to further our understanding of arterial remodeling.

Biomechanical signal communication in vascular smooth muscle cells

Biomechanical stresses are closely associated with cardiovascular development and diseases. In vivo, vascular smooth muscle cells are constantly stimulated by biomechanical factors caused by increased blood pressure leading to the non-specific activation of cell transmembrane proteins. Thus, various intracellular signal molecules are simultaneously activated via signaling cascades, which are closely related to alterations in the differentiation, phenotype, inflammation, migration, pyroptosis, calcification, proliferation, and apoptosis of vascular smooth muscle cells. Meanwhile, mechanical stress-induced miRNAs and epigenetics modification on vascular smooth muscle cells play critical roles as well. Eventually, the overall pathophysiology of the cells is altered, resulting in the development of many major clinical diseases, including hypertension, atherosclerosis, grafted venous atherosclerosis, and aneurysm, among others. In this paper, important advances in mechanical signal communication in vascular smooth muscle cells are reviewed.

Using prediction models to identify miRNA-based markers of low dose rate chronic stress

Robust biomarkers of exposure to chronic low dose stressors such as ionizing radiation, particularly following chronic low doses and dose-rates, are urgently needed. MicroRNAs (miRNA) have emerged as promising markers of exposure to high dose and dose-rate. Here, we evaluated the feasibility of classifying γ-radiation exposure at different dose rates based on miRNA expression levels. Our objective was to identify miRNA-signatures discriminating between exposure to γ-radiation or not, including exposure to chronic low dose rates. We exposed male CBA/CaOlaHsd and C57BL/6NHsd wild-type mice to 0, 2.5, 10 and 100 mGy/h γ-irradiation (3 Gy total-dose). From an initial screening of 576 miRNAs, a set of 21 signature-miRNAs was identified based on differential expression (>± 2-fold or p < 0.05). This 21-signature miRNA panel was investigated in 39 samples from 4/5 livers/group/mouse strain. A set of significantly differentially expressed miRNAs was identified in all γ-irradiated samples. Most miRNAs were upregulated in all γ-irradiated groups compared to control, and functional analysis of these miRNAs revealed involvement in several cancer-related signaling pathways. To identify miRNAs that distinguished exposed mice from controls, nine prediction methods; i.e., six variants of generalized regression models, random-forest, boosted-tree and nearest-shrunken-centroid (PAM) were used. The generalized regression methods seem to outperform the other prediction methods for classification of irradiated and control samples. Using the 21-miRNA panel in the prediction models, we identified sets of candidate miRNA-markers that predict exposure to γ-radiation. Among the top10 miRNA predictors, contributing most in each of the three γ-irradiated groups, three miRNA predictors (miR-140-3p, miR-133a-5p and miR-145a-5p) were common. Three miRNAs, miR-188-3p/26a-5p/26b-5p, were specific for lower dose-rate γ-radiation. Similarly, exposure to the high dose-rates was also correctly predicted, including mice exposed to X-rays. Our approach identifying miRNA-based signature panels may be extended to classify exposure to environmental, nutritional and life-style-related stressors, including chronic low-stress scenarios.

miR-137 and its target T-type CaV 3.1 channel modulate dedifferentiation and proliferation of cerebrovascular smooth muscle cells in simulated microgravity rats by regulating calcineurin/NFAT pathway

Objectives

Postflight orthostatic intolerance has been regarded as a major adverse effect after microgravity exposure, in which cerebrovascular adaptation plays a critical role. Our previous finding suggested that dedifferentiation of vascular smooth muscle cells (VSMCs) might be one of the key contributors to cerebrovascular adaptation under simulated microgravity. This study was aimed to confirm this concept and elucidate the underlying mechanisms.

Materials and Methods

Sprague Dawley rats were subjected to 28‐day hindlimb‐unloading to simulate microgravity exposure. VSMC dedifferentiation was evaluated by ultrastructural analysis and contractile/synthetic maker detection. The role of T‐type Ca_V3.1 channel was revealed by assessing its blocking effects. MiR‐137 was identified as the upstream of Ca_V3.1 channel by luciferase assay and investigated by gain/loss‐of‐function approaches. Calcineurin/nuclear factor of activated T lymphocytes (NFAT) pathway, the downstream of Ca_V3.1 channel, was investigated by detecting calcineurin activity and NFAT nuclear translocation.

Results

Simulated microgravity induced the dedifferentiation and proliferation in rat cerebral VSMCs. T‐type Ca_V3.1 channel promoted the dedifferentiation and proliferation of VSMC. MiR‐137 and calcineurin/NFATc3 pathway were the upstream and downstream signalling of T‐type Ca_V3.1 channel in modulating the dedifferentiation and proliferation of VSMCs, respectively.

Conclusions

The present work demonstrated that miR‐137 and its target T‐type Ca_V3.1 channel modulate the dedifferentiation and proliferation of rat cerebral VSMCs under simulated microgravity by regulating calcineurin/NFATc3 pathway.

Deletion of the microRNA-degrading nuclease, translin/trax, prevents pathogenic vascular stiffness

Vascular stiffness plays a key role in the pathogenesis of hypertension. Recent studies indicate that the age-associated reduction in miR-181b levels in vascular smooth muscle cells (VSMCs) contributes to increased vascular stiffness. As these findings suggest that inhibiting degradation of miR-181b might prevent vascular stiffening, we have assessed whether the microRNA-degrading translin/trax (TN/TX) complex mediates degradation of miR-181b in the aorta.We found that TN^-/- mice display elevated levels of miR-181b expression in the aorta. Therefore, we tested whether TN deletion prevents vascular stiffening in a mouse model of hypertension, induced by chronic high-salt intake (4%NaCl in drinking water for 3 wk; HSW). TN^-/- mice subjected to HSW stress do not show increased vascular stiffness, as monitored by pulse wave velocity and tensile testing. The protective effect of TN deletion in the HSW paradigm appears to be mediated by its ability to increase miR-181b in the aorta since HSW decreases levels of miR-181b in WT mice, but not in TN KO mice. We demonstrate for the first time that interfering with microRNA degradation can have a beneficial impact on the vascular system and identify the microRNA-degrading TN/TX RNase complex as a potential therapeutic target in combatting vascular stiffness.NEW & NOTEWORTHY While the biogenesis and mechanism of action of mature microRNA are well understood, much less is known about the regulation of microRNA via degradation. Recent studies have identified the protein complex, translin(TN)/trax(TX), as a microRNA-degrading enzyme. Here, we demonstrate that TN/TX is expressed in vascular smooth muscle cells. Additionally, deletion of the TN/TX complex selectively increases aortic miR-181b and prevents increased vascular stiffness caused by ingestion of high-salt water. To our knowledge, this is first report describing the role of a microRNA RNAse in cardiovascular biology or pathobiology.

MicroRNA-145 Involves in the Pathogenesis of Renal Vascular Lesions and May Become a Potential Therapeutic Target in Patients with Juvenile Lupus Nephritis

AIMS

The current study was conducted with the central objective of investigating the expression of microRNA-145 (miR-145) in renal vascular lesions (RVLs) in juvenile lupus nephritis (JLN) and its possible mechanism.

METHODS

The clinical data of 49 JLN patients confirmed by renal biopsy were collected and followed by grouping according to the RVLs score after hematoxylin-eosin staining: mild, moderate, and severe groups. In situ hybridization was used to detect the expression of miR-145 in renal vessels which was then being compared among different RVLs groups. Up-LV-miR-145 and LV-miR-NC lentiviral vectors were constructed and transfected into human vascular smooth muscle cells (HVSMCs), respectively. After HVSMCs were treated with 10.0 µg/L platelet-derived growth factor (PDGF)-BB for 24 h, the proliferation, migration, and apoptosis of endothelial cells were detected by MTT, Transwell assay, and flow cytometry, respectively. Western blot was used to detect expression of alpha-smooth muscle actin (α-SM-actin) and osteopontin (OPN).

RESULTS

The expression of miR-145 in renal vascular cells was statistically significant. The higher the inner membrane ratio, the lesser the miR-145 expression. After treatment with PDGF-BB, expression of miR-145 in HVSMCs decreased, proliferation and migration ability enhanced, apoptosis decreased, α-SM-actin decreased, and OPN increased. The proliferation and migration ability of HVSMCs in the LV-miR-145 group suppressed, apoptosis enhanced, α-SM-actin increased, and OPN decreased.

CONCLUSIONS

Our study revealed that miR-145 expression decreased with the increase of vascular damage. miR-145 can inhibit proliferation, migration, and differentiation phenotypic transformation of HVSMCs induced by PDGF-BB. miR-145 may be involved in the pathogenesis of RVLs and may be a new target for treatment of RVLs in lupus nephritis.

Loss of Vascular Myogenic Tone in miR-143/145 Knockout Mice Is Associated With Hypertension-Induced Vascular Lesions in Small Mesenteric Arteries

OBJECTIVE

Pressure-induced myogenic tone is involved in autoregulation of local blood flow and confers protection against excessive pressure levels in small arteries and capillaries. Myogenic tone is dependent on smooth muscle microRNAs (miRNAs), but the identity of these miRNAs is unclear. Furthermore, the consequences of altered myogenic tone for hypertension-induced damage to small arteries are not well understood.

APPROACH AND RESULTS

The importance of smooth muscle-enriched microRNAs, miR-143/145, for myogenic tone was evaluated in miR-143/145 knockout mice. Furthermore, hypertension-induced vascular injury was evaluated in mesenteric arteries in vivo after angiotensin II infusion. Myogenic tone was abolished in miR-143/145 knockout mesenteric arteries, whereas contraction in response to calyculin A and potassium chloride was reduced by ≈30%. Furthermore, myogenic responsiveness was potentiated by angiotensin II in wild-type but not in knockout mice. Angiotensin II administration in vivo elevated systemic blood pressure in both genotypes. Hypertensive knockout mice developed severe vascular lesions characterized by vascular inflammation, adventitial fibrosis, and neointimal hyperplasia in small mesenteric arteries. This was associated with depolymerization of actin filaments and fragmentation of the elastic laminae at the sites of vascular lesions.

CONCLUSIONS

This study demonstrates that miR-143/145 expression is essential for myogenic responsiveness. During hypertension, loss of myogenic tone results in potentially damaging levels of mechanical stress and detrimental effects on small arteries. The results presented herein provide novel insights into the pathogenesis of vascular disease and emphasize the importance of controlling mechanical factors to maintain structural integrity of the vascular wall.

MicroRNA-Dependent Control of Serotonin-Induced Pulmonary Arterial Contraction

BACKGROUND

Serotonin (5-HT) is considered to play a role in pulmonary arterial hypertension by regulating vascular remodeling and smooth muscle contractility. Here, arteries from mice with inducible and smooth muscle-specific deletion of Dicer were used to address mechanisms by which microRNAs control 5-HT-induced contraction.

METHODS

Mice were used 5 weeks after Dicer deletion, and pulmonary artery contractility was analyzed by wire myography.

RESULTS

No change was seen in right ventricular systolic pressure following dicer deletion, but systemic blood pressure was reduced. Enhanced 5-HT-induced contraction in Dicer KO pulmonary arteries was associated with increased 5-HT2A receptor mRNA expression whereas 5-HT1B and 5-HT2B receptor mRNAs were unchanged. Contraction by the 5-HT2A agonist TCB-2 was increased in Dicer KO as was the response to the 5-HT2B agonist BW723C86. Effects of Src and protein kinase C inhibition were similar in control and KO arteries, but the effect of inhibition of Rho kinase was reduced. We identified miR-30c as a potential candidate for 5-HT2A receptor regulation as it repressed 5-HT2A mRNA and protein.

CONCLUSION

Our findings show that 5-HT receptor signaling in the arterial wall is subject to regulation by microRNAs and that this entails altered 5-HT2A receptor expression and signaling.

Expression levels of atherosclerosis-associated miR-143 and miR-145 in the plasma of patients with hyperhomocysteinaemia

Background

An elevated level of homocysteine (Hcy) in the blood is designated hyperhomocysteinaemia (Hhcy) and is regarded as a strong risk factor for the development of atherosclerosis (ATH), although the association remains controversial. Considered to be essential gene expression regulators, micro-RNAs (miRNAs) modulate cardiovascular disease development and thus can be regarded as potential biomarkers and therapeutic targets in atherosclerosis. The aim of the current study is to investigate the expression levels of atherosclerosis-associated miR-143 and miR-145 in Hhcy patients and predict the progress of atherosclerosis in Hhcy patients.

Methods

A total of 100 participants were enrolled and included normal control subjects (NC = 20), hyperhomocysteinaemia alone subjects (Hhcy = 25), hyperhomocysteinaemia and carotid artery atherosclerosis combined subjects (Hhcy + ATH = 30) and patients with standalone carotid artery atherosclerosis (ATH = 25). Plasma Hcy, supplementary biochemical parameters and carotid artery ultrasonography (USG) were measured in all participants. MicroRNA expression levels in the peripheral blood were calculated by real-time reverse transcription-polymerase chain reaction (qRT-PCR). The correlations of miR-143 and miR-145 with Hcy, blood lipid parameters and carotid artery atherosclerotic plaques were evaluated using Pearson’s correlation coefficients. Receiver operating characteristic (ROC) curve analyses were performed to evaluate the capacities of miR-143 and miR-145 for the detection of Hhcy and atherosclerosis patients.

Results

MiR-143 and miR-145 exhibited trends towards significance with stepwise decreases from the NC to Hhcy groups and then to the Hhcy + ATH and ATH groups. Similar results were observed in the carotid artery plaque group (Hhcy + ATH and ATH grups) compared with the no-plaque group (NC and Hhcy groups). The miR-143 expression level exhibited significant negative correlations with Hcy, total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-c). The miR-145 expression level exhibited significant negative correlations with Hcy, TC, triglyceride (TG) and LDL-c. MiR-143 and miR-145 exhibited the greatest area under the curves (AUCs) (0.775 and 0.681, respectively) for the detection of every Hhcy patient, including those in the Hhcy and Hhcy + ATH groups, from among all subjects.

Conclusion

The results indicated that the levels of atherosclerosis-associated circulating miR-143 and miR-145 are linked to Hhcy. MiR-143 may be used as a potential non-invasive biomarkers of Hhcy and thus may be helpful in predicting the progress of atherosclerosis in Hhcy patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-017-0596-0) contains supplementary material, which is available to authorized users.

Hypertension reduces soluble guanylyl cyclase expression in the mouse aorta via the Notch signaling pathway

Hypertension is a dominating risk factor for cardiovascular disease. To characterize the genomic response to hypertension, we administered vehicle or angiotensin II to mice and performed gene expression analyses. AngII treatment resulted in a robust increase in blood pressure and altered expression of 235 genes in the aorta, including Gucy1a3 and Gucy1b3 which encode subunits of soluble guanylyl cyclase (sGC). Western blotting and immunohistochemistry confirmed repression of sGC associated with curtailed relaxation via sGC activation. Analysis of transcription factor binding motifs in promoters of differentially expressed genes identified enrichment of motifs for RBPJ, a component of the Notch signaling pathway, and the Notch coactivators FRYL and MAML2 were reduced. Gain and loss of function experiments demonstrated that JAG/NOTCH signaling controls sGC expression together with MAML2 and FRYL. Reduced expression of sGC, correlating with differential expression of MAML2, in stroke prone and spontaneously hypertensive rats was also seen, and RNA-Seq data demonstrated correlations between JAG1, NOTCH3, MAML2 and FRYL and the sGC subunits GUCY1A3 and GUCY1B3 in human coronary artery. Notch signaling thus provides a constitutive drive on expression of the major nitric oxide receptor (GUCY1A3/GUCY1B3) in arteries from mice, rats, and humans, and this control mechanism is disturbed in hypertension.

Cavin-3 (PRKCDBP) deficiency reduces the density of caveolae in smooth muscle

Cavins belong to a family of proteins that contribute to the formation of caveolae, which are membrane organelles with functional roles in muscle and fat. Here, we investigate the effect of cavin-3 ablation on vascular and urinary bladder structure and function. Arteries and urinary bladders from mice lacking cavin-3 (knockout: KO) and from controls (wild type: WT) were examined. Our studies revealed that the loss of cavin-3 resulted in ∼40% reduction of the caveolae protein cavin-1 in vascular and bladder smooth muscle. Electron microscopy demonstrated that the loss of cavin-3 was accompanied by a reduction of caveolae abundance by 40-45% in smooth muscle, whereas the density of caveolae in endothelial cells was unchanged. Vascular contraction in response to an α₁-adrenergic agonist was normal but nitric-oxide-dependent relaxation was enhanced, in parallel with an increased relaxation on direct activation of soluble guanylyl cyclase (sGC). This was associated with an elevated expression of sGC, although blood pressure was similar in WT and KO mice. Contraction of the urinary bladder was not affected by the loss of cavin-3. The proteomic response to outlet obstruction, including STAT3 phosphorylation, the induction of synthetic markers and the repression of contractile markers were identical in WT and KO mice, the only exception being a curtailed induction of the Golgi protein GM130. Loss of cavin-3 thus reduces the number of caveolae in smooth muscle and partly destabilizes cavin-1 but the functional consequences are modest and include an elevated vascular sensitivity to nitric oxide and slightly disturbed Golgi homeostasis in situations of severe cellular stress.

Regulation of microRNA expression in vascular smooth muscle by MRTF-A and actin polymerization

The dynamic properties of the actin cytoskeleton in smooth muscle cells play an important role in a number of cardiovascular disease states. The state of actin does not only mediate mechanical stability and contractile function but can also regulate gene expression via myocardin related transcription factors (MRTFs). These transcriptional co-activators regulate genes encoding contractile and cytoskeletal proteins in smooth muscle. Regulation of small non-coding microRNAs (miRNAs) by actin polymerization may mediate some of these effects. MiRNAs are short non-coding RNAs that modulate gene expression by post-transcriptional regulation of target messenger RNA. In this study we aimed to determine a profile of miRNAs that were 1) regulated by actin/MRTF-A, 2) associated with the contractile smooth muscle phenotype and 3) enriched in muscle cells. This analysis was performed using cardiovascular disease-focused miRNA arrays in both mouse and human cells. The potential clinical importance of actin polymerization in aortic aneurysm was evaluated using biopsies from mildly dilated human thoracic aorta in patients with stenotic tricuspid or bicuspid aortic valve. By integrating information from multiple qPCR based miRNA arrays we identified a group of five miRNAs (miR-1, miR-22, miR-143, miR-145 and miR-378a) that were sensitive to actin polymerization and MRTF-A overexpression in both mouse and human vascular smooth muscle. With the exception of miR-22, these miRNAs were also relatively enriched in striated and/or smooth muscle containing tissues. Actin polymerization was found to be dramatically reduced in the aorta from patients with mild aortic dilations. This was associated with a decrease in actin/MRTF-regulated miRNAs. In conclusion, the transcriptional co-activator MRTF-A and actin polymerization regulated a subset of miRNAs in vascular smooth muscle. Identification of novel miRNAs regulated by actin/MRTF-A may provide further insight into the mechanisms underlying vascular disease states, such as aortic aneurysm, as well as novel ideas regarding therapeutic strategies. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Ca2+/Calmodulin-Dependent Protein Kinase II in Vascular Smooth Muscle

Ca²⁺-dependent signaling pathways are central regulators of differentiated vascular smooth muscle (VSM) contractile function. In addition, Ca²⁺ signals regulate VSM gene transcription, proliferation, and migration of dedifferentiated or "synthetic" phenotype VSM cells. Synthetic phenotype VSM growth and hyperplasia are hallmarks of pervasive vascular diseases including hypertension, atherosclerosis, postangioplasty/in-stent restenosis, and vein graft failure. The serine/threonine protein kinase Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is a ubiquitous mediator of intracellular Ca²⁺ signals. Its multifunctional nature, structural complexity, diversity of isoforms, and splice variants all characterize this protein kinase and make study of its activity and function challenging. The kinase has unique autoregulatory mechanisms, and emerging studies suggest that it can function to integrate Ca²⁺ and reactive oxygen/nitrogen species signaling. Differentiated VSM expresses primarily CaMKIIγ and -δ isoforms. CaMKIIγ isoform expression correlates closely with the differentiated phenotype, and some studies link its function to regulation of contractile activity and Ca²⁺ homeostasis. Conversely, synthetic phenotype VSM cells primarily express CaMKIIδ and substantial evidence links it to regulation of gene transcription, proliferation, and migration of VSM in vitro, and vascular hypertrophic and hyperplastic remodeling in vivo. CaMKIIδ and -γ isoforms have opposing functions at the level of cell cycle regulation, proliferation, and VSM hyperplasia in vivo. Isoform switching following vascular injury is a key step in promoting vascular remodeling. Recent availability of genetically engineered mice with smooth muscle deletion of specific isoforms and transgenics expressing an endogenous inhibitor protein (CAMK2N) has enabled a better understanding of CaMKII function in VSM and should facilitate future studies.

Calcineurin/NFAT Activation-Dependence of Leptin Synthesis and Vascular Growth in Response to Mechanical Stretch

Background and Aims: Hypertension and obesity are important risk factors of cardiovascular disease. They are both associated with high leptin levels and have been shown to promote vascular hypertrophy, through the RhoA/ROCK and ERK1/2 phosphorylation. Calcineurin/NFAT activation also induces vascular hypertrophy by upregulating various genes. This study aimed to decipher whether a crosstalk exists between the RhoA/ROCK pathway, Ca²⁺/calcineurin/NFAT pathway, and ERK1/2 phosphorylation in the process of mechanical stretch-induced vascular smooth muscle cell (VSMC) hypertrophy and leptin synthesis.

Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch and exogenous leptin (3.1 nM) on VSMC hypertrophy and leptin synthesis. Results showed that stretching the RPV significantly upregulated leptin secretion, mRNA, and protein expression, which were inhibited by the calcium channel blocker nifedipine (10 μM), the selective calcineurin inhibitor FK506 (1 nM), and the ERK1/2 inhibitor PD98059 (1 μM). The transcription inhibitor actinomycin D (0.1 μM) and the translation inhibitor cycloheximide (1 mM) significantly decreased stretch-induced leptin protein expression. Mechanical stretch or leptin caused an increase in wet weight changes and protein synthesis, considered as hypertrophic markers, while they were inhibited by FK506 (0.1 nM; 1 nM). In addition, stretch or exogenous leptin significantly increased calcineurin activity and MCIP1 expression whereas leptin induced NFAT nuclear translocation in VSMCs. Moreover, in response to stretch or exogenous leptin, the Rho inhibitor C3 exoenzyme (30 ng/mL), the ROCK inhibitor Y-27632 (10 μM), and the actin depolymerization agents Latrunculin B (50 nM) and cytochalasin D (1 μM) reduced calcineurin activation and NFAT nuclear translocation. ERK1/2 phosphorylation was inhibited by FK506 and C3.

Conclusions: Mechanical stretch-induced VSMC hypertrophy and leptin synthesis and secretion are mediated by Ca²⁺/calcineurin/NFAT activation. RhoA/ROCK and ERK1/2 activation are critical for mechanical stretch-induced calcineurin activation.

Large-Scale microRNA Expression Profiling Identifies Putative Retinal miRNA-mRNA Signaling Pathways Underlying Form-Deprivation Myopia in Mice

Development of myopia is associated with large-scale changes in ocular tissue gene expression. Although differential expression of coding genes underlying development of myopia has been a subject of intense investigation, the role of non-coding genes such as microRNAs in the development of myopia is largely unknown. In this study, we explored myopia-associated miRNA expression profiles in the retina and sclera of C57Bl/6J mice with experimentally induced myopia using microarray technology. We found a total of 53 differentially expressed miRNAs in the retina and no differences in miRNA expression in the sclera of C57BL/6J mice after 10 days of visual form deprivation, which induced -6.93 ± 2.44 D (p < 0.000001, n = 12) of myopia. We also identified their putative mRNA targets among mRNAs found to be differentially expressed in myopic retina and potential signaling pathways involved in the development of form-deprivation myopia using miRNA-mRNA interaction network analysis. Analysis of myopia-associated signaling pathways revealed that myopic response to visual form deprivation in the retina is regulated by a small number of highly integrated signaling pathways. Our findings highlighted that changes in microRNA expression are involved in the regulation of refractive eye development and predicted how they may be involved in the development of myopia by regulating retinal gene expression.

MicroRNA-203 mimics age-related aortic smooth muscle dysfunction of cytoskeletal pathways

Increased aortic stiffness is a biomarker for subsequent adverse cardiovascular events. We have previously reported that vascular smooth muscle Src-dependent cytoskeletal remodelling, which contributes to aortic plasticity, is impaired with ageing. Here, we use a multi-scale approach to determine the molecular mechanisms behind defective Src-dependent signalling in an aged C57BL/6 male mouse model. Increased aortic stiffness, as measured in vivo by pulse wave velocity, was found to have a comparable time course to that in humans. Bioinformatic analyses predicted several miRs to regulate Src-dependent cytoskeletal remodelling. qRT-PCR was used to determine the relative levels of predicted miRs in aortas and, notably, the expression of miR-203 increased almost twofold in aged aorta. Increased miR-203 expression was associated with a decrease in both mRNA and protein expression of Src, caveolin-1 and paxillin in aged aorta. Probing with phospho-specific antibodies confirmed that overexpression of miR-203 significantly attenuated Src and extracellular signal regulated kinase (ERK) signalling, which we have previously found to regulate vascular smooth muscle stiffness. In addition, transfection of miR-203 into aortic tissue from young mice increased phenylephrine-induced aortic stiffness ex vivo, mimicking the aged phenotype. Upstream of miR-203, we found that DNA methyltransferases (DNMT) 1, 3a, and 3b are also significantly decreased in the aged mouse aorta and that DNMT inhibition significantly increases miR-203 expression. Thus, the age-induced increase in miR-203 may be caused by epigenetic promoter hypomethylation in the aorta. These findings indicate that miR-203 promotes a re-programming of Src/ERK signalling pathways in vascular smooth muscle, impairing the regulation of stiffness in aged aorta.

MicroRNA-153 targeting of KCNQ4 contributes to vascular dysfunction in hypertension

Aims

Kv7.4, a voltage-dependent potassium channel expressed throughout the vasculature, controls arterial contraction and is compromised in hypertension by an unknown mechanism. MicroRNAs (miRs) are post-transcriptional regulators of protein production and are altered in disease states such as hypertension. We investigated whether miRs regulate Kv7.4 expression.

Methods and results

In renal and mesenteric arteries (MAs) of the spontaneously hypertensive rat (SHR), Kv7.4 protein decreased compared with the normotensive (NT) rat without a decrease in KCNQ4 mRNA, inferring that Kv7.4 abundance was determined by post-transcriptional regulation. In silico analysis of the 3′ UTR of KCNQ4 revealed seed sequences for miR26a, miR133a, miR200b, miR153, miR214, miR218, and let-7d with quantitative polymerase chain reaction showing miR153 increased in those arteries from SHRs that exhibited decreased Kv7.4 levels. Luciferase reporter assays indicated a direct targeting effect of miR153 on the 3′ UTR of KCNQ4. Introduction of high levels of miR153 to MAs increased vascular wall thickening and reduced Kv7.4 expression/Kv7 channel function compared with vessels receiving a non-targeting miR, providing a proof of concept of Kv7.4 regulation by miR153.

Conclusion

This study is the first to define a role for aberrant miR153 contributing to the hypertensive state through targeting of KCNQ4 in an animal model of hypertension, raising the possibility of the use of miR153-related therapies in vascular disease.

MicroRNA-30 inhibits neointimal hyperplasia by targeting Ca(2+)/calmodulin-dependent protein kinase IIδ (CaMKIIδ)

The multifunctional Ca²⁺/calmodulin-dependent protein kinase II δ-isoform (CaMKIIδ) promotes vascular smooth muscle (VSM) proliferation, migration, and injury-induced vascular wall neointima formation. The objective of this study was to test if microRNA-30 (miR-30) family members are endogenous regulators of CaMKIIδ expression following vascular injury and whether ectopic expression of miR-30 can inhibit CaMKIIδ-dependent VSM cell function and neointimal VSM hyperplasia induced by vascular injury. The CaMKIIδ 3′UTR contains a consensus miR-30 binding sequence that is highly conserved across species. A significant decrease in miR-30 family members and increase in CaMKIIδ₂ protein expression, with no change in CaMKIIδ mRNA expression, was observed in medial layers of VSM 7 days post-injury. In vitro, overexpression of miR-30c or miR-30e inhibited CaMKIIδ₂ protein expression by ~50% in cultured rat aortic VSM cells, and inhibited VSM cell proliferation and migration. In vivo, lenti-viral delivery of miR-30c into injured rat carotid arteries prevented the injury-induced increase in CaMKIIδ₂. Furthermore, neointima formation was dramatically inhibited by lenti-viral delivery of miR-30c in the injured medial smooth muscle. These studies define a novel mechanism for regulating CaMKIIδ expression in VSM and provide a new potential therapeutic strategy to reduce progression of vascular proliferative diseases, including atherosclerosis and restenosis.

Noncoding RNAs in smooth muscle cell homeostasis: implications in phenotypic switch and vascular disorders

Vascular smooth muscle cells (SMC) are a highly specialized cell type that exhibit extraordinary plasticity in adult animals in response to a number of environmental cues. Upon vascular injury, SMC undergo phenotypic switch from a contractile-differentiated to a proliferative/migratory-dedifferentiated phenotype. This process plays a major role in vascular lesion formation and during the development of vascular remodeling. Vascular remodeling comprises the accumulation of dedifferentiated SMC in the intima of arteries and is central to a number of vascular diseases such as arteriosclerosis, chronic obstructive pulmonary disease or pulmonary hypertension. Therefore, it is critical to understand the molecular mechanisms that govern SMC phenotype. In the last decade, a number of new classes of noncoding RNAs have been described. These molecules have emerged as key factors controlling tissue homeostasis during physiological and pathological conditions. In this review, we will discuss the role of noncoding RNAs, including microRNAs and long noncoding RNAs, in the regulation of SMC plasticity.

MicroRNA-145 regulates platelet-derived growth factor-induced human aortic vascular smooth muscle cell proliferation and migration by targeting CD40

The objective of this study is to investigate the expression of microRNA (miR)-145 in human aortic vascular smooth muscle cells (VSMCs) and the effect of miR-145 in the biological behavior and expression of CD40 in VSMCs. Cells were treated with either miR-145 or miR-145 inhibitor. Cell proliferation was analyzed by a colony formation assay and a methyl thiazolyl tetrazolium assay. Cell migration and invasion were assessed using a transwell assay, an invasion assay, and a wound healing assay. A luciferase reporter assay was used to detect the interaction between miR-145 and CD40. Expression of α-SMA, calponin, osteopontin (OPN), epiregulin, activator protein-1 (AP-1) and CD40 was measured using real-time RT-PCR for mRNA levels and Western blotting for protein levels. Overexpression of miR-145 significantly inhibited VSMC proliferation, invasion and migration. Furthermore, OPN, epiregulin, AP-1 and CD40 expression at the mRNA and protein levels was down-regulated by overexpression of miR-145. However, α-SMA and calponin expression at the mRNA and protein levels was up-regulated by overexpression of miR-145. In addition, the luciferase reporter assay showed that CD40 may be a direct target gene of miR-145 in VSMC initiation and development. Moreover, these data demonstrate that the up-regulation of CD40 is critical for miR-145-mediated inhibitory effects on platelet-derived growth factor-induced cell proliferation and migration in human VSMCs. In summary, CD40, a direct target of miR-145, reverses the inhibitory effects of miR-145. These results suggest that the specific modulation of miR-145 in human VSMCs may be an attractive approach for the treatment of proliferative vascular diseases.

Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders

The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.

Elevated Glucose Levels Promote Contractile and Cytoskeletal Gene Expression in Vascular Smooth Muscle via Rho/Protein Kinase C and Actin Polymerization

Both type 1 and type 2 diabetes are associated with increased risk of cardiovascular disease. This is in part attributed to the effects of hyperglycemia on vascular endothelial and smooth muscle cells, but the underlying mechanisms are not fully understood. In diabetic animal models, hyperglycemia results in hypercontractility of vascular smooth muscle possibly due to increased activation of Rho-kinase. The aim of the present study was to investigate the regulation of contractile smooth muscle markers by glucose and to determine the signaling pathways that are activated by hyperglycemia in smooth muscle cells. Microarray, quantitative PCR, and Western blot analyses revealed that both mRNA and protein expression of contractile smooth muscle markers were increased in isolated smooth muscle cells cultured under high compared with low glucose conditions. This effect was also observed in hyperglycemic Akita mice and in diabetic patients. Elevated glucose activated the protein kinase C and Rho/Rho-kinase signaling pathways and stimulated actin polymerization. Glucose-induced expression of contractile smooth muscle markers in cultured cells could be partially or completely repressed by inhibitors of advanced glycation end products, L-type calcium channels, protein kinase C, Rho-kinase, actin polymerization, and myocardin-related transcription factors. Furthermore, genetic ablation of the miR-143/145 cluster prevented the effects of glucose on smooth muscle marker expression. In conclusion, these data demonstrate a possible link between hyperglycemia and vascular disease states associated with smooth muscle contractility.

Spontaneous activity and stretch-induced contractile differentiation are reduced in vascular smooth muscle of miR-143/145 knockout mice

AIM

Stretch is essential for maintaining the contractile phenotype of vascular smooth muscle cells, and small non-coding microRNAs are known to be important in this process. Using a Dicer knockout model, we have previously reported that microRNAs are essential for stretch-induced differentiation and regulation of L-type calcium channel expression. The aim of this study was to investigate the importance of the smooth muscle-enriched miR-143/145 microRNA cluster for stretch-induced differentiation of the portal vein.

METHODS

Contractile force and depolarization-induced calcium influx were determined in portal veins from wild-type and miR-143/145 knockout mice. Stretch-induced contractile differentiation was investigated by determination of mRNA expression following organ culture for 24 h under longitudinal load by a hanging weight.

RESULTS

In the absence of miR-143/145, stretch-induced mRNA expression of contractile markers in the portal vein was reduced. This was associated with decreased amplitude of spontaneous activity and depolarization-induced contractile and intracellular calcium responses, while contractile responses to 5-HT were largely maintained. We found that these effects correlated with a reduced basal expression of the pore-forming subunit of L-type calcium channels and an increased expression of CaMKIIδ and the transcriptional repressor DREAM.

CONCLUSION

Our results suggest that the microRNA-143/145 cluster plays a role in maintaining stretch-induced contractile differentiation and calcium signalling in the portal vein. This may have important implications for the use of these microRNAs as therapeutic targets in vascular disease.

Mechanical stretch-induced vascular hypertrophy occurs through modulation of leptin synthesis-mediated ROS formation and GATA-4 nuclear translocation

Background: Obesity and hypertension are associated with increased leptin production contributing to cardiovascular remodeling. Mechanisms involving mechanical stretch-induced leptin production and the cross talk between signaling pathways leading to vascular remodeling have not been fully elucidated.

Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch on leptin protein expression in vascular smooth muscle cells (VSMCs). Moreover, the involvement of reactive oxygen species (ROS), the RhoA/ROCK pathway, actin cytoskeleton dynamics and the transcriptional factor GATA-4 activation in mechanical stretch-induced vascular remodeling were investigated. Stretching the RPV for 1 or 24 h significantly increased leptin protein level and ROS formation in VSMCs, which was prevented by 1 h pretreatment with the ROCK inhibitor Y-27632 and the actin cytoskeleton depolymerization agent cytochalasin D. Moreover, Western blotting and immunohistochemistry revealed that mechanical stretch or treatment with 3.1 nmol/L leptin for 24 h significantly increased actin polymerization, as reflected by an increase in the F-actin to G-actin ratio. Increases in blood vessels’ wet weight and [³H]-leucine incorporation following a 24 h treatment with conditioned media from cultured stretched RPVs indicated RPV hypertrophy. This effect was prevented by 1 h pretreatment with anti-leptin antibody, indicating leptin’s crucial role in promoting VSMC hypertrophy. As an index of GATA-4 activation, GATA-4 nuclear translocation was assessed by immunohistochemistry method. Pretreating VSMC with leptin for 1 h significantly activated GATA-4 nuclear translocation, which was potently attenuated by the NADPH oxidase inhibitor apocynin, Y-27632, and cytochalasin D.

Conclusion: Our results demonstrate that ROS formation, RhoA/ROCK pathway, and GATA-4 activation play a pivotal role in mechanical stretch-induced leptin synthesis leading to VSMC remodeling.

Interleukin-33 in Tissue Homeostasis, Injury, and Inflammation

Interleukin-33 (IL-33) is a nuclear-associated cytokine of the IL-1 family originally described as a potent inducer of allergic type 2 immunity. IL-33 signals via the receptor ST2, which is highly expressed on group 2 innate lymphoid cells (ILC2s) and T helper 2 (Th2) cells, thus underpinning its association with helminth infection and allergic pathology. Recent studies have revealed ST2 expression on subsets of regulatory T cells, and for a role for IL-33 in tissue homeostasis and repair that suggests previously unrecognized interactions within these cellular networks. IL-33 can participate in pathologic fibrotic reactions, or, in the setting of microbial invasion, can cooperate with inflammatory cytokines to promote responses by cytotoxic NK cells, Th1 cells, and CD8(+) T cells. Here, we highlight the regulation and function of IL-33 and ST2 and review their roles in homeostasis, damage, and inflammation, suggesting a conceptual framework for future studies.

Variability in vascular smooth muscle cell stretch-induced responses in 2D culture

The pulsatile nature of blood flow exposes vascular smooth muscle cells (VSMCs) in the vessel wall to mechanical stress, in the form of circumferential and longitudinal stretch. Cyclic stretch evokes VSMC proliferation, apoptosis, phenotypic switching, migration, alignment, and vascular remodeling. Given that these responses have been observed in many cardiovascular diseases, a defined understanding of their underlying mechanisms may provide critical insight into the pathophysiology of cardiovascular derangements. Cyclic stretch-triggered VSMC responses and their effector mechanisms have been studied in vitro using tension systems that apply either uniaxial or equibiaxial stretch to cells grown on an elastomer-bottomed culture plate and ex vivo by stretching whole vein segments with small weights. This review will focus mainly on VSMC responses to the in vitro application of mechanical stress, outlining the inconsistencies in acquired data, and comparing them to in vivo or ex vivo findings. Major discrepancies in data have been seen in mechanical stress-induced proliferation, apoptosis, and phenotypic switching responses, depending on the stretch conditions. These discrepancies stem from variations in stretch conditions such as degree, axis, duration, and frequency of stretch, wave function, membrane coating, cell type, cell passage number, culture media content, and choice of in vitro model. Further knowledge into the variables that cause these incongruities will allow for improvement of the in vitro application of cyclic stretch.

MicroRNA-143/-145 in Cardiovascular Diseases

MicroRNAs (miRNAs) play an essential role in the onset and development of many cardiovascular diseases. Increasing evidence shows that miRNAs can be used as potential diagnostic biomarkers for cardiovascular diseases, and miRNA-based therapy may be a promising therapy for the treatment of cardiovascular diseases. The microRNA-143/-145 (miR-143/-145) cluster is essential for differentiation of vascular smooth muscle cells (VSMCs) and determines VSMC phenotypic switching. In this review, we summarize the recent progress in knowledge concerning the function of miR-143/-145 in the cardiovascular system and their role in cardiovascular diseases. We discuss the potential role of miR-143/-145 as valuable biomarkers for cardiovascular diseases and explore the potential strategy of targeting miR-143 and miR-145.

Regulation of smooth muscle contractility by competing endogenous mRNAs in intracranial aneurysms

Alterations in vascular smooth muscle cells (SMCs) contribute to the pathogenesis of intracranial aneurysms (IAs), but the genetic mechanisms underlying these alterations are unclear. We used microarray analysis to compare tissue small noncoding RNA and messenger RNA expression profiles in vessel wall samples from patients with late-stage IAs. We identified myocardin (MYOCD), a key contractility regulator of vascular SMCs, as a critical factor in IA progression. Using a multifaceted computational and experimental approach, we determined that depletion of competitive endogenous RNAs (ARHGEF12, FGF12, and ADCY5) enhanced factors that downregulate MYOCD, which induces the conversion of SMCs from differentiated contractile states into dedifferentiated phenotypes that exhibit enhanced proliferation, synthesis of new extracellular matrix, and organization of mural thrombi. These effects may lead to the repair and maintenance of IAs. This study presents guidelines for the prediction and validation of the IA regulator MYOCD in competitive endogenous RNA networks and facilitates the development of novel therapeutic and diagnostic tools for IAs.

The short and long of noncoding sequences in the control of vascular cell phenotypes

The two principal cell types of importance for normal vessel wall physiology are smooth muscle cells and endothelial cells. Much progress has been made over the past 20 years in the discovery and function of transcription factors that coordinate proper differentiation of these cells and the maintenance of vascular homeostasis. More recently, the converging fields of bioinformatics, genomics, and next generation sequencing have accelerated discoveries in a number of classes of noncoding sequences, including transcription factor binding sites (TFBS), microRNA genes, and long noncoding RNA genes, each of which mediates vascular cell differentiation through a variety of mechanisms. Alterations in the nucleotide sequence of key TFBS or deviations in transcription of noncoding RNA genes likely have adverse effects on normal vascular cell phenotype and function. Here, the subject of noncoding sequences that influence smooth muscle cell or endothelial cell phenotype will be summarized as will future directions to further advance our understanding of the increasingly complex molecular circuitry governing normal vascular cell differentiation and how such information might be harnessed to combat vascular diseases.

Stretch-dependent smooth muscle differentiation in the portal vein-role of actin polymerization, calcium signaling, and microRNAs

The mechanical forces acting on SMC in the vascular wall are known to regulate processes such as vascular remodeling and contractile differentiation. However, investigations to elucidate the underlying mechanisms of mechanotransduction in smooth muscle have been hampered by technical limitations associated with mechanical studies on pressurized small arteries, due primarily to the small amount of available tissue. The murine portal vein is a relatively large vessel showing myogenic tone that in many respects recapitulates the properties of small resistance vessels. Studies on stretched portal veins to elucidate mechanisms of mechanotransduction in the vascular wall have shown that stretch-sensitive regulation of contractile differentiation is mediated via Rho-activation and actin polymerization, while stretch-induced growth is regulated by the MAPK pathway. In this review, we have summarized findings on mechanotransduction in the portal vein with focus on stretch-induced contractile differentiation and the role of calcium, actin polymerization and miRNAs in this response.

Detrusor induction of miR-132/212 following bladder outlet obstruction: association with MeCP2 repression and cell viability

The microRNAs (miRNAs) miR-132 and miR-212 have been found to regulate synaptic plasticity and cholinergic signaling and recent work has demonstrated roles outside of the CNS, including in smooth muscle. Here, we examined if miR-132 and miR-212 are induced in the urinary bladder following outlet obstruction and whether this correlates with effects on gene expression and cell growth. Three to seven-fold induction of miR-132/212 was found at 10 days of obstruction and this was selective for the detrusor layer. We cross-referenced putative binding sites in the miR-132/212 promoter with transcription factors that were predicted to be active in the obstruction model. This suggested involvement of Creb and Ahr in miR-132/212 induction. Creb phosphorylation (S-133) was not increased, but the number of Ahr positive nuclei increased. Moreover, we found that serum stimulation and protein kinase C activation induced miR-132/212 in human detrusor cells. To identify miR-132/212 targets, we correlated the mRNA levels of validated targets with the miRNA levels. Significant correlations between miR-132/212 and MeCP2, Ep300, Pnkd and Jarid1a were observed, and the protein levels of MeCP2, Pnkd and Ache were reduced after obstruction. Reduction of Ache however closely matched a 90% reduction of synapse density arguing that its repression was unrelated to miR-132/212 induction. Importantly, transfection of antimirs and mimics in cultured detrusor cells increased and decreased, respectively, the number of cells and led to changes in MeCP2 expression. In all, these findings show that obstruction of the urethra increases miR-132 and miR-212 in the detrusor and suggests that this influences gene expression and limits cell growth.

Induction of angiotensin-converting enzyme after miR-143/145 deletion is critical for impaired smooth muscle contractility

MicroRNAs have emerged as regulators of smooth muscle cell phenotype with a role in smooth muscle-related disease. Studies have shown that miR-143 and miR-145 are the most highly expressed microRNAs in smooth muscle cells, controlling differentiation and function. The effect of miR-143/145 knockout has been established in the vasculature but not in smooth muscle from other organs. Using knockout mice we found that maximal contraction induced by either depolarization or phosphatase inhibition was reduced in vascular and airway smooth muscle but maintained in the urinary bladder. Furthermore, a reduction of media thickness and reduced expression of differentiation markers was seen in the aorta but not in the bladder. Supporting the view that phenotype switching depends on a tissue-specific target of miR-143/145, we found induction of angiotensin-converting enzyme in the aorta but not in the bladder where angiotensin-converting enzyme was expressed at a low level. Chronic treatment with angiotensin type-1 receptor antagonist restored contractility in miR-143/145-deficient aorta while leaving bladder contractility unaffected. This shows that tissue-specific targets are critical for the effects of miR-143/145 on smooth muscle differentiation and that angiotensin converting enzyme is one such target.

Regulation of Pancreatic Beta Cell Stimulus-Secretion Coupling by microRNAs

Increased blood glucose after a meal is countered by the subsequent increased release of the hypoglycemic hormone insulin from the pancreatic beta cells. The cascade of molecular events encompassing the initial sensing and transport of glucose into the beta cell, culminating with the exocytosis of the insulin large dense core granules (LDCVs) is termed "stimulus-secretion coupling." Impairment in any of the relevant processes leads to insufficient insulin release, which contributes to the development of type 2 diabetes (T2D). The fate of the beta cell, when exposed to environmental triggers of the disease, is determined by the possibility to adapt to the new situation by regulation of gene expression. As established factors of post-transcriptional regulation, microRNAs (miRNAs) are well-recognized mediators of beta cell plasticity and adaptation. Here, we put focus on the importance of comprehending the transcriptional regulation of miRNAs, and how miRNAs are implicated in stimulus-secretion coupling, specifically those influencing the late stages of insulin secretion. We suggest that efficient beta cell adaptation requires an optimal balance between transcriptional regulation of miRNAs themselves, and miRNA-dependent gene regulation. The increased knowledge of the beta cell transcriptional network inclusive of non-coding RNAs such as miRNAs is essential in identifying novel targets for the treatment of T2D.

LKB1 signalling attenuates early events of adipogenesis and responds to adipogenic cues

cAMP-response element-binding protein (CREB) is required for the induction of adipogenic transcription factors such as CCAAT/enhancer-binding proteins (C/EBPs). Interestingly, it is known from studies in other tissues that LKB1 and its substrates AMP-activated protein kinase (AMPK) and salt-inducible kinases (SIKs) negatively regulate gene expression by phosphorylating the CREB co-activator CRTC2 and class IIa histone deacetylases (HDACs), which results in their exclusion from the nucleus where they co-activate or inhibit their targets. In this study, we show that AMPK/SIK signalling is acutely attenuated during adipogenic differentiation of 3T3-L1 preadipocytes, which coincides with the dephosphorylation and nuclear translocation of CRTC2 and HDAC4. When subjected to differentiation, 3T3-L1 preadipocytes in which the expression of LKB1 was stably reduced using shRNA (Lkb1-shRNA), as well as Lkb1-knockout mouse embryonic fibroblasts (Lkb1(-/-) MEFs), differentiated more readily into adipocyte-like cells and accumulated more triglycerides compared with scrambled-shRNA-expressing 3T3-L1 cells or Wt MEFs. In addition, the phosphorylation of CRTC2 and HDAC4 was reduced, and the mRNA expression of adipogenic transcription factors Cebpa, peroxisome proliferator-activated receptor γ (Pparg) and adipocyte-specific proteins such as hormone-sensitive lipase (HSL), fatty acid synthase (FAS), aP2, GLUT4 and adiponectin was increased in the absence of LKB1. The mRNA and protein expression of Ddit3/CHOP10, a dominant-negative member of the C/EBP family, was reduced in Lkb1-shRNA-expressing cells, providing a potential mechanism for the up-regulation of Pparg and Cebpa expression. These results support the hypothesis that LKB1 signalling keeps preadipocytes in their non-differentiated form.

Role of non-coding RNAs in pancreatic beta-cell development and physiology

The progression of diabetes is accompanied by increasing demand to the beta-cells to produce and secrete more insulin, requiring complex beta-cell adaptations. Functionally active and ubiquitous non-coding RNAs (ncRNAs) have the capacity to take part in such adaptations as they have been shown to be key regulatory molecules in various biological processes. In the pancreatic islets, the function of ncRNAs and their contribution to disease development is beginning to be understood. Here, we review the different classes of ncRNAs, such as long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), and their potential contribution to insulin secretion. A special focus will be on miRNAs and their regulatory function in beta-cell physiology and insulin exocytosis. As important players in gene regulation, ncRNAs have huge potential in opening innovative therapeutic avenues against diabetes and associated complications.

MiR-17-5p impairs trafficking of H-ERG K+ channel protein by targeting multiple er stress-related chaperones during chronic oxidative stress

BACKGROUND

To investigate if microRNAs (miRNAs) play a role in regulating h-ERG trafficking in the setting of chronic oxidative stress as a common deleterious factor for many cardiac disorders.

METHODS

We treated neonatal rat ventricular myocytes and HEK293 cells with stable expression of h-ERG with H2O2 for 12 h and 48 h. Expression of miR-17-5p seed miRNAs was quantified by real-time RT-PCR. Protein levels of chaperones and h-ERG trafficking were measured by Western blot analysis. Luciferase reporter gene assay was used to study miRNA and target interactions. Whole-cell patch-clamp techniques were employed to record h-ERG K(+) current.

RESULTS

H-ERG trafficking was impaired by H2O2 after 48 h treatment, accompanied by reciprocal changes of expression between miR-17-5p seed miRNAs and several chaperones (Hsp70, Hsc70, CANX, and Golga2), with the former upregulated and the latter downregulated. We established these chaperones as targets for miR-17-5p. Application miR-17-5p inhibitor rescued H2O2-induced impairment of h-ERG trafficking. Upregulation of endogenous by H2O2 or forced miR-17-5p expression either reduced h-ERG current. Sequestration of AP1 by its decoy molecule eliminated the upregulation of miR-17-5p, and ameliorated impairment of h-ERG trafficking.

CONCLUSIONS

Collectively, deregulation of the miR-17-5p seed family miRNAs can cause severe impairment of h-ERG trafficking through targeting multiple ER stress-related chaperones, and activation of AP1 likely accounts for the deleterious upregulation of these miRNAs, in the setting of prolonged duration of oxidative stress. These findings revealed the role of miRNAs in h-ERG trafficking, which may contribute to the cardiac electrical disturbances associated with oxidative stress.

Mir-29 repression in bladder outlet obstruction contributes to matrix remodeling and altered stiffness

Recent work has uncovered a role of the microRNA (miRNA) miR-29 in remodeling of the extracellular matrix. Partial bladder outlet obstruction is a prevalent condition in older men with prostate enlargement that leads to matrix synthesis in the lower urinary tract and increases bladder stiffness. Here we tested the hypothesis that miR-29 is repressed in the bladder in outlet obstruction and that this has an impact on protein synthesis and matrix remodeling leading to increased bladder stiffness. c-Myc, NF-κB and SMAD3, all of which repress miR-29, were activated in the rat detrusor following partial bladder outlet obstruction but at different times. c-Myc and NF-κB activation occurred early after obstruction, and SMAD3 phosphorylation increased later, with a significant elevation at 6 weeks. c-Myc, NF-κB and SMAD3 activation, respectively, correlated with repression of miR-29b and miR-29c at 10 days of obstruction and with repression of miR-29c at 6 weeks. An mRNA microarray analysis showed that the reduction of miR-29 following outlet obstruction was associated with increased levels of miR-29 target mRNAs, including mRNAs for tropoelastin, the matricellular protein Sparc and collagen IV. Outlet obstruction increased protein levels of eight out of eight examined miR-29 targets, including tropoelastin and Sparc. Transfection of human bladder smooth muscle cells with antimiR-29c and miR-29c mimic caused reciprocal changes in target protein levels in vitro. Tamoxifen inducible and smooth muscle-specific deletion of Dicer in mice reduced miR-29 expression and increased tropoelastin and the thickness of the basal lamina surrounding smooth muscle cells in the bladder. It also increased detrusor stiffness independent of outlet obstruction. Taken together, our study supports a model where the combined repressive influences of c-Myc, NF-κB and SMAD3 reduce miR-29 in bladder outlet obstruction, and where the resulting drop in miR-29 contributes to matrix remodeling and altered passive mechanical properties of the detrusor.

A novel system for studying mechanical strain waveform-dependent responses in vascular smooth muscle cells

While many studies have examined the effects mechanical forces on vSMCs, there is a limited understanding of how the different arterial strain waveforms that occur in disease and different vascular beds alter vSMC mechanotransduction and phenotype. Here, we present a novel system for applying complex, time-varying strain waveforms to cultured cells and use this system to understand how these waveforms can alter vSMC phenotype and signaling. We have developed a highly adaptable cell culture system that allows the application of mechanical strain to cells in culture and can reproduce the complex dynamic mechanical environment experienced by arterial cells in the body. Using this system, we examined whether the type of applied strain waveform altered phenotypic modulation of vSMCs by mechanical forces. Cells exposed to the brachial waveform had increased phosphorylation of AKT, EGR-1, c-Fos expression and cytoskeletal remodeling in comparison to cells treated with the aortic waveform. In addition, vSMCs exposed to physiological waveforms had adopted a more differentiated phenotype in comparison to those treated with static or sinusoidal cyclic strain, with increased expression of vSMC markers desmin, calponin and SM-22 as well as increased expression of regulatory miRNAs including miR-143, -145 and -221. Taken together, our studies demonstrate the development of a novel system for applying complex, time-varying mechanical forces to cells in culture. In addition, we have shown that physiological strain waveforms have powerful effects on vSMC phenotype.

Expression of microRNAs is essential for arterial myogenic tone and pressure-induced activation of the PI3-kinase/Akt pathway

AIMS

The myogenic response is the intrinsic ability of small arteries to constrict in response to increased intraluminal pressure. Although microRNAs have been shown to play a role in vascular smooth muscle function, their importance in the regulation of the myogenic response is not known. In this study, we investigate the role of microRNAs in the regulation of myogenic tone by using smooth muscle-specific and tamoxifen-inducible deletion of the endonuclease Dicer in mice.

METHODS AND RESULTS

In order to avoid effects of Dicer deletion on smooth muscle differentiation and growth, we used an early time point (5 weeks) after the tamoxifen-induction of Dicer knockout (KO). At this time point, we found that myogenic tone was completely absent in the mesenteric arteries of Dicer KO mice. This was associated with a reduced pressure-induced Akt-phosphorylation, possibly via increased phosphatase and tensin homologue (PTEN) expression, which was found to be a target of miR-26a. Furthermore, loss of myogenic tone was associated with a decreased depolarization-induced calcium influx, and was restored by the L-type channel agonist Bay K 8644 or by transient stimulation with angiotensin II (Ang II). The effect of Ang II was dependent on AT1-receptors and activation of the PI3-kinase/Akt pathway.

CONCLUSION

In this study we have identified novel mechanisms that regulate myogenic tone in resistance arteries, which involves microRNA-dependent control of PI3-kinase/Akt signalling and L-type calcium influx. Furthermore, we have demonstrated that transient stimulation by Ang II can have long-lasting effects by potentiating myogenic tone.

Regulation of vascular smooth muscle mechanotransduction by microRNAs and L-type calcium channels

The phenotype of smooth muscle cells is regulated by multiple environmental factors including mechanical forces. Mechanical stretch of mouse portal veins ex vivo has been shown to promote contractile differentiation by activation of the Rho-pathway, an effect that is dependent on the influx of calcium via L-type calcium channels. MicroRNAs have recently been demonstrated to play a significant role in the control of smooth muscle phenotype and in a recent report we investigated their role in vascular mechanosensing. By smooth muscle specific deletion of Dicer, we found that microRNAs are essential for smooth muscle differentiation in response to stretch by regulating CamKIIδ and L-type calcium channel expression. Furthermore, we suggest that loss of L-type calcium channels in Dicer KO is due to reduced expression of the smooth muscle-enriched microRNA, miR-145, which targets CamKIIδ. These results unveil a novel mechanism for miR-145 dependent regulation of smooth muscle phenotype.