[Show abstract][Hide abstract] ABSTRACT: MicroRNA (miR)-92a is an important regulator of endothelial proliferation and angiogenesis after ischemia, but the effects of miR-92a on re-endothelialization and neointimal lesion formation after vascular injury remain elusive. We tested the effects of lowering miR-92a levels using specific LNA-based antimiRs as well as endothelial-specific knock out of miR-92a on re-endothelialization and neointimal formation after wire-induced injury of the femoral artery in mice.
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRNAs, miRs) emerged as key regulators of gene expression. Germline hemizygous deletion of the gene that encodes the miR-17∼92 miRNA cluster was associated with microcephaly, short stature and digital abnormalities in humans. Mice deficient for the miR-17∼92 cluster phenocopy several features such as growth and skeletal development defects and exhibit impaired B cell development. However, the individual contribution of miR-17∼92 cluster members to this phenotype is unknown. Here we show that germline deletion of miR-92a in mice is not affecting heart development and does not reduce circulating or bone marrow-derived hematopoietic cells, but induces skeletal defects. MiR-92a-/- mice are born at a reduced Mendelian ratio, but surviving mice are viable and fertile. However, body weight of miR-92a-/- mice was reduced during embryonic and postnatal development and adulthood. A significantly reduced body and skull length was observed in miR-92a-/- mice compared to wild type littermates. µCT analysis revealed that the length of the 5th mesophalanx to 5th metacarpal bone of the forelimbs was significantly reduced, but bones of the hindlimbs were not altered. Bone density was not affected. These findings demonstrate that deletion of miR-92a is sufficient to induce a developmental skeletal defect.
PLoS ONE 01/2014; 9(6):e101153. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ageing is the predominant risk factor for cardiovascular diseases and contributes to a significantly worse outcome in patients with acute myocardial infarction. MicroRNAs (miRNAs) have emerged as crucial regulators of cardiovascular function and some miRNAs have key roles in ageing. We propose that altered expression of miRNAs in the heart during ageing contributes to the age-dependent decline in cardiac function. Here we show that miR-34a is induced in the ageing heart and that in vivo silencing or genetic deletion of miR-34a reduces age-associated cardiomyocyte cell death. Moreover, miR-34a inhibition reduces cell death and fibrosis following acute myocardial infarction and improves recovery of myocardial function. Mechanistically, we identified PNUTS (also known as PPP1R10) as a novel direct miR-34a target, which reduces telomere shortening, DNA damage responses and cardiomyocyte apoptosis, and improves functional recovery after acute myocardial infarction. Together, these results identify age-induced expression of miR-34a and inhibition of its target PNUTS as a key mechanism that regulates cardiac contractile function during ageing and after acute myocardial infarction, by inducing DNA damage responses and telomere attrition.
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRs) are small non-coding RNAs that recently emerged as potent regulators of gene expression. The members of the miR-17-92 cluster have been shown to control endothelial cell functions and neovascularization; however, the regulation and function of the cluster in endothelial cell lineage commitment has not been explored. This project aimed to test the role of the miR-17-92 cluster during endothelial differentiation. We demonstrate that miR-17, miR-18, miR-19 and miR-20 are increased upon the induction of endothelial cell differentiation of murine embryonic stem cells or induced pluripotent stem cells. In contrast, miR-92a and the primary miR-17-92 transcript were downregulated. The inhibition of each individual miR of the cluster by cholesterol-modified antagomirs did not affect endothelial marker gene expression. Moreover, the combination of all antagomirs had no effect. These findings illustrate that although the miR-17-92 cluster regulates vascular integrity and angiogenesis, none of the members has a significant impact on the endothelial differentiation of pluripotent stem cells.
Journal of Vascular Research 07/2012; 49(5):447-60. · 2.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRs) are small RNAs that regulate gene expression at the posttranscriptional level. miR-27 is expressed in endothelial cells, but the specific functions of miR-27b and its family member miR-27a are largely unknown. Here we demonstrate that overexpression of miR-27a and miR-27b significantly increased endothelial cell sprouting. Inhibition of both miR-27a and miR-27b impaired endothelial cell sprout formation and induced endothelial cell repulsion in vitro. In vivo, inhibition of miR-27a/b decreased the number of perfused vessels in Matrigel plugs and impaired embryonic vessel formation in zebrafish. Mechanistically, miR-27 regulated the expression of the angiogenesis inhibitor semaphorin 6A (SEMA6A) in vitro and in vivo and targeted the 3'-untranslated region of SEMA6A. Silencing of SEMA6A partially reversed the inhibition of endothelial cell sprouting and abrogated the repulsion of endothelial cells mediated by miR-27a/b inhibition, indicating that SEMA6A is a functionally relevant miR-27 downstream target regulating endothelial cell repulsion. In summary, we show that miR-27a/b promotes angiogenesis by targeting the angiogenesis inhibitor SEMA6A, which controls repulsion of neighboring endothelial cells.
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRs) control various cellular processes in tissue homeostasis and disease by regulating gene expression on the posttranscriptional level. Recently, it was demonstrated that the expression of miR-21 and members of the miR-17-92 cluster was significantly altered in experimental pulmonary hypertension (PH).
To evaluate the therapeutic efficacy and antiremodeling potential of miR inhibitors in the pathogenesis of PH.
We first tested the effects of miR inhibitors (antagomirs), which were specifically designed to block miR-17 (A-17), miR-21 (A-21), and miR-92a (A-92a) in chronic hypoxia-induced PH in mice and A-17 in monocrotaline-induced PH in rats. Moreover, biological function of miR-17 was analyzed in cultured pulmonary artery smooth muscle cells.
In the PH mouse model, A-17 and A-21 reduced right ventricular systolic pressure, and all antagomirs decreased pulmonary arterial muscularization. However, only A-17 reduced hypoxia-induced right ventricular hypertrophy and improved pulmonary artery acceleration time. In the monocrotaline-induced PH rat model, A-17 treatment significantly decreased right ventricular systolic pressure and total pulmonary vascular resistance index, increased pulmonary artery acceleration time, normalized cardiac output, and decreased pulmonary vascular remodeling. Among the tested miR-17 targets, the cyclin-dependent kinase inhibitor 1A (p21) was up-regulated in lungs undergoing A-17 treatment. Likewise, in human pulmonary artery smooth muscle cells, A-17 increased p21. Overexpression of miR-17 significantly reduced p21 expression and increased proliferation of smooth muscle cells.
Our data demonstrate that A-17 improves heart and lung function in experimental PH by interfering with lung vascular and right ventricular remodeling. The beneficial effects may be related to the up-regulation of p21. Thus, inhibition of miR-17 may represent a novel therapeutic concept to ameliorate disease state in PH.
American Journal of Respiratory and Critical Care Medicine 12/2011; 185(4):409-19. · 11.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs are small RNAs that control gene expression. Besides their cell intrinsic function, recent studies reported that microRNAs are released by cultured cells and can be detected in the blood.
To address the regulation of circulating microRNAs in patients with stable coronary artery disease.
To determine the regulation of microRNAs, we performed a microRNA profile using RNA isolated from n=8 healthy volunteers and n=8 patients with stable coronary artery disease that received state-of-the-art pharmacological treatment. Interestingly, most of the highly expressed microRNAs that were lower in the blood of patients with coronary artery disease are known to be expressed in endothelial cells (eg, miR-126 and members of the miR-17 approximately 92 cluster). To prospectively confirm these data, we detected selected microRNAs in plasma of 36 patients with coronary artery disease and 17 healthy volunteers by quantitative PCR. Consistent with the data obtained by the profile, circulating levels of miR-126, miR-17, miR-92a, and the inflammation-associated miR-155 were significantly reduced in patients with coronary artery disease compared with healthy controls. Likewise, the smooth muscle-enriched miR-145 was significantly reduced. In contrast, cardiac muscle-enriched microRNAs (miR-133a, miR-208a) tend to be higher in patients with coronary artery disease. These results were validated in a second cohort of 31 patients with documented coronary artery disease and 14 controls.
Circulating levels of vascular and inflammation-associated microRNAs are significantly downregulated in patients with coronary artery disease.
Circulation Research 09/2010; 107(5):677-84. · 11.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs are endogenously expressed small non-coding RNAs that regulate gene expression on the posttranscriptional level. During the last years microRNAs have emerged as key regulators of several physiological and pathophysiological processes in the vascular wall. Endothelial cell functions and angiogenesis are critically regulated by microRNAs such as miR-126 and the miR-17-92 cluster in vitro and in vivo. Tumor angiogenesis is additionally controlled by miR-296 and miR-378. MicroRNAs also regulate smooth muscle cell phenotypes and control neointima formation and atherosclerosis. In this respect, miR-143 and miR-145 have been shown to play a crucial role. In this review, we summarize the role of microRNAs and their target genes in endothelial and smooth muscle cells and discuss their applicability as drug targets.
Current drug targets 08/2010; 11(8):943-9. · 3.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs are endogenously expressed small noncoding RNAs that regulate gene expression on the posttranscriptional level. The miR-17-92 cluster (encoding miR-17, -18a, -19a/b, -20a, and miR-92a) is highly expressed in tumor cells and is up-regulated by ischemia. Whereas miR-92a was recently identified as negative regulator of angiogenesis, the specific functions of the other members of the cluster are less clear. Here we demonstrate that overexpression of miR-17, -18a, -19a, and -20a significantly inhibited 3-dimensional spheroid sprouting in vitro, whereas inhibition of miR-17, -18a, and -20a augmented endothelial cell sprout formation. Inhibition of miR-17 and miR-20a in vivo using antagomirs significantly increased the number of perfused vessels in Matrigel plugs, whereas antagomirs that specifically target miR-18a and miR-19a were less effective. However, systemic inhibition of miR-17/20 did not affect tumor angiogenesis. Further mechanistic studies showed that miR-17/20 targets several proangiogenic genes. Specifically, Janus kinase 1 was shown to be a direct target of miR-17. In summary, we show that miR-17/20 exhibit a cell-intrinsic antiangiogenic activity in endothelial cells. Inhibition of miR-17/20 specifically augmented neovascularization of Matrigel plugs but did not affect tumor angiogenesis indicating a context-dependent regulation of angiogenesis by miR-17/20 in vivo.
[Show abstract][Hide abstract] ABSTRACT: Atrial fibrillation (AF) is associated with increased inward-rectifier current activity that may stabilize atrial rotors maintaining the arrhythmia. Left atrial (LA) structures are important for AF maintenance, but previous studies have mostly evaluated changes in the right atrium. MicroRNA-1 (miR-1) reciprocally regulates inwardly rectifying potassium channel (Kir)2.1 expression in coronary disease, contributing to arrhythmogenesis.
This study sought to evaluate changes in miR-1 and Kir2 subunit expression in relation to I(K1) alterations in LA of patients with persistent AF.
Atrial tissue was obtained from 62 patients (31 with AF) undergoing mitral valve repair or bypass grafting. Currents were recorded from isolated cells. Proteins were quantified from immunoblots. mRNA and miR-1 levels were measured with real-time polymerase chain reaction. Immunohistochemistry was applied to localize connexin (Cx) 43.
I(K1) density was increased in LA cells from patients with AF (at -100 mV: -5.9 +/- 1.3 vs. -2.7 +/- 0.7 sinus rhythm, P <.05). There was a corresponding increase in Kir2.1 protein expression, but no change in other Kir or Cx proteins. Expression of inhibitory miR-1 was reduced by approximately 86% in tissue samples of AF patients. Kir2.1 mRNA was significantly increased. No change in Cx43 localization occurred. Ex vivo tachystimulation of human atrial slices up-regulated Kir2.1 and down-regulated miR-1, suggesting a primary role of atrial rate in miR-1 down-regulation and I(K1) up-regulation.
miR-1 levels are greatly reduced in human AF, possibly contributing to up-regulation of Kir2.1 subunits, leading to increased I(K1). Because up-regulation of inward-rectifier currents is important for AF maintenance, these results provide potential new insights into molecular mechanisms of AF with potential therapeutic implications.
Heart rhythm: the official journal of the Heart Rhythm Society 12/2009; 6(12):1802-9. · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression by binding to target mRNAs, leading to translational repression or degradation. The polycistronic microRNA cluster comprises seven mature micro-RNAs (miR-17-5p and -3p, miR-18a, miR-19a and b, miR-20a and miR-92a) and has initially been linked to tumorigenesis. Meanwhile, additional functions have been assigned to the cluster such as the regulation of hematopoiesis and immune functions. Recently, loss-off-function studies revealed a critically role of the miR-17-92 cluster in heart and lung development and the individual miRNAs encoded by the cluster such as miR-17 and miR-92a were shown to control lung development and postnatal neovascularization, respectively. The present article summarizes the functions of the miR-17-92 cluster in health and disease and discusses the specific contribution and the targets of the individual miRNAs encoded by the cluster.
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression by binding to target messenger RNAs (mRNAs), leading to translational repression or degradation. Here, we show that the miR-17approximately92 cluster is highly expressed in human endothelial cells and that miR-92a, a component of this cluster, controls the growth of new blood vessels (angiogenesis). Forced overexpression of miR-92a in endothelial cells blocked angiogenesis in vitro and in vivo. In mouse models of limb ischemia and myocardial infarction, systemic administration of an antagomir designed to inhibit miR-92a led to enhanced blood vessel growth and functional recovery of damaged tissue. MiR-92a appears to target mRNAs corresponding to several proangiogenic proteins, including the integrin subunit alpha5. Thus, miR-92a may serve as a valuable therapeutic target in the setting of ischemic disease.