Identification and treatment of abdominal aortic aneurysm (AAA) remain among the most prominent challenges in vascular medicine. MicroRNAs (miRNAs) are crucial regulators of cardiovascular pathology ...and represent intriguing targets to limit AAA expansion. Here we show, by using two established murine models of AAA disease along with human aortic tissue and plasma analysis, that miR-24 is a key regulator of vascular inflammation and AAA pathology. In vivo and in vitro studies reveal chitinase 3-like 1 (Chi3l1) to be a major target and effector under the control of miR-24, regulating cytokine synthesis in macrophages as well as their survival, promoting aortic smooth muscle cell migration and cytokine production, and stimulating adhesion molecule expression in vascular endothelial cells. We further show that modulation of miR-24 alters AAA progression in animal models, and that miR-24 and CHI3L1 represent novel plasma biomarkers of AAA disease progression in humans.
MicroRNAs (miRs) regulate gene expression at the posttranscriptional level and play crucial roles in vascular integrity. As such, they may have a role in modifying abdominal aortic aneurysm (AAA) ...expansion, the pathophysiological mechanisms of which remain incompletely explored. Here, we investigate the role of miRs in 2 murine models of experimental AAA: the porcine pancreatic elastase (PPE) infusion model in C57BL/6 mice and the AngII infusion model in Apoe-/- mice. AAA development was accompanied by decreased aortic expression of miR-29b, along with increased expression of known miR-29b targets, Col1a1, Col3a1, Col5a1, and Eln, in both models. In vivo administration of locked nucleic acid anti-miR-29b greatly increased collagen expression, leading to an early fibrotic response in the abdominal aortic wall and resulting in a significant reduction in AAA progression over time in both models. In contrast, overexpression of miR-29b using a lentiviral vector led to augmented AAA expansion and significant increase of aortic rupture rate. Cell culture studies identified aortic fibroblasts as the likely vascular cell type mediating the profibrotic effects of miR-29b modulation. A similar pattern of reduced miR-29b expression and increased target gene expression was observed in human AAA tissue samples compared with that in organ donor controls. These data suggest that therapeutic manipulation of miR-29b and its target genes holds promise for limiting AAA disease progression and protecting from rupture.
Identification and treatment of abdominal aortic aneurysm (AAA) remains among the most prominent challenges in vascular medicine. MicroRNAs are crucial regulators of cardiovascular pathology and ...represent possible targets for the inhibition of AAA expansion. We identified microRNA-21 (miR-21) as a key modulator of proliferation and apoptosis of vascular wall smooth muscle cells during development of AAA in two established murine models. In both models (AAA induced by porcine pancreatic elastase or infusion of angiotensin II), miR-21 expression increased as AAA developed. Lentiviral overexpression of miR-21 induced cell proliferation and decreased apoptosis in the aortic wall, with protective effects on aneurysm expansion. miR-21 overexpression substantially decreased expression of the phosphatase and tensin homolog (PTEN) protein, leading to increased phosphorylation and activation of AKT, a component of a pro-proliferative and antiapoptotic pathway. Systemic injection of a locked nucleic acid-modified antagomir targeting miR-21 diminished the pro-proliferative impact of down-regulated PTEN, leading to a marked increase in the size of AAA. Similar results were seen in mice with AAA augmented by nicotine and in human aortic tissue samples from patients undergoing surgical repair of AAA (with more pronounced effects observed in smokers). Modulation of miR-21 expression shows potential as a new therapeutic option to limit AAA expansion and vascular disease progression.
The purpose of this study was to investigate the effect of hepatocyte growth factor (HGF) on the pathogenesis of cardiac fibrosis induced by pressure overload in mice. Although cardiac fibrosis is ...attributed to excess pathological deposition of extracellular matrix components, the mechanism remains unclear. Recent reports revealed that α-smooth muscle actin–expressing myofibroblasts are primarily responsible for fibrosis. It is believed that myofibroblasts are differentiated from resident fibroblasts, whereas the transformation of vascular endothelial cells into myofibroblasts, known as endothelial-mesenchymal transition, has been suggested to be intimately associated with perivascular fibrosis. Thus, we hypothesized that HGF prevents cardiac fibrosis by blocking these pathways. We analyzed the pressure-overloaded HGF-transgenic mouse model made by transverse aortic constriction. Human coronary artery endothelial cells and human cardiac fibroblasts were examined in vitro after being treated with transforming growth factor-β1 or angiotensin II with or without HGF. The amount of cardiac fibrosis significantly decreased in pressure-overloaded HGF-transgenic mice compared with pressure-overloaded nontransgenic controls, particularly in the perivascular region. This was accompanied by a reduction in the expression levels of fibrosis-related genes and by significant preservation of echocardiographic measurements of cardiac function in the HGF-transgenic mice (P<0.05). The survival rate 2 months after transverse aortic constriction was higher by 45% (P<0.05). HGF inhibited the differentiation of human coronary artery endothelial cells into myofibroblasts induced by transforming growth factor-β1 and the phenotypic conversion of human cardiac fibroblasts into myofibroblasts. We conclude that HGF reduced cardiac fibrosis by inhibiting endothelial-mesenchymal transition and the transformation of fibroblasts into myofibroblasts.
OBJECTIVE—To evaluate the safety and feasibility of intramuscular gene transfer using naked plasmid DNA-encoding hepatocyte growth factor (HGF) and to assess its potential therapeutic benefit in ...patients with critical limb ischemia.
METHODS AND RESULTS—Gene transfer was performed in 22 patients with critical limb ischemia by intramuscular injection of HGF plasmid, either 2 or 4 mg, 2 times. Safety, ankle-brachial index, resting pain on a 10-cm visual analog scale, wound healing, and walking distance were evaluated before treatment and at 2 months after injection. No serious adverse event caused by gene transfer was detected over a follow-up of 6 months. Of particular importance, no peripheral edema, in contrast to that seen after treatment with vascular endothelial growth factor, was observed. In addition, the systemic HGF protein level did not increase during the study. At 2 months after gene transfer, the mean±SD ankle-brachial index increased from 0.46±0.08 to 0.59±0.13 (P<0.001), the mean±SD size of the largest ischemic ulcers decreased from 3.08±1.54 to 2.32±1.88 cm (P=0.007), and the mean±SD visual analog scale score decreased from 5.92±1.67 to 3.04±2.50 cm (P=0.001). An increase in ankle-brachial index by >0.1, a reduction in ulcer size by >25%, and a reduction in visual analog scale score by >2 cm at 2 months after gene transfer were observed in 11 (64.7%) of 17 limbs, 18 (72%) of 25 ulcers, and 8 (61.5%) of 13 limbs, respectively.
CONCLUSION—Intramuscular injection of naked HGF plasmid is safe and feasible and can achieve successful improvement of ischemic limbs as sole therapy.
We previously reported that overexpression of full-length periostin, Pn-1, resulted in ventricular dilation with enhanced interstitial collagen deposition in a rat model. However, other reports have ...documented that the short-form splice variants Pn-2 (lacking exon 17) and Pn-4 (lacking exons 17 and 21) promoted cardiac repair by angiogenesis and prevented cardiac rupture after acute myocardial infarction. The apparently differing findings from those reports prompted us to use a neutralizing antibody to selectively inhibit Pn-1 by blockade of exon 17 in a rat acute myocardial infarction model. Administration of Pn neutralizing antibody resulted in a significant decrease in the infarcted and fibrotic areas of the myocardium, which prevented ventricular wall thinning and dilatation. The inhibition of fibrosis by Pn neutralizing antibody was associated with a significant decrease in gene expression of fibrotic markers, including collagen I, collagen III, and transforming growth factor-β1. Importantly, the number of α-smooth muscle actin-positive myofibroblasts was significantly reduced in the hearts of animals treated with Pn neutralizing antibody, whereas cardiomyocyte proliferation and angiogenesis were comparable in the IgG and neutralizing antibody groups. Moreover, the level of Pn-1 expression was significantly correlated with the severity of myocardial infarction. In addition, Pn-1, but not Pn-2 or Pn-4, inhibited fibroblast and myocyte attachment, which might account for the cell slippage observed during cardiac remodeling. Collectively, these results indicate that therapeutics that specifically inhibit Pn exon-17, via a neutralizing antibody or drug, without suppressing other periostin variants might offer a new class of medication for the treatment of acute myocardial infarction patients.
Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California
Submitted 16 June 2009
; accepted in final form 19 October 2009
The recently discovered peptide ...apelin is known to be involved in the maintenance of insulin sensitivity. However, questions persist regarding its precise role in the chronic setting. Fasting glucose, insulin, and adiponectin levels were determined on mice with generalized deficiency of apelin (APKO). Additionally, insulin (ITT) and glucose tolerance tests (GTT) were performed. To assess the impact of exogenously delivered apelin on insulin sensitivity, osmotic pumps containing pyroglutamated apelin-13 or saline were implanted in APKO mice for 4 wk. Following the infusion, ITT/GTTs were repeated and the animals euthanized. Soleus muscles were harvested and homogenized in lysis buffer, and insulin-induced Akt phosphorylation was determined by Western blotting. Apelin-13 infusion and ITTs/GTTs were also performed in obese diabetic db/db mice. To probe the underlying mechanism for apelin's effects, apelin-13 was also delivered to cultured C 2 C 12 myotubes. 2- 3 Hdeoxyglucose uptake and Akt phosphorylation were assessed in the presence of various inhibitors. APKO mice had diminished insulin sensitivity, were hyperinsulinemic, and had decreased adiponectin levels. Soleus lysates had decreased insulin-induced Akt phosphorylation. Administration of apelin to APKO and db/db mice resulted in improved insulin sensitivity. In C 2 C 12 myotubes, apelin increased glucose uptake and Akt phosphorylation. These events were fully abrogated by pertussis toxin, compound C, and siRNA knockdown of AMPK 1 but only partially diminished by LY-294002 and not at all by L -NAME. We conclude that apelin is necessary for the maintenance of insulin sensitivity in vivo. Apelin's effects on glucose uptake and Akt phosphorylation are in part mediated by a G i and AMPK-dependent pathway.
insulin resistance; obesity; diabetes; hormones
Address for reprint requests and other correspondence: P. Yue and Philip S. Tsao, Div. of Cardiovascular Medicine, Stanford University School of Medicine, 300 Pasteur Dr., Falk CVRC, Stanford, CA 94305-5406 (e-mail: pyue{at}stanford.edu ).
The release of free fatty acids (FFAs) from adipocytes (i.e. lipolysis) is increased in obesity and is a contributory factor to the development of insulin resistance. A recently identified adipokine, ...apelin, is up-regulated in states of obesity. Although apelin is secreted by adipocytes, its functions in them remain largely unknown. To determine whether apelin affects lipolysis, FFA, glycerol, and leptin levels, as well as abdominal adiposity, were measured at baseline and after reintroduction of exogenous apelin in apelin-null mice. To examine apelin’s effects in vitro, isoproterenol-induced FFA/glycerol release, and hormone-sensitive lipase (HSL) and acetyl CoA carboxylase phosphorylation were investigated in 3T3-L1 cells and isolated wild-type adipocytes. Serum FFA, glycerol, and leptin concentrations, as well as abdominal adiposity, were significantly increased in apelin-null vs. wild-type mice; these changes were ameliorated in response to exogenous apelin. Apelin also reduced isoproterenol-induced FFA release in adipocytes isolated from wild-type but not APJ-null mice. In 3T3-L1 cells and isolated adipocytes, apelin attenuated isoproterenol-induced FFA/glycerol release. Apelin’s inhibition was reversed by pertussis toxin, the Gq inhibitor glycoprotein antagonist 2A, and the AMP-activated protein kinase inhibitors compound C and dorsomorphin. Apelin increased HSL phosphorylation at Ser-565 and also abrogated isoproterenol-induced HSL phosphorylation at Ser-563. Notably, apelin increased acetyl CoA carboxylase phosphorylation, suggesting AMPK activation. In conclusion, apelin negatively regulates lipolysis. Its actions may be mediated by pathways involving Gq, Gi, and AMP-activated protein kinase.
Apelin, a recently discovered peptide hormone, exerts an inhibitory effect on lipolysis which may be mediated by interactions with the G-proteins Gq and Gi.
OBJECTIVE—As angiogenic growth factors can stimulate the development of collateral arteries, a concept called therapeutic angiogenesis, we performed a phase I/IIa open-label clinical trial using ...intramuscular injection of naked plasmid DNA encoding hepatocyte growth factor (HGF). We reported long-term evaluation of 2 years after HGF gene therapy in 22 patients with severe peripheral arterial disease.
METHODS AND RESULTS—Twenty-two patients with peripheral arterial disease or Buerger disease staged by Fontaine IIb (n=7), III (n=4), and IV (n=11) were treated with HGF plasmid, either 2 mg or 4 mg ×2. Increase in ankle-branchial pressure index >0.1 was observed in 11 of 14 patients (79 %) at 2 years after gene therapy and in 11 of the 17 patients (65%) at 2 months. Reduction in rest pain (>2 cm in visual analog scale) was observed in 9 of 9 patients (100%) at 2 years and in 8 of 13 (62%) patients at 2 months. At 2 years, 9 of 10 (90%) ischemic ulcers reduced by >25%, accompanied by a reduction in the size of ulcer. Severe complications and adverse effects caused by gene transfer were not detected in any patient throughout the period up to 2 years.
CONCLUSION—Overall, the present study demonstrated long-term efficacy of HGF gene therapy up to 2 years. These findings may be cautiously interpreted to indicate that intramuscular injection of naked HGF plasmid is safe, feasible, and can achieve successful improvement of ischemic limbs as sole therapy.
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