miR-17 targets tissue inhibitor of metalloproteinase 1 and 2 to modulate cardiac matrix remodeling.

We aimed to investigate the role of miR-17 in cardiac matrix remodeling following myocardial infarction (MI). Using real-time PCR, we quantified endogenous miR-17 in infarcted mouse hearts. Compared with related microRNAs, miR-17 was up-regulated most dramatically: 3.7-fold and 2.4-fold in the infarct region 3 and 7 d post-MI, respectively, and 2.4-fold in the border zone at d 3 compared to sham control (P<0.01). Chimeric luciferase reporter constructs were cloned for miR-17 target validation. miR-17 targeted the 3'-UTR of TIMP2 and the protein coding region of TIMP1. The miR-17 mimic decreased TIMP2 (P<0.01) and TIMP1 (P<0.05) protein expression compared with the scrambled control. Inhibition of endogenous miR-17 by in vivo antagomir delivery enhanced TIMP2 (P<0.01) and TIMP1 (P<0.05) protein expression compared to the mismatch group, decreased MMP9 activity (P<0.05), reduced infarct size as early as 7 d post-MI (P<0.05), and improved cardiac function (fractional shortening and fractional area contraction, P<0.05) at d 21 and 28 post-MI. Transgenic mice overexpressing miR-17 in the heart confirmed the deleterious role of miR-17 in matrix modulation. Our study suggests that miR-17 participates in the regulation of cardiac matrix remodeling and provides a novel therapeutic approach using miR-17 inhibitors to prevent remodeling and heart failure after MI.

Elastin overexpression by cell-based gene therapy preserves matrix and prevents cardiac dilation.

After a myocardial infarction, thinning and expansion of the fibrotic scar contribute to progressive heart failure. The loss of elastin is a major contributor to adverse extracellular matrix remodelling of the infarcted heart, and restoration of the elastic properties of the infarct region can prevent ventricular dysfunction. We implanted cells genetically modified to overexpress elastin to re-establish the elastic properties of the infarcted myocardium and prevent cardiac failure. A full-length human elastin cDNA was cloned, subcloned into an adenoviral vector and then transduced into rat bone marrow stromal cells (BMSCs). In vitro studies showed that BMSCs expressed the elastin protein, which was deposited into the extracellular matrix. Transduced BMSCs were injected into the infarcted myocardium of adult rats. Control groups received either BMSCs transduced with the green fluorescent protein gene or medium alone. Elastin deposition in the infarcted myocardium was associated with preservation of myocardial tissue structural integrity (by birefringence of polarized light; P < 0.05 versus controls). As a result, infarct scar thickness and diastolic compliance were maintained and infarct expansion was prevented (P < 0.05 versus controls). Over a 9-week period, rats implanted with BMSCs demonstrated better cardiac function than medium controls; however, rats receiving BMSCs overexpressing elastin showed the greatest functional improvement (P < 0.01). Overexpression of elastin in the infarcted heart preserved the elastic structure of the extracellular matrix, which, in turn, preserved diastolic function, prevented ventricular dilation and preserved cardiac function. This cell-based gene therapy provides a new approach to cardiac regeneration.

Gene delivery of soluble vascular endothelial growth factor receptor-1 (sFlt-1) inhibits intra-plaque angiogenesis and suppresses development of atherosclerotic plaque.

Intra-plaque angiogenesis plays an important role in the development of atherosclerotic plaque. Vascular endothelial growth factor (VEGF) is a major initiating factor in this pathologic progress. One selective and specific inhibitor of VEGF is soluble VEGF receptor-1 (sFlt-1). The anti-angiogenic utilization of sFlt-1 in treatment of atherosclerotic plaque has not been fully confirmed yet. Our study was designed to construct eukaryotic expression recombinant pEGFP-N1-sFlt-1, evaluate sFlt-1 recombinant's effects on endothelial cells proliferation and tube formation in vitro, and investigate effects of local high-expressed sFlt-1 on atherosclerotic plaque in vivo. Rabbit models of atherosclerotic plaque were established by high-lipid diet combined with injury induced by balloon catheter on iliac artery intima. Animals were divided into four groups randomly: control group (C), atherosclerotic plaque group (AP), atherosclerotic plaque with blank vector pEGFP-N1 transfection group (APV), and atherosclerotic plaque with pEGFP-N1-sFlt-1 transfection group (APsFlt-1). The local expression of sFlt-1 protein in target artery was detected by western blotting. The plaque area (PA), plaque circumference (PC), and maximum plaque thickness (MPT) were measured via HE staining. Degree of intra-plaque angiogenesis was evaluated by CD34+ cells immunohistochemistry. As results, we observed that pEGFP-N1-sFlt-1 transfection suppressed the HUVECs proliferation and ability of tube formation, against the effect of VEGF. We obtained higher local expression of sFlt-1 protein in Group APsFlt-1 than that in other groups (P < 0.05). PA, PC, and MPT of plaque in group APsFlt-1 were significantly decreased when compared with other groups (P < 0.05). Amount of annulations surrounded by CD34-positive cells was significantly decreased in pEGFP-N1-sFlt-1 transfection group, which represented decreased level of intra-plaque neovessels formation. The present study confirmed that local gene delivery of sFlt-1 can suppress plaque formation, as one of possible mechanisms, via inhibitive effect on intra atherosclerotic plaque angiogenesis, which hints at the clinical utility of sFlt-1 in atherosclerosis therapy.

Tracking cardiac engraftment and distribution of implanted bone marrow cells: Comparing intra-aortic, intravenous, and intramyocardial delivery.

OBJECTIVES: Cell therapy improved cardiac function after a myocardial infarction in several preclinical studies; however, the functional benefits were limited in the initial clinical trials, perhaps because of inadequate cell engraftment. We used noninvasive molecular imaging to compare the distribution and myocardial retention of cells implanted by using clinical delivery routes. METHODS: Bone marrow stromal cells isolated from male rats and transfected with a firefly luciferase reporter gene were injected by using 3 increasingly invasive techniques (ie, intravenous, intra-aortic, and intramyocardial) into female rats 3 or 28 days after coronary ligation. Whole-body bioluminescence imaging was performed 2, 24, and 48 hours later; implanted cells were quantified at 48 hours in explanted organs by means of bioluminescence and real-time polymerase chain reaction. RESULTS: Variations in cell distribution among groups were profound, with nearly complete trapping of the injected cells in the lungs after intravenous delivery. Cell delivery into the aortic root (with the distal aorta occluded) produced minimal cell retention in the heart. Direct intramyocardial injection facilitated the best early targeting of the cells (P < .05 vs intravenous and intra-aortic injection). Rapid signal loss over 48 hours indicated very poor cell survival in all 3 groups, although implanted cell retention was greater in mature compared with acute infarcts. CONCLUSIONS: This is the first study to correlate live cell imaging with quantitative genetic and histologic techniques. Noninvasive molecular imaging tracked delivered cells and will permit the evaluation of new and improved delivery platforms designed to increase cell homing, retention, and engraftment.