2093 CMR reveals that cardiac-specific overexpression of the inducible form of nitric oxide synthase induces Left Ventri
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BioMed Central
Open Access
Meeting abstract
2093 CMR reveals that cardiac-specific overexpression of the inducible form of nitric oxide synthase induces Left Ventricular Hypertrophy in wild-type mice after AAV-Mediated direct gene transfer Konkal MR Prasad, Ronald J Beyers, Yaqin Xu, Frederick H Epstein and Brent A French* Address: University of Virginia, Charlottesville, VA, USA * Corresponding author
from 11th Annual SCMR Scientific Sessions Los Angeles, CA, USA. 1–3 February 2008 Published: 22 October 2008 Journal of Cardiovascular Magnetic Resonance 2008, 10(Suppl 1):A362
doi:10.1186/1532-429X-10-S1-A362
Abstracts of the 11th Annual SCMR Scientific Sessions - 2008
Meeting abstracts – A single PDF containing all abstracts in this Supplement is available here. http://www.biomedcentral.com/content/pdf/1532-429X-10-S1-info.pdfThis abstract is available from: http://jcmr-online.com/content/10/S1/A362 © 2008 Prasad et al; licensee BioMed Central Ltd.
Introduction
Methods
CMR has previously shown that left ventricular remodeling (LVR) resulting from reperfused myocardial infarction (MI) is dramatically reduced in iNOS knock-out mice [1]. However, previous studies using transgenic mice with cardiac-specific overexpression of iNOS have yielded disparate results. One study reported a benign phenotype while a second reported that iNOS overexpression resulted in cardiac fibrosis, hypertrophy and dilatation. One explanation is that transgenic mice may develop compensatory mechanisms to down-regulate iNOS overexpression. Another possiblity is that the phenotype of iNOS overexpression may be variable in its penetrance due to limited availability of a necessary co-factor (tetrahydrobiopterin).
High-efficiency, cardiac-specific gene transfer was achieved by using a cardiac-specific troponin T (cTnT) promoter in an adeno-associated viral (AAV) genome packaged into an AAV9 capsid. Thus the cDNA for murine iNOS was subcloned behind the cTnT promoter in an AAV-generating plasmid and packaged into AAV9 capsids using a system kindly provided by Dr. James M. Wilson (U. Penn, PA) to create AcTnTiNOS. The resulting viral particles were purified and viral titers were determined as genomic particles/ml by real-time PCR. A total of twelve C57Bl/6 mice were used. Three were injected via jugular vein with increasing doses of AcTnTiNOS for Western blot analysis at 4 weeks post-injection. Four mice were similarly injected with 1E+11 AcTnTiNOS particles at 4 weeks of age for CMR analysis. Starting 10 weeks after vector injection, these mice were additionally treated for 4 weeks with sepiapterin (50 μg/day by Alzet micro-osmotic pump). Another 5 untreated C57Bl/6 mice served as agematched controls. CMR was performed at the end of sepiapterin treatment to assess the impact of iNOS overexpression using a 4.7 T Varian system and a black-blood pulse sequence as described [2]. Excised hearts from the control and AcTnTiNOS-treated groups were immunostained for iNOS and for cleaved caspase III (a sensitive marker of apoptosis).
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