Noninvasive imaging of hypoxia-inducible factor-1α gene therapy for myocardial ischemia
Chen, Ian Y × Gheysens, Olivier Li, Zongjin Rasooly, Julia A Wang, Qian Ramasamy, Paulmurugan Rosenberg, Jarrett Rodriguez-Porcel, Martin Willmann, Juergen K Wang, David S Contag, Christopher H Robbins, Robert C Wu, Joseph C Gambhir, Sanjiv #
Mary Ann Liebert, Inc. Publishers
Human Gene Therapy, Part B-Methods vol:24 issue:5 pages:279-88
Hypoxia-inducible factor-1 alpha (HIF-1α) gene therapy holds great promise for the treatment of myocardial ischemia. Both pre-clinical and clinical evaluations of this therapy are underway, and can benefit from a vector strategy that allows noninvasive assessment of HIF-1α expression as an objective measure of gene delivery. We have developed a novel bi-directional plasmid vector (pcTnT-HIF-1α-VP2-TSTA-fluc), which employs the cardiac troponin T (cTnT) promoter in conjunction with a two-step transcriptional amplification (TSTA) system to drive the linked expression of a recombinant HIF-1α gene (HIF-1α-VP2) and the firefly luciferase gene (fluc). The firefly luciferase (FLuc) activity serves as a surrogate for HIF-1α-VP2 expression, and can be noninvasively assessed in mice using bioluminescence imaging following vector delivery. Transfection of cultured HL-1 cardiomyocytes with pcTnT-HIF-1α-VP2-TSTA-fluc led to a strong correlation between FLuc and HIF-1α-dependent vascular endothelial growth factor expression (<i>r</i><sup>2</sup>=0.88). Intramyocardial delivery of pcTnT-HIF-1α-VP2-TSTA-fluc into infarcted mouse myocardium led to persistent HIF-1α-VP2 expression for 4 weeks, even though it improved neither CD31+ microvessel density nor echocardiographically determined left ventricular systolic function. These results lend support to recent findings of suboptimal efficacy associated with plasmid-mediated HIF-1α therapy. The imaging techniques developed herein should be useful for further optimizing HIF-1α-VP2 therapy in pre-clinical models of myocardial ischemia.