Abstract 12368: Cardiac Cellular Reprogramming With "Triplet" Polycistronic Vectors Encoding Gata 4, Mef2c and Tbx5 Enhances Post-Infarct Ventricular Functional Improvement Compared to Singlet Vectors
Reprogramming of cardiac fibroblasts into induced cardiomyocytes (iCMs) by in situ Gata4 (G), Mef 2c (M) and Tbx5 (T) administration has been shown to improve post-infarct ventricular function in myocardial infarction models, and scar pre-vascularization with VEGF has been shown to further enhance this intervention. However, the efficacy of this gene transfer strategy has been limited by the need for cell targets to be infected three times - once by each of the single G, M and T vectors. We hypothesized that a polycistronic vector encoding all three GMT transcription factors would enhance post-infarct ventricular function compared to use of single transgene vectors.
Methods: Following in vitro validation studies, adult male Fischer 344 rats (n=6) underwent coronary ligation and intramyocardial administration 3 wks later of a polycistronic GMT “triplet” lentivirus vector construct (3x105 TU) or the same total dose of three vectors each individually encoding G, M, or T. GMT-treated animals also underwent intramyocardial delivery at the time of coronary ligation of an adenovirus encoding all three major VEGF isoforms (AdVEGF-All; 1 X 109 pu); while control animals (n=6) were administered corresponding vectors without therapeutic transgenes.
Results: Western blots demonstrated that polycistronic (triplet) and “singlet” vectors yielded equivalent GMT transgene expression. Cardiomyocyte marker immunofluorescence and FACS studies likewise demonstrated fibroblast transdifferentiation into iCMs. In subsequent in vivo studies, echocardiography demonstrated a ≈ 50% decrease in ejection fraction (EF) following coronary ligation. After pre-conditioning with VEGF, GMT vector administration was associated with an increase in EF from 33% ± 2% to 45% ± 8% 4 wks after triplet vector administration (p≤0.05) and from 38% ± 4% to 43% ± 4%, after singlet vector administration, while EF decreased from 43% ± 4% to 40% ± 6% in the control group. The corresponding change in EF for each animal from its own baseline was: 37 ± 9%, 14 ± 3% and (-) 9 ± 5%, respectively (p≤0.05).
Conclusion: These data validate that GMT cellular reprogramming improves cardiac function after myocardial infarction, and that polycistronic vectors further enhance the efficiency of this strategy.
- © 2013 by American Heart Association, Inc.