Abstract 10492: Preclinical Evaluation of Transient and Cardiomyocyte Specific Gene Therapy for the Treatment of Subacute Ischemic Heart Failure

Abstract

Rationale: Treatment of heart failure is limited due to the limited regenerative capacity of cardiomyocytes. Our group has shown that ectopic expression of Cdk1/CyclinB1 and Cdk4/CyclinD1 (named 4F) via adenovirus vector promotes cardiomyocyte proliferation in 20% of infected cardiomyocytes in vitro and in vivo and improves cardiac function after myocardial infarction (MI). Objective: To introduce 4F specifically and transiently into cardiomyocytes to induce selective cardiomyocyte regeneration and limit any tumorigenic potential in other organs. Methods and Results: A polycistronic non-integrating lentivirus encoding 4F, each driven by a TNNT2 promoter (TNNT2-4F-NIL), was generated to induce transient and specific expression of 4F cardiomyocytes. TNNT2-4F-NIL promotes proliferation of 15% of cardiomyocytes in vivo after MI as assessed in lineage-tracing mice (α-MHC-Cre-MADM). Rats and pigs were subjected to coronary occlusion/reperfusion to induce MI. One week later, animals were injected (intramyocardially) with either TNNT2-4F-NIL or control-NIL. Four weeks after injection, TNNT2-4F-NIL treated rats and pigs showed a significant improvement in left ventricular ejection fraction (EF) compared to controls (TNNT2-4F-NIL rats 54.3±1.78% vs control-NIL 42.97±2.60%; n=9/group, p =0.003, TNNT2-4F-NIL pigs 37±2.3% vs control-NIL 28.4±1.2%; n=6/group, p =0.01). Histological analyses showed a 25-30% reduction in scar size in both rats and pigs treated with TNNT2-4F-NIL vs. control-NIL (p<0.05). To assess the long-term efficacy and safety of TNNT2-4F-NIL, a 4-months follow-up experiment after MI and virus treatment was performed during which cardiac function was assessed monthly. TNNT2-4F-NIL treated rats showed sustained improvement in cardiac function (EF in TNNT2-4F-NIL 48.4±3% vs in control-NIL 33.6±3%; n=6/group, p =0.008). There was no obvious development of arrhythmias and no evidence of oncogenicity or toxicity in other organs in TNNT2-4F-NIL treated rats or in the control group. Conclusion: This study provides a novel approach to treat heart failure, with the use of transient and cardiomyocyte-specific gene therapy that promotes long-term functional improvement after a single treatment with no obvious adverse effect.