Abstract 2880: Novel Minicircle Vector for Gene Therapy in Murine Myocardial Infarction
Introduction: In this study, we develop a novel non-viral vector which not only persistently expresses the therapeutic gene in the heart but also allows monitoring of the targeted gene expression level in vivo.
Methods: Compared to normal plasmids, minicircles lack an origin of replication, carry only short bacterial sequences, and are of smaller size. We created minicircles with CMV promoter driving firefly luciferase and hypoxia inducible factor 1 alpha . Mouse C2C12 myoblasts were used for in vitro confirmation. Afterwards, adult FVB mice underwent LAD ligation and were injected intramyocardiallly with (1) minicircle carrying Fluc-HIF1α, (2) normal plasmid carrying Fluc-HIF1α as positive control, and (3) PBS as negative control (n=10/group).
Results: For in vitro cell culture, Western blot showed minicircle expressed >50% higher HIF1α level than normal plasmid. In vivo imaging showed stable minicircle gene expression in the heart for >12 weeks and the activity level was 5.6±0.7 fold stronger compared to regular plasmid at week 1 (P<0.01). Echocardiographic study showed significant improvement of LVEF in the minicircle (51.3%±3.6%) compared to regular plasmid group (42.3%±4.1%) and saline group (30.5%±2.8%) at week 4 (P<0.05 for both). Histology demonstrated increased neoangiogenesis in both treatment groups.
Conclusion: Taken together, this is the first study to demonstrate that minicircles can significantly improve transfection efficiency, duration of transgene expression, and cardiac contractility. Given the serious drawbacks associated with most viral vectors, we believe this novel non-viral vector can be of great usage for cardiac gene therapy protocols.
This research has received full or partial funding support from the American Heart Association, AHA Western States Affiliate (California, Nevada & Utah).