Abstract 18088: Myocardial Delivery of Lipidoid Nanoparticle mRNA Designed for Tailored Expression of Cardiogenic Factors

Abstract

Introduction: Nanoparticle-based delivery of mRNA offers a potential alternative to viral vectors for gene therapy, but efficacy has not been demonstrated in the heart. As a proof of concept, we report the first successful lipidoid nanoparticle (LNP) mediated delivery of mRNA to rat myocardium as a novel approach for controlling the timing and distribution of expression of therapeutic factors for cardiac repair. Methods and Results: Custom lipidoid formulation yielded functionally stable LNPs containing modified eGFP mRNA. LNP solution (600 uL) was delivered by injection at 8 to 10 sites into adult rat myocardium, followed by recovery. At time of sacrifice, the heart was cut in two: 1) mRNA level was quantified by real time-PCR, and 2) eGFP protein was detected by immunofluorescence of cryosections. To test the dose response (Fig. A), rats received 1, 5 or 10 ug eGFP mRNA (n = 3 per group) and were sacrificed 20 h after injection; compared to saline control, the fold increase in eGFP mRNA in the heart was 142 ± 116, 5628 ± 1292 and 5470 ± 3103 fold, respectively, with higher dosages showing a significant effect (p < 0.05). Fluorescence microscopy confirmed GFP-positive cells in the subepicardium of all treated hearts. Expression kinetics at different time points after injection of 5 ug of eGFP mRNA showed that expression at 6 h (18,380 ± 5457 fold) was significantly higher than at 20 h (p < 0.05), with expression still detectable at 48 h. Biodistribution of eGFP mRNA in harvested lung, liver, spleen, kidney, skeletal muscle, and brain (Fig. B) showed the delivery was cardiac specific, with off-target expression levels less than 1% of that in the heart. Conclusion: Adult rat myocardium was successfully transduced, supporting our hypothesis that lipidoid nanoparticles carrying mRNA allow effective message delivery to cardiac cells in vivo, with potential to optimize gene therapy for enhanced cardiac function and regeneration.