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BackgroundThe optimal delivery route to enhance effectiveness of regenerative therapeutics to the human heart is poorly understood. Direct intra-myocardial (IM) injection is the gold standard, however, it is relatively invasive. We thus compared targeted IM against less invasive, catheter-based intra-coronary (IC) delivery to porcine myocardium for the acute retention of nanoparticles using cardiac magnetic resonance (CMR) imaging and viral vector transduction using qPCR.MethodsFerumoxytol iron oxide (IO) nanoparticles (5 ml) were administered to Yorkshire swine (n = 13) by: (1) IM via thoracotomy, (2) catheter-based IC balloon-occlusion (BO) with infusion into the distal left anterior descending (LAD) coronary artery, (3) IC perforated side-wall (SW) infusion into the LAD, or (4) non-selective IC via left main (LM) coronary artery infusion. Hearts were harvested and imaged using at 3T whole-body MRI scanner. In separate Yorkshire swine (n = 13), an adeno-associated virus (AAV) vector was similarly delivered, tissue harvested 4–6 weeks later, and viral DNA quantified from predefined areas at risk (apical LV/RV) vs. not at risk in a potential mid-LAD infarct model. Results were analyzed using pairwise Student's t-test.ResultsIM delivery yielded the highest IO retention (16.0 ± 4.6% of left ventricular volume). Of the IC approaches, BO showed the highest IO retention (8.7 ± 2.2% vs. SW = 5.5 ± 4.9% and LM = 0%) and yielded consistent uptake in the porcine distal LAD territory, including the apical septum, LV, and RV. IM delivery was limited to the apex and anterior wall, without septal retention. For the AAV delivery, the BO was most efficient in the at risk territory (Risk: BO = 6.0 × 10−9, IM = 1.4 × 10−9, LM = 3.2 × 10−10 viral copies per μg genomic DNA) while all delivery routes were comparable in the non-risk territory (BO = 1.7 × 10−9, IM = 8.9 × 10−10, LM = 1.2 × 10−9).ConclusionsDirect IM injection has the highest local retention, while IC delivery with balloon occlusion and distal infusion is the most effective IC delivery technique to target therapeutics to a heart territory most in risk from an infarct.

Introduction: The optimal cardiac delivery route for stem cell and gene therapeutics is poorly understood. Direct intramyocardial (IM) injection has been proposed as the gold standard, however, it is invasive and not studied in detail against targeted intra-coronary (IC) delivery techniques. We sought to compare effectiveness of IM and targeted IC methods using cardiac magnetic resonance imaging (CMR) of nanoparticles in a porcine model. Hypothesis: IM provides the highest retention of delivered therapeutic, while targeted IC delivery yields high-volume retention in the perfused coronary territory. Methods: In Yorkshire swine (n=10), 5ml of ferumoxytol iron oxide (IO) nanoparticles, similar in size to therapeutic viral vectors, were injected: 1) IM via thoracotomy (n=3), 2) catheter based IC balloon-occlusion (BO) with distal infusion of the LAD (n=4), 3) IC with perforated balloon side wall (SW) infusion in the LAD (n=2), or 4) IC non-selective left main (LM) (n=1). Hearts were harvested and imaged with CMR using T1 and 3D inversion-recovery sequences. Retention of nanoparticles was quantified by percent of myocardium occupied. Results: IM delivery yielded the highest retention (16.3±5.5% of myocardial volume, p=0.04). Of the IC approaches, BO had the highest retention (8.7±2.2%, p=0.13 vs IM) compared to SW (5.5±4.9%) and LM (0%). On 3D CMR, BO yielded consistent uptake in the distal LAD territory, including the anterior wall and septum. IM delivery was limited to the anterior wall with no nanoparticles in the septum. Troponin increased 15,600±4,910 with IM vs.184±262 with IC (p=0.14). Conclusions: Direct IM injection offers the highest retention of delivered therapeutics to the heart. IC balloon occlusion-distal infusion has highest retention among IC techniques and provides an effective approach to direct therapeutics to the vascular bed most impacted by an infarct.