Abstract 16818: Frozen in Time: Endothelial Progenitor Cell-Derived Extracellular Vesicles Maintain Therapeutic Efficacy for Clinically Translatable Treatment of Acute Myocardial Infarction After Long Term Storage

Introduction: Extracellular vesicles (EV) derived from progenitor cells are a novel therapy for ischemic cardiomyopathy, with promise for “off-the-shelf” delivery. Clinical translation and timely delivery post-myocardial infarction (MI) requires assurance of EV stability after storage. Bioactivity studies of EVs after freezing are currently lacking and are necessary to establish quality standards for widespread clinical use of EVs. Hypothesis: We hypothesize that endothelial progenitor cell-derived EVs (EPC-EVs) can be frozen at -80 °C for at least 2 months without decrement of therapeutic effect when delivered intramyocardially to ischemic tissue. Methods: EVs were isolated from male Wistar rat bone marrow EPCs. Fresh preparations of EVs isolated from 700,000 EPCs were compared to frozen EVs stored in dPBS for 2-4 months at -80 °C. Particle size of EVs was analyzed via nanoparticle tracking analysis. In vitro angiogenesis was measured with Matrigel assay. A rat model of MI via left anterior descending artery ligation was used to assess EPC-EV function. Hemodynamics, scar thickness and vasculogenesis were assessed 4 weeks post-intramyocardial injection of EPC-EV within a shear-thinning gel (STG). Results: After 4 months’ storage at -80 °C, frozen EVs had stable mean particle diameter. In vivo analysis demonstrated equivalent hemodynamic outcomes between fresh and 2-month frozen EVs (p=1.0), both of which had statistically significantly improved measures of contractility over PBS as measured by Ees (p=0.0001; p=0.0008) and dp/dt (p=0.01; p=0.03, respectively). Scar thickness was increased in fresh, but not frozen EVs vs PBS (0.68, 0.64 v 0.50; p=0.031, p=0.22). On IHC, fresh and frozen EVs had significantly increased vascular density vs PBS (Δ665.5, Δ907.5; p=0.05). Conclusions: EPC-EVs retain adequate functionality after 2 months of freezing to produce hemodynamic benefits equivalent to freshly prepared EPC-EVs when delivered in STG to ischemic myocardium.