Injectable Hydrogels To Deliver Extracellular Vesicles For Treatment After Myocardial Infarction

There is a tremendous clinical need to develop new therapies to limit the progression to heart failure after myocardial infarction (MI). Recent studies have suggested that extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) can mediate cardioprotection and preserve function post-MI due to their key roles in paracrine signaling with angiogenic, proliferative, anti-inflammatory, and anti-apoptotic effects via transfer of proteins and miRNAs. Despite this interest, there are still challenges related to EV scale-up, sustained delivery, and analysis in clinically-relevant animal models that need to be addressed prior to their translation.With these considerations in mind, the overall goals of this dissertation were to (i) develop injectable hydrogels, which allow localization and sustained release, for minimally invasive delivery of EVs to the heart, (ii) scale-up production of MSC-EVs to generate doses required for preclinical large animal studies, and (iii) investigate the timing of EV presentation on cardiac repair. First, three MSC culture systems (tissue culture plastic, microcarriers in a spinner flask, and perfusion bioreactor) were explored towards scaling up EV production to generate large doses. MSC-EVs were characterized for size, distribution, yield, morphology, content and in vitro potential, which motivated microcarriers to create large doses for pre-clinical studies. The therapeutic potential of MSC-EVs delivered from injectable hydrogels was then investigated in a porcine MI model, which indicated improvements in infarct area with EV delivery. Secondly, extended delivery of EVs through an interpenetrating network (IPN) hydrogel was studied with metabolic labeling to understand the timing, release, and biodistribution of MSC-EVs. The therapeutic potential of extended MSC-EV delivery was studied in a rat model of MI, with the IPN delivery of EVs improving outcomes of vascularization over controls. Finally, a radiopaque hydrogel system was developed to evaluate hydrogel localization after injection via a SPECT/CT imaging system towards clinical translation. Overall, this thesis highlights the importance of cell culture conditions for scale-up of MSC-EVs for cardiac repair and the use of injectable hydrogels as a therapeutic delivery vehicle towards translation of these therapeutics for clinical use