Abstract 12242: Nanoporous Microgel Encapsulation of Extracellular Vesicles Enhances Lung Delivery for the Treatment of Pulmonary Vascular Diseases

Introduction: Pulmonary arterial hypertension (PAH) is a devastating lung disease with no curative treatments available. Cell-based therapies are a promising regenerative approach, including the direct application of stem cell derived extracellular vesicles (EVs). Mesenchymal stromal cells (MSCs) have shown promise as a treatment for many cardiovascular diseases; their therapeutic effects are predominately mediated by paracrine mechanisms, in particular the release of EVs. Yet, systemically administered EVs are rapidly cleared to the liver and spleen, with minimal lung accumulation. Hypothesis: We hypothesized that encapsulation of EVs within nanoporous microgels would provide a novel therapeutic product to improve EV lung delivery and retention and therefore enhance their therapeutic benefits. Methods & Results: MSC-derived EVs were purified using tangential flow filtration resulting in a median size of 108±53nm by nanoparticle tracking analysis, and positive for CD63 by Western blot. EV-loaded microgels were prepared using a microfluidic device producing agarose-gelatin (1%-1%) microgels of 47.2±0.4um diameter. In vitro uptake assays were performed with DiR or pkh26 labelled EVs and quantified by microscopy. Encapsulated EVs demonstrated a delayed-release profile in vitro with reduced HUVEC uptake over 24h (9.7±1.1% encap. vs. 46±5.3% free). In vivo biodistribution studies were performed in the monocrotaline model of PAH using central intravenous delivery. EV-loaded microgels were efficiently retained within the lungs after 24h (81±12% encap vs. 7.5±0.4% free), while free EVs accumulated in the liver (74±2.3% free vs 10±2.5% encap). Furthermore, lung digestion and flow cytometry analysis revealed that encapsulated EVs were readily taken up by CD45+ immune cells and CD31+ endothelial cells to a greater extent than free EVs, indicating enhanced interaction with the local lung microenvironment. Conclusion: Microencapsulation of EVs results in significantly enhanced local retention within the lung, leading to increased local cellular uptake compared to systemically administered EVs.