Abstract Th0006: Clickable Extracellular Vesicles for Localized Abdominal Aortic Aneurysm Repair

Introduction: Abdominal aortic aneurysm (AAA) features a degradative environment and loss of vascular elastin, which we believe could be treated with an engineered regenerative therapy. Our group and others have investigated using mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (EVs) for regeneration, but a key barrier to successful implementation is delivery. To address this problem, we have developed an EV delivery system that utilizes click chemistry to improve EV retention within a hydrogel. Hypothesis: Click-bound EVs will have better retention within hydrogels compared to non-clicked EVs. Methods: MSCs were cultured with or without Ac4ManNAz to metabolize an azido tag onto the EVs. After isolation the EVs were labeled with NHs-Cy5 and excess dye was removed by dialysis. DBCO-conjugated fibrinogen and collagen were mixed to form a “hybridgel” with different release characteristics depending on the concentration of each protein. The final concentration of the gel was 7.5 mg/mL with the DBCO collagen gel being a 2:1 mixture with WT collagen and the hybridgel being a 50:50 mixture of collagen and fibrinogen. EVs were characterized by Western blot and nanoparticle tracking analysis. EVs were co-cultured with SMCs in fibrin gels for 6h to assess EV uptake. Results and Conclusions: DBCO-conjugated collagen and fibrinogen had better EV retention than their wild type counterparts. Collagen had better retention compared to fibrinogen, and the hybridgel had a retention profile between the two. Co-culture of EVs with fibrin gels demonstrated uptake into SMCs compared to dye controls. Conclusions/Interpretations: A hybridgel of collagen and fibrinogen can be used to tailor retention. EVs can be taken up by SMCs in 3D fibrin constructs.