Abstract 11550: Human Mesenchymal Stem Cell-Derived Microvesicles Mitigate Aortic Smooth Muscle Cell Activation via miR-147 and Attenuate Aortic Aneurysm Formation

Abstract

Objective: Mesenchymal stem cells (MSCs) can release microvesicles (MVs) but their effects on aortic aneurysm (AA) formation are unknown. We hypothesize that MSC-derived MVs can inhibit AA formation via modulation of specific microRNAs (miRs). Methods: An elastase-perfusion abdominal AA model was used with 8- to 12- week old male mice. The abdominal aorta was perfused for 5 minutes with porcine pancreatic elastase and treated with or without human umbilical cord MSC-derived MVs (1x10 6 given intravenously on day 1). On day14 following perfusion, the abdominal aortic diameter was measured by video micrometry and expressed as percentage increase over baseline. miRNA microarray was performed on aortic tissue using Affymetrix GeneChip hybridization. MVs were transfected with either miR-147b mimic or inhibitor (25nM, Invitrogen, CA) using Lipofectamine RNAiMAX and co-cultured with aortic smooth muscle cells (AoSMCs) followed by treatment with transient elastase (5 minutes) or recombinant IL-17 (10 ng/ml). Cytokines were analyzed in cell culture supernatants after 24 hrs. Groups were compared by ANOVA followed by Bonferroni post hoc test. Results: Treatment of elastase-perfused WT mice with MVs caused a significant attenuation of aortic diameter compared to elastase-perfused mice alone (102.4±6 vs. 162.6±17.9% respectively; mean +/- S.E.; n=5, p=0.03). A significant mitigation of pro-inflammatory cytokines (IL-17, HMGB1, MCP-1, TNF-α and KC), inflammatory cell infiltration (CD3+ T cells, macrophages and neutrophils) and decrease in elastic fiber disruption occurred in aortic tissue from elastase-perfused mice treated with MVs compared to elastase-perfused mice alone. miRNA analysis of aortic tissue demonstrated a significant upregulation of miR-147b (10-fold; p<0.001), miR-19a (9-fold; p<0.001) and a downregulation of miR-98 (1.2 fold; p<0.05) in mice with AA compared to controls (n=5 mice/group). Treatment of AoSMCs with elastase or IL-17 induced cytokines (IL-6, RANTES, MCP-1, TNF-α and KC) which were attenuated by co-cultures with MVs transfected with miR-147 inhibitor. Conclusions: MSC-derived MVs attenuate aortic inflammation and inhibit AoSMC activation via miR-147 suggesting a novel protective mechanism in AA pathobiology.