Abstract 12464: Exosomes Loaded with Microrna-126 Prevents Sepsis-induced Cardiac Dysfunction in Endothelial Cell Hspa12b Deficient Mice

We have previously shown that increased expression of endothelial heat shock protein A12B (HSPA12B) attenuates LPS-induced cardiac dysfunction. MicroRNA-126 (miR-126) specifically targets adhesion molecules in endothelial cells. This study examined the role of miR-126 in HSPA12B-induced cardioprotection in sepsis. Endothelial HSPA12B-/- (n=6) and wild type (WT, n=6) mice were subjected to cecal ligation and puncture (CLP)-induced sepsis. Sham surgery served as sham control (n=6). Cardiac function was examined by echocardiography before and 6 h after CLP. CLP sepsis significantly decreased ejection fraction (EF%) by 34.8% and fractional shortening (%FS) by 43.1% in WT mice. EF% and FS% values in HSPA12B-/- septic mice showed further decreases of 19.9% and 22.5% compared with WT septic mice. The levels of ICAM1 and VCAM1 and the infiltration of immune cells (macrophages and neutrophils) into the myocardium of HSPA12B-/- septic mice were markedly greater than WT septic mice. The vascular permeability in HSPA12B-/- septic mice was much more severe than in WT septic mice. Importantly, the levels of circulating miR-126 in HSPA12B-/- septic mice were much lower than in WT septic mice. To examine whether decreased miR-126 is responsible for cardiac dysfunction in HSPA12B-/- septic mice, we loaded exosomes with miR-126 by transfection of bone marrow stromal cells with miR-126 mimics followed by isolation of exosomes 24 hours after transfection. Scrambled miR served as the miR control (miR-control). Exosomes loaded with miR-126 or miR-control were delivered into the myocardium through the right carotid artery immediately after induction of CLP (n=5-6/group). Cardiac function was significantly improved by delivery of miR-126 into the myocardium as evidenced by increased the values of EF% (51%) and FS% (59%), when compared with HSPA12B-/- septic mice. MiR-126 delivery significantly suppressed the expression of adhesion molecules, reduced immune cell infiltration in the myocardium, and improved vascular permeability in HSPA12B-/- septic mice. Delivery of miR-control did not alter cardiac dysfunction in HSPA12B-/- septic mice. We conclude that miR-126 plays a critical protective role in endothelial HSAP12B in preservation of cardiac function in sepsis.