Abstract 13586: Osteopontin RNA Aptamer Protects Against Pressure Overload-Induced Cardiac Dysfunction
Objective: Osteopontin (OPN) expression increases in the heart during hypertrophy and heart failure. OPN knockout mice subjected to pressure overload by trans-aortic constriction (TAC) were reported to have a reduced hypertrophic response. We hypothesized that use of an RNA aptamer targeting OPN protein would be an effective, cardiac-specific approach to modulating the hypertrophic response to overload stress.
Method and Results: C57BL6 male mice were subjected to sham or TAC surgeries. TAC mice were injected with 2’OMe OPN RNA aptamer, 2’ OMe mutant OPN aptamer, or PBS. Each treated mouse received a total of 10 injections - one jugular injection during surgery, followed by 9 tail vein injections every other day. Cardiac function was measured by echocardiography at 4 and 6wks post TAC. At 4wks, the OPN aptamer group (n=13) showed increase in %EF (25%) and %FS (35%), and decrease in LVPWd (0.63 fold) - p<.01 for all, relative to mut group (n=13). Identical significant improvement was recorded relative to the PBS group (n=3) with no significant difference to the normal Sham and no-surgery group (n=11). This significant cardiac improvement was sustained at 6wks post surgery. At 4wks post TAC, qPCR, western blots, and histology were performed on left ventricular (LV) samples. OPN aptamer treatment reduced (p<.05) the expression of Nppb, Opn, and Col3a1 transcripts relative to mut aptamer group (n=5/group). OPN and downstream targets FN1, PI3K, and p-AKT proteins were reduced (p<.05) in the OPN aptamer-treated LVs relative to mut group (n=4-6/group). Picrosirius Red and Wheat Germ Agglutinin staining showed respectively that the OPN aptamer reduced cardiac fibrosis (0.32 fold) and myocyte cross sectional area (.77 fold) - p<.01. In neonatal rat cardiac myocytes, 24h treatment with 250nM FAM-labeled OPN aptamer, followed by Actinin immunostaining and microscopy, showed impressive intracellular uptake of the OPN aptamer by the cardiac myocytes.
Conclusion: OPN RNA aptamer protected against cardiac dysfunction in the mouse TAC model of cardiac hypertrophy. The cardioprotective effect of the OPN aptamer, together with the efficient uptake by cardiomyocytes make it a promising therapeutic molecule and a potential platform for targeted RNA delivery into the heart.
- © 2013 by American Heart Association, Inc.