Osteopontin RNA Aptamer Reverses Heart Failure and Increases Plasma HDL Levels

Objective: Osteopontin (OPN) expression increases in the heart during hypertrophy and heart failure and in the aorta during atherosclerosis. OPN KO mice were reported to have a reduced hypertrophic response after trans-aortic constriction (TAC), and a reduced plaque burden on an APOE-/- background. We hypothesized that an RNA aptamer targeting OPN protein would effectively modulate the responses to TAC and atherogenesis. Method and Results: C57BL6 male mice were subjected to sham or TAC surgeries. TAC mice were injected starting day1 with OPN RNA aptamer or mutant OPN aptamer. At 4wks, OPN aptamer treatment increased %EF (25%) relative to mut control (n=13, p<.01). This significant cardiac improvement was sustained at 8 wks (n=7) and 12wks (n=4-7). WGA and PR staining showed respectively that the OPN aptamer significantly reduced myocyte size (.8 fold at 4wks and 0.7 fold at 12 wks) and cardiac fibrosis (0.4 fold at 4wks and 0.3 fold at 12 wks). In 4 and 12wk LVs and RVs, OPN aptamer reduced Nppb, Nppa, Opn, Fn1, Col3a1, and Lum transcripts (n=3-6 - p<.05). At 12 wk, FN1 protein was reduced in the LVs and RVs by the OPN Apt (n=3 p<.05) and serum HDL was increased (20% p=.001; n=5-7). In 6 mo APOE-/- mice, systemic injections of OPN aptamer also increased plasma HDL (13%; p=.02; n=8-10).To assess effect of OPN aptamer on reversal of cardiac remodeling, at 8 wks post TAC (n=3-4), cardiac function was assessed followed by a total of 7 OPN aptamer injections (one every other day), and then assessed again at 10 wks. The OPN aptamer improved %EF in TAC mice (.6 fold p=.02 TAC vs Sham before treatment to .85 fold p=NS after treatment). In wild type but not OPN KO neonatal mouse cardiomyocytes-fibroblast co-culture, 16h treatment with FAM-labeled OPN aptamer, followed by Phalloidin and TNT staining, showed successful intracellular uptake of the OPN aptamer by cardiac myocytes and more so by fibroblasts. Conclusion: OPN RNA aptamer protected against and reversed cardiac dysfunction in a mouse TAC model of cardiac hypertrophy, and increased serum HDL in WT and APOE-/- mice. The cardioprotective effect of the OPN aptamer, together with the efficient uptake by cardiac myocytes and fibroblasts make it a promising therapeutic molecule and a potential platform for targeted RNA delivery into the heart.