Abstract 14662: Targeted Delivery of an Anti-miR to Cardiomyocytes Using Ultrasound and Microbubbles Suppresses Hypertrophy

Abstract

Introduction: MicroRNAs (miRs) are dysregulated in various cardiovascular diseases and anti-miRs have been developed to therapeutically inhibit the activity of specific miRs. An anti-miR against miR-23a suppressed hypertension-induced cardiac hypertrophy in preclinical models, but clinical translation is limited by a lack of targeted cardiac delivery systems. Ultrasound (US) targeted microbubble (MB) destruction (UTMD) is a novel therapeutic delivery platform that utilizes MBs as nucleic acid carriers. We hypothesized that UTMD-mediated delivery of anti-miR-23a suppresses cardiomyocyte hypertrophy and assessed UTMD-mediated functional delivery of anti-miR-23a to cultured cardiomyocytes (CMs) in vitro to lay the groundwork for future in vivo translational studies. Methods: Neonatal CMs were isolated from hearts of 1 to 2 day old Sprague Dawley rats. MBs were loaded with LNA-modified negative control anti-miR (NC) or anti-miR-23a, added to CM cultures (anti-miR concentration 300 pM) and insonified with a clinical US imaging system (1.3 MHz, MI setting=1.6). CMs were exposed to 100 μM phenylephrine (PE) to induce hypertrophy. Levels of miR-23a and FOXO3a (miR-23a target) were assessed by qRT-PCR 48 hr after UTMD and normalized to that in NC treated CMs. To quantify hypertrophy, CM surface areas pre- and post-PE were measured by a blinded observer. Results: UTMD treatment with anti-miR-23a knocked down CM miR-23a levels by 51 ± 24% compared to UTMD treatment with NC (N=5-6 per group, p < 0.01). Expression of FOXO3a mRNA (miR-23a target) was 47 ± 16% higher following UTMD-mediated anti-miR-23a delivery compared to NC (N=3 per group, p < 0.05). The increase in CM surface area upon PE exposure was 22 ± 13% less with UTMD-mediated anti-miR-23a delivery compared to NC (N=3 per group, p < 0.05). Conclusions: To our knowledge, this is the first study of UTMD-mediated modulation of miR levels in cardiac tissue with an anti-miR. UTMD mediated delivery of anti-miR-23a to CMs caused knockdown of miR-23a levels, restored expression of downstream target mRNA levels, and suppression of CM hypertrophy. These results lay important groundwork for future in vivo studies leading to targeted clinical strategies to therapeutically modulate miRNA activity in the human heart.