Inhibition of miR-15 Protects Against Cardiac Ischemic Injury

RATIONALE:Myocardial infarction (MI) is a leading cause of death worldwide. Because endogenous cardiac repair mechanisms are not sufficient for meaningful tissue regeneration, MI results in loss of cardiac tissue and detrimental remodeling events. MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression in a sequence dependent manner. Our previous data indicate that miRNAs are dysregulated in response to ischemic injury of the heart and actively contribute to cardiac remodeling after MI. OBJECTIVE:This study was designed to determine whether miRNAs are dysregulated on ischemic damage in porcine cardiac tissues and whether locked nucleic acid (LNA)-modified anti-miR chemistries can target cardiac expressed miRNAs to therapeutically inhibit miR-15 on ischemic injury. METHODS AND RESULTS:Our data indicate that the miR-15 family, which includes 6 closely related miRNAs, is regulated in the infarcted region of the heart in response to ischemia-reperfusion injury in mice and pigs. LNA-modified chemistries can effectively silence miR-15 family members in vitro and render cardiomyocytes resistant to hypoxia-induced cardiomyocyte cell death. Correspondingly, systemic delivery of miR-15 anti-miRs dose-dependently represses miR-15 in cardiac tissue of both mice and pigs, whereas therapeutic targeting of miR-15 in mice reduces infarct size and cardiac remodeling and enhances cardiac function in response to MI. CONCLUSIONS:Oligonucleotide-based therapies using LNA-modified chemistries for modulating cardiac miRNAs in the setting of heart disease are efficacious and validate miR-15 as a potential therapeutic target for the manipulation of cardiac remodeling and function in the setting of ischemic injury

Plasma microRNAs serve as biomarkers of therapeutic efficacy and disease progression in hypertension-induced heart failure

AIMS: Recent studies have shown that microRNAs (miRNAs), besides being potent regulators of gene expression, can additionally serve as circulating biomarkers of disease. The aim of this study is to determine if plasma miRNAs can be used as indicators of disease progression or therapeutic efficacy in hypertension-induced heart disease. METHODS AND RESULTS: In order to define circulating miRNAs that change during hypertension-induced heart failure and that respond to therapeutic treatment, we performed miRNA arrays on plasma RNA from hypertensive rats that show signs of heart failure. Array analysis indicated that approximately one-third of the miRNAs on the array are detectable in plasma. Quantitative real-time polymerase chain reaction (PCR) analysis for a selected panel of miRNAs indicated that circulating levels of miR-16, miR-20b, miR-93, miR-106b, miR-223, and miR-423-5p were significantly increased in response to hypertension-induced heart failure, while this effect was blunted in response to treatment with antimiR-208a as well as an ACE inhibitor. Moreover, treatment with antimiR-208a resulted in a dramatic increase in one miRNA, miR-19b. A time course study indicated that several of these miRNA changes track with disease progression. CONCLUSIONS: Circulating levels of miRNAs are responsive to therapeutic interventions and change during the progression of hypertension-induced heart disease

The Efficacy of Cardiac Anti-miR-208a Therapy Is Stress Dependent

MicroRNAs (miRNAs) are important regulators of biology and disease. Recent animal efficacy studies validate the therapeutic benefit of miRNA modulation and underscore the therapeutic value of miRNA-targeting oligonucleotides. However, whether disease conditions (stress) influence the pharmacological effects of an anti-miR is currently unknown. To study the effect of disease on target regulation after anti-miR treatment, we injected animals with anti-miR-208a, a synthetic oligonucleotide that inhibits the cardiomyocyte-specific miR-208a. Our data indicate that the presence of stress increases the number of regulated miR-208a targets, and that higher stress levels correlate with stronger target derepression. Additionally, the type of stress also influences which targets are regulated upon miR-208a inhibition. Studies in a large animal model indicate a similar stress-dependent anti-miR effect. Subsequent in vitro studies suggest that the influence of stress on anti-miR efficacy depends at least in part on increased cellular anti-miR uptake. These data indicate that the pharmacological effect of anti-miRs is stronger under disease conditions, and that both the type and severity of disease determine the therapeutic outcome. These facts will be important for assessing the therapeutic dose and predicting the therapeutic outcome when applying anti-miRs in a clinical setting

Inhibition of miR-15 Protects Against Cardiac Ischemic Injury

RATIONALE: Myocardial infarction (MI) is a leading cause of death worldwide. Because endogenous cardiac repair mechanisms are not sufficient for meaningful tissue regeneration, MI results in loss of cardiac tissue and detrimental remodeling events. MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression in a sequence dependent manner. Our previous data indicate that miRNAs are dysregulated in response to ischemic injury of the heart and actively contribute to cardiac remodeling after MI. OBJECTIVE: This study was designed to determine whether miRNAs are dysregulated on ischemic damage in porcine cardiac tissues and whether locked nucleic acid (LNA)-modified anti-miR chemistries can target cardiac expressed miRNAs to therapeutically inhibit miR-15 on ischemic injury. METHODS AND RESULTS: Our data indicate that the miR-15 family, which includes 6 closely related miRNAs, is regulated in the infarcted region of the heart in response to ischemia-reperfusion injury in mice and pigs. LNA-modified chemistries can effectively silence miR-15 family members in vitro and render cardiomyocytes resistant to hypoxia-induced cardiomyocyte cell death. Correspondingly, systemic delivery of miR-15 anti-miRs dose-dependently represses miR-15 in cardiac tissue of both mice and pigs, whereas therapeutic targeting of miR-15 in mice reduces infarct size and cardiac remodeling and enhances cardiac function in response to MI. CONCLUSIONS: Oligonucleotide-based therapies using LNA-modified chemistries for modulating cardiac miRNAs in the setting of heart disease are efficacious and validate miR-15 as a potential therapeutic target for the manipulation of cardiac remodeling and function in the setting of ischemic injury