LAUSR

Objective: Pulmonary arterial hypertension (PAH), is a chronic disorder characterized by excessive pulmonary vascular remodelling, resulting in elevated pulmonary vascular resistance and right ventricle (RV) overload and failure. PAH remains incurable, and new therapeutic approaches are required. The microRNA-146a (miR-146a) promotes vascular smooth muscle cell proliferation and vascular neointimal hyperplasia, both important hallmarks of PAH. This study aimed to investigate the role of miR-146a in the pathophysiology of PAH and in the progression to RV hypertrophy and failure. Design and method: Sprague Dawley rats received a subcutaneous injection of monocrotaline (MCT group) or vehicle (CTRL group) and, after fourteen days they were treated, by intratracheal nebulization, with an anti-miR-146a, forming four distinct groups: CTRL-treated; CTRL-untreated, MCT-treated, and MCT-untreated. Twenty-seven days after MCT injection, echocardiographic and invasive hemodynamic evaluations were performed in all animal groups. Also, wild-type (WT) and miR-146a knock-out (KO) (miR-146a-/-) mice were submitted to either 3 weeks of chronic hypoxia-induced PAH with weekly Sugen 5416 administration (SuHx). Results: Compared to MCT-untreated rats, the MCT-treated rats showed decreased RV hypertrophy, (as measured by the Fulton index), decreased RV end-diastolic diameter/left ventricle end-diastolic diameter (RVEDD/LVEDD) ratio, and decreased in RV diastolic pressures. KO-SuHx group, when compared to WT-SuHx group, showed decreased RV hypertrophy (as measured by the Fulton index), and decreased RV systolic pressures and dilation, as well as lower RV end end-diastolic diameter (RVEDDi) and right atria area (RAAi). Conclusions: Our findings show that miR-146a pharmacological or genetic inhibition reduces RV remodelling and improves cardiac function. Thus, miR-146a represents a promising therapeutic target in PAH.