Abstract 18691: Asporin Attenuates Pulmonary Arterial Smooth Muscle Cell Proliferation and Regulates Pulmonary Hypertension Development

Abstract

Introduction: Pulmonary arterial hypertension (PAH) is a devastating pulmonary vascular lung disease characterized by increased pressure in the pulmonary arteries (PA) leading to cardiac right ventricular (RV) hypertrophy, RV failure, and ultimately death. Current PAH therapies merely improve symptoms temporarily and patients often need lung and heart transplantation. There is dire need for new insights into PAH pathophysiology to find novel therapeutic approaches. A key mechanism driving PAH is medial hyperplasia resulting from enhanced pulmonary arterial smooth muscle cell (PASMC) proliferation. Methods: We employed an unbiased bioinformatics approach in online-available microarray expression and single-cell sequencing datasets of dissected PA from PAH patients. In vitro experiments were performed in PASMC isolated from a female donor and PAH patient. Human lung tissue sections were obtained from the Pulmonary Hypertension Breakthrough Initiative Biobank. The Sugen/Hypoxia model was used to induce PH in rats. Results: We discovered that a novel gene, small leucine-rich proteoglycan Asporin (Aspn), is highly and significantly upregulated in PAH compared to donor PA and is most highly expressed in PASMC. We validated higher Aspn mRNA expression in human lungs and PASMC from PAH patients compared to controls, supporting our bioinformatics approach. Moreover, Aspn protein expression is elevated in PASMC in lung tissue sections from PAH patients compared to donors, as well as in PAH patient plasma . Functionally, silencing Aspn in PASMC from PAH patients promoted proliferation, whereas recombinant Aspn exerted opposite effects. To find potential downstream mediators of Aspn, STRING database analysis revealed that Aspn binds to the pro-proliferative mediator TGFβ1. Accordingly, TGFβ1 downstream mediator p-SMAD2/3 is enhanced upon Aspn silencing in PASMC. Intratracheal delivery of Aspn siRNA in rats aggravated Sugen/Hypoxia-induced PH, as assessed by RVSP, echocardiography and vascular remodeling. Conclusions: We hypothesize that elevated Aspn expression in PAH is a compensatory mechanism that inhibits PASMC proliferation, leading to decreased PA vascular remodeling, and that Aspn may be a novel therapeutic target against PAH.