Right Ventricular Stiffening and Function Are Associated With Main Pulmonary Artery Remodeling in a Rat Model of Pulmonary Hypertension

This study investigated how pulmonary arterial stiffening contributes to right ventricular (RV) remodeling, mechanics, and dysfunction in a sugen-hypoxia rat model of pulmonary arterial hypertension (PAH). The main pulmonary artery (mPA) and RV free wall were examined for structure, composition, and passive mechanical properties using biaxial testing, histology, and biochemical assays. The results demonstrated marked increases in collagen deposition, glycosaminoglycan content, and collagen-to-elastin ratios in both mPA and RV tissues, leading to anisotropic stiffening—particularly in the longitudinal direction. The degree of mPA stiffening correlated strongly with RV wall stiffness, active tension, and reduced RV-PA coupling efficiency, suggesting that proximal artery compliance plays a central role in right heart failure progression.