Progressive right ventricular functional and structural changes in a mouse model of pulmonary arterial hypertension.

Right ventricle (RV) dysfunction occurs with progression of pulmonary arterial hypertension (PAH) due to persistently elevated ventricular afterload. A critical knowledge gap is the molecular mechanisms that govern the transition from RV adaptation to RV maladaptation, which leads to failure. Here, we hypothesize that the recently established mouse model of PAH, via hypoxia and SU5416 treatment (HySu), captures that transition from adaptive to maladaptive RV remodeling including impairments in RV function and decreases in the efficiency of RV interactions with the pulmonary vasculature. To test this hypothesis, we exposed C57BL6 male mice to 0 (control), 14, 21, and 28 days of HySu and then obtained synchronized RV pressure and volume measurements in vivo. With increasing HySu exposure duration, arterial afterload increased monotonically, leading to a continuous increase in RV stroke work, RV fibrosis, and RV wall stiffening (P < 0.05). RV contractility increased at 14 days of HySu exposure and then plateaued (P < 0.05). As a result, ventricular-vascular coupling efficiency tended to increase at 14 days and then decrease. Our results suggest that RV remodeling may begin to shift from adaptive to maladaptive with increasing duration of HySu exposure, which would mimic changes in RV function with PAH progression found clinically. However, for the duration of HySu exposure used here, no drop in cardiac output was found. We conclude that the establishment of a mouse model for overt RV failure due to PAH remains an important task.