Abstract 17226: Role of BMPR2 Mutation in the Development of RV Failure in Rat Experimental Pulmonary Hypertension

Abstract

Introduction: BMPR2 mutations are the major genetic risk factor for pulmonary arterial hypertension (PAH) and are associated with increased disease severity and worse survival. Although worsening disease severity and prognosis in BMPR2 mutation carriers has been explained by more severe pulmonary vascular disease (PVD), recent reports suggest that BMPR2 mutations affect right ventricular (RV) myocardium and its function independently of PAH. However, mechanism of dysfunctional RV in BMPR2 mutations carriers are unknown.[Hypothesis]Rats with Bmpr2 mutation have impaired RV function independently of PVD compared to wild-type (WT) rats. Methods: Bmpr2 mutant rats were generated by CRISPR/Cas9 genome editing. Monocrotaline (MCT)-PH model was generated in mutant rats and WT littermates and changes in RV function over time with disease progression were assessed by echocardiography and catheterization in rats with (n=23) or without tadalafil treatment (n=88) Results: In untreated setting, there were no significant differences in RV systolic pressure (RVSP) and RV function between the two groups on 21 days after MCT, whereas RV-fractional area change (FAC) and cardiac index (CI), assessed at later disease stage (23 to 25 days), were significantly lower in Bmpr2 mutant rats than in WT (RV-FAC: WT 41.0±8.3 vs Bmpr2 mutant 27.5±11.5%, p<.0001; CI: 413.2±114.0 vs 263.0±92.9ml/min/kg, p<.0001) at comparable RVSP (64.5±11.6 vs 66.7±8.0mmHg) but higher total pulmonary resistance index (TPRI: 0.16±0.06 vs 0.27±0.09mmHg/ml/min/kg, p<.0001). In rats with tadalafil treatment, Bmpr2 mutant rats had significantly lower RV-FAC (34.4±8.2 vs 23.6±5.4%, p<.05) and more severe RV myocardial fibrosis compared to WT littermates despite no significant differences in RVSP (75.4±8.7 vs 71.0±8.2mmHg) and TPRI (0.19±0.06 vs 0.22±0.08mmHg/ml/min/kg) on 30 days after MCT. Conclusion: In untreated setting, RV dysfunction in Bmpr2 mutant was associated with increased afterload due to exacerbation of vascular lesions; rats treated with PDE5i and with prolonged survival had reduced RV function at comparable afterload, indicating the importance of managing RV function under treatment of PAH.