Abstract 2103: Prevention of Pulmonary Hypertension by ACE2 Gene Transfer to Lungs
Pulmonary hypertension (PH) is characterized by increase in pulmonary vascular resistance, and narrowing and loss of pulmonary microvasculare. There is an indispensable need to develop innovative approaches for its control since PH becomes refractory to current therapies in later stages. Recent discovery of angiotensin converting enzyme 2 (ACE2), its involvement in cardiac remodeling, coupled with the limited success of ACE inhibitors in PH has led us to hypothesize that shifting the balance of renin-angiotensin system (RAS) to vasoprotective ACE2-Ang1–7-mas receptor axis would result the beneficial outcome in PH. We tested this hypothesis with the use of ACE2 overexpression in lungs by lentiviral vector-mediated gene transfer. Lentiviral vector particle(3x10^8 TU) containing murine ACE2 (letni-ACE2) were injected into 6 weeks old C57BL/6 mice prior to induction of PH by administration of weekly 600 mg/kg of monocrotaline (MCT) for 8 weeks for prevention studies. In addition, lenti-ACE2 was delivered following 6 weeks MCT treatment in reversal studies. Right ventricle systolic pressure (RVSP), Real-time RT-PCR, immunohisitochemistory of ACE2 and Ang (1–7) and histology of lungs in control and lent-ACE2 treated mice were carried out to evaluated the outcome on PH. Delivery of lenti-ACE2 resulted in a long-term increase in ACE2 expression in the lungs. A 60% and 100 % increases in protein and mRNA levels for ACE2 were observed. ACE2 and Ang (1–7) immunoreactivity were observed in epithelial and alveolar cells and alveolar macrophages. MCT treatment increased in RVSP (MCT 44.5+/−5.7 mmHg, control 24+/−1.0mmHg), RV hypertrophy (RV/LV+Sp ratio; 0.31+/−0.01), and wall thickness of pulmonary vessels. ACE2 gene transfer prevented increases in RVSP (26.1+/− 1.1mmHg), and RV hypertrophy (0.26+/−0.1), and reduced vessel wall thickness. In addition, ACE2 overexpression resulted in a significant reversal of RVSP (23.5+/−0.6mmHg). Futhermore, ACE2 overexpression in mice exhibited better general appearance and gained weight compared to MCT-treated mice. ACE2 gene transfer to lungs prevents and reverses vascular remodeling and PH in MCT model of PH. These observations suggest that targeting of pulmonary ACE2 holds novel therapeutic potential for PH.