Abstract 12688: Augmenting Mitofusin-2 in Females With Pulmonary Arterial Hypertension Increases Mitochondrial Fusion, Reduces Smooth Muscle Cell Hyperproliferation and Regresses Experimental Disease
Introduction: Pulmonary arterial hypertension (PAH) is a lethal vascular disease primarily affecting females. Mitochondrial fragmentation, due to excessive fission contributes to and permits excessive proliferation of pulmonary artery smooth muscle cells (PASMC). We hypothesize that impaired mitochondrial fusion, due to decreased mitofusin-2 (MFN2), contributes to mitochondrial fragmentation and excessive proliferation in human and experimental PAH.
Methods: MFN2 expression was measured in human lungs and PASMCs (PAH versus control, n= 5 each, female/male 4/1) and in lungs of female rats with PAH induced by monocrotaline and chronic hypoxia+Sugen 5416 (CH+SU), (n=8-10/group). Mitochondrial-targeted photoactivated Green Fluorescent Protein and tetramethylrhodamine methyl ester were used to quantify mitochondrial fragmentation count (MFC). The effects on PASMC proliferation and apoptosis of adenoviral-MFN2 (Ad-MFN2) or empty vector (Ad-Empty) were measured using flow cytometry. Ad-MFN2 was administered in vivo to regress PAH in female CH+SU and monocrotaline rats.
Results: MFN2 was decreased and mitochondrial fragmentation increased in PAH PASMC (increased MFC). Si-MFN2 fragmented mitochondria and increased proliferation in normal PASMC. Conversely, Ad-MFN2 increased expression of MFN2 and other fusion mediators, including OPA1. Ad-MFN2 also increased expression of PGC-1α, the regulator of mitochondrial biogenesis, 65-fold. Ad-MFN2 decreased proliferation (24±0.5 vs 29±0.5 % Edu (+), p<0.05) and increased apoptosis (2.5±0.15 vs 1.5±0.03 % Annexin V (+), p<0.05) in PAH PASMC. In CH+SU rats, Ad-MFN2 improved treadmill-walking distance (381±35 vs 245±39m, p<0.05), decreased pulmonary vascular resistance (0.2±0.02 vs 0.4±0.14 mmHg/ml/min, p<0.05), decreased the proliferation/apoptosis ratio and reduced medial hypertrophy of small PAs (14.5±0.8 vs 19.0±1.7% medial thickness, p<0.05). Similar findings were noted in female monocrotaline-rats.
Conclusion: MFN2 is downregulated in human and experimental PAH. The resulting mitochondrial fragmentation and PASMC hyperproliferation contributes to PAH. Augmenting MFN2 regresses experimental PAH in females.
- © 2012 by American Heart Association, Inc.