Abstract 9348: ROCK2 in Vascular Smooth Muscle Cells Plays a Crucial Role for Hypoxia-Induced Pulmonary Hypertension in Mice
Background: Pulmonary hypertension (PH) still remains a fatal disease characterized by progressive increase in pulmonary vascular resistance. We have previously demonstrated that the Rho-kinase (ROCK) pathway in vascular smooth muscle cells (VSMC) plays an important role in the pathogenesis of cardiovascular diseases by enhancing their migration and proliferation. Rho-kinase has 2 isoforms, ROCK1 and ROCK2, with different functions; ROCK1 for circulating inflammatory cells and ROCK2 for the vasculature. In this study, we thus examined whether ROCK2 in VSMC is involved in the pathogenesis of PH.
Methods and Results: We developed VSMC-specific ROCK2-deficient (ROCK2+/-) and VSMC-specific ROCK2-overexpressing (ROCK2-Tg) mice. Both genotypes showed normal growth under physiological conditions. Chronic hypoxia (10% O2 for 4 weeks) significantly increased ROCK2 expression and ROCK activity in lung tissues from littermates (P<0.05, n=4 each). The extent of the hypoxia-induced PH, as evaluated by the extent of pulmonary vascular remodeling, right ventricular (RV) systolic pressure and RV hypertrophy, was significantly reduced in ROCK2+/- mice and was significantly enhanced in ROCK2-Tg mice compared with the littermates (all P<0.05). Immunostaining showed that the number of CD45+ inflammatory cells in the lung was significantly reduced in the ROCK2+/- mice and was increased in the ROCK2-Tg mice compared with the littermates, suggesting the role of vascular ROCK2 in inflammatory cell recruitment. In addition, VSMC proliferation (Ki67+ cells) significantly correlated with the ROCK2 expression after chronic hypoxia, suggesting the role of ROCK2 in VSMC proliferation. In cultured mouse aortic VSMC, ROCK2 expression was decreased in ROCK2+/- VSMC (-21%) and was increased in ROCK2-Tg VSMC (+100%) compared with littermate VSMC. Hypoxia (1% O2 for 24 hours) significantly increased ROCK activity in littermate VSMC (P<0.05, n=5 each). Scratch assay showed that migration activity was significantly reduced in the ROCK2+/- VSMC and was increased in the ROCK2-Tg VSMC compared with littermate VSMC (P<0.01).
Conclusions: ROCK2 in VSMC plays a crucial role in the pathogenesis of hypoxia-induced PH through enhanced VSMC migration and proliferation.
- © 2011 by American Heart Association, Inc.