Dominant negative mutation of the TGF-β receptor blocks hypoxia-induced pulmonary vascular remodeling

The present study utilized a novel transgenic mouse model that expresses an inducible dominant negative mutation of the transforming growth factor (TGF)-beta type II receptor (DnTGF beta RII mouse) to test the hypothesis that TGF-beta signaling plays an important role in the pathogenesis of chronic hypoxia-induced increases in pulmonary arterial pressure and vascular and alveolar remodeling. Nine- to 10-wk-old male DnTGF beta RII and control nontransgenic (NTG) mice were exposed to normobaric hypoxia (10% O-2) or air for 6 wk. Expression of DnTGF beta RII was induced by drinking 25 mM ZnSO4 water beginning 1 wk before hypoxic exposure. Hypoxia-induced increases in right ventricular pressure, right ventricular mass, pulmonary arterial remodeling, and muscularization were greatly attenuated in DnTGF beta RII mice compared with NTG controls. Furthermore, the stimulatory effects of hypoxic exposure on pulmonary arterial and alveolar collagen content, appearance of alpha-smooth muscle actin-positive cells in alveolar parenchyma, and expression of extracellular matrix molecule ( including collagen I and III, periostin, and osteopontin) mRNA in whole lung were abrogated in DnTGF beta RII mice compared with NTG controls. Hypoxic exposure had no effect on systemic arterial pressure or heart rate in either strain. These data support the hypothesis that endogenous TGF-beta plays an important role in pulmonary vascular adaptation to chronic hypoxia and that disruption of TGF-beta signaling attenuates hypoxia-induced pulmonary hypertension, right ventricular hypertrophy, pulmonary arterial hypertrophy and muscularization, alveolar remodeling, and expression of extracellular matrix mRNA in whole lung.