TWIST1 Drives Smooth Muscle Cell Proliferation in Pulmonary Hypertension via Loss of GATA-6 and BMPR2.

Abstract

<b>Rationale:</b> The bHLH (basic helix-loop-helix) transcription factor TWIST1 (Twist-related protein 1) controls cell proliferation and differentiation in tissue development and disease processes. Recently, endothelial TWIST1 has been linked to pulmonary hypertension (PH) and endothelial-to-mesenchymal transition, yet the role of TWIST1 in smooth muscle cells (SMCs) remains so far unclear.<b>Objectives:</b> To define the role of TWIST1 in SMCs in the pathogenesis of PH.<b>Methods:</b> SMC-specific TWIST1-deficient mice, SMC-specific TWIST1 silencing in rats, mass spectrometry, immunoprecipitation, and chromatin immunoprecipitation were used to delineate the role of SMC TWIST1 in PH.<b>Measurements and Main Results:</b> In pulmonary vessels from patients with PH and rodent PH models, TWIST1 expression was markedly increased and predominantly localized to SMCs. SMC-specific TWIST1 deficiency or silencing attenuated the development of PH and distal vessel muscularization in chronically hypoxic mice and in monocrotaline-treated rats. <i>In vitro</i>, TWIST1 inhibition or silencing prevented pulmonary artery SMC proliferation and migration. Mechanistically, the observed effects were mediated, at least in part, by TWIST1-dependent degradation of GATA-6 (GATA-binding protein 6). BMPR2 (bone morphogenetic protein receptor-2) was identified as a novel downstream target of GATA-6, which directly binds to its promoter. Inhibition of TWIST1 promoted the recruitment of GATA-6 to the <i>BMPR2</i> promoter and restored BMPR2 functional expression.<b>Conclusions:</b> Our findings identify a key role for SMC TWIST1 in the pathogenesis of lung vascular remodeling and in PH that is partially mediated via reduced GATA-6-dependent <i>BMPR2</i> expression. Inhibition of SMC TWIST1 may constitute a new therapeutic strategy for the treatment of PH.