BIX-01294 treatment blocks cell proliferation, migration and contractility in ovine foetal pulmonary arterial smooth muscle cells

Objective: Recent studies have indicated a role of epigenetic phenomena in pathogenesis of pulmonary hypertension, but in foetal pulmonary artery smooth muscle cell (PASMC) proliferation this is still largely unknown. G9a is a key enzyme for histone H3 dimethylation at position lysine-9. In this study, we have investigated the function of G9a in ovine foetal PASMC proliferation, migration and contractility. Material and methods: Cell proliferation was measured by cell counting and BrdU incorporation assay and cell cycle analysis was performed by flow cytometry. Expression of cell cycle-related genes was determined by real-time PCR and the wound-healing scratch assay was used to measure cell migration. A gel contraction assay was used to determine contractility of foetal PASMCs. Global DNA methylation was measured by liquid chromatography-mass spectroscopy. Results: Inhibition of G9a by its inhibitor BIX-01294 reduced proliferation of foetal PASMCs and induced cell cycle arrest in G ₁ phase. This was accompanied by increased p21 expression, but not p53 and other cell cycle-related genes. Treatment of foetal PASMCs with BIX-01294 inhibited platelet-derived growth factor-induced cell proliferation and migration. Contractility of foetal PASMCs was also markedly inhibited by BIX-01294. Expression of calponin and ROCK-II proteins was reduced by BIX-01294 in a dose-dependent manner and BIX-01294 significantly increased global methylation level in the foetal PASMCs. Conclusion: Our results demonstrate for the first time that histone lysine methylation is involved in cell proliferation, migration, contractility and global DNA methylation in foetal PASMCs. Further understanding of this mechanism may provide insight into proliferative vascular disease in the lungs.