BMPR2 gene delivery reduces mutation-related PAH and counteracts TGF-β-mediated pulmonary cell signalling.

BACKGROUND AND OBJECTIVE: Idiopathic, familial and secondary pulmonary arterial hypertension (PAH) are associated with reduced bone morphogenetic protein receptor type 2 (BMPR2) expression, and in some contexts, TGF-β upregulation. Our aims were to assess BMPR2 gene therapy in a PAH mouse model and to assess the impact on TGF-β signalling.

METHODS: Using a targeted in vivo gene delivery approach, we assessed the impact of BMPR2 gene delivery in a transgenic mouse model in which PAH was first induced by doxycycline driven expression of a dominant negative BMPR2 mutant (R899X). We also assessed the impact of BMPR2 gene delivery on TGF-β-induced changes in cell signalling in human pulmonary vascular endothelial and smooth muscle cells.

RESULTS: In the mouse model, changes in TGF-β levels were not detected, but BMPR2 gene delivery reversed the increase in right ventricle systolic pressure (RVSP) and Fulton Index (FI), associated with a trend to increased pulmonary endothelial nitric oxide synthase (eNOS) gene expression. In vitro, BMPR2 gene transfer reduced TGF-β effects on Smad2, Smad1/5/8 and Erk1/2 phosphorylation in human pulmonary arterial smooth muscle cells (HPASMC). BMPR2 was also found to upregulate nitric oxide (NO) production in lung derived human microvascular endothelial cells (HMVEC-L).

CONCLUSION: This study provides further evidence that BMPR2 modulation may have therapeutic potential. See Editorial, page 406.