However, increased Nox4 expression or activity has been observed during hypoxia or TGFβ1‐induced angiogenesis as well as a number of pathological conditions including haemangioma (endothelial tumour cells) formation 47, retinal neovascularization 48, 49, cardiac failure 50, fibrosis 51, pulmonary hypertension 52 and stroke 53. Here, NOX4 is linked to pulmonary arterial hypertension.