TGFB1 and pulmonary arterial hypertension: 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.