FOXO4 and pulmonary arterial hypertension: However, in a mouse model of hypoxia-induced PAH, in which pulmonary vascular endothelial cells are senescent, FOXO4-DRI paradoxically increases pulmonary hypertension, with the elimination of senescent endothelial cells (Born et al, 2023), which is potentially an example of the heterogeneous function of senescent cells in different contexts.