Figure 2.

Current theory of change in endothelial cell phenotype in pulmonary artery hypertension and progression to irreversible disease. During the early stages of pulmonary artery hypertension, initial endothelial cell injury (shear stress, hypoxia, inflammation) leads to endothelial cell apoptosis (1), causing a reduction in pulmonary vessels. The remaining endothelial cells become hyperproliferative and resistant to apoptosis (2), leading to formation of plexiform lesions. In the terminal stages of pulmonary artery hypertension, endothelial cells become senescent (3), making the disease irreversible.