EDN1 and pulmonary hypertension, primary, 1: Indeed, ectopic expression of placenta growth factor in normal mice, using a lentiviral vector or an adenoviral vector to generate similar placenta growth factor levels seen in sickle mice, resulted in increased ET-1 and plasminogen activator inhibitor-1 (PAI-1) production and development of PHT, similar to PHT seen in sickle mice [535, 536].