Use of prolyl hydroxylase domain (PHD) inhibitors to increase HIF protein levels improved lung growth in a preterm baboon model of BPD [42] Interestingly, Hif-1α activity is increased, when human umbilical vein endothelial cells are returned to normoxic conditions after being exposed to hyperoxia [43]. This evidence concerns the gene HIF1A and bronchopulmonary dysplasia.