Based on the results that IGF-1 deficiency can alter lung and vascular development, we hypothesized that IGF-1 treatment would increase PPHN PAEC proliferation, tube formation and increase the production of two downstream proteins associated with angiogenesis, vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS). Here, IGF1 is linked to persistent fetal circulation syndrome.