In the present study, we tested the hypothesis that decreased cord Klotho levels in preterm infants is associated with increased BPD–PH risk and that early Klotho supplementation decreases oxidative stress, suppresses fibrosis, improves lung vascular development and prevents BPD-like phenotype and PH in rodents exposed to neonatal hyperoxia. The gene discussed is KL; the disease is bronchopulmonary dysplasia.