Angiopoietin-1 has been shown to ameliorate experimental BPD in a rodent model21, while angiopoietin-2 worsens hyperoxia-mediated lung injury in nitric oxide- synthase 2-deficient mice30, and increased angiopoietin-2 is associated with BPD in preterm infants31. Here, NOS2 is linked to bronchopulmonary dysplasia.