EDN1 and bronchopulmonary dysplasia: Multiple serum and plasma biomarkers have already been proven as robust predictors for BPD/death or BPD-PH in preterm infants (e.g., n-terminal pro b-type natriuretic peptide [NTproBNP], endothelin-1 [ET-1], intercellular adhesion molecule 1 [ICAM-1], soluble fragment of cytokeratin 19 [Cyfra 21–1], and kallistin) [9–12].