IL6 and bronchopulmonary dysplasia: However, a separate study comparing serum of patients diagnosed with the “old” vs. “new” BPD definition found increased levels of profibrotic/angiogenic factors [transforming growth factor-beta1 (TGFβ-1); PDGF BB fraction, PDGF-BB, and VEGF] and decreased levels of IL-6 in “new BPD” patients, but no differences in the “old BPD” patients (87).