CXCR4 and bronchopulmonary dysplasia: To assess whether increased SDF-1/CXCL12 was accompanied by the fibrocytes trafficing during BPD, we measured the concentration of SDF-1/CXCL12, the ligand of CXCR4 in plasma and bronchoalveolar lavage from patients with BPD, ARDS and normal subjects.