It has been further found that in the early stage of pulmonary edema of BPD, there is the destruction of the tight connection of the pulmonary vascular endothelium, and the abnormal expression of connexin Cx40 in the lung tissue, which may be related to the increase of the vascular permeability in the stage of pulmonary edema (8). The gene discussed is GJA5; the disease is pulmonary edema.