KDR and pulmonary emphysema: In our study, the elevated lever of VEGF and VEGFR1, VEGFR2 presented ongoing evidence of increased angiogenic activity and proved that VEGF activity related angiogenesis and microvascular remodelling in the airways are the parts of structural airway remodelling in the COPD model, which is similar to the clinical research about asthma and emphysema patients27, 28.