Increased circulating alveolar epithelial microparticles in COPD patients

Background: Growing evidences suggested that endothelial injury in pulmonary capillary vasculatures is closely related to alveolar destruction in COPD. Microparticles (MPs) are membrane vesicles that are released by budding or shedding from the plasma membrane in response to injury. We reported that circulating endothelial MP levels significantly increase in COPD patients due to the presence of endothelial injury (Takahashi T,et al. Thorax 2012; 67:1067-74). We hypothesized that circulating alveolar epithelium-derived MPs (Alveolar Epithelial MPs) increased in COPD patients. Aims: To compare Alveolar Epithelial MP levels between stable COPD patients and healthy non-COPD volunteers. Methods: 46 stable COPD patients and 16 healthy volunteers matched with age and smoking history were enrolled. Blood samples were collected, and plasma was stained with antibodies and analyzed using FACS. Ep-CAM and E-cadherin are specific markers for epithelial cells. RAGE is highly expressed in alveolar type I cells. We defined Alveolar Epithelial MPs as follow; RAGE+/Ep-CAM+ MPs (Alveolar Ep-CAM MPs) and RAGE+/E-cadherin+ MPs (Alveolar E-cad MPs). Results: Both Alveolar Ep-CAM and E-cad MPs were significantly higher in the stable COPD patients than in the healthy volunteers (Alveolar Ep-CAM MPs: p= 0.001, Alveolar E-cad MPs: p Conclusions: Alveolar epithelial MPs are released into the circulation in COPD patients, indicating the presence of epithelial injury and disruption of the alveolar epithelial-endothelial barrier function.