Considerations on the mechanisms of alveolar remodeling in centriacinar emphysema

Chronic obstructive pulmonary disease is mainly characterized by irreversible airflow limitation, and its major pathological change is alveolar destruction and enlargement, which induces emphysema. In this study, we used stereoscopic microscopy to observe the cut surfaces of 21 surgically resected or autopsied lungs showing centriacinar emphysema. We identified columnar structures of various sizes in the cystic spaces. These columnar structures constituted two types: one that was associated with pulmonary artery and another that was not. We examined these structures in detail by light microscopy and performed statistical analyses. Columnar structures without pulmonary artery showed destruction and accumulation of alveoli, including abnormally aggregated elastic fibers. In contrast, pulmonary architecture was preserved in columnar structures with pulmonary artery. In columnar structures without pulmonary artery, statistically significant correlations were observed between the thickness of columnar structures and size of centriacinar cystic spaces and between the thickness of columnar structures and aggregation of elastic fibers in columnar structures. Electron microscopy showed that the columns were composed of aggregated elastic fibers, collagen fibers, mesenchymal cells, pigmented macrophages, and the alveolar epithelial cells covering them. Immunohistochemistry showed that the aggregated elastic fibers were positive for alpha-1 antitrypsin. We concluded that columnar structures without pulmonary artery are a hallmark of alveolar wall destruction seen in pulmonary emphysema.