[Endothelial metaplasia of the alveolar capillaries in experimental silicosis of rats].
We studied, by immunohistochemical and ultrastructural observations, the basic mechanism of interstitial fibrosis and endothelial metaplasia of alveolar capillaries in the lungs of Sprague-Dawley rats that received a single intratracheal infusion of silica particles. Immediately after silica administration, alveolar capillaries collapsed and their endothelial cells became necrotic over wide ranges. Alveolar myofibroblasts migrated into luminal silicaladen granulomas through defects in the alveolar linings. They proliferated and produced collagenous matrices that were incorporated into adjacent walls by coverage of regenerating epithelial cells. By day 4, endothelial cells of peribronchiolar small vessels had become positive for proliferating cell nuclear antigen. These endothelial cells apparently migrated along alveolar capillary tubes to replace injured endothelial cells through the processes of interdigitation of their cytoplasms. After one month, these alveolar endothelial cells, which were originally negative for factor VIII-related antigen (F-VIII) had become positive, especially in those segments in fibrotic scars. These endothelial cells developed numerous Weibel-Palade bodies containing F-VIII. Some endothelial cells formed specific ultrastructural fenestrations, which are unique to capillary endothelial cells that originated from bronchial arteries. The mechanism of endothelial metaplasia might consist of the following processes in endothelial cells that originated from broncho-pulmonary anastomoses: proliferation, migration, replacement, and differentiation of endothelial cells of bronchial arteries in the chronic fibrotic stages.
Mochimaru
H
H
Pathology and Clinical Research Laboratory, Nippon Medical School Second Hospital, Kanagawa-ken, Japan.
Kawanami
O
O
Kudoh
S
S
Niitani
H
H
D000818:Animals; D002196:Capillaries / Q000473:pathology; D004730:Endothelium, Vascular / Q000473:pathology*; D008297:Male; D008679:Metaplasia; D011650:Pulmonary Alveoli / Q000098:blood supply*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012829:Silicosis / Q000473:pathology*