Immunohistochemical detection of bone morphogenetic protein-2 and transforming growth factor beta-1 in tracheopathia osteochondroplastica.

Tracheopathia osteochondroplastica (TO) is an unusual condition characterized by cartilaginous or bony submucosal nodules in the tracheobronchial tree. Bone morphogenetic protein-2 (BMP-2) and transforming growth factor beta-1 (TGF-beta 1) are potent inducers for new bone formation. We studied the precise localization of BMP-2 and TGF-beta 1 in two autopsied cases of TO, using immunohistochemical methods. Positive BMP-2 immunoreactivity was detected in numerous mesenchymal cells and chondroblasts lining the nodules in the tracheal submucosa. BMP-2 was not found in mature lamellar bony nodules. TGF-beta 1 was not seen in mesenchymal cells, though it did appear in chondrocytes and osteocytes in the nodules. These results suggest that BMP-2 plays an important role in nodule formation and acts synergistically with TGF-beta 1 to promote the nodules inductive cascade in the tracheal submucosa.