Tenascin is expressed in post-transplant obliterative bronchiolitis

Tenascin is expressed in inflammatory and fibroproliferative processes, both contributing to posttransplant obliterative bronchiolitis (OB) in association with epithelial cell injury and airway obliteration. We studied bronchial allografts to elucidate the role of tenascin during this alloimmune response. Bronchial segments were subcutaneously implanted into eight pigs. Allografts and autograft controls were serially obtained until total obliteration in allografts and processed for histology and immunocytochemistry for CD4, CD8, and tenascin. Findings were graded on a scale from 0 to 3. In autografts the operative epithelial damage recovered and bronchi stayed patent with mild-graded fibrosis and inflammation. Partial recovery was observed in allografts on day 4, thereafter the epithelial loss gradually increased. Total recovery was achieved on day 11 (P < .001). Fibroblast proliferation resulted in total luminal obliteration on day 21 (P < .001). The number of inflammatory cells increased rapidly (P < .05) with numerous CD4+ and CD8+ cells on day 14 (P < .0001). Prior to total epithelial loss in allografts, tenascin expression was observed on day 7 in 69% of epithelial cells, whereas in only 5% of epithelial cells in recovered autografts. Paralleling the most intense fibroproliferation, tenascin-positive cells were observed in the bronchial wall on day 7 and day 11 (P < .001). Tenascin expression was demonstrated during the inflammatory response and fibroblast proliferation during the early stage of obliterative bronchiolitis showing that tenascin contributes to posttransplant obliterative bronchiolitis development.