Patterns of Cartilage Structural Protein Loss in Human Tracheal Stenosis

Objectives The study sought to identify which of the major structural proteins in tracheal cartilage are lost in the inflammatory process, and to determine whether damaged cartilage shows signs of regeneration and whether this is an age‐dependent phenomenon. Study Design Immunohistochemical analysis. Methods Archival human tracheal and subglottic stenosis segments removed for the treatment of airway compromise were investigated by means of immunohistochemical analysis for differential loss of collagen type I or type II or aggrecan. Results Specimens were found to have preferentially lost collagen I and aggrecan in areas of severe disruption of the cartilage ring. Collagen II was preserved. In addition, areas of apparent cartilage regeneration were identified based on increased collagen II and aggrecan relative to baseline levels in uninjured sections of the rings. Regenerative capacity was present in most of the specimens investigated and was not age specific. Conclusions Collagen I and aggrecan are lost in areas of severe ring compromise, indicating that at least one of these two molecules is responsible for structural integrity. The remaining cartilage has some regenerative capacity, but it is small relative to the degree of cartilage damage. No new collagen I was identified in the cartilage ring, indicating that, although an intense inflammatory reaction occurred, fibroblasts did not deposit new collagen I as seen in other scar tissues.