Expression of cathepsin K in periodontitis and in gingival fibroblasts

Objective To study non‐osteoclastic sources of cathepsin K in periodontitis. Materials and Methods Tissue samples were obtained from 10 otherwise healthy periodontitis pati‐ents during routine periodontal flap operations and 10 systemically and periodontally healthy individuals who underwent extraction operations for retained third molars. Methods used were immunohistochemistry, image analysis, immunofluorescence double‐staining, gingival fibroblast culture, tumour necrosis factor‐α (TNF‐α) stimulation and Western blotting. Results Macrophage‐like cells, fibroblast‐like cells, vascular endothelial cells and gingival epithelial cells were more intensively stained for cathepsin K and also more frequent in periodontitis than in controls (665 ± 104 vs 258 ± 40 cells mm−2, P