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 < 0.01). Some cathepsin K(+) cells in periodontal tissues were CD68(+) , but some were CD68(-) and probably fibroblasts. Indeed, in gingival fibroblast culture, resting fibroblasts released cathepsin K, more 43 kD procathepsin K than 29 kD active cathepsin K. TNF-α increased the release of the activated cathepsin K 4- to 5-fold. CONCLUSIONS: Results suggest that GCF-cathepsin K is not only osteoclast-derived, but in periodontitis, also other cells contribute to it. GCF-cathepsin K, perhaps together with intracellular, lysosomal collagenolytically active cathepsin K in fibroblasts, macrophages and gingival epithelial cells, can contribute to the loss of attachment and destruction of the periodontal ligament.