title: Cathepsin K expression is increased in oral lichen planus.
abstract: BACKGROUND
  Oral lichen planus (OLP) is an idiopathic T-cell-mediated mucosal inflammatory disease. Cathepsin K (Cat K) is one of the lysosomal cysteine proteases. It is involved in many pathological conditions, including osteoporosis and cancer. The expression and role of Cat K in OLP are unknown.
  
  
  METHODS
  Twenty-five oral mucosal specimens diagnosed histopathologically as OLP and fourteen healthy controls (HC) were used to study the immunohistochemical (IHC) expression of Cat K. Colocalization of Cat K with CD1a, Melan-A, CD68, CD45, mast cell tryptase (MCT), and Toll-like receptors (TLRs) 4 and 9 were studied using double IHC and/or immunofluorescence (IF) staining. Expression of Cat K was also evaluated in OLP tissue samples before and after topical tacrolimus treatment.
  
  
  RESULTS
  Cat K was expressed in a higher percentage of cells in the epithelial zone, and the staining intensity was stronger in the stroma in OLP compared to controls (P < 0.001). In OLP, Cat K was present mostly in melanocytes and macrophages and sporadically in basal keratinocytes, endothelial cells, and extracellularly. Cat K was found also in some fibroblasts in HC and OLP samples. Coexpression of Cat K and TLRs 4 and 9 was seen in some dendritic cells (presumably melanocytes) and macrophages. In OLP, tacrolimus treatment reduced the expression of Cat K in the epithelium but increased it in the stroma.
  
  
  CONCLUSIONS
  These results suggest that Cat K is involved in the pathogenesis of OLP. Cat K possibly takes part in the modulation of matrix molecules and cellular receptors.
authors.affiliation: Cancer and Translational Medicine Research Unit, University of Oulu, Oulu, Finland. maria.siponen@oulu.fi, mariasiponen@yahoo.com.|Department of Oral and Maxillofacial Diseases, Kuopio University Hospital, Kuopio, Finland. maria.siponen@oulu.fi, mariasiponen@yahoo.com.
authors.forename: Maria
authors.initials: M
authors.lastname: Siponen
authors.affiliation: Cancer and Translational Medicine Research Unit, University of Oulu, Oulu, Finland.
authors.forename: Carolina Cavalcante
authors.initials: CC
authors.lastname: Bitu
authors.affiliation: Department of Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Al-Samadi
authors.affiliation: Medical Informatics and Statistics Research Group, University of Oulu, Oulu, Finland.
authors.forename: Pentti
authors.initials: P
authors.lastname: Nieminen
authors.affiliation: Cancer and Translational Medicine Research Unit, University of Oulu, Oulu, Finland.|Department of Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland.|Medical Research Center, Oulu University Hospital, Oulu, Finland.|HUSLAB, Department of Pathology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland.
authors.forename: Tuula
authors.initials: T
authors.lastname: Salo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000378:metabolism; D018949:Antigens, CD1 / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D016022:Case-Control Studies; D056657:Cathepsin K / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017493:Leukocyte Common Antigens / Q000378:metabolism; D017676:Lichen Planus, Oral / Q000188:drug therapy / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D058965:MART-1 Antigen / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D016559:Tacrolimus / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000378:metabolism; D053802:Tryptases / Q000378:metabolism; D055815:Young Adult; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D018949:Antigens, CD1; D015214:Antigens, Differentiation, Myelomonocytic; D056657:Cathepsin K; D017493:Leukocyte Common Antigens; D058965:MART-1 Antigen; D016559:Tacrolimus; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D053802:Tryptases; C419393:CD1a antigen; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C495345:TLR4 protein, human; C495371:TLR9 protein, human; C516769:PTPRC protein, human
keywords: cathepsin K; oral lichen planus; tacrolimus