title: Attenuated kallikrein-related peptidase activity disrupts desquamation and leads to stratum corneum thickening in human skin equivalent models.
abstract: BACKGROUND
  Epidermal homeostasis is maintained through the balance between keratinocyte proliferation, differentiation and desquamation; however, human skin equivalent (HSE) models are known to differentiate excessively. In native tissue, proteases such as kallikrein-related peptidase (KLK) 5 and KLK7 cleave the extracellular components of corneodesmosomes; proteins corneodesmosin, desmocollin 1 and desmoglein 1, loosening the cellular connections and enabling desquamation. The actions of KLK7 are tightly controlled by protease inhibitors, skin-derived antileucoproteinase (SKALP) and lymphoepithelial Kazal-type-related inhibitor (LEKTI), which also inhibits KLK5, localizing protease activity to the stratum corneum.
  
  
  OBJECTIVE
  To investigate the mechanisms that inhibit the desquamation cascade in HSE models.
  
  
  METHODS
  Human skin tissue and HSE models were investigated using gene microarray, real-time polymerase chain reaction (PCR), immunohistochemistry and Western blot analysis to examine key components of the desquamation pathway. To elucidate proteolytic activity in HSEs and native skin, in situ and gel zymography was performed.
  
  
  RESULTS
  Histological analysis indicated that HSE models form a well-organized epidermis, yet develop an excessively thick and compact stratum corneum. Gene microarray analysis revealed that the desquamation cascade was dysregulated in HSE models and this was confirmed using real-time PCR and immunohistochemistry. Immunohistochemistry and Western blot indicated overexpression of LEKTI and SKALP in HSEs. Although KLK7 was also highly expressed in HSEs, zymography indicated that protease activation and activity was lower than in native skin.
  
  
  CONCLUSIONS
  These findings demonstrate that stratum corneum thickening is due to inhibited KLK5 and KLK7 activation and a subsequent lack of corneodesmosome degradation in the HSE model epidermis.
authors.affiliation: Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.|School of Biomedical Sciences, Faculty of Health, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: J A
authors.initials: JA
authors.lastname: McGovern
authors.affiliation: Cartilage Regeneration Laboratory, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Meinert
authors.affiliation: Molecular Simulation Group, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: S J
authors.initials: SJ
authors.lastname: de Veer
authors.affiliation: Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: B G
authors.initials: BG
authors.lastname: Hollier
authors.affiliation: Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.|School of Biomedical Sciences, Faculty of Health, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: T J
authors.initials: TJ
authors.lastname: Parker
authors.affiliation: Tissue Repair and Regeneration Program, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.|School of Biomedical Sciences, Faculty of Health, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.|Institute of Medical Biology, Agency for Science, Technology and Research (A*STAR), Biomedical Grove, Singapore.
authors.forename: Z
authors.initials: Z
authors.lastname: Upton
mesh_terms: D000328:Adult; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation / Q000502:physiology; D002478:Cells, Cultured; D003896:Desmosomes / Q000235:genetics; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism / Q000473:pathology*; D015870:Gene Expression; D015894:Genome, Human / Q000235:genetics; D006801:Humans; D007610:Kallikreins / Q000378:metabolism*; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D019394:Ki-67 Antigen / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D046228:Microarray Analysis / Q000379:methods; D008954:Models, Biological; D011506:Proteins / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D019394:Ki-67 Antigen; D008565:Membrane Proteins; D011506:Proteins; C064554:loricrin; C497170:KLK12 protein, human; C082472:KLK7 protein, human; D007610:Kallikreins