title: Cathepsin B is essential for regeneration of scratch-wounded normal human epidermal keratinocytes.
abstract: Migration, proliferation and differentiation of keratinocytes are important processes during tissue regeneration and wound healing of the skin. Here, we focussed on proteases that contribute to extracellular matrix (ECM) remodeling as a prerequisite of keratinocyte migration. In particular, we assessed the significance of the mammalian cysteine peptidase cathepsin B for human keratinocytes during regeneration from scratch wounding. We describe the construction of a scratch apparatus that allows applying scratches of defined length, width and depth to cultured cells in a reproducible fashion. The rationale for our approach derived from our previous work where we have shown that HaCaT keratinocytes secrete cathepsin B into the extracellular space during spontaneous and induced migration. Here, we observed rapid removal of type IV collagen from underneath lamellipodial extensions of keratinocytes at the advancing fronts of regenerating monolayers, indicating that proteolytic ECM remodeling starts upon initiation of keratinocyte migration. Furthermore, we verified our previous results with HaCaT cells by using normal human epidermal keratinocytes (NHEK) and show that non-cell-permeant cathepsin B-specific inhibitors delayed full regeneration of the monolayers from scratch wounding in both cell systems, HaCaT and NHEK. Application of a single dose of cathepsin B inhibitor directly after scratch wounding of keratinocytes demonstrated that cathepsin B is essential during initial stages of wound healing, while its contribution to the subsequent processes of proliferation and differentiation of keratinocytes was of less significance. This notion was supported by our observation that the cathepsin B inhibitors used in this study did not affect proliferation rates of keratinocytes of regenerating cultures. Thus, we conclude that cathepsin B is indeed involved in ECM remodeling after its secretion from migrating keratinocytes. Cathepsin B might directly cleave ECM constituents or it may initiate proteolytic cascades that involve other proteases with the ability to degrade ECM components. Because cathepsin B is important for enabling migration of both, HaCaT cells and NHEK, our results support the notion that HaCaT keratinocytes represent an excellent cell culture model for analysis of human epidermal skin keratinocyte migration.
authors.affiliation: School of Engineering and Science, Jacobs University Bremen (formerly International University Bremen), Campus Ring 6, Research II-107, D-28759 Bremen, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Büth
authors.forename: Pier
authors.initials: P
authors.lastname: Luigi Buttigieg
authors.forename: Raluca
authors.initials: R
authors.lastname: Ostafe
authors.forename: Maren
authors.initials: M
authors.lastname: Rehders
authors.forename: Stefanie R
authors.initials: SR
authors.lastname: Dannenmann
authors.forename: Norbert
authors.initials: N
authors.lastname: Schaschke
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Stark
authors.forename: Petra
authors.initials: P
authors.lastname: Boukamp
authors.forename: Klaudia
authors.initials: K
authors.lastname: Brix
mesh_terms: D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004817:Epidermis / Q000187:drug effects / Q000201:enzymology / Q000473:pathology* / Q000502:physiology*; D005109:Extracellular Matrix / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012038:Regeneration / Q000187:drug effects; D015203:Reproducibility of Results
chemical_list: D004791:Enzyme Inhibitors; D002401:Cathepsin B