Integrin β6-Deficient Mice Show Enhanced Keratinocyte Proliferation and Retarded Hair Follicle Regression after Depilation  Yanshuang Xie, Kevin J. McElwee, Gethin R. Owen, Lari Häkkinen, Hannu S. Larjava  Journal of Investigative Dermatology  Volume 132, Issue 3, Pages 547-555 (March 2012) DOI: 10.1038/jid.2011.381 Copyright © 2012 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 The abundance of αvβ6 integrin was strongly upregulated during hair regeneration in wild-type (WT) hair follicles (HFs), and its expression was hair cycle dependent. (a) Immunoreactivity for β6 integrin was constitutively present in the HFs in the day 0 nonwounded skin of the WT mice. (b) Expression of β6 was analyzed in WT mice in regenerating HFs at defined stages of the hair cycle by immunohistochemistry. Bar=100μm. (a, b) The high-magnification images of the boxed area are shown in a and b. Arrowheads indicate the β6 integrin–positive keratinocytes in the outer root sheath (ORS) of the HFs; arrows indicate nonspecific staining at the sebaceous glands (SGs). (c) Semiquantitative presentation of spatial and temporal expression pattern of αvβ6 during the hair cycle. Journal of Investigative Dermatology 2012 132, 547-555DOI: (10.1038/jid.2011.381) Copyright © 2012 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 β6−/− mice show significantly accelerated skin thickness increase during early anagen, and retarded hair regression during catagen development. (a) Frozen sections of wild-type (WT) and β6 integrin knockout (β6−/−) mouse back skin were stained with hematoxylin and eosin (H&E). D, dermis; E, epidermis. Bars=200μm. Quantification of the thickness of the (b) epidermis or (c) dermis (n=3; Student's t-test; *P<0.05; **P<0.01; error bars represent SD). (d) Catagen development was compared at day 18 post depilation (p.d.) by quantitative histomorphometry (n=5 mice per group; Student's t-test; *P<0.05; **P<0.01; ***P<0.001; error bars represent SD). In the x axis: Early cat, catagen II–III; Mid cat, catagen IV–V; Late cat, catagen VI–VIII. Journal of Investigative Dermatology 2012 132, 547-555DOI: (10.1038/jid.2011.381) Copyright © 2012 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 The β6 integrin knockout (β6−/−) mice contained significantly higher numbers of proliferating keratinocytes in interfollicular epidermis and hair follicles (HFs) than wild-type (WT) controls at an identical hair growth cycle stage. (a) Keratinocyte proliferation was assessed by immunohistochemistry of the proliferating cell marker Ki67 at different time points in WT and β6−/− mice. E, epithelium. Arrows indicate the Ki67-positive cell nuclei. Bar=200μm. Quantification of the Ki67-positive keratinocytes showed a significant increase in β6−/− (b) interfollicular epidermis (IFE) and (c) HFs compared with WT controls during early anagen development. Five representative high-power fields (HPFs, × 200 magnification) per time point per mouse were counted (n=3; Student's t-test; *P<0.05; **P<0.01; error bars represent SD). Journal of Investigative Dermatology 2012 132, 547-555DOI: (10.1038/jid.2011.381) Copyright © 2012 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 Deficiency of αvβ6 integrin leads to reduced transforming growth factor-β1 (TGF-β1) levels during hair regeneration. (a) The abundance and distribution of TGF-β1 was studied by immunofluorescence staining in wild-type (WT) and β6 integrin knockout (β6−/−) mouse skin before and after depilation. Shown is immunofluorescence of TGF-β1 antibody (green) and 4,6-diamidino-2-phenylindole (DAPI; blue). Arrowheads denote hair shaft autofluorescence. Bar=100μm. (b) TGF-β1 score showed significantly reduced levels of total TGF-β1 during the early anagen (day 3) and the anagen–catagen transition (day 18) in β6−/− mice (n=3; Student's t-test; **P<0.01; error bars represent SD). (c) The expression of TGF-β1 was analyzed by western blotting. (d) Quantification of the relative expression of TGF-β1 (n=3; Student's t- test; *P<0.05; **P<0.01; error bars represent SD). Journal of Investigative Dermatology 2012 132, 547-555DOI: (10.1038/jid.2011.381) Copyright © 2012 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 Transforming growth factor-β1 (TGF-β1) activation is reduced in β6 integrin knockout (β6−/−) mouse skin compared with wild-type (WT) mouse skin during hair regeneration. (a) Phosphorylated Smad2 (P-Smad2) was detected by immunohistochemistry in WT and β6−/− mouse skin before and after depilation. Arrows indicate the P-Smad2 positively stained cell nuclei. Bar=100μm. (b) Quantification of phospho-Smad2-positive keratinocytes. Five representative high-power fields (HPFs, × 200 magnification) per time point per mouse were counted (n=3; Student's t-test; *P<0.05; **P<0.01; error bars represent SD). (c) The expression of P-Smad2 and total Smad2 (T-Smad2) was analyzed by western blotting. Quantification of the relative expression of (d) P-Smad2 and (e) T-Smad2 (n=3; Student's t-test; *P<0.05; **P<0.01; error bars represent SD). Journal of Investigative Dermatology 2012 132, 547-555DOI: (10.1038/jid.2011.381) Copyright © 2012 The Society for Investigative Dermatology, Inc Terms and Conditions