Collagen VII plays a dual role in wound healing
Alexander Nyström, … , Johannes S. Kern, Leena Bruckner-Tuderman
Alexander Nyström, … , Johannes S. Kern, Leena Bruckner-Tuderman
Published July 8, 2013
Citation Information: J Clin Invest. 2013;123(8):3498-3509. https://doi.org/10.1172/JCI68127.
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Research Article Dermatology

Collagen VII plays a dual role in wound healing

Abstract

Although a host of intracellular signals is known to contribute to wound healing, the role of the cell microenvironment in tissue repair remains elusive. Here we employed 2 different mouse models of genetic skin fragility to assess the role of the basement membrane protein collagen VII (COL7A1) in wound healing. COL7A1 secures the attachment of the epidermis to the dermis, and its mutations cause a human skin fragility disorder coined recessive dystrophic epidermolysis bullosa (RDEB) that is associated with a constant wound burden. We show that COL7A1 is instrumental for skin wound closure by 2 interconnected mechanisms. First, COL7A1 was required for re-epithelialization through organization of laminin-332 at the dermal-epidermal junction. Its loss perturbs laminin-332 organization during wound healing, which in turn abrogates strictly polarized expression of integrin α6β4 in basal keratinocytes and negatively impacts the laminin-332/integrin α6β4 signaling axis guiding keratinocyte migration. Second, COL7A1 supported dermal fibroblast migration and regulates their cytokine production in the granulation tissue. These findings, which were validated in human wounds, identify COL7A1 as a critical player in physiological wound healing in humans and mice and may facilitate development of therapeutic strategies not only for RDEB, but also for other chronic wounds.

Authors

Alexander Nyström, Daniela Velati, Venugopal R. Mittapalli, Anja Fritsch, Johannes S. Kern, Leena Bruckner-Tuderman

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Figure 7

COL7A1 affects dermal fibroblasts during wound healing.

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COL7A1 affects dermal fibroblasts during wound healing. (A) Granulation ...
(A) Granulation tissue in 7- and 16-day wounds in wild-type and Col7a1-hypomorphic mice stained for COL7A1 (green). Note the presence of COL7A1 aggregates (arrows) within the healing dermis in wild-type mice. Scale bar: 50 μm. (B) In vitro scratch wound assay. Col7a1-hypomorphic fibroblasts closed the scratch wound significantly slower than did wild-type cells. n = 7. (C) Serum-response assay, which replicates fibroblast signaling events during wound healing (26). Dermal fibroblasts were starved in 0.1% FCS for 48 hours, stimulated with 10% serum for 5 hours, and analyzed for gene expression. Tgfb1 and Fgf2 mRNA expression were normalized to Gapdh and a nonstimulated control. Serum stimulation substantially increased Tgfb1 mRNA expression, but reduced Fgf2 expression, in Col7a1-hypomorphic compared with wild-type fibroblasts. n = 5. (D) P-SMAD2 staining (green) of granulation tissue in day-7 wounds confirmed increased activation of TGF-β1 signaling in the Col7a1-hypomorphic wound. Nuclei were visualized with DAPI (blue). Scale bar: 20 μm. (E) Supplementation of recombinant COL7A1 to Col7a1-hypomorphic fibroblasts normalized Tgfb1 and Fgf2 expression. Dermal fibroblasts were grown on 1.5 μg collagen I (CI), with or without 1.5 μg/well recombinant COL7A1, until they reached confluence, then serum-starved for 48 hours and stimulated with 10% FCS for 5 hours. mRNA expression was analyzed as in C. n ≥ 4. All values represent mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001.