A hypomorphic mouse model of dystrophic epidermolysis bullosa reveals mechanisms of disease and response to fibroblast therapy

Abstract

Dystrophic epidermolysis bullosa (DEB) is a severe skin fragility disorder associated with trauma-induced blistering, progressive soft tissue scarring, and increased risk of skin cancer. DEB is caused by mutations in type VII collagen. In this study, we describe the generation of a collagen VII hypomorphic mouse that serves as an immunocompetent animal model for DEB. These mice expressed collagen VII at about 10% of normal levels, and their phenotype closely resembled characteristics of severe human DEB, including mucocutaneous blistering, nail dystrophy, and mitten deformities of the extremities. The oral blistering experienced by these mice resulted in growth retardation, and repeated blistering led to excessive induction of tissue repair, causing TGF-β1-mediated contractile fibrosis generated by myofibroblasts and pseudosyndactyly in the extremities. Intradermal injection of WT fibroblasts resulted in neodeposition of collagen VII and functional restoration of the dermal-epidermal junction. Treated areas were also resistant to induced frictional stress. In contrast, untreated areas of the same mouse showed dermal-epidermal separation following induced stress. These data demonstrate that fibroblast-based treatment can be used to treat DEB in a mouse model and suggest that this approach may be effective in the development of clinical therapeutic regimens for patients with DEB. IntroductionSkin integrity and resistance to mechanical stress rely on the function of the dermal-epidermal junction zone (DEJZ), which anchors the epidermis to the underlying dermal matrix. The supramolecular cell adhesion complexes at the DEJZ mediate interactions of the cytoskeleton in basal keratinocytes with the basement membrane and the extracellular anchoring fibrils, which emanate from the basement membrane into the dermis and entrap dermal collagen bundles, thus establishing stable dermal-epidermal cohesion (1).The main component of the anchoring fibrils is collagen VII, a homotrimeric collagen synthesized by keratinocytes and fibroblasts (2). Fibril formation and deposition at the DEJZ requires proteolytic processing of procollagen VII to mature collagen (3). Loss of collagen VII functions in dystrophic epidermolysis bullosa (DEB) leads to absence or anomalies of the anchoring fibrils and to dermal-epidermal tissue separation. DEB refers to a clinically heterogeneous group of disorders including recessively and dominantly inherited subtypes (4, 5). All forms of DEB are allelic and caused by mutations in the collagen VII gene, COL7A1. Early investigations demonstrated reduced amounts of anchoring fibrils and collagen VII in the skin of patients with mild and moderate, reces-

Impaired lymphoid extracellular matrix impedes antibacterial immunity in epidermolysis bullosa

“…PCR analysis of mRNA extracted from RDEB mouse spleens generated products corresponding to the aberrantly spliced Col7a1 detected in this mouse model (Fig. 2B) (25), and Western blot analysis of protein lysates from RDEB mouse spleens showed barely detectable levels of full-length collagen VII (Fig. 2C), thus collectively validating the expression analysis.…”

“…For the studies, samples from human individuals with molecularly confirmed severe generalized recessive RDEB were used, as well as two genetic mouse models, the collagen VII hypomorphic RDEB mouse and a tamoxifen-inducible Col7a1 knockout mouse (1). The RDEB mouse shows all major signs of severe RDEB (25), and the tamoxifen-inducible Col7a1 knockout mouse allows targeted ablation of Col7a1 expression in time and space (1). RDEB is a progressive disease.…”

“…(31). Arrow points to wild-type Col7a1 transcript, and arrowhead to aberrantly spliced Col7a1 transcript (25). S1 and S2A) (22,34), but the luminal interaction partners remained elusive.…”

Keratinocyte-/Fibroblast-Targeted Rescue of Col7a1-Disrupted Mice and Generation of an Exact Dystrophic Epidermolysis Bullosa Model Using a Human COL7A1 Mutation

“…3 A surviving DEB mouse that was reported recently was the DEB hypomorphic mouse model. 4 These mice, which had about 10% of the normal mouse COL7, did not show the abnormal form and function of anchoring fibrils seen in human patients of RDEB. Second, no studies have examined in detail whether the introduction of the human COL7 gene into DEB mouse cells can rescue the DEB phenotype without causing adverse effects in a living DEB model.…”

Cell-Extracellular Matrix Interactions in Normal and Diseased Skin

“…However, it is exciting that gene therapy has already been used to repair a laminin-332 (laminin-5) defect in a patient with junctional epidermolysis bullosa (Mavilio et al 2006). Furthermore, a potential alternative to gene therapy may be to restore a functional ECM in blistering disorders by injection of nonmutant fibroblasts (Fritsch et al 2008). Another advance that is highly appealing is to use extracellular matrix biomaterials for skin repair (Cornwell et al 2009;Wolf et al 2009).…”