Collagen VII deficient mice show morphologic and histologic corneal changes that phenotypically mimic human dystrophic epidermolysis bullosa of the eye

Abstract

Background: Absence of collagen VII causes blistering of the skin, eyes and many other tissues. This disease is termed dystrophic epidermolysis bullosa (DEB). Corneal fibrosis occurs in up to 41% and vision loss in up to 64% of patients. Standard treatments are supportive and there is no cure. The hypomorphic mouse model for DEB shows production of collagen VII at 10% of wild type levels in skin and spleen, but the eyes have not been described. Our purpose is to characterize the corneas to determine if this is an appropriate model for study of ocular therapeutics.

Methods: Western blot analysis (WB) and immunohistochemistry (IHC) were performed to assess presence and location of collagen VII protein within the hypomorphic mouse cornea. Additional IHC for inflammatory and fibrotic biomarkers transforming growth factor-beta-1 (TGF-β1), alpha-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF), proteinase 3, tenascin C and collagen III were performed. Clinical photographs documenting corneal opacification were assessed and scored independently by 2 examiners. Histology was then used to investigate morphologic changes.

Results: IHC and WB confirmed that hypomorphic mice produce less collagen VII production at the level of the basement membrane when compared with wild-types. IHC showed anomalous deposition of collagen III throughout the stroma. Of the 5 biomarkers tested, TGF-β1 showed the strongest and most consistently staining. Photographs documented corneal opacities only in mice older than 10 weeks, opacities were not seen in younger animals. Histology showed multiple abnormalities, including epithelial hyperplasia, ulceration, fibrosis, edema, dysplasia, neovascularization and bullae formation.

Conclusions: The collagen VII hypomorphic mouse shows reduced collagen VII production at the level of the corneal basement membrane. Corneal changes are similar to pathology seen in humans with this disease. The presence of anomalous stromal collagen III and TGF-β1 appear to be the most consistent and strongest staining biomarkers in diseased mice. This mouse appears to mimic human corneal disease. It is an appropriate model for testing of therapeutics to treat EB ocular disease.

Keywords: Blindness; Collagen VII; Cornea; DEB; Epidermolysis bullosa; Eye; Mouse; Murine; Opacity; RDEB; Scarring; Vision loss.