Scleral proteome in noninfectious scleritis unravels upregulation of filaggrin-2 and signs of neovascularization

Vergouwen, D.P.C.; Berge, J.C.T.; Guzel, C.; Bosch, T.P.P.; Verdijk, R.M.; Rothova, A.; ... ; Schreurs, M.W.J. (2023)

Article / Letter to editor

PURPOSE. Scleritis is a severe inflammatory ocular disorder with unknown pathogenesis. We investigated healthy sclera as well as sclera affected by noninfectious scleritis for differentially expressed proteins using a mass spectrometry approach. METHODS. We collected scleral samples of enucleated eyes due to severe noninfectious scleritis (n = 3), and control scleral tissues (n = 5), all exenterated eyes for eyelid carcinomas (n = 4), or choroidal melanoma (n = 1) without scleral invasion. Samples were prepared for the nano liquid-chromatography mass spectrometer (LC-MS), data were analyzed using proteomics software (Scaffold), and is available via ProteomeXchange (identifier PXD038727). Samples were also stained for immuno-histopathological evaluation. RESULTS. Masspc spectrometry identified 629 proteins within the healthy and diseased scleral tissues, whereof collagen type XII, VI, and I were the most abundantly expressed protein. Collagen type II-XII was also present. Filaggrin-2, a protein that plays a crucial role in epidermal barrier function, was found upregulated in all scleritis cases. In addition, other epithelial associated proteins were upregulated (such as keratin 33b, 34, and 85, epiplakin, transglutaminase-3, galectin 7, and caspase-14) in scleritis. Further, upregulated proteins involved in regulation of the cytoskeleton (vinculin and myosin 9), and housekeeping proteins were found (elongation factor-2 and cytoplasmic dynein 1) in our study. Upregulation of filaggrin-2 and myosin-9 was confirmed with immunohistochemistry, the latter protein showing co-localization with the endothelial cell marker ETCrelated gene (ERG), indicating neovascularization in scleral tissue affected by scleritis. CONCLUSIONS. We found upregulation of filaggrin-2 and signs of neovascularization in scleral tissue of patients with noninfectious scleritis. Further research, ideally including more scleritis cases, is needed to validate our findings.

• scleritis
• pathogenesis
• mass spectrometry
• proteomics
• histopathology
• filaggrin-2

• All authors: Vergouwen, D.P.C.; Berge, J.C.T.; Guzel, C.; Bosch, T.P.P.; Verdijk, R.M.; Rothova, A.; Luider, T.M.; Schreurs, M.W.J.
• Date: 2023-03-01
• Journal: Investigative Ophthalmology & Visual Science
• Volume: 64
• Issue: 3
• DOI: doi:10.1167/iovs.64.3.27
• Link: https://iovs.arvojournals.org/article.aspx?articleid=2785453