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Tina T Wong, Li Zhen Toh, Stephanie Chu, Jocelyn Chua, Li Fong Seet; Collagen VIII and XI as Biomarkers for Post-operative Conjunctival Fibrosis. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2925.
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© 2017 Association for Research in Vision and Ophthalmology.
Collagen, in particular collagen I, is the major extracellular matrix responsible for the development and persistence of fibrosis. The study aims to identify other collagen genes that may significantly define subconjunctival fibrosis following experimental glaucoma filtration surgery.
Subconjunctival scarring was induced using a mouse model of glaucoma filtration surgery (GFS). The early and late phases of wound healing were analyzed by RNA sequencing (RNA-seq). The top ten highest expressed collagen genes in the late phase were validated by quantitative polymerase chain reaction (qPCR). Immunoblotting and immunolocalization were performed to verify and determine the expression profiles of the top three highest expressed collagen genes. Mouse and human conjunctival fibroblasts were treated with TGF-β2 to determine the inducibility of the collagen transcripts. Conjunctival tissues, collected from 20 and 15 patients requiring initial and repeat GFS respectively were also analyzed by qPCR.
RNA-seq identified Col8a1 (70-fold), Col11a1 (40-fold) and Col8a2 (20-fold) as the three most highy expressed collagen genes in the late phase conjunctival transcriptome. These collagens were also induced at the protein level in late phase tissues. Type VIII collagen co-localized with type I collagen in fibrous structures and in ACTA-2-positive pericytes, appearing to fill gaps where type I collagen was low. Type XI collagen showed little co-localization with both collagens but was associated with the presence of macrophages. TGF-β2 induced the top ten collagen genes in both mouse and human conjunctival fibroblasts. Conjunctival tissues from eyes undergoing repeat trabeculectomy surgery expressed 3.60-fold and 2.78-fold increase in type VIII and I collagen transcripts respectively compared to conjunctival tissues from primary trabeculectomy.
The high induction and unique expression profiles of types VIII and XI collagen suggest that together with collagen I, form a group of collagen biomarkers for the evaluation of fibrosis in the mouse model of GFS and post trabeculectomies.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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