Label-free LC-MSMS analysis of vitreous from autoimmune uveitis reveals a significant decrease in secreted Wnt signalling inhibitors DKK3 and SFRP2.

The study explores the changes in protein composition in the inner eye as a result of Equine Recurrent Uveitis (ERU), a common blinding disease in horses. Specifically, the research discovered a decrease in two Wnt signalling inhibitors, DKK3 and SFRP2, which could contribute to the pathogenesis of ERU.

Study Overview

• The research focused on Equine recurrent uveitis (ERU), a severe eye disease in horses that often leads to blindness. ERU presents with auto-reactive T-cells that attack and destroy the inner structures of the eye.
• One therapeutic intervention for ERU is the surgical removal of the vitreous, a clear gel that fills the space between the lens and the retina. The removal of vitreous has been found to alleviate symptoms of ERU.
• The researchers believed that examining the protein composition of the vitreous could reveal the presence and concentrations of proteins that drive disease progression.

Methodology

• The team conducted a label-free LC-MSMS analysis (a type of mass spectrometry) of vitreous samples taken from healthy and ERU-affected horses.
• The analysis measured the peak intensities across samples to quantify the concentrations of different proteins.

Findings

• They found significant changes in protein concentrations between healthy and ERU-affected samples.
• Specifically, they discovered an upregulation of proteins associated with complement and coagulation cascades. This suggests an increase of inflammation and blood clotting in the eye.
• More notably, they observed a significant reduction in two Wnt signalling inhibitors, DKK3 and SFRP2. This decrease indicates that Wnt signalling pathways, which regulate cell growth and differentiation, may be affected in ERU.

Implications

• Additional immunohistochemistry analysis showed these two proteins are mainly found in the retina, particularly in the retinal Müller glial cells (RMG). Thus, suggesting that RMG cells could be the prime responders to autoimmune triggers in ERU.
• The findings in this study broaden our understanding of the pathogenic mechanisms of ERU. Moreover, it could help develop therapeutic interventions targeting Wnt signalling pathways for treating ERU.