Investigating the role of α5β1-integrin in fibrotic posterior capsular opacification (PCO)
Date
2021
Authors
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Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Posterior capsular opacification (PCO) is a major complication of cataract surgery. The lens epithelial cells remaining behind post cataract surgery undergo epithelial mesenchymal transition (EMT) and transform into myofibroblasts. The migration of fibroblasts to the posterior capsule blocks the visual axis resulting in the secondary cataract, PCO. It is believed that TGF-β is the orchestrator of fibrotic PCO. However, recent findings in the M Duncan’s lab have shown that fibronectin, an extracellular matrix protein, plays several roles in PCO pathogenesis. This discovery has opened new paths for investigation. The mechanism by which fibronectin acts is still unknown. Thus, since fibronectin binds integrin receptors, the purpose of this project is to understand the relative extent to which fibronectin contributes to PCO via binding its main canonical receptor α5β1-integrin. α5-integrin mRNA levels increase at 6 hours PCS in remnant lens epithelial cells. While immunostaining shows that α5-integrin protein expression is low in unoperated lenses, the levels upregulate significantly at 48 hours PCS. Thus, to investigate the role of α5β1-integrin in PCO pathogenesis, conditional α5cKO lenses were generated using α5-integrin exon1 floxed mice and mice carrying MLR10 cre recombinase. Immunostaining and PCR have revealed the near complete loss of α5-integrin in α5cKO lenses at both the protein and the gene levels, respectively. Lens development and adult phenotype appear to be normal in α5cKO. Additionally, the immunostaining of α-SMA and tenascin C, two fibrotic markers, showed an overall decrease in the fibrotic response PCS in the α5cKO, indicating that α5β1-integrin plays a role in PCO pathogenesis. Similar outcomes were seen in fibronectin knockout mice (FNcKO), which suggests that fibronectin might be playing a role in fibrosis through binding to α5β1-integrin. Moreover, the size of the plaque surrounding the lens capsule appeared to be larger in the WT mice. The analysis of proliferation using Ki67 antibody has showed a significant increase in proliferation 48 hours PCS in WT, while α5cKO mice showed a late upregulation of proliferation around 3 days PCS. However, the FNcKO mice have exhibited an increased proliferation at 48 hours PCS, similar to the WT. Overall, many of fibronectin’s functions in fibrotic PCO pathogenesis appear to be mediated through its binding to α5β1-integrin. Thus, α5β1-integrin antagonists may be efficacious in preventing fibrotic PCO.
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Keywords
Cataract, Epithelial mesenchymal transition, Fibronectin receptor, Posterior capsular opacification, α5β1-integrin