Abstract
Purpose :
Posterior capsular opacification, the major post cataract surgery (PCS) complication, has both fibrotic and regenerative features. Fibrotic PCO is driven by transforming growth factor β (TGFβ) signaling. However, the mechanisms that activate the TGFβ pathway PCS are not well understood. Previously, we found that αV-integrins are critical for fibrotic PCO pathogenesis. However, the specific β subunit that heterodimerizes with αV-integrin to drive fibrotic PCO is not known.
Methods :
Homozygous β5 and β6-integrin null mice and β8- integrin conditional knockout mice (β8ITG cKO) were subjected to lens fiber cell removal. The dynamic localization of epithelial-mesenchymal transition (EMT) and fiber cell markers, ki67, pSMAD3, and matrix metalloproteinase 14 (MMP14) were determined by immunolocalization. RNAseq was performed on RNA isolated from lens epithelial cells (LECs) obtained from control and β8ITG cKO mice at 0 hr. & 24 hrs. PCS.
Results :
Both β5- and β6-integrin null lenses exhibited normal fibrotic responses PCS. In contrast, β8ITG cKO LECs did not undergo a fibrotic response as measured by the lack of αSMA, fibronectin, and tenascin C upregulation and canonical TGFβ signaling PCS. β8ITG cKO LECs also proliferate less PCS, but still attempt fiber cell regeneration PCS as measured by aquaporin 0 expression. RNAseq revealed that over 800 genes exhibited altered expression levels in β8ITG cKO LECs at 24 hrs. PCS compared to control. MMP14, a αVβ8- integrin co-factor involved in the activation of latent TGFβ upregulates both at the mRNA and protein levels in control lenses PCS. In contrast, MMP14 protein deposition is attenuated in β8ITG cKO LECs at 5 days PCS. Interestingly, some of the identified differentially expressed genes (DEGs) are known inflammatory cytokines, such as LY6a, Cxcl3, Ccl5, and Ptx3, suggesting that αVβ8-integrin may play a critical role in the pathophysiology of the inflammation that develops post cataract surgery as well.
Conclusions :
Our data suggest that αvβ8 integrin is the main αV- integrin heterodimer mediating fibrotic PCO. Further, we have identified a possible critical role for αvβ8 integrin in the regulation of post cataract surgical inflammation. As αVβ8-integrin is a "druggable" target, the outcome of this study suggests effective therapeutics to prevent fibrotic PCO.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.