A switch from α5β1 to αvβ3 integrin activity contributes to the development of a profibrotic mesenchymal phenotype in trabecular meshwork cells.

PURPOSE: Fibrogenic changes in the trabecular meshwork (TM) are considered to be a major cause for the restriction in aqueous humor outflow from the anterior chamber associated with primary open angle glaucoma. In this study, we investigated whether integrin switching from α5β1 to αvβ3 integrin expression could initiate fibrotic-like changes in the TM that could restrict outflow.

METHODS

Human TM cells were isolated from young (<40 years) and old (>50 years) donor eyes. RT-PCR, western blots and immunofluorescence microscopy were used to evaluate levels of integrin and αSMA expression. Lentiviral shRNA vectors were used to knockdown α5 and β3 integrin levels. Paraffin embedded anterior segments of young and old donor eyes were used to evaluate αSMA levels in situ.

RESULTS

Studies revealed an age-related decrease in α5 integrin mRNA expression in TM cells. This loss was accompanied by an increase in αSMA mRNA and protein levels and an increase in activated αvβ3 integrin levels. Knockdown of β3 integrin mRNA and protein levels decreased the expression of αSMA mRNA and protein levels. Elevated mRNA levels of the EndMT biomarkers, VIM, SNAI2, and TWIST1, observed in older TM cells were decreased when β3 integrin was knockdown.

CONCLUSION

These studies suggest that crosstalk between α5β1 and αvβ3 integrin signaling controls expression of αSMA mRNA and protein levels and that β3 integrins may play a role in the development of the fibrogenic phenotype in TM cells and associated with POAG.