YAP/TAZ Mediate TGFβ2-Induced Schlemm's Canal Cell Dysfunction.

Abstract

Elevated transforming growth factor beta2 (TGFβ2) levels in the aqueous humor have been linked to glaucomatous outflow tissue dysfunction. Potential mediators of dysfunction are the transcriptional coactivators, Yes-associated protein (YAP) and transcriptional coactivator with PDZ binding motif (TAZ). However, the molecular underpinnings of YAP/TAZ modulation in Schlemm's canal (SC) cells under glaucomatous conditions are not well understood. Here, we investigate how TGFβ2 regulates YAP/TAZ activity in human SC (HSC) cells using biomimetic extracellular matrix hydrogels, and examine whether pharmacological YAP/TAZ inhibition would attenuate TGFβ2-induced HSC cell dysfunction. Primary HSC cells were seeded atop photo-cross-linked extracellular matrix hydrogels, made of collagen type I, elastin-like polypeptide and hyaluronic acid, or encapsulated within the hydrogels. HSC cells were induced with TGFβ2 in the absence or presence of concurrent actin destabilization or pharmacological YAP/TAZ inhibition. Changes in actin cytoskeletal organization, YAP/TAZ activity, extracellular matrix production, phospho-myosin light chain levels, and hydrogel contraction were assessed. TGFβ2 significantly increased YAP/TAZ nuclear localization in HSC cells, which was prevented by either filamentous-actin relaxation or depolymerization. Pharmacological YAP/TAZ inhibition using verteporfin without light stimulation decreased fibronectin expression and actomyosin cytoskeletal rearrangement in HSC cells induced by TGFβ2. Similarly, verteporfin significantly attenuated TGFβ2-induced HSC cell-encapsulated hydrogel contraction. Our data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in HSC cells under simulated glaucomatous conditions and suggest that pharmacological YAP/TAZ inhibition has promising potential to improve outflow tissue dysfunction.