YAP/TAZ mediate TGFβ2-induced Schlemm’s canal cell dysfunction

AbstractPurposeElevated 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 co-activators, 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 (ECM) hydrogels, and examine whether pharmacologic YAP/TAZ inhibition would attenuate TGFβ2-induced HSC cell dysfunction.MethodsPrimary HSC cells were seeded atop photocrosslinked ECM 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 pharmacologic YAP/TAZ inhibition. Changes in actin cytoskeletal organization, YAP/TAZ activity, ECM production, phospho-myosin light chain levels, and hydrogel contraction were assessed.ResultsTGFβ2 significantly increased YAP/TAZ nuclear localization in HSC cells, which was prevented by either filamentous (F)-actin relaxation or depolymerization. Pharmacologic YAP/TAZ inhibition using verteporfin without light stimulation decreased fibronectin expression and reduced actomyosin cytoskeletal rearrangement in HSC cells induced by TGFβ2. Similarly, verteporfin significantly attenuated TGFβ2-induced HSC cell-encapsulated hydrogel contraction.ConclusionsOur data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in HSC cells under simulated glaucomatous conditions, and suggest that pharmacologic YAP/TAZ inhibition has promising potential to improve outflow tissue dysfunction.