Abstract
Purpose :
Extracellular matrix stiffening acts as a promoter and perpetuator of pathological fibrotic remodelling. We have recently described how quiescent Lamina Cribrosa (LC) cells adopt an activated myofibroblast phenotype when cultured on stiff substrates. Here, we investigate the role of Yes-Associated Protein (YAP), a mediator of the HIPPO pathway, in LC cell mechanotransduction, and its inhibition with verteporfin.
Methods :
GFAP-negative LC cells from non-glaucomatous human donors were cultured on soft (4kPa) and stiff (100kPa) Collagen-1 coated polyacrylamide hydrogel substrates to mimic physiological and pathological cellular environments respectively. Verteporfin without light activation (2μM for 24 h) was introduced as a YAP inhibitor. Quantitative polymerase chain reaction was performed to measure the expression of YAP, Transforming growth factor beta (TGF-β), α-smooth muscle actin (α-SMA) and Collagen type I, alpha 1( COL1A1). Immunohistochemistry, to detect phosphorylated and active non-phosphorylated YAP, was performed to measure the effects of substrate stiffening on LC cells, and potential inhibition with verteporfin.
Results :
LC cells cultured on stiff substrates showed a significant increase in YAP expression. Verteporfin treatment significantly decreased YAP on both soft and stiff substrates, along with reduction in downstream pro-fibrotic genes COL1A1 and α-SMA. Furthermore, these changes occurred despite increased TGF-β on stiff substrates. Immunohistochemistry demonstrated nuclear accumulation of non-phosphorylated YAP with phosphorylated YAP being retained in the cytosol.
Conclusions :
These data suggest that verteporfin acts as a YAP inhibitor in LC cells and thereby may provide an attractive and novel therapeutic target for the prevention of maladaptive, fibrotic remodelling at the lamina cribrosa in patients with glaucoma.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.