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Joshua A. Wood, Sara M. Thomasy, Marissa L. Hughbanks, Irene Ly, Christopher J. Murphy, Paul Russell; Biophysical Cues and Dexamethasone Modulate YAP/TAZ Expression in Human Trabecular Meshwork Cells. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3269.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the interaction of substratum compliance and dexamethasone (dex) on the recently identified mechanotransducers, yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding domain (TAZ). The compliance of the HTM has been shown to be dramatically stiffer in glaucomatous patients and sustained dex treatment has been shown to induce ocular hypertension in approximately 30-40% of human patients. This study was conducted to determine if these distinct soluble and biophysical cues modulate these factors with a view towards determining their potential involvement in the onset and progression of ocular hypertension.
HTM cells were cultured on hydrogels possessing values for compliance that mimic those reported for normal (4 kPa) and glaucomatous (75 kPa) HTM, or tissue culture plastic (TCP > 1GPa). Cells were treated with 10^-8 M or 10^-7 M dex in EtOH or EtOH alone for 3 days. mRNA was extracted and real time PCR was performed.
HTM cells had profoundly increased expression of both of the mechanosensors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding domain (TAZ) on 75 kPa hydrogels compared to TCP. Expression of YAP was also elevated on the softer, 4 kPa hydrogels but TAZ expression was dramatically downregulated. Treatment with 10^-7 M dex resulted in a 53% increase in YAP expression and a 22% decrease in TAZ expression on 4 kPa surfaces. In contrast, 10^-7 M dex treatment on the stiffer, 75 kPa substratum induced a 47% decrease in YAP expression and a 60% decrease in TAZ expression. Treatment with 10^-8 dex resulted in a 19% decrease in YAP and a 2-fold increase in TAZ expression on 4 kPa surfaces. On 75 kPa surfaces, YAP expression was increased 55% and TAZ expression was only slightly elevated as a result of 10^-8 dex treatment.
Biophysical and biochemical cues interact in a complex fashion in the modulation of YAP and TAZ expression. Significantly, the inclusion of relevant biophysical cues altered the response of the HTM cells to dex treatment. The inclusion of substratum compliance that reflects healthy or glaucomatous HTM results in cell behaviors and responses to therapeutic agents in vitro that may more accurately reflect in vivo conditions.
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