Abstract
Purpose::
To compare gene expression between normal and glaucomatous trabecular meshwork (TM) in order to identify novel signaling pathways involved in regulating intraocular pressure (IOP).
Methods::
Gene expression was compared using total RNA isolated from normal (n=6) and glaucomatous (n=6) cultured human TM cells. Differential gene expression was confirmed using QPCR. Western immunoblot and ELISA were used to determine protein differences. The effect of altered gene/protein expression on IOP was determined using perfusion cultured human anterior segments and viral expression vector transduction of mouse eyes.
Results::
Expression of the WNT signaling inhibitor sFRP1 was elevated in glaucomatous TM cells (5-fold increase in mRNA, p<0.01; 50% increase in protein, p<0.05). Human TM cells express various components of the WNT signaling system, including WNTs 2b, 5a, 5b and FZD 1,2,6,7. Increased sFRP1 caused decreased levels of the WNT signaling intermediate ß-catenin in the TM of perfusion cultured eyes (p<0.05) as well as in cultured TM cells. Recombinant sFRP1 significantly decreased the aqueous outflow facility in perfusion cultured human eyes (40-60% decrease, n=4, p<0.05). Transduction of mouse eyes with Ad5.sFRP1 significantly elevated IOP (2-fold increase, p<0.05). There was a positive correlation between anterior segment sFRP1 expression and level of IOP elevation (r2=0.81).
Conclusions::
The TM contains a functional WNT signaling pathway. Perturbation of the WNT signaling pathway by the WNT inhibitor sFRP1 leads to elevated IOP, which may play a role in glaucoma pathogenesis.
Keywords: trabecular meshwork • intraocular pressure • gene/expression