Transforming growth factor β2 is elevated in the aqueous humor and trabecular meshwork of mouse model of myocilin and glucocorticoid-induced glaucoma

Abstract

Purpose : Accumulation of extracellular matrix (ECM) in the trabecular meshwork (TM) is associated with the glaucomatous TM damage. Transforming growth factor (TGF) β2 is elevated in the aqueous humor of glaucoma patients and TGF-β2 is shown to increase ECM in the TM. The purpose of this study was to examine outflow facility, TGF-β2 and ECM changes in the ocular hypertensive Tg-MYOC^Y437H and dexamethasone (Dex)-treated mice.

Methods : Conscious IOP and outflow facility were measured in Tg-MYOC^Y437H mice (10-month old) and 7-weeks Dex-treated mice. TGF-β2 and ECM protein levels in the aqueous humor and TM tissues were examined in both models at various stages of ocular hypertension by Western blotting and immunostaining. We next examined whether expression of mutant MYOC or Dex (100nm for 7 days) treatment induces TGF-β2 and ECM proteins in primary human TM cells by QPCR and Western blot analysis of cell lysates and conditioned media.

Results : Adult Tg-MYOC^Y437H mice significantly elevated IOP (13.5 in WT vs 17.6mmHg in Tg-MYOC^Y437H mice, p<0.0001, n=16) and also demonstrated significant reduction in outflow facility (0.0332 in WT vs 0.0137 µl/min/mmHg in Tg-MYOC^Y437H littermates, p<0.024, n=8). Topical ocular Dex treatment of C57 mice significantly elevated IOP (13.9 in vehicle vs 19.2mmHg in Dex, p<0.0001, n=8) and also reduced outflow facility (0.0197 in vehicle vs 0.0135 µl/min/mmHg in Dex-treated mice, p<0.053, n=8) compared to vehicle-treated mice. Western blot analysis and immunostaining demonstrated increased fibronectin, collagen IV and actin levels in the TM of Tg-MYOC^Y437H and Dex-treated mice (n=3-4). TGF-β2 and fibronectin levels were increased in the aqueous humor of ocular hypertensive Tg-MYOC^Y437H and Dex-treated mice (n=6-8 each) compared to control mice (n=6). Treatment of primary human TM cells with 100nM Dex for 7 days dramatically increased cellular and secreted TGF-β2 in primary human TM cells. Furthermore, TM-5 cells expressing mutant myocilin demonstrated increased TGF-β2 and fibronectin secretion in conditioned media.

Conclusions : These studies suggest that both mutant myocilin and Dex treatment induce TGF-β2 secretion, which may be responsible ECM remodeling in the TM and IOP elevation in these mouse models.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.