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Urmimala Raychaudhuri, J Cameron Millar, Abbot F Clark; Tissue transglutaminase mediated ocular hypertension and effects of a small molecule crosslinking modulator. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3494.
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© ARVO (1962-2015); The Authors (2016-present)
Transforming Growth Factor-β2 (TGF-β2) induces expression of the crosslinking enzyme tissue transglutaminase (TGM2) in human trabecular meshwork (TM) cells. We studied (1) whether TGM2 overexpression in the TM can increase intraocular pressure (IOP) and decrease aqueous humor (AH) outflow facility (C) in mice and (2) whether a small molecule TGM2 inhibitor can decrease ECM crosslinking in-vitro.
2μl of the expression vector Ad5.CMV.TGM2 (1-50 × 106 pfu) was injected intravitreally (OS) in BALBc/J (n=18) or C57BL/6J mice (n=9) while contralateral eyes served as uninjected controls. Daytime conscious IOPs were measured (Tonolab) twice/week. C was measured following IOP elevation in BALBc/J (n=6) and C57BL/6J (n=3) mice. In vitro, primary human glaucoma TM cells (GTM 125, GTM 60 A and GTM 46) were treated with a small molecule TGM2 inhibitor (5nM).
Ad5.CMV.TGM2 injection significantly elevated IOP, where BALBc/J showed maximum IOP at Day 19, [15.86 mmHg (injected) vs. 10.7 mmHg (control), (p<0.0001, ANOVA)] and C57BL/6J showed maximum IOP at Day 17 [(17.09 mmHg (injected) vs. 12.01 mmHg (control), (p<0.05), ANOVA]. In BALBc/J, C in transduced eyes (0.013 μl/min/mmHg) was significantly lower than uninjected eyes (0.021 μL/min/mmHg), p = 0.01, paired Student’s t-test. In C57BL/6J, C in injected eyes (0.012 μl/min/mmHg) was significantly lower than uninjected eyes (0.019 μL/min/mmHg), p = 0.046, paired Student’s t-test. In GTM cells, primary GTM cells showed high endogenous ECM crosslinking, and treatment with a TGM2 inhibitor (5nM) reduced fibronectin expression and crosslinking but did not affect TGM2 expression as seen with immunocytochemistry and western immunoblotting.
TGM2 overexpression in the mouse TM significantly elevates IOP and decreases the AH outflow facility. A TGM2 inhibitor decreased crosslinking in TM primary cells. In future, we will study the role of TGM2 and the TGM2 small molecule inhibitor in TGFβ2 induced ocular hypertension.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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