TAZ (Wwtr1) deficiency: A murine model of late-onset Fuchs endothelial corneal dystrophy

Abstract

Purpose : To determine the effect of TAZ, a key signaling molecule in the Hippo pathway that governs organ size and an intracellular mechanotransducer, in corneal endothelial cell (CEnC) development, Descemet’s membrane biomechanics, and CEnC wound healing using a cryoinjury model.

Methods : Six-month-old TAZ knockout (Wwtr1^+/- and Wwtr1^-/-)and wildtype (WT) mice were examined using slit lamp biomicroscopy and advanced imaging with in vivo confocal microscopy (IVCM) and Fourier-domain optical coherence tomography (FD-OCT). Tissue compliance of Descemet’s membrane (DM) was determined using atomic force microscopy (AFM). Corneal cryoinjury was performed on Wwtr1^+/- and WT animals, and slit lamp exam and advanced imaging assessments were performed over 7 days. Following euthanasia (day 7), globes were excised and stained with Alizarin red and probed for zonula occludens-1 (ZO-1) to evaluate CEnC density and morphology.

Results : At baseline, there were no clinical differences on slit lamp exam between Wwtr1 deficient and WT mice, but Wwtr1^+/- and Wwtr1^-/- mice had significantly reduced CEnC density compared to controls (Fig 1A). Heterozygote mice (Wwtr1^+/-) had significantly reduced DM stiffness (Wwtr1^+/-: 1.2 kPa, WT: 4.2 kPa; P< 0.0001). After cryoinjury, a subjective increase in corneal edema and central corneal thickness in Wwtr1^+/-mice was observed on slit lamp exam and FD-OCT (Fig 1B). The most striking finding was the marked, statistically significant, reduction in CEnC density with lack of endothelial cell proliferation, and concomitant increased polymorphism and pleomorphism post-wounding in the Wwtr1^+/- mice (Fig 2A and B).

Conclusions : Mice deficient in Wwtr1 had an inherent defect in CEnC development and proliferation which coincided with a softening of DM when compared to WT mice. In addition, CEnC proliferation post-cryoinjury was severely impaired due to deficiency in Wwtr1. Increasing evidence demonstrate that patients with Fuchs corneal endothelial dystrophy (FECD) have altered corneal biomechanics with a softer DM. These findings suggest that TAZ signaling may play an important role in FECD and the Wwtr1 deficient mice may serve as a model of late-onset FECD.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

(A) Wwtr1 deficient mice have reduced CEnC density assessed via IVCM. (B) After cryoinjury, Wwtr1^+/- mice have increased corneal thickness on OCT.

 

(A) There was markedly reduced CEnC density determined by IVCM and (B) Alizarin red and ZO-1.