Biomechanical changes to Descemet's membrane precede endothelial cell loss in an early-onset murine model of Fuchs endothelial corneal dystrophy

Abstract

Early-onset Fuchs endothelial corneal dystrophy (FECD) has been associated with nonsynonymous mutations in collagen VIII α2 (COL8A2), a key extracellular matrix (ECM) protein in Descemet's membrane (DM). Two knock-in strains of mice have been generated to each express a mutant COL8A2 protein (Col8a2 L450W/L450W and Col8a2 Q455K/Q455K) that recapitulate the clinical phenotype of early-onset FECD including endothelial cell loss, cellular polymegathism and pleomorphism, and guttae. Due to abnormalities in ECM protein composition and structure in FECD, the stiffness of DM in Col8a2 knock-in mice and wildtype (WT) controls was measured using atomic force microscopy at 5 and 10 months of age, coinciding with the onset of FECD phenotypic abnormalities. At 5 months, only sporadic guttae were identified via in vivo confocal microscopy (IVCM) in Col8a2 Q455K/Q455K mice, otherwise both strains of Col8a2 transgenic mice *

Animal models of corneal endothelial dysfunction to facilitate development of novel therapies

“…Preliminary investigations of TAZ (Wwtr1) deficient mice demonstrate a lower CEC density with a softer DM in comparison to wild-type controls as well as reduced CEC proliferation following cryoinjury (129). Furthermore, FECD patients have a softer DM due to more widely spaced collagen fibrils in DM and CECs were displaced and distorted around the guttae in FECDaffected corneas (130,131). Finally, the Q455K and L450W murine models demonstrated reduced DM stiffness prior to CEC loss, mimicking the mechanobiology seen in FECD patients (131).…”

“…Furthermore, FECD patients have a softer DM due to more widely spaced collagen fibrils in DM and CECs were displaced and distorted around the guttae in FECDaffected corneas (130,131). Finally, the Q455K and L450W murine models demonstrated reduced DM stiffness prior to CEC loss, mimicking the mechanobiology seen in FECD patients (131). Collectively, these observations suggest that mechanotransduction is critical in CEC health and disease and the interrelationship between DM and CECs is understudied (119).…”

COL8A2 Regulates the Fate of Corneal Endothelial Cells

“…COL8A2 is involved in determining the structure and integrity of the cell shape. 23 Mutation of COL8A2 led to biomechanical changes to the DM preceding endothelial cell loss in an early-onset murine model of FECD 13 and inhibition of COL8A2 impaired CEC function. Although silencing the COL8A2 gene did not disrupt the structural integrity of DM, it could change the expression of proteins present and the functions of cells.…”

“…COL8A2 is a key extracellular matrix protein associated with cell structure and integrity. 13 siCOL8A2 induced changes in cell shape in vitro and in vivo, which are similarly induced during EMT or mesenchymal-endothelial transition (MET). 32 Thus, EMT-associated proteins were evaluated in cultured hCECs.…”

“… 7 COL8A2 mutations affect DM stiffness, causing guttae to form and contributing to the onset and progression of FECD. 13 Homozygous knock-in mice with this mutation ( Col8a2(Q455K/Q455K) ) exhibited endoplasmic reticulum (ER) stress that led to hCEC death. 14 Nevertheless, the role of COL8A2 in CECs is not thoroughly understood.…”