Characterization of Cell Migration and Descemet's Membrane Mechanical Properties in the Context of Fuchs Endothelial Corneal Dystrophy and Cell-based Treatments

Abstract

Fuchs endothelial corneal dystrophy (FECD) is a degenerative disease that causes dysfunction and abnormal cell death of corneal endothelial cells (CECs). It is hallmarked by changes in the extracellular matrix (ECM) including thickening and softening of the Descemet’s membrane (DM) and the development collagenous guttae. Once the CEC count falls below a critical level, hydration levels in the cornea will increase, leading to corneal swelling, damage to other corneal layers, and eventual corneal blindness. Currently, FECD patients rely on corneal transplants to repair vision. There has been development in cell-based treatments to avoid the need for the transplantation of donor tissue including cell injection therapy (CIT) and Descemet’s stripping only (DSO). During these procedures, patients remain in a prone posture to aid in recovery. Corneal curvature mimicking substrates, placed in prone, supine, and upright positions, were used to study the effects of patient positioning on CEC wound-healing. Scratch wounds were made in monolayers of healthy and FECD affected cell-lines. Differences in wound closure between orientations were primarily observed during the early-to-middle stages of healing. Across experiments, wound closure in the upright orientation generally lagged behind the prone and supine orientations. These findings provide some evidence that gravitational orientation may influence CEC migration, particularly in the upright orientation, although the relationship was not definitive. Additionally, the mechanical properties of the DM across three regions, the central endothelium (CE), peripheral endothelium (PE), and transition zone (TZ) were measured. Previous literature has reported modulus values for human DMs with wide variation. Using three-point bend testing and measurement of the exact DM thickness, the flexural modulus for the CE, PE, and TZ were determined. The measured DM flexural moduli were on the megapascal (MPa) scale and were within the range of previously reported values from tensile inflation-based measurements but exceeded values reported using atomic force microscopy. No statistically significant differences in mean modulus were observed between the CE, PE, and TZ or between donor sex. However, in review of stiffnesses across the DM from individual donors, most had decreased PE stiffness compared to the other regions. Further studies are required to see if CECs subscribe to positive durotaxis or if substrate stiffness gradients affect migration.