Morphofunctional status of endothelium in Fuchs endothelial corneal dystrophy

Relevance Fuchs endothelial dystrophy (FED) is a multigenic disease characterized by dysfunction of the endothelial layer, growth of guttae on the Descemet membrane (DM) and decreased corneal transparency. Currently, the main method of treating FED is endothelial keratoplasty (DM transplantation or posterior automated keratoplasty) [1–3]. Objective To evaluate the morphofunctional state of endothelial cells (EnC) in FED. Material and methods The main group included 21 DM-EnC complexes obtained from 20 patients (21 eyes) with FED during endothelial keratoplasty. The control group consisted of 6 samples of DM-EnC (donor tissue). In an immunohistochemical study, the expression of tight junction protein (ZO-1, Thermo Fisher Scientific, USA, 1:100) in EnC was assessed. EnC nuclei were stained with Hoechst 33342 (Thermo Fisher Scientific, USA, 1 μg/ml). Visualization was performed on a Leica DM-2500 microscope with a Leica DFC 295 camera (Leica Microsystems, Switzerland) in phase contrast and fluorescence detection modes. In 5–6 images (size 173.52 × 128.81 μm) of each sample, the area of ​​EnC and their nuclei was determined in the ImageJ program (USA), then the NCR was calculated. The number of EnC was estimated by the number of their nuclei. Results Phase-contrast microscopy of the DM-EnC samples of the main group revealed deformation of the cytoskeleton (elongated nuclei shifted to the periphery) and the shape of the EnC by rounded formations - guttae. In the altered EnC, the expression of ZO-1 is reduced. With EDF, the amount of EnC in the DM-EnC samples is 27.19 ± 12.77, in the control DM-EnC - 50.82 ± 10.73 (p < 0.05). The area of ​​the EnC and their nuclei with EDF is significantly increased (EnC - 490.99 ± 146.12 μm2, nuclei - 55.14 ± 19.02 μm2), compared to the control (EnC - 343.69 ± 85.14 μm2, nuclei - 50.82 ± 10.73). NCR – an indicator of the functional state of the EnC – does not differ in the samples of both groups (0.14 ± 0.05 and 0.12 ± 0.04, respectively, p = 0.329). Conclusion In EDF, progressive growth of guttae causes damage to the endothelial layer. However, the absence of deviation of NCR from the control parameters indicates that the altered EnC are in a state of relative compensation and retain functional activity. Key words: Fuchs' endothelial dystrophy; endothelium; nuclear-cytoplasmic ratio