Structural and biochemical alterations of the posterior cornea associated with diabetes mellitus

Abstract

Purpose : Previous studies have reported on diabetes mellitus as a risk factor for unsuccessful graft preparation in Descemet membrane endothelial keratoplasty (DMEK). Greater adhesion strength of Descemet membrane (DM) to corneal stroma has been postulated as a cause for this finding. The aim of this study was to perform a comparative analysis of potentially causative structural and biochemical alterations in the posterior cornea of diabetic and non-diabetic donors.

Methods : Corneoscleral tissue was obtained from 25 donors 49-75 years of age. Corneas were classified from a medical records review as non-diabetic (n=10) or diabetic (n=15). Transmission electron microscopy was used to analyze ultrastructural alterations in DM and posterior stroma. Light and electron microscopic immunohistochemistry was performed using a panel of antibodies against adhesive matrix glycoproteins and advanced glycation endproducts (AGEs). ImageJ was used to quantitate fluorescence intensity after correcting for negative control background.

Results : Transmission electron microscopy showed a moderate but statistically not significant increase in thickness of DM in diabetic samples (12.3±2.7µm) compared to non-diabetic controls (10.2±1.8µm). Diabetic corneas revealed a more prominent interfacial matrix at the DM-stroma boundary containing pronounced vacuolar inclusions as well as abnormal accumulations of banded, collagen type III-positive material in the posterior layer of DM. These ultrastructural alterations were not observed in control corneas. Quantitative analysis of immunofluorescence signals revealed increased amounts of AGEs in diabetic vs. non-diabetic corneas (p<0.001; t test). Staining reaction was most pronounced at the interface region and co-localized with ECM proteins such as fibronectin and vitronectin representing obvious targets of glycation reactions.

Conclusions : These findings support the concept that chronic hyperglycemia from diabetes mellitus results in an altered, more adhesive interface between DM and posterior stroma in donor corneas. The impact of diabetes on structural and biochemical interface matrix changes is considered relevant for eye banking and graft preparation during DMEK surgery.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.