Abstract
Purpose: :
This study aimed to evaluate morphological changes in various corneal layers of the Goto-Kakizaki (GK) rats, a spontaneous model of type 2 diabetes.
Methods: :
Thirteen-week-year-old (n=6 eyes) and one-year-old (n=6 eyes) GK rats were included in the study. A corneal confocal microscope was used to generate in vivo images of the corneal microstructures which were compared to those of non-diabetic rats. Morphological changes were observed by histological analysis. The distribution of OX-42 and sFlt-1 were examined by immunochemistry.
Results: :
In vivo, corneal abnormalities were observed in GK rats as early as 13 weeks of age. Epithelial basal membrane was irregular with focal thickening area and adjacent hyper-reflective deposits. On histology, the epithelium of diabetic cornea showed increased layers of proliferative cells and decreased layers of superficial cells together with inflammatory cell infiltration in the anterior stroma which were OX-42 positive. In the stroma, confocal microscopy highlighted cell infiltration in young, as well as, in old diabetic rats. Interestingly confocal in vivo imaging allowed visualizing corneal peripheral neovessels on 360° in one of the older GK rats. In non vascularized diabetic cornea, the distribution of sFlt-1 was more pronounced in the anterior stroma than in non diabetic corneas. At the Descemet membrane, a hyper-signal under the form of deposit was observed by confocal microscopy in the peripheral corneal of the younger GK rats, and in all the cornea of the older ones. This observation was also made with a lesser extent in the old non-diabetic rats, but not in the younger ones, suggesting that diabetes amplified a phenomenon due to ageing.
Conclusions: :
Pathological findings are observed early in the development of diabetes in GK rats. Such abnormalities increased with age and could predispose to corneal pathologies. Whether corneal abnormalization precedes diabetic retinopathy in patients remains to be demonstrated.
Keywords: diabetes • cornea: basic science • microscopy: confocal/tunneling