Age-related anatomical changes in the cornea of spontaneous type 2 diabetes model rats

Abstract

Purpose : We previously reported that aged Spontaneously Diabetic Torii (SDT) rats or SDT fatty rats, an animal model of type 2 diabetes mellitus without or with obesity, showed delayed corneal wound healing and corneal angiogenesis associated with increased inflammatory cell infiltration. In this study, we compared aging changes SDT and SDT fatty model rat corneas by electron microscopy.

Methods : Male SDT and male SDT fatty rats of 8, 24, and 40 weeks of age were used for experiments (n=3 each). Male Sprague Dawley (SD) rats with same age were used as control (n=3). We examined rat cornea histologically with an electron microscope. We compared the changes due to aging in SD rats, and compared changes due to diabetes in the same age rats.

Results : SD rats at 40 weeks of age showed normal age-related changes such as disrupted epithelial layer structures, increased thickness of Descemet's membrane, and decreased corneal endothelial microvilli. There was no particular difference in each rat at 8 weeks of age. In the SDT rats at 24 weeks of age, the epithelial basement membrane was rough, and poor adhesion between Descemet's membrane and endothelium was observed compared to control. In SDT fatty rats at 24 weeks of age, adherence of epithelial basal cells and basement membrane was poor, and corneal endothelial cell cytoplasmic components decreased compared with control. In SDT rats at 40 weeks of age, there was a gap between epithelial basal cell and basement membrane, and many deposits were observed on the endothelial side of Descemet's membrane. In SDT fatty rats at 40 weeks of age, epithelial basement membrane was thick, and endothelial cell cytoplasm was small. In total, changes in the basal epithelial cells were stronger in SDT rats than control, and most prominent in SDT fatty rats. Abnormal proliferation of epithelial mitochondria and structural changes of epithelial hemidesmosomes were seen only in aged SDT and SDT fatty rats.

Conclusions : The changes in corneal epithelium observed only in diabetic rats may be related to delayed corneal epithelial wound healing in these rats. Prominent morphological changes of the endothelium were also observed in diabetic rats.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.