Otsuka Long-Evans Tokushima fatty (OLETF) rat is not a suitable animal model for the study of angiopathic diabetic retinopathy

We have previously shown that the peak latency of oscillatory potential (OP), the earliest electroretinographic manifestation of diabetic retina, was prolonged in Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of non-insulin-dependent diabetes. These observations suggest that retinal neuronal dysfunction revealed by the OP abnormality in the electroretinogram takes place prior to the angiopathic diabetic changes in this animal model. However whether acellular capillaries and pericyte ghosts, one of the histopathological hallmarks of early diabetic retinopathy in humans, could occur in OLETF rat remains to be elucidated. In the present study, we first prepared the retinal trypsin digests of OLETF and control Long-Evans Tokushima Otsuka (LETO) rats at 45 weeks old and then compared the number of acellular capillaries and pericyte ghosts in the retinas of OLETF rats with that in LETO rats. Blood glucose levels were higher in the OLETF rats than those in LETO rats. Retinal capillaries of OLETF rats were found to remain morphologically normal and pericyte ghosts were barely detectable. There was no difference in the number of acellular capillaries in the retinas between OLETF and LETO rats. The present study indicates that acellular capillaries and pericyte ghosts, the characteristic morphological changes in early diabetic retinopathy, are not accelerated in OLETF rats. Our data suggest that OLETF rat is not a suitable animal model for the study of angiopathic diabetic retinopathy.