Abstract
Abstract: :
Purpose: The Ins2Akita mouse carries a spontaneous mutation of one insulin gene and develops diabetes 4–5 weeks after birth. The purpose of this study was to test the hypothesis that neurons degenerate in the inner retina of Ins2Akita mice. Methods: Histological sections of eyes from male C57BL/6J Ins2Akita heterozygote mice (22 to 28 weeks old) were stained with H&E and Hoechst for morphometric analysis. Apoptotic cells in whole retinas were counted after dUTP nick end labeling (TUNEL). Other retinas were analyzed for changes in neuronal cell markers by western blot and confocal microscopy. In all cases, age–matched wild–type mice were used as controls. Results: Ins2Akita mice had significantly elevated blood glucose (>250 mg/dL) and lower body weight compared to controls. In Ins2Akita retinas stained with H&E, the thickness of the inner plexiform layer was reduced in central and peripheral regions by 17% and 27%, respectively, and the thickness of the inner nuclear layer (INL) was decreased by 16% in the peripheral retina, compared to controls. There were no significant changes in the outer retinal layers or photoreceptors. In Hoechst stained sections there were 23% fewer nuclei in the ganglion cell layer (GCL) of Ins2Akita mice, and the number of TUNEL–positive cells in whole–mount retinas was significantly greater compared to controls. The content of choline acetyltransferase, a specific marker for starburst amacrine cells in the INL and GCL, was significantly less in Ins2Akita retinas compared to controls. Conclusions: There is increased apoptosis and accelerated loss of neurons in the retina of Ins2Akita mice. These changes parallel and extend observations of neuronal degeneration in streptozotocin–diabetic rats and postmortem tissue from humans with diabetes and may explain the loss of vision in diabetic retinopathy.
Keywords: diabetic retinopathy • apoptosis/cell death • retina: proximal (bipolar, amacrine, and ganglion cells)