Matthew J Gastinger1, Ravi S J Singh, Alistair J Barber. 1. Milton S. Hershey Medical Center, Penn State Retina Research Group, Ulrich Ophthalmology Research Laboratory, Pennsylvania State College of Medicine, Hershey, Pennsylvania 17033, USA.
Abstract
PURPOSE: To identify amacrine cells that are vulnerable to degeneration during the early stages of diabetes. METHODS: Whole retinas from streptozotocin (STZ)-diabetic rats and Ins2(Akita) mice were fixed in paraformaldehyde. Apoptotic cells in the retina were quantified using terminal dUTP nick-end labeling (TUNEL) and active caspase-3 (CM-1) immunohistochemistry. Immunohistochemical markers for choline acetyltransferase (ChAT) and tyrosine hyroxylase (TH) were also used to quantify populations of amacrine cells in the Ins2Akita mouse retinas. RESULTS: The number of TUNEL-positive nuclei increased from 29+/-4 in controls to 72+/-9 in the STZ-diabetic rat retinas after only 2 weeks of diabetes. In rats, CM-1-immunoreactive (IR) cells were found primarily in the inner nuclear and ganglion cell layers after 2, 8, and 16 weeks of diabetes. At each end point, the number of CM-1-IR cells in the retina was elevated by diabetes. Approximately 2% to 6% of the CM-1-IR cells in the inner nuclear layer (INL) were double-labeled for TH immunoreactivity. After 6 months of diabetes in the Ins2Akita mouse, the morphology of the labeled ChAT-IR and TH-IR amacrine cell somas and dendrites appeared normal. A quantitative analysis revealed a 20% decrease in the number of cholinergic and a 16% decrease in dopaminergic amacrine cells in the diabetic mouse retinas, compared with the nondiabetic control. CONCLUSIONS: Dopaminergic and cholinergic amacrine cells are lost during the early stages of retinal neuropathy in diabetes. Loss of these neurons may play a critical role in the development of visual deficits in diabetes.
PURPOSE: To identify amacrine cells that are vulnerable to degeneration during the early stages of diabetes. METHODS: Whole retinas from streptozotocin (STZ)-diabeticrats and Ins2(Akita) mice were fixed in paraformaldehyde. Apoptotic cells in the retina were quantified using terminal dUTP nick-end labeling (TUNEL) and active caspase-3 (CM-1) immunohistochemistry. Immunohistochemical markers for choline acetyltransferase (ChAT) and tyrosine hyroxylase (TH) were also used to quantify populations of amacrine cells in the Ins2Akita mouse retinas. RESULTS: The number of TUNEL-positive nuclei increased from 29+/-4 in controls to 72+/-9 in the STZ-diabeticrat retinas after only 2 weeks of diabetes. In rats, CM-1-immunoreactive (IR) cells were found primarily in the inner nuclear and ganglion cell layers after 2, 8, and 16 weeks of diabetes. At each end point, the number of CM-1-IR cells in the retina was elevated by diabetes. Approximately 2% to 6% of the CM-1-IR cells in the inner nuclear layer (INL) were double-labeled for TH immunoreactivity. After 6 months of diabetes in the Ins2Akita mouse, the morphology of the labeled ChAT-IR and TH-IR amacrine cell somas and dendrites appeared normal. A quantitative analysis revealed a 20% decrease in the number of cholinergic and a 16% decrease in dopaminergic amacrine cells in the diabeticmouse retinas, compared with the nondiabetic control. CONCLUSIONS: Dopaminergic and cholinergic amacrine cells are lost during the early stages of retinal neuropathy in diabetes. Loss of these neurons may play a critical role in the development of visual deficits in diabetes.
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