Retinal gene expression and visually evoked behavior in diabetic long evans rats

Area of Science:

• Ophthalmology and visual science
• Molecular biology
• Diabetic complications

Background:

• Diabetic retinopathy (DR) leads to vision loss via macular edema and neovascularization.
• Early functional deficits in contrast sensitivity, color perception, and dark adaptation precede apparent DR abnormalities.
• Understanding early molecular and functional changes is crucial for timely intervention.

Purpose of the Study:

• To investigate early changes in retinal gene expression, visual cycle proteins, and optokinetic tracking (OKT) in streptozotocin (STZ)-induced diabetic rats.
• To correlate molecular alterations with functional visual deficits within the first 3 months of diabetes.

Main Methods:

• Whole genome microarray analysis of retinal gene expression at 7 days, 4 weeks, and 3 months post-hyperglycemia onset.
• Polymerase chain reaction (PCR) and immunohistochemistry to validate gene and protein expression changes.
• Optokinetic tracking (OKT) thresholds measured using a virtual optokinetics system.

Main Results:

• Microarray identified affected functions including cell signaling, cell death, and molecular transport.
• Reduced expression of visual cycle genes (LRAT, RPE65, RGR) observed.
• Decreased OKT thresholds by 4 weeks correlated with molecular changes; RPE65 decreased by 3 months.

Conclusions:

• Hyperglycemia affects inner retinal cells concurrently with blood-retinal barrier breakdown.
• Glial and neuronal dysfunction likely contribute to early visual deficits in diabetes.
• Early molecular and functional changes provide insights into the pathogenesis of diabetic vision impairment.