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S. Lee, W. Ma, A. Aleshin, L. Chen, V. D. D'Agati, A. Schmidt, G. R. Barile; Retinal Capillary Basement Membrane Thickness in Diabetic Swine. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4965.
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To determine the thickness of retinal capillary basement membranes (BMs) in the eyes of a swine model of type 1 diabetes.
Type 1 diabetes was induced in 20kg Yorkshire pigs by injecting streptozotocin (50 mg/kg), and diabetic dyslipidemia was enhanced with high fat diet containing 1.2% cholesterol and 15% lard (Harlan Teklad). Pigs were sacrificed at 26 weeks of diabetes. The retina sections within 3 disc diameters of the optic disc were fixed (half-strength Karnovsky's solution). Transmission electron microscopy was performed to measure capillary BM thickness, and capillaries with circumference less than 25.12 µm (8µm diameter) were included for study. Retinal capillary BMs with clear margins were outlined in Photoshop (Adobe 7.0) and the area of BM measured. The width of basement membrane was calculated by dividing the area by the length of BM, which itself was measured in ImageJ software (NIH).
Type 1 diabetic pigs maintained hyperglycemia (fasting glucose levels: 284.4 ± 100.3 mg/dL). Plasma cholesterol levels were also elevated in diabetic pigs (>400 mg/dL). On gross examination of diabetic eyes, there were no obvious signs of retinopathy. Transmission electron microscopic analysis demonstrated thicker retinal capillary BMs in the setting of severe diabetes, with these vessels having significantly mean BM width (121.6 ± 21.8 nm) compared to control retinal vessels (92.6 ± 15.0 nm, p<0.0001).
The retinal capillaries of type 1 diabetic pigs can develop basement membrane thickening. The swine model of diabetic complications may facilitate further study of mechanisms contributing to diabetic retinopathy.
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