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Kristin J. Al-Ghoul, Jessica R. Zahn; Apical Fiber End Migration And Morphology In Lenses From Streptozotocin-Induced Diabetic Rats. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3040.
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© ARVO (1962-2015); The Authors (2016-present)
Although the initial structural compromise in diabetic lenses is typically a posterior subcapsular cataract, anterior and cortical cataracts usually manifest subsequently. This investigation was conducted to evaluate the early gross anatomical changes on the anterior surface of the lens as a result of diabetes, specifically abnormal suture sub-branch formation and opacification. We also assessed whether migration paths of elongating anterior fiber ends were disrupted after diabetic onset and if the actin cytoskeleton at the epithelial-fiber interface was altered.
Male Wistar rats (125-150g; n=20) were randomized into 5 groups, four of which received a single 75 mg/kg intravenous dose of streptozotocin (STZ); the remaining group served as a naïve control. Animals were euthanized at 1, 2, 3 and 4 weeks post-injection, blood glucose levels recorded and lenses removed and photographed to evaluate changes in anterior suture patterns and lens transparency. Subsequently, F-actin distribution in apical elongating fiber ends was examined by cytochemistry and laser scanning confocal microscopy.
All naïve control lenses had normal blood glucose levels (80-120 mg/dL), exhibited the upright "Y" 3-branched suture pattern anteriorly and were fully transparent. Blood glucose levels in experimental animals were measured 48 hours after STZ treatment and at sacrifice and were consistent with a diabetic state (>200 mg/dL). Examination of lenses from experimental groups (1-4 weeks post-STZ treatment) demonstrated a progressively distorted anterior "Y" suture pattern wherein sub-branches were noted and opacities could be visualized. Sutural changes were typically observed beginning 2-3 weeks post-STZ treatment, whereas anterior opacities were not apparent until nearly 4 weeks after diabetic induction. Labeling for F-actin revealed that anterior fiber segments had distorted morphology consistent with enlargement of the extracellular space and mild fiber disruption by 3 weeks after STZ treatment.
The formation of abnormal suture sub-branches indicates that migration patterns of apical fiber ends were altered in lenses of diabetic rats. Our prior studies of basal fiber ends in the STZ-induced diabetic rat model demonstrated that migrational and structural alterations usually manifest within 1 week after diabetic induction. In comparison, the data from the present study indicates that apical ends of elongating fibers are not adversely affected until 2-3 weeks post-injection. This suggests that the anterior fiber ends are not as susceptible to hyperglycemia and/or metabolic alterations during diabetes as the posterior fiber ends.
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