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Kristin J Al-Ghoul, Dushyant A Sharma; Morphology and Organization of Anterior Fiber Ends in Lenses from Streptozotocin-Induced Diabetic Rats. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2507.
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© ARVO (1962-2015); The Authors (2016-present)
Anterior and cortical cataracts typically manifest subsequent to the development of a posterior subcapsular cataract in streptozotocin (STZ)-induced diabetic rats. Our prior studies revealed that abnormal anterior suture sub-branches formed in these lenses by 3 weeks post-induction. This investigation was conducted to evaluate the overall organization and ultrastructural changes in elongating fibers on the anterior surface of the lens during STZ-induced diabetes.
Male Wistar rats (125-150g; n=30) were randomized into 5 groups, four of which received a single 75 mg/kg intravenous dose of STZ; the remaining group served as naïve controls. Animals were euthanized at 1, 2, 3 and 4 weeks post-injection, blood glucose levels (BGL) recorded and lenses removed, photographed and fixed for structural evaluation via scanning electron microscopy (SEM).
All naïve control lenses had normal BGL (avg.=114 mg/dL), exhibited 3-branched “Y” suture patterns anteriorly and were fully transparent. At time of sacrifice, BGL in experimental animals was consistent with diabetes (avg.=360 mg/dL). SEM examination of control lenses showed that anterior fiber ends were irregularly ovoid with an ordered, tightly packed arrangement, and filopodia extended in the general direction of migration towards sutures. Examination of lenses from STZ-induced diabetics demonstrated progressive changes in overall organization and ultrastructure of anterior fiber ends. Specifically, by 2 weeks post-induction 50% of lenses had regions of elongated, swirled fiber ends and occasional zones of fiber disruption manifested as dilations of the extracellular space between fibers. By three weeks after diabetic induction, all lenses displayed regions of elongated, swirled fiber ends which frequently displayed long disorganized filopodia. Localized areas of fiber breakdown were common. Increasingly severe disruptions of fiber end arrangement and morphology were noted at 4 weeks post-induction.
The data indicates that elongating fibers on the anterior surface of the lens undergo a shift in their migration patterns which manifests 2-3 weeks after diabetic induction. Because the changes are delayed with respect to the posterior fiber ends, this suggests that the anterior fiber ends are not as susceptible to hyperglycemia and/or metabolic alterations during diabetes.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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