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K.J. Al–Ghoul, T.A. Mohammed; ABERRANT LENS FIBER MIGRATION IN ROYAL COLLEGE OF SURGEONS RATS DURING POSTERIOR SUBCAPSULAR CATARACT FORMATION . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2660.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Structural studies of posterior subcapsular cataract (PSC) development in Royal College of Surgeons (RCS) rats suggest that both migration and detachment of elongating basal fiber ends were disrupted, resulting in a PSC. Therefore the goal of this study was to assess changes in basal fiber ends during PSC development. Methods: Juvenile (4–6 week old) RCS rat lenses were enucleated, photographed under a stereo dissecting microscope and fixed. Lenses were mounted to obtain posterior polar sections and sectioned with a vibrating knife microtome. F–actin was localized with phalloidin–FITC and cadherins were localized by immuno–fluorescent labeling with pan–cadherin antibody. Specimens were visualized on a laser scanning confocal microscope. Results: At 4 weeks old freshly dissected lenses did not have discernable PSC plaques, but instead were characterized by abnormal posterior suture sub–branches. F–actin labeling revealed that basal fiber ends were disorganized. However, as in normal lenses, actin fluorescence was enhanced at sutures and was localized mainly at the periphery of the basal membrane complex (BMC). At 5 weeks old, lenses had perceptible polar opacities that were always located within the region described by the posterior suture branches. Further, the disorganization of migrating basal ends was more pronounced. Inspection of individual profiles within the forming PSC revealed that F–actin was rearranged into bright foci around the periphery of BMC profiles. In contrast, BMC profiles located outside the PSC plaque displayed normal actin organization. At 6 weeks old all RCS rat lenses displayed prominent PSC plaques upon dissection from the eye. Within the plaques fiber ends near the posterior pole and located where suture branches should have formed, displayed extremely large, irregular profiles. Consistent with lenses from 5–week–old animals, BMC profiles had bright foci of F–actin fluorescence. As expected, cadherin labeling within the BMC was co localized with F–actin. At all ages examined, cadherin distribution was consistent with results from normal rat lenses, i.e. cadherin labeling was significantly reduced directly adjacent to and at the suture branches. Conclusions: The data indicates that migration patterns are disrupted, leading to sub–branch formation and fiber end disorganization. Subsequently, F–actin is rearranged in the BMC of elongating fibers. This molecular organization is unlike that seen in normal migrating fiber ends and may indicate that fibers have ceased moving toward their sutural destinations.
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