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GB Jaissle, CA May, J Reinhard, E Zrenner, E Luetjen-Drecoll, MW Seeliger; Late Retinal and RPE-Changes in Rhodopsin Knockout Mice . Invest. Ophthalmol. Vis. Sci. 2002;43(13):721.
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Purpose:The rhodopsin knockout (Rho-/-) mouse, a model for autosomal-recessive retinitis pigmentosa, does not build rod outer segments and develops a progressive cone degeneration with no photoreceptor nuclei left in the outer nuclear layer at 3-4 months of age. In this study, we investigated the pattern and time course of retinal and RPE-changes in subsequent, more advanced degenerative stages. Methods:Using a Scanning-Laser-Ophthalmoscope (SLO), in vivo imaging of the fundus morphology was performed in Rho-/- mice aged 4 to 8 months. The confocal SLO -by changing the focus of the laser beam- allowed to determine the retinal layer where macroscopic fundus changes were located. These investigations were paralleled by light and electron microscopy. Electroretinography was performed with a Ganzfeld setup following ISCEV standards. Results:The ERG in the Rho-/- mice showed the typical drop of function, until at 3-4 months of age there was a complete lack of responses, paired with a complete loss of cone outer segments. Histologically, other retinal layers including the RPE and the choroid showed no abnormalities up to this age. At about 4 months, SLO imaging of the fundus revealed a fine hexagonal pattern at the RPE level. In histology, a flattening of RPE cells was found, which may explain the observed pattern by an increased light transmission due to a loss of pigment. With increasing age, hyperfluorescent lesions became visible, ultimately leading to large confluent areas of RPE loss. Staining for gap junctions was altered right from the onset of RPE changes, whereas tight junctions appeared unaffected for a long period of time. Conclusion:Our data show late macroscopic and microscopic retinal and RPE-changes subsequent to functional and photoreceptor cell loss in Rho-/- mice. These mice could thus serve as a model for the process of degeneration in AMD and hereditary retinal diseases.
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