ADVANCED ELECTRON MICROSCOPIC STUDIES OF CRYSTALLINE LEN

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The long term objective of our research program has been, and continues to be, the elucidation of normal human lens morphology as it relates to lens function, and how age-related and/or pathological changes in the lens are manifested as compromised lens optics leading ultimately to specific cataracts. Our preliminary studies of posterior subcapsular cataracts (PSC) from experimental animal models for Retinitis Pigmentosa (RP) and for the effects of Hydroxymethlyglutaryl (HMG)-CoA reductase inhibitors on PSC formation, suggest that the PSC opacities of these lenses result from a progressive compromise in posterior sutural anatomy rather than from a proliferation of dysplastic "Wedl" cell migrating to the posterior pole. In our previous studies we have developed, and successfully applied, correlative techniques that allow for the accurate quantification of progressive, negative changes in lens sutural anatomy, prior to and resulting in opacification. Thus, the studies proposed in the five years of this grant are designed to accomplish the following specific aims: First, to determine if a comparable, progressive, and quantifiable, negative relationship exists between lens structure (particularly sutural anatomy) and function (spherical aberration, i.e. focal length variability) before, during and after PSC formation, as a consequence of different etiologies including: 1) long term therapeutic treatment with HMG-CoA reductase inhibitors; 2) RP; 3) therapeutic treatment with steroids; 4) diabetes; and 5) AIDS. Second, to further elucidate the ultrastructure of primate lens cells (central, pre-germinative, germinative, and transitional zone epithelial cells, as well as elongating, mature and aged fibers) as a function of development, growth, age and pathology. As regards the first set of specific aims: The optical quality (focal length variability; i.e spherical aberration) of the experimental animal lenses will be assessed by analysis with a low power helium-neon laser scan unit of our own design with particular reference to lens sutures. The laser scanned lenses will then be precisely dissected by a method that we have developed permitting the retrieval of complete intact suture patterns at progressive depths from the anterior and posterior poles for structural analysis by scanning electron microscopy (SEM). In this manner, lens sutural anatomy as a function of development, growth, age and cataractogenesis can be accurately characterized. The in situ 3D sutural anatomy of all lenses dissected as above, will then be ascertained by 3D-CAD reconstructional analysis to determine if structural correlates found to adversely effect lens function by laser scan analysis, correspond to the PSC opacities. Comparable groups of experimental animal lenses will also be examined by biomicroscopic slit-lamp analysis to determine if compromised lens growth manifested as abnormal sutures, correlate with the production of zones of discontinuity that are not normally characteristic of these non- primate lenses. These results will be compared to simulated slit-lamp images taken from the 3D-CAD reconstructions of laser scanned lenses and with slit-lamp images taken of human PSCs resulting from the above described etiologies. With a greater understanding of the inter-relationship between lens structure/function afforded by techniques that we have developed and applied in our laboratories, then the results of studies described in this proposal could lead to the earlier detection and improved clinical management of human PSCs as a consequence of different etiologies.