CONTROL OF CELL DIVISION IN THE OCULAR LENS

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An understanding of age-related changes in the lens epithelium is important since one in ten new cases of blindness in the United States is caused by senile cataract. The long-term objective of this work is to identify functional changes in the epithelia which precede and accompany cataract formation and aging. This information should further clarify the role of epithelial cells in the maintenance of lens transparency. The long-term goals are to determine: 1) the factors that regulate mitosis in lens epithelia in vivo and in vitro, 2) the mechanism by which lens cells detoxify H2O2, and 3) if the response to growth factors and ability to detoxify H2O2 changes with age. Specific aims are to determine the influence of hypophysectomy, thyroidectomy and under-nutrition on mitosis in the ocular lens. Whole-mounts of the epithelium will be analyzed and the number of mitotic figures and DNA synthesizing cells quantitated. Levels of IGF, T3, and T4 will be measured via radioimmunoassay and the mitogenicity of serum from treated animals will be determined on cultured lens cells. The requirements for long-term growth of rabbit and human lens cells in serum-free medium will be investigated. The response of lens cells to polypeptide growth factors and to factors that enhance the mitogenicity of these peptides will be determined. The number of binding sites and apparent dissociation constant of iodinated insulin on cells from young and old rabbits will be quantitated. Immunological techniques and molecular probes will be used to demonstrate the retention of lens-specific function in cultured cells. The mechanism by which lens epithelia from young and old rabbits detoxifies H2O2 will be determined. Emphasis will be placed on the role of the GSH redox cycle and on enzymes, e.g. GSH reductase, GSH peroxidase, and superoxide dismutase, that may be impaired with age. Lines will be established from mice programmed to develop cataracts and from age-matched non-cataractous controls in an effort to determine changes in the epithelium that may typify precataractous and cataractous conditions. The H2O2 detoxifying ability of lens cells from 6-month and 1-year-old mice will be determined. TEM techniques will be used to localize catalase and peroxidase in normal and H2O2-treated lens epithelia.