Transglutaminase, Donor Age, and in Vitro Cellular Senescence
Human diploid fibroblast-like cells (HDF) exhibit a limited lifespan when maintained in culture, a property which has led to their use as a model system for the study of cellular senescence1. The lifespan is characteristic for each cell strain and is inversely related to the age of the donor from which the cells were obtained2. Upon continuous subcultivation, HDF gradually lose their ability to traverse the cell cycle and divide. This loss of proliferative potential results in a viable, post-mitotic population which is still metabolically active3. Although the mechanisms responsible for the loss of proliferative potential have not been defined, they appear to be regulated by a timing system that is based on the number of previous cellular divisions4. This biological clock has been postulated to be the result of a series of programmed and/or stochastic events which lead to alterations in genetic expression3. A primary focus for such alterations would appear to involve one or more of the many biochemical processes which are necessary for cells to proceed through Gl and enter the S phase of the division cycle5.
KeywordsHuman Diploid Fibroblast Human Diploid Cell Isopeptide Bond Cornified Envelope Transglutaminase Activity
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