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The Effect of Growth-Promoting Agents on Replication and Cell Cycle Withdrawal in Cultures of Epidermal Keratinocytes

Franklin Greif, Harry S. Soroff, R. Woodrow Setzer and Lorne B. Taichman
In Vitro Cellular & Developmental Biology
Vol. 24, No. 10 (Oct., 1988), pp. 985-989
Stable URL: http://www.jstor.org/stable/4296333
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Effect of Growth-Promoting Agents on Replication and Cell Cycle Withdrawal in Cultures of Epidermal Keratinocytes
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Abstract

Epidermal keratinocytes grow in culture to form a stratified squamous epithelium. These cultures contain a replicating as well as a terminally differentiating population and undergo surface desquamation. Epidermal growth factor (EGF) and cholera toxin are usually employed as growth-promoting agents because they reduce the population doubling time; that is, the period required to increase the total cell number twofold. There are three ways in which this reduction in population doubling time could be achieved: (a) the time for one cell cycle or the cell cycle length may be shortened; (b) the number of cells that withdraw from the cell cycle and terminally differentiate may be reduced; or (c) the number of cells that desquamate into the medium over a set period of time may be reduced. We have explored these possibilities in growing cultures of epidermal keratinocytes using a newly developed double-label assay. This assay gives a measure of both cell length and cell cycle withdrawal. Results show that the growth enhancement induced by EGF and cholera toxin can be attributed primarily to a reduction in cell cycle withdrawal and, to a lesser degree, to a reduction in cell cycle length. EGF and cholera toxin have no significant effect on the rate of desquamation. A linear correlation was noted between cell cycle lengths and withdrawal, suggesting an interconnection between the rate of cell renewal and the likelihood of undergoing terminal differentiation.

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