The waste-product theory of aging: cell division rate as a function of waste volume

The rate of cell division is calculated as a function of waste product volume in U-787CG human diploid glial cells grown in vitro. The calculation is based on two earlier mathematical models. One is a compartmental analysis in which cell division rate is obtained from data on the fraction of cells which become sterile as the passage level increases. A second model is used to calculate the amount of waste per cell from the observed rate of waste accumulation in a non-dividing population and from the division rate calculated with the use of the first model. Results from the two models are correlated to obtain the desired function relating cell division rate to waste volume. If cellular aging is taken to mean loss of the ability of cells to divide, and if, as in the waste-product theory, this loss is attributed to waste accumulation, the calculated results show that aging is evident at waste levels well below those at which non-dividing populations can survive. Thus the process of cell division may be much more sensitive to waste accumulation than other cellular processes needed for the maintenance of life.