Umasking large and persistent reductions in proliferation rate of aging cells |
| |
Authors: | Ming Chow Monica Kong Harry Rubin |
| |
Institution: | (1) Department of Molecular and Cell Biology and Virus Laboratory, University of California, 229 Stanley Hall, 94720-3206 Berkeley, California |
| |
Abstract: | Summary We have reported that nontransformed sublines of NIH 3T3 cells that are incubated under the growth constraint of confluence
for 10 d or longer exhibit heritable reductions of growth rate upon serial subculture at low density, which simulate the effects
of aging in vivo on cell growth. There is also a marked increase in the likelihood of neoplastic transformation. After switching to a new
batch of calf serum (CS), we found the reduced growth rate was no longer produced within the previously established timeframe.
However, substitution of fetal bovine serum (FBS) for CS during the period of recovery from confluence or the following tests
of growth rate resulted in profound inhibition of growth in cells serially subcultured from confluent cultures. In some cases,
fewer than one in a thousand cells from subcultures of confluent cultures formed colonies in FBS although they cloned at relatively
high efficiency in CS. The reduced growth in FBS was retained in the postconfluent subcultures after many generations of multiplication
at low density in CS. Generally, similar results with individual variations were obtained with three other batches of FBS.
The numbers of cells per 3-d colony initiated from subcultures of confluent cultures were lower than those of control cultures
that had never been confluent. Supplementation of FBS-containing medium with CS fully restored the growth of the postconfluent
subcultures to the rate in CS medium, indicating that there is a deficiency of growth factor(s) in FBS rather than the presence
of an inhibitor. The results show that prolonged incubation at confluence induces a populationwide heritable increase in requirement
for growth factor(s) in short supply in FBS. Because clonal studies have shown that the reduction in growth rate is irreversible
and varies in degree from clone to clone, we propose it arises from damage to DNA at any of many different genetic loci or
from chromosome aberrations. Such genetic damage is also consistent with the increased tendency for neoplastic transformation
in subcultures from the long-term confluent cultures. |
| |
Keywords: | senescence growth factors transformation genetic damage |
本文献已被 SpringerLink 等数据库收录! |
|