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Age vs. Cell Division Rate
Name: Carl S.
Status: Educator
Age: 30s
Location: N/A
Country: N/A
Date: June 2002
Question:
Do rates of cellular division for the same type of cell
change over the course of a human life. For example, do skin cells in
the epidermis divide more quickly in a fetus than in a teen, than in a 20
year old, etc.? If so, is it possible to mark the age (pre or post
natal) at which cells seem to be their most robust? And, if varying
rates do exist, can they be attributed to changes in nutrition delivery
or do they appear to be tied do some other factor? Would a cell culture
continue to divide at a steady rate ad infinitum given perpetual optimal
nutrition and environment?
Replies:
Dear Carl:
Cells from older individuals generally do proliferate at a slower rate than
those from younger individuals when grown in culture. The difference is not
usually very dramatic, however, perhaps half the rate of cells from a
newborn infant at most. This evidence would indicate that the phenomenon is
not dependent upon nutrition, since these cells would be grown under
identical conditions. But it is difficult to know how the growth rates of
these cells would compare in the organism itself rather than in culture,
since other exogenous factors could act to either accelerate or decelerate
proliferation differently depending upon age of the organism. Nonetheless,
aging does seem to reduce the intrinsic proliferative capacity of many cell
types. Although difficult to generalize, maximum proliferative capacity
would probably be observed in the cells from the youngest individuals, as
you suggest.
Our current knowledge from cells in culture indicates that unless they are
"transformed" or "immortalized", as occurs in cancer cells, they all have a
finite life span. The only qualification to this conclusion would be that
perhaps they are not growing under completely optimum conditions in these
cultures, e.g. in the presence of some yet-to-be discovered super-growth
factor. Along these lines, there is actually a great deal of current
interest in the effect of an endogenous enzyme known as telomerase, which
controls the length of the chromosomal termini, on cellular aging. In fact,
it's been shown that delaying the natural shortening of these terminal
sequences, known as telomeres, by activating telomerase can extend cellular
life span. This phenomenon is actually thought to play a role in cellular
transformation to a cancerous state, in some instances. An article by Dr.
Jerry Shay, one of the experts in this field from the University of Texas, is
available that reviews these concepts very nicely, if you're interested:
http://www.swmed.edu/home_pages/cellbio/shay-wright/publications/review.pdf
It does require Adobe Acrobat Reader to load, though, but it is freely
available if you need it. Thank you for the excellent questions,
Jeff Buzby, Ph.D.
Children's Hospital of Orange County
NEWTON AAS
Div. of Educational Programs
Argonne National Laboratory
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Update: June 2012
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