decreasing proliferative capacity theory

Iuval clejan clejan at mindspring.com
Fri Feb 9 07:25:34 EST 2001


Does anyone know any arguments against the theory stating that the main
cause of aging is the decreasing proliferative capacity of most cells as
they differentiate away from stem cells. I think this theory is a
generalized telomere shortening one, saying that telomere shortening is
not necessarily the cause of decreased proliferative capacity, but is
correlated with this unidirectional differentiation, and the decrease in
stem cells (?) may be due to changes in e.g. extracelllular matrix. (Is
it true that it is not the case that stem cells have a decreased
proliferative capacity with time, but that there are less stem cells and
more differentiated cells, and the more differentiated a cell is, the
less its proliferative capacity?)

I suppose this is coupled with the idea that there is a constant
fraction of damage that escapes repair, and that while there is a good
supply of stem cells (and perhaps descendants which still have some
proliferative capacity), cells escaping damage repair are replaced, but
when proliferative cells run out, damage accumulates.

The only thing I can think of is that by birth there are no cardiac stem
cells left, and there are very few in the neuron population, but maybe
these cell types are pretty efficient at damage repair and other organs
are going to accumulate more damage first.

-Iuval







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