Cellular senescence- is it aging? was Defining...

Andrew K. Groves grovesa at starbase1.caltech.edu
Sun Apr 2 17:14:56 EST 1995

In article <-EwfvAeABh107h at chambers.ak.planet.co.nz>,
steve at chambers.ak.planet.co.nz (Steve Chambers) wrote:

> There's a tendency for those of us who've spent most of our studies
> in cellular and molecular biology to think that the term senescence 
> (and by implication aging) only applies to cells.  It doesn't - and
> for most of the community the terms apply principally to whole
> organisms.

I agree. But the reason why much work has been done on cells is that they
represent a relatively simple way of examining the control of cell

> The processes that dictate the "lifespan" of a cell or clone are but 
> a small subset of those that should be examined when studying aging.
> Genetic control is plainly a major factor in cellular senescence but 
> cellular senescence probably doesn't "explain why people die."  There's 
> a hackneyed quote in gerontology: "Nobody dies of old skin."
> You have to ask yourself a question: If current definitions of aging
> (including one that relies upon cellular senescence) don't "explain why 
> people die" then how useful are they?

I would suggest that one reason why we don't understand why people die is
that we don't understand the mechanisms of even simple systems such as
fibroblast senescence.  You can define a phenomenon, but that is worlds
away from suggesting that you understand it. 

Another reason why simple culture models of cell growth are so popular is
that whilst "Nobody dies of old skin", a lot of people die of cancer, and
studies on cell division, senescence, transformation and death are a way
of getting at the molecular mechanisms of such processes.

I'm not suggesting for a moment that other ways of thinking about ageing
are invalid. Quite the opposite. But part of the problem with the
discussion over the past few days is that people from different
backgrounds have been arguing about the meaning of concepts such as
immortality and senescence. Explaining one's own perspective may go some
way to clarifying the discussion.

Andy Groves
Division of Biology, 216-76
California Institute of Technology

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