Hayflick limit for rapid dividing cells

Sydney Shall bafa1 at central.susx.ac.uk
Fri Oct 14 04:58:58 EST 1994


Sydney Shall (bafa1 at central.susx.ac.uk) wrote:
: Tsung-Jui Yeh (tjyeh at soda.CSUA.Berkeley.EDU) wrote:

: : I was wondering about the Hayflick limit for rapid dividing cells like 
: : ones that line the stomach and also cells of the cornea.  Do these cells 
: : have the same Hayflick limit as fibroblasts?  If so, why can these cells 
: : afford to divide so fast?

: : Thanks
: Cells from different tissues display different Hayflick limits.  This
: means that some cells like fibroblasts may go through about 50 to 70
: population doublings, in about 150 cell generations.  On the other hand,
: adult dermal fibroblasts, chondrocytes experience many fewer
: generations.  Lymphocytes seem in most growth media, to experience only
: about 23 population doublings.  So, at the moment we do not really know
: whether there is one fixed Hayflick limit; the evidence available so far
: would suggest that there are specific Hayflick limits for different
: tissues.  This clearly has important implications for the homeostasis of
: each individual tissue.
: Moreover, it is very well established that the same cell type from
: different animal species show a species-specific Hayflick limit; this is
: part of the evidence for the notion that the Hayflick limit is
: genetically controlled.

: -- 
: Sydney SHALL,
: Laboratory of Cell and Molecular Biology,
: Biology Building, University of Sussex, Brighton, East Sussex BN1 9QG, ENGLAND.
: Telephone: +44.273.67.83.03         FAX: +44.273.67.84.33


RESPONSE:

I think the major question to arise from this discussion is whether a
Hayflick limit exists in vivo, that is in intact bodies.  Regrettably,
there is very little published evidence on this question.  The only
evidence that I can adduce is (1) Werner's syndrome, where a very
evident premature ageing is correlated with a changed Hayflick limit in
vitro, and (2) secondly a paper by Rohme in which he convincingly shows
a correlation between both average and maximum lifespans of different
animals and the life-span of there cells in vitro (their Haflick limit
number).
Both of these items of evidence are correlations; so although they are
persuasive to me, I would say the question as to whether there is an in
vivo Hayflick limit is completely open and unresolved.

The second question raised abou whether the Hayflick limit has an
COMPONENT of culture conditions in it is different.  I think that the
question being asked is whether the hayflick limit is an artifact; this
means, is it TOTALLY due to the way we grow the cells.  There is no
doubt that the way we grow cells influences the value of the Hayflick
limit.  But the direct question is: can we grow cells in such a way that
there is NO Hayflick limit.  This question has been directly addressed
by one author, who has given the answer that for mice one can grow cells
in the absence of serum and then they are immortal.  But I understand
that the same author says that this does NOT work for human cells. 
Furthermore, I observe that so far there is no published confirmation of
this one report.  So, I think that this must be viewed with some
caution.  Again, I would say that culture conditions modulate the value
of the Hayflick limit, but the existence of such a limit is abiological
property of the cells.  The real issue in my view is whether this limit
is a biological property, at least in part, or SOLELY,a consequence of
the culture conditions.  If the latter, then one should not look for
genes which are important in this process.  If the former is true, then
one is probably justified in searching for genes which are relevant to
the phenomenon.

-- 
Sydney SHALL, Laboratory of Cell and Molecular Biology, Biology Building,
University of Sussex, Brighton, East Sussex BN1 9QG, ENGLAND.
Tel:+44.273.67.83.03 FAX:+44.273.67.84.33; E-Mail:Janet:S.Shall at uk.ac.sussex 
Elsewhere:S.Shall at sussex.ac.uk      EARN/BITNET:S.Shall%sussex at ukacrl




More information about the Ageing mailing list