Protocol Online logo  Cells stop to grow - (Jan/28/2013 )   I
have the problem that over the weekend my cells did not grow. We
started to use Mouse Embryonic Fibroblasts (MEF) and observed
last week they grow nice in DMEM + FCS. Now after only two
passages they stopped growing. They are not dead but won't
proliferate anymore. How to explain? Is there a medium other
than DMEM suitable for MEF? Usually I work with HEK and NIH3T3
cells which both like DMEM.  Thank you, cheers   What passage
are they? Have a google for Hayflick limit.   Hi Bob,  cells
were in passage 2, after splitting they are now in passage 5.
The Hayflick limit is interesting but should not be the problem
here. Some of the cells don't even have a fibroblast like
phenotype anymore but others do. Next steps I plan to do is
defreeze new aliquots and repeat the procedure. Maybe this
helps.   Yes, the Hayflick limit will be the problem you are
having.  We do not use our MEFs past passage 4 (5 at the most,
if they are a particularly good batch) but