Normal human fibroblasts display a limited lifespan in
culture, which is due to a steadily decreasing fraction of
cells that are able to proliferate. Using antibodies that react
with antigens present in proliferating cells only, in an
indirect immunofluorescence assay, we have estimated the
fraction of proliferating cells in cultures of normal human
fibroblasts. Furthermore, we have estimated the rate of
decline in the fraction of proliferating cells during the
process of cellular ageing by application of the assay to
normal human fibroblasts throughout their lifespan in
culture. Werner’s Syndrome is an autosomal recessive
disease in which individuals display symptoms of ageing
prematurely. Werner’s Syndrome fibroblasts display a
reduced lifespan in culture compared with normal human
fibroblasts. Like normal human fibroblasts, the growth of
Werner’s Syndrome fibroblasts is characterised by a
decreasing fraction of cells reacting with the proliferationassociated
antibodies throughout their lifespan in culture.
However, the rate of loss of proliferating cells in Werner’s
Syndrome fibroblasts during the process of cellular ageing
is accelerated 5- to 6-fold compared with the rate determined
for normal human fibroblasts