Cell cultures used in biology and medical research
may not act as a faithful mimic of real tissue,
according to research published in Genome Biology.
The study finds that laboratory-grown cells
experience altered cell states within three days as
they adapt to their new environment. Studies of
human disease, including cancer, rely on the use of
cell cultures that have often been grown for decades.
The findings could therefore affect the
interpretation of past studies and provide important
clues for improving cell cultures in the future.
Scientists typically use models to study the basics
of human biology. The most common model system is
cultured cells, which are taken from the body and
coaxed into growing on a plastic dish in the
laboratory.
Though a linchpin of modern research, it has long
been known that the cells in the laboratory can
behave differently from those in the body, affecting
the understanding of diseases and the development of
drugs.
Researchers from the MRC Human Genetics Unit at the
University of Edinburgh, UK, and Linköping
University, Sweden, have revealed just how quickly
cells change their identity when grown in the
laboratory. They found that cells adapt to cell
culture systems within one week of growth in a
laboratory dish. The analysis provides new insight
into how faithfully these cells mimic real tissue,
and how models of human disease can still be
improved.
Study author Richard Meehan from the MRC Human
Genetics Unit at the University of Edinburgh, UK,
said: “We were astonished by the speed and spread of
the changes. Many cultured cells used in research
have been grown for decades and as a result are
likely to have very different properties from the
cells they are supposed to model. Our findings
suggest that we have to be circumspect about the
interpretation of some previous experiments, and our
data reinforces a growing realisation that cell line
models of human diseases, particularly cancer, can
be poor surrogates for many aspects of in-vivo
biology.”
The researchers compared the DNA of mouse cells,
taken from male and female embryos, with cells that
were cultured in plastic dishes. They found a number
of indicators that the cultured cells underwent an
altered cell state as they became adapted to the
cell culture environment, including a decrease in
gender differences between male and female cultured
cells.
The mouse cells in culture experienced a rapid
reprogramming of their ‘epigenomes’ – a layer of
chemical modifications that mark the genome to
control how genes are expressed. This was indicated
by a near-complete loss of one epigenetic mark,
5-hydroxymethylcytosine (5hmC), within three days
over the whole genome.
They also found similar results in an unrelated
tissue. Using mouse CD4+ T-cells, which have a role
in the immune system, they found an almost five-fold
reduction in 5hmC levels after three days in
culture.
In addition, the researchers saw that there were
widespread changes in gene expression for cells in
culture, affecting over 7,200 genes. Some of these
genes were linked to cell adhesion, possibly
reflecting adaptation to growth on a two-dimensional
plastic surface, and others were involved in a
variety of epigenetic processes.
The researchers went on to show that some of these
changes could be prevented by adding Vitamin C to
the culture medium. This suggests that by improving
culturing techniques, researchers may be able to
more accurately match cells grown on a dish to cells
that are taken directly from tissues. These
improvements should allow researchers to have more
confidence that what they observe in the laboratory
accurately reflects what is happening in the body.
This work was supported by the MRC, IMI-MARCAR,
BBSRC, Linköping University strategic research
funding and the Åke Wibergs fund.
For more information
‘Rapid
reprogramming of epigenetic and transcriptional
profiles in mammalian culture systems’ by Colm E
Nestor, Raffaele Ottaviano, Diana Reinhardt, Hazel A
Cruickshanks, Heidi K Mjoseng, Rhoanne C McPherson,
Antonio Lentini, John P Thomson, Donncha S Dunican,
Sari Pennings, Stephen M Anderton, Mikael Benson and
Richard R Meehan, is published in Genome Biology.
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