Public release date: 23-Jan-2002

Contact: Claire Bowles
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New Scientist

Is this the cell that could revolutionise medicine?

IT MIGHT turn out to be the most important cell ever discovered.
It's a stem cell found in adults that can turn into every single
tissue in the body.

Until now, only stem cells from early embryos were thought
to be able to do this. If the finding is confirmed, it will mean cells
from your own body could one day be turned into all sorts
of perfectly matched replacement tissues and even organs.

If so, there would be no need to resort to therapeutic
cloning-cloning people to get matching stem cells from
the resulting embryos. Nor would you have to genetically
engineer embryonic stem cells (ESCs) to create a
"one cell fits all" line that doesn't trigger immune rejection.
The discovery of such versatile adult stem cells will also
fan the debate about whether embryonic stem cell research
is justified.

"The work is very exciting," says Ihor Lemischka of Princeton
University. "They can differentiate into pretty much everything
that an embryonic stem cell can differentiate into."

The cells were found in the bone marrow of adults by
Catherine Verfaillie at the University of Minnesota.
Extraordinary claims require extraordinary proof,
and though the team has so far published little,
a patent application seen by New Scientist shows
the team has carried out extensive experiments.

These confirm that the cells-dubbed multipotent
adult progenitor cells, or MAPCs-have the same
potential as ESCs. "It's very dramatic, the kinds
of observations [Verfaillie] is reporting," says
Irving Weissman of Stanford University. "The findings,
if reproducible, are remarkable."

At least two other labs claim to have found similar cells
in mice, and one biotech company, MorphoGen
Pharmaceuticals of San Diego, says it has found them
in skin and muscle as well as human bone marrow.
But Verfaillie's team appears to be the first to carry out
the key experiments needed to back up the claim
that these adult stem cells are as versatile as ESCs.

Verfaillie extracted the MAPCs from the bone marrow
of mice, rats and humans in a series of stages.

Cells that don't carry certain surface markers,
or don't grow under certain conditions, are gradually
eliminated, leaving a population rich in MAPCs.
Verfaillie says her lab has reliably isolated the cells
from about 70 per cent of the 100 or so human volunteers
who donated marrow samples.

The cells seem to grow indefinitely in culture, like ESCs.
Some cell lines have been growing for almost two years
and have kept their characteristics, with no signs
of ageing, she says. Given the right conditions,
MAPCs can turn into a myriad of tissue types:
muscle, cartilage, bone, liver and different types
of neurons and brain cells. Crucially, using a technique
called retroviral marking, Verfaillie has shown that
the descendants of a single cell can turn into all
these different cell types-a key experiment in proving
that MAPCs are truly versatile.

Also, Verfaillie's group has done the tests that are
 perhaps the gold standard in assessing a cell's
plasticity. She placed single MAPCs from humans
and mice into very early mouse embryos, when they
are just a ball of cells. Analyses of mice born after
the experiment reveal that a single MAPC can
contribute to all the body's tissues.

MAPCs have many of the properties of ESCs,
but they are not identical. Unlike ESCs, for example,
they do not seem to form cancerous masses if you
inject them into adults. This would obviously be
highly desirable if confirmed.

"The data looks very good, it's very hard to find
any flaws," says Lemischka. But it still has to be
independently confirmed by other groups, he adds.

Meanwhile, there are some fundamental questions
that must be answered, experts say. One is whether
MAPCs really form functioning cells. Stem cells that
differentiate may express markers characteristic
of many different cell types, says Freda Miller
of McGill University. But simply detecting markers
for, say, neural tissue doesn't prove that a stem cell
really has become a working neuron.

Verfaillie's findings also raise questions about the
nature of stem cells. Her team thinks that MAPCs
are rare cells present in the bone marrow that can
be fished out through a series of enriching steps.
But others think the selection process actually
creates the MAPCs. "I don't think there is 'a cell'
that is lurking there that can do this. I think that
Catherine has found a way to produce a cell that
can behave this way," says Neil Theise of
New York University Medical School.

###

Author: Sylvia Pagan Westphal, Boston

New Scientist issue: 26th January 2002

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SOURCE: EurekAlert
http://www.eurekalert.org/pub_releases/2002-01/ns-itt012302.php

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