Bone marrow stem cell might turn out to be the most important cell ever discovered

New Scientist Reports January 23, 2002

A stem cell has been found in adults that can turn into every single tissue in the body. It might turn out to be the most important cell ever discovered.

According to a January 23rd breaking story on the New Scientist website (http://www.newscientist.com) the stem cells found in adult bone marrow have passed every test proving that:

• It can form every single tissue in the body
• It can be grown in culture indefinitely, with no signs of aging
• It can be isolated from humans
• It does not form cancerous masses when injected into adults

If this research is confirmed, it offers extraordinary promise both to researchers pursuing cures and to patients in need of medical treatments.  It offers a way to pursue needed research while eliminating any justification for ethically unjustifiable destructive human embryo research by making embryonic stem cell research and “therapeutic” cloning obsolete.

Until now, only stem cells from early embryos were thought to have such properties. 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 does not 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.”

Remarkable findings

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 do not carry certain surface markers, or do not 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.

Indefinite growth

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.

Fundamental questions

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 does not 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.

Comments from Scientists & Physicians

“Cells taken ethically from adults with no loss of life have already shown tremendous potential and proven benefits. This discovery should remove any last vestiges of doubt in the lifesaving potential of adult stem cells. As many had predicted, it now appears that adult stem cells are the avenues to providing real cures for real people,” observed Christian Medical Association Executive Director David Stevens, MD.  “If the remarkable results of this study prove consistent with early published reports, then no reasonable person could justify violating ethical barriers to clone and harvest human embryos for their cells.”

Dr. Stevens added, “Given this breakthrough news and the consistent performance of adult stem cells, if you were investing in the stock of companies pursuing therapies from adult stem cells or from cloned human embryonic stem cells, where would you put your money?”

Center for Bioethics and Human Dignity President John Kilner said, “This comes as great news during this sanctity of life week-both for those who mourn the huge loss of unborn human life in recent decades as well as those who have challenging medical conditions.  If confirmed, we no longer need to wait until human cloning becomes reliable-something that may never happen-to pursue therapies and treatments. The genetically appropriate, flexible stem cells patients need are right there in their own bodies.”

Center Senior Fellow C. Ben Mitchell, Ph.D: “This announcement is a palpable reminder that stem cell research is still in its infancy.  We should only pursue research that is scrupulously ethical. This discovery will allay everyone’s concerns about embryo-destructive research. There will be no possible justification for destroying human embryos for their cells.”

Sources:
The Pro-Life Infonet infonet@prolifeinfo.org
Center for Bioethics and Human Dignity; January 23, 2002
New Scientist (Sylvia Pagan)