BOSTON, Massachusetts, JAN. 24, 2002 (Zenit.org).- Researchers have found a stem cell in adults that they say can turn into every single tissue in the body. It might turn out to be the most important cell ever discovered, reports New Scientist magazine.
Until now, only stem cells from early embryos were believed to have such properties. If the finding is confirmed, it will mean cells from someone´s 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 so-called therapeutic cloning — an ethically questionable procedure that clones people to get matching stem cells from the resulting embryos. Nor would someone 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 fuel the debate about whether embryonic stem cell research is justified at all. Last week U.S. President George W. Bush appointed a bioethics advisory panel to counsel him on stem-cell research, among others topics.
«The work is very exciting,» says Ihor Lemischka of Princeton University, referring to the adult stem cell research. «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. Though the team has so far published little, a patent application shows the team has carried out extensive experiments, New Scientist reports.
These experiments confirm that the cells — called 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, California, 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% 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 aging, 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. 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 crucial experiment in proving that MAPCs are truly versatile.
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 does not prove that a stem cell really has become a working neuron.
