Alternative to Embryonic Stem Cells
"Master Cell" Found in Adult Bone Marrow

By Dave Andrusko

Thanks to research coming out of the University of Minnesota's Stem Cell Institute, what had seemed to be a logjam in the debate over both cloning and embryonic stem cell research that requires the destruction of human embryos may have been broken.

Dr. Catherine M. Verfaillie and her colleagues have discovered a type of adult stem cell found in bone marrow that holds out the possibility of growing into any kind of tissue in the body.

The work of Dr. Verfaillie and her colleagues is part of a broader pattern of recent discoveries which challenge the conventional wisdom - - that because stem cells found in human embryos are "unspecialized," they have a monopoly on the ability to become any tissue type found in the human body.

Dubbed "multipotent adult progenitor cells" (MAPCs), the adult stem cells isolated by Dr. Verfaillie's team appear to offer the best of all possible worlds. They seem to possess all the advantages attributed to embryonic cells but avoid the two major drawbacks researchers have encountered with embryonic stem cells: (1) Coming from the patient's own body, the immune system would not attack the tissue as foreign invaders; and (2) the MPACs don't turn cancerous!

As reported first in the November 1, 2001, edition of the journal Blood and then amplified in a piece that appeared January 26 in the journal New Scientist, Verfaillie et al. have shown that MAPCs can be coaxed into turning into muscle, bone, liver, cartilage, and a variety of types of neurons and brain cells. In addition, at least in the lab, these cells went about their business without showing any signs of slowing down. (According to the Boston Globe, "MAPCs express an enzyme called telomerase that keeps cells from aging.")

"The work is very exciting," said Ihor Lemischka of Princeton University. Irving Weissman of Stanford University said, "It's very dramatic the kinds of observations Verfaillie is reporting. The findings, if reproducible, are remarkable."

Even Rudolph Jaenisch of MIT, a vocal proponent of research that requires the destruction of human embryos to obtain their stem cells, admitted to the New York Times, "I haven't seen the data, but if they did it, that's pretty good."

An intriguing technical question is what exactly MAPCs are. For instance, are they "rare cells present in the bone marrow that can be fished out through a series of enriching steps," as the British Broadcasting Company described it--"a small population of embryonic stem cells [that linger] on in the adult, morphing into the various types of adult stem cell as needed," in the words of the New York Times?

Or had Dr. Verfaillie "somehow reprogramed the cells back to a semi-embryonic state," as the Times speculated?

In fact, the news about the capacities of adult stem cells is not new. Verfaillie's work is just the latest evidence that adult stem cells are much friskier than first advertised.

Initially, the argument was that only human embryos possessed stem cells that were sufficiently "versatile" or "malleable" or " plastic" to potentially be capable of becoming any tissue in the human body. That was a powerful weapon in the arsenal of those who wanted federal funding (and the respectability that comes from tapping into the federal spigot) to underwrite research that required the destruction of human embryos.

However, more and more research of late has shown that adult stem cells possess similar properties. Those wedded to procuring stem cells that require the destruction of human embryos grudgingly concede that adult stem cells "had their place," but insist that the real action is in embryonic stem cells.

But as a public relations statement describing Verfaillie's work sent out by the University of Minnesota stated, the team had found an adult stem cell with characteristics "much like embryonic stem cells."

Beyond the potential benefit to people with various diseases--everything from Parkinson's and Alzheimer's through degenerative diseases such as osteoporosis to single gene disorders such as hemophilia--this breakthrough is hugely important for another reason. As the Associated Press discreetly put it, "[U]sing embryonic stem cells is controversial, because embryos must be destroyed to harvest them."

As the New Scientist article explains, the Stem Cell Institute's results are not unique. Two other labs say they have made similar cells in mice "and one biotech company, MorophoGen Pharmaceuticals of San Diego, says it has found them in skin and muscle as well as human bone marrow."

The difference (the New Scientist writes) is Verfaillie "appears" to be the first to carry out the kind of experiments that back up a claim that these adult stem cells are as "versatile" as embryonic stem cells.

According to the New Scientist, "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."

With a historic debate over cloning about to begin in the Senate, Verfaillie's discoveries also undercut the primary advantage that proponents of cloning attribute to stem cells that are extracted from cloned embryos.

Proponents maintain that stem cells taken from an embryonic human being and used in another human being would trigger an attack by the recipient's immune system. But, they tell us, if an individual creates his/her own clone, supposedly by definition, an attack on "foreign" tissue is impossible. Proponents place great weight on what they call the "compatibility" argument.

But a Wired News story quite accurately summarized the potential bombshell: "If Verfaillie's research were reproducible, it would eliminate any need to use embryos, as well as the need to clone embryos. Stem cells could be taken from one's own bone marrow, eliminating the potential for rejection."

Proponents agree. According to Wired News, the director of the Reproductive Cloning Network e-mailed a fellow cloning advocate this message:

"All I could think about while reading this story is that if it were true, we would lose our greatest arguing point," wrote Randolfe Wicker. "I have always believed that the compatibility argument was our 'ace in the hole' that they could never really defeat."