The Wall Street Journal - Tuesday, April 13, 1999
Laura Johannes, Staff Reporter

But a humbler type of stem cell may prove much more useful to medical science. Unlike the embryonic cell, this type, called a "precursor" cell, has already had its fate broadly determined. For example, scientists have discovered a blood precursor cell that can become any type of blood cell --say, a white cell or red cell -- but never a skin or bone cell.

While precursor cells' morphing potential is narrower, many scientists believe that turning them into medical treatments will be much easier, because they are further along in their development. That opens up a whole world of potential injectable therapies that would harness the body's capacity to regenerate itself.

"If you're trying to travel from Boston to San Francisco, this would be the equivalent of starting in Des Moines instead of Boston," says Mitchell J. Weiss, a senior scientist at Ontogeny Inc., of Cambridge, Mass. Ontogeny is working with Biogen Inc. to activate precursor cells that it believes are in the brain in an effort to regenerate brain cells lost in Parkinson's disease.

Scientists used to think that such potential for cellular regeneration was present only in embryos -- that, for example, humans had made their lifetime supply of brain cells by age 17.

But that canon is steadily eroding. In the early 1990s, researchers isolated human blood stem cells from adults. And earlier this month, researchers at Osiris Therapeutics Inc. in Baltimore found a stem cell in adult bone marrow that is capable of becoming bone, cartilage or fat. Researchers also believe they may be close to identifying stem cells in the liver, brain and pancreas.

They're Everywhere

"I think we will find these stem cells in any organ that we look," says Harvard Medical School researcher Evan Y. Snyder, who has already isolated brain stem cells from a human fetus and believes it won't be long before someone finds them in adult humans. "I think that when nature develops a strategy for development and a strategy for self-repair, it doesn't make it up each time for every organ."

Some scientists remain skeptical that stem cells will be found in every organ. And hunting is a laborious process. Brain stem cells were found in animals a decade ago, but scientists are still working to find them in humans. But if and when they are found, precursor cells would circumvent the ethical and legal problems of working with embryonic stem cells taken from aborted fetuses.

Douglas A. Melton, chairman of the department of molecular and cell biology at Harvard University, has found promising results in mouse and frog stem cells but hasn't been able to obtain human embryonic cells to apply the work to humans.

The National Institutes of Health has said it will permit federally funded researchers to use stem cells as long as they don't actually handle aborted fetuses, but the cells won't be available until formal guidelines for their use have been published. Meanwhile, work with the stem cells found in adults is moving along rapidly.

In early clinical trials in the area of AIDS, Novartis AG is purifying blood stem cells from HIV patients' own blood, altering them by inserting anti-HIV genes and then reinjecting them in the patients. "We expect the modified stem cells will give rise to progeny cells that are HIV-resistant," says Carol Grundfest, a Novartis spokeswoman.

Cytotherapeutics Inc., of Lincoln, R.I., is looking for stem cells in the liver, the pancreas and the brain. It reasons that a single type of stem cell may prove useful against many conditions -- a brain precursor cell, for example, could be used against Parkinson's, Alzheimer's and other degenerative brain diseases.

"The best concept is a drug-in-a-bottle concept -- a cell product that is not patient-specific that could be used to treat a wide spectrum of diseases," says the company's chief executive, Richard Rose.

Developing Substances

Some companies aren't waiting for specific types of precursor cells to be discovered. Instead, acting on the belief that such cells do exist in certain body areas, they are developing substances that can activate them.

One such company is Creative BioMolecules Inc. of Hopkinton, Mass. Its drug, osteogenic protein, is now being implanted in broken legs that have been slow to heal in clinical trials, and the company says results are promising. It believes the drug works by spurring bone stem cells to create new bone, says in-house scientist Marc Charette.

"The body has a large amount of stem cells, and what you really need is the signals to cause them to differentiate," he says.

If the Food and Drug Administration approves the company's drug, it will be sold by partner Stryker Corp., of Kalamazoo, Mich.

Biogen is hoping it has found a chemical signal that causes brain stem cells to become the type of cells that produce the neurotransmitter dopamine. Those cells are damaged in people with Parkinson's disease, causing its sufferers to have difficulty moving and talking. In a collaboration with Ontogeny, Biogen is injecting rats with a type of protein known as a "hedgehog," which has been shown to play a key role in fetal development.

To simulate Parkinson's disease, the rats are injected with a toxic chemical. Normally, the toxin shuts down the animal's fine motor control and causes the rat to spin uncontrollably, like a top. But the company found that rats given brain injections of the hedgehog protein in addition to the toxic injection got a much less severe case of the spins, says Joseph M. Davie, the company's senior vice president of research

At the very least, says Dr. Davie, the hedgehog protein appears to be protecting the brain from the toxin. At best, hedgehog may actually direct stem cells in the brain to create new nerve cells to replace those destroyed. In a separate project, Ontogeny is hoping to generate a therapy that would cause pancreatic tissue to regenerate itself, restoring insulin-making capability and freeing diabetics from daily injections.

The first step, which the company is now working on, is to find the chemical signals -- generally proteins -- that tell a developing embryo to make a pancreas in the first place. If they can be found, they could be injected into the pancreas in order to spur stem cells to turn into insulin-producing cells.

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