Bone Marrow Cells Can Become Brain Stem Cells
Transplants from patient's body may someday fight Alzheimer's, Parkinson's
THURSDAY, April 29, 2004 (HealthDayNews) -- Cells found in a patient's own bone marrow might someday be a safe, ethical source for replacing brain cells lost to Alzheimer's, Parkinson's and other neurological conditions, researchers report.
The potential breakthrough may also allow doctors to bypass complex moral issues surrounding the use of stem cells derived from human embryos.
"It's exciting to think that some day a person with Alzheimer's disease could use their own bone marrow to create brain cells that could potentially restore their functioning and make up for cells that were lost," lead researcher Dr. Alexander Storch of the University of Ulm, Germany, said in a statement.
The research was presented Thursday in San Francisco at the annual meeting of the American Academy of Neurology.
The profound disability that characterizes degenerative brain disorders such as Alzheimer's, Parkinson's, Huntington's and amyotrophic lateral sclerosis (Lou Gehrig's disease) is caused by the steady destruction of cells within the brain. Experts have long speculated that the introduction of new brain cells could restore neurological function.
Stem cells are unique in that they have the potential to convert into any type of cell found in the body -- heart, bone, muscle, organ, even brain cells. Stem cell research has come under fire in recent years, however, due to moral issues surrounding the use of cells sourced from human embryos.
Looking for less controversial alternatives, Storch and his team focused on a type of cell found in bone marrow called the stromal cell.
"Bone marrow is the repository of a lot of tissues in the body," explained Samuel Saporta, a brain disease expert at the University of South Florida's Center for Aging & Brain Repair, in Miami. "It's the source of white blood cells and red blood cells, and the stromal cells can be the source for other kinds of tissues as well."
The German researchers removed stromal cells from human bone marrow and then cultured them in the lab using special growth factors.
Within a few weeks these bone marrow stromal cells had multiplied into "neuroprogenitor cells" -- brain stem cells capable of maturing into either neurons or glial cells, the two most common types of neural cells.
The fact that Storch's team used human bone marrow cells is what makes this study "unique," Saporta said.
"People have taken rat and mouse bone marrow and have pushed it into a neuronal, glial type of cell, but these researchers are taking from the knowledge that's been gained from the animal model and applied it to humans," he said.
Saporta cautioned, however, that it's one thing to create brain stem cells, and quite another to get them to survive and thrive within the brain. "You have to get them into the brain or the nervous system someplace," he said. "They have to engraft into the nervous system and actually form some kind of functional arrangement with the existing cells, if we're talking about cell replacement therapy."
So far, in experiments done with cell replacement in the human heart, "not a lot of the cells survive," Saporta noted. "That's the real challenge."
Still, cells derived from a patient's own bone marrow would provide a way around certain medical and moral issues.
Tissue transplants sourced from other than the patient's own body can be rejected by the body's immune system, Saporta pointed out. Suppressing this immune response with powerful drugs "is very, very onerous therapy, it's really hard on the individual and the system," he said. "If you can find a way of minimizing the amount of immunosuppression you have to do -- or not have to do any at all --- that's the ideal situation."
Stem cells derived from bone marrow stromal cells also avoid moral and legal issues surrounding embryonic stem cells. "Bone marrow donations are done all the time, there are thousands done every day in the United States," Saporta said. "There's not the ethical issue here of obtaining stem cells from an embryo."
Bone marrow now joins the growing list of body sites with known reservoirs of stem cells or "stem-like" cells, Saporta added. "People have already described stem-like cells in fat tissue, in bone, skin, and in tooth pulp. Each organ seems to have its own niche of stem-like cells. Even the brain has stem cells that produce neurons," he said.
However, much more research lies ahead before stem cell research translates into effective bedside therapies. "The problem is that we don't understand enough about the 'instructions set' that makes the stem cell become what we would like it to become," Saporta said. "A lot more basic biology needs to be done."