Fetal Stem Cells Repair Spinal Injury
United Press International
TOKYO, Aug 29, 2002 (United Press International via COMTEX) -- Japanese scientists said Thursday they have shown for the first time that stem cells expanded from a single fetus can become specialized cells, called neurons, and improve movement in rats with spinal injuries.
The finding could reduce the number of fetuses needed to yield effective therapies for treating disease.
Scientists have been able to expand the number of neuronal stem cells obtained from a fetus but it was unclear if these cells could then become specialized cells, capable of treating spinal cord injuries and brain diseases. Some previous studies had suggested the brain stem cells propagated in this fashion would only become a type of cell called an astrocyte with little potential for repairing spinal injuries.
However, Hideyuki Okano and colleagues at the Keio University School of Medicine in Tokyo found the timing for transplanting these cells is critical in getting them to become neurons.
"New neurons are generated from the donor brain stem cells in the host spinal cord when they were transplanted nine days after injury but not when the transplantation is done within a few days of the injury," Okano told United Press International.
The reason is that the local environment around the injury site appears to release chemicals that inhibit the stem cells from becoming neurons, Okano said. But this inhibitory process subsides nine days after injury and the stem cells then are able to become functional neurons.
Ronald McKay, chief of the molecular biology lab at the National Institute of Neurological Disorders and Stroke in Bethesda, Md., told UPI, "The secret to their success is the timing."
He added, "The age-old idea that you can't make new neurons is being displaced by the notion that actually you can if you know how to do it."
There's a critical time after injury when that can happen, and this study suggests researchers should look very carefully at this period, he added.
"It is too soon to know whether it's going to hold promise for treating disease in any direct way" but it does increase understanding of the basic biological mechanisms involved in these conditions, McKay said.
That ultimately could lead to treatments for disease, although it may be several years down the road and may not even involve the use of fetal stem cells, he said.
The finding is considered important because although stem cells obtained from fetuses hold great potential for treating disease, they are controversial and political, and legal issues often prevent researchers from obtaining access to them. Fetal tissue for these purposes generally comes from aborted human fetuses.
Experiments in rats and cats have shown transplanting fetal tissue into damaged spinal cords can improve movement and function, Okano said, but this has not led to treatments in humans because "a large number of fetuses are required to obtain enough tissue to treat even one patient, thus causing both practical and ethical problems."
For example, fetal tissue has been shown to benefit patients with Parkinson's disease but currently four to eight fetuses are needed to provide enough cells to treat one patient.
This study, however, shows it would be possible to expand stem cells taken from one fetus and thus would limit the number of fetuses required and lessen the ethical burden.
In the study, Okano's team derived neural stem cells from one rat fetus and multiplied them in test tubes until they had enough to treat spinal cord injuries in at least 450 rats.
The stem cells then were transplanted into rats with spinal cord injuries nine days after the injuries had occurred. Rats that received the transplants were better able to retrieve and eat food pellets and had better control over their limb movements five weeks after treatment. Assessment of the spinal cords revealed the transplanted cells had become neurons and integrated with the host tissue.
The study appears in the Sept. 15 issue of the Journal of Neuroscience Research.