Stem cells from brains help rats walk, study says

WASHINGTON, Mar 29 (Reuters) Stem cells harvested from the brains of mice can restore some walking ability in laboratory rats with spinal-cord damage, Canadian scientists have reported.

The findings are the latest success in rodent experiments to improve movement using a type of stem cell, an immature cell that can turn into different cells and tissues. Researchers hope to eventually test stem-cell therapies in people who are paralyzed and help them walk again.

In the new study, scientists took cells known as neural precursor cells, a type of stem cell that has started turning into a central nervous system cell, from mouse brains.

The researchers injected the cells into rats that could no longer walk after their spines were crushed, and gave them immune-suppressing drugs to prevent rejection.

The cells migrated to the spinal cord, merged into the injured tissue and developed into cells that produced myelin, the insulating layer around nerve fibers that transmits signals to the brain. Many patients with spinal cord damage have intact nerve fibers at the point of injury but no myelin, causing paralysis.

While the rats did not return to normal, they ''recovered significant walking ability. They had better coordination of their joints and better ability to support their weight,'' said Dr. Michael Fehlings, a neurosurgeon at the Krembil Neuroscience Center at Toronto Western Research Institute.

The research was funded in part by the Canadian Institutes of Health Research and published in the Journal of Neuroscience.

MORE STUDIES NEEDED Fehlings said he was hopeful studies of a similar method in people could start in five to 10 years after more animal studies. One question to answer is why injections of stem cells given weeks after an injury appear less effective.

In humans, researchers might be able to extract neural precursor cells by inserting a biopsy needle into a part of the brain where they believe the cells could be found, he said. If successful, the cells could be injected close to the injury site.

Stem cells from the brains of human organ donors also could be a source, he said.

''This type of strategy could potentially be relevant to about 50 per cent of individuals with spinal cord injuries who still have enough nerves at the injury site but have lost myelin,'' Fehlings said.

The research team said it was noteworthy that more than one-third of the stem cells survived after they were injected, moved to the injury site and produced myelin. The scientists also found the stem cells worked well when given up to two weeks after injury but less so when injected eight weeks later.

Stem cells come from various sources, from bone marrow to fetal tissue to embryos. Use of stem cells from human embryos is controversial because some consider it immoral to destroy an embryo to get the cells.

Other experiments have shown various types of cells can help heal spinal injuries in rodents. Last year, scientists reported improvement among mice with stem cells from aborted human fetuses and among rats with genetically engineered stem cells from rat embryos.

REUTERS SB KP0902