The cord blood cells survived, migrated to the areas of the brain injured by the stroke and improved the rats' motor and sensory abilities, even when administered a week after the onset of stroke, the researchers report in this month's issue of the journal Stroke. The cord cells included a significant number of stem cells — immature. undifferentiated cells with the potential to become any cell in the body, including neurons.
"The study suggests that human umbilical cord blood may be a noncontroversial, more readily available source of therapeutic cells for treating early stroke and other traumatic brain injuries," said Paul Sanberg, PhD, DSc, director of the USF Center for Aging and Brain Repair and a senior author of the report. "It's exciting because it means that IV administration of stem cells, a less invasive procedure than neurosurgical implantation, may be an effective option in the early stages of brain injury."
Dr. Sanberg emphasized that the research is young, and studies in humans are still a few years away.
The researchers are unsure exactly how the cord blood cells promote such early functional recovery, but they suspect that the cells release growth factors that prompt the brain to repair damaged tissue.
Human umbilical cord blood stored following the birth of babies has been used on a limited basis to successfully treat certain childhood leukemias, but little is known about its potential benefit for central nervous system disorders. Stem cells from cord blood, as well as those found in adult bone marrow, skin and muscle, are being investigated as an alternative to human embyronic stem cells for the treatment of stroke or other neurodegenerative diseases.
In the Henry Ford/USF study, a saline solution containing a stem-cell rich fraction of cells from cord blood was injected into the tail veins of rats previously induced to have symptoms of stroke. The rats showed improvement in movement, balance and reflex responses even when treatment with cord blood cells was begun a week after the onset of the stroke. However, the greatest recovery of function occurred when the cells were administered within 24 hours after a stroke. Both groups of rats receiving transfusions of cord blood cells — at one day and seven days post-stroke — recovered quicker than control rats receiving no treatment.
The cord cells migrated to the side of the brain injured by the stroke and were distributed throughout the damaged areas. Few cells were detected in the unaffected side of the brain.
Only a small percentage of the cord blood cells in the brain actually expressed proteins typical of those in early neural cells.
"This leads us to believe that the mechanism of action is not necessarily replacement of damaged or dead brain cells by cord blood cells," said Michael Chopp, PhD, a neuroscientist at Henry Ford Hospital and senior author of the journal article. "It is more likely that the cells somehow encourage the brain's own recovery system to work better at repairing the areas damaged by stroke."
In another recent study by USF and Henry Ford Hospital, USF neurologist Juan Sanchez-Ramos, MD, PhD, and colleagues showed that stem cells extracted from human umbilical cord blood can be reprogrammed in the laboratory to become immature nerve cells. The cord blood cell study appeared in the October issue of Experimental Neurology.
"This animal model study extends our earlier laboratory findings," said Dr. Sanchez-Ramos, an author of the recent report in Stroke. "It is another small step forward in showing the potential of umbilical cord blood for treating neural deficits. But the mechanism by which cord blood cells seemed to improve functional recovery is still unclear."
Currently, the only treatment for early stroke is tissue plasminogen activator (TPA), a drug that must be intravenously administered within three hours of the onset of stroke symptoms to have a chance of working. In the animal stroke model at least, the cord blood cells offered a longer window of opportunity for beginning intravenous treatment — days rather than hours.
Other co-investigators for the study were Jieli Chen, MD; Yi Li, MD; Lei Wang, MD; Mei Lu, PhD, all of Henry Ford Hospital, and Allison Willing, PhD, of USF.
The study was supported by Saneron CCEL Therapeutics Inc., an affiliate of Cryo-Cell International, Inc., a Clearwater, FL company that collects and stores umbilical cord blood. A State of Florida High Tech Corridor Grant also funded the research.