Researchers at The Hospital for Sick Children (SickKids) and the University of British Columbia (UBC) have used skin-derived stem cells to repair spinal cord injuries in rats.
Skin-derived precursors (SKPs) are self-renewing stem cells that reside within the dermis of both rodents and humans and share characteristics with embryonic neural crest stem cells, which are responsible for the generation of the nervous system. The most important characteristic being their ability to turn into neural crest derived cell types like peripheral neurons.
“We previously discovered that SKPs can efficiently generate a type of glial cell, called Schwann cells that have been shown to provide a good growth environment for injured central nervous system axons,” said Dr. Freda Miller, the study’s principal investigator, a senior scientist in Developmental Biology in the SickKids Research Institute, a professor of Molecular and Medical Genetics, and Physiology at the University of Toronto, Howard Hughes Medical Institute International Research Scholar and Canada Research Chair in Developmental Neurobiology. “These types of axons normally do not regenerate.”
The mammalian spinal cord does not recover well following injury. This is due to secondary damage to the spinal cord and surrounding tissue, and loss of a conductive insulation on axons called myelin, as well as the failure of axons to overcome myelin-associated inhibiting molecules.
Studies have shown that Schwann cells help promote axonal regeneration and that transplantation of these cells facilitates the remyelination of the injured spinal cord. However, Schwann cells cannot be harvested without invasive surgical biopsies and there are substantial difficulties with purifying the cells once they have been extracted.
“Knowing that harvesting Schwann cells from nerves is invasive and difficult, we wanted to test whether SKPs could be used to repair the injured rat spinal cord,” said Dr. Wolfram Tetzlaff, professor at the University of British Columbia, associate director of ICORD (International Collaboration on Repair Discoveries) and Edie Ehlers Chair in Spinal Cord Injury Research. “To do this the Miller lab isolated and expanded genetically-tagged SKPs, differentiated them into Schwann cells and we transplanted them directly into the injured rat spinal cord.”
Analysis after 12 weeks following transplantation revealed that the SKP-derived Schwann cells survived well within the injured spinal cord, reduced the size of the contusion cavity, myelinated endogenous host axons, and recruited endogenous Schwann cells into the injured cord.
These results indicate that transplantation of SKP-Schwann cells represent a viable alternative strategy for repairing the injured spinal cord. Cells to repair a spinal cord injury could be taken from the injured individual’s own skin potentially bypassing issues of transplanted cell rejection during the healing process.
"You can imagine a scenario for people with spinal cord injuries, that maybe, just maybe, we could take a piece of their skin, grow the cells up and transplant them (the patient) with their own cells," Miller said. "You wouldn't have to give them immunosuppressive drugs. That's a tremendous clinical advantage if it comes true."
This research was made possible with the support of a $1.5-million NeuroScience Canada Brain Repair Program™ team grant that enabled scientists from across Canada to work together and fast track their research. This research is reported in the September 5, 2007 issue of the Journal of Neuroscience.
Illustration: MicroSoft clipart.
The Hospital for Sick Children (09/05/07)
The Star (09/06/07)
The Journal of Neuroscience (Abstract: The Journal of Neuroscience, September 5, 2007, 27(36):9545-9559; doi:10.1523/JNEUROSCI.1930-07.2007)