This is a summary of a paper published in the Journal of Neuroscience.
Schwann cells generated from neonatal skin-derived precursors or neonatal peripheral nerve improve functional recovery after acute transplantation into the partially Injured Cervical Spinal Cord of the Rat
by J.S. Sparling, F. Bretzner, J. Biernaskie, P. Assinck, Y. Jiang, H. Arisato, W.T. Plunet, J. Borisoff, J. Liu, F.D. Miller, and W. Tetzlaff. Journal of Neuroscience 35(17) 6714-6730, April 29 2015.
Access the full article here.
Cell transplantation for the repair of the injured spinal cord is being studied in many laboratories around the world, including here at ICORD. Many candidate cells exist and there is no consensus which type of cell is best. A small number of cell types are currently in human trial to determine the feasibility of their application and their safety. This is not to be mistaken with the many cell treatments offered around for the world for money that are poorly researched, and not proven effective or safe.
But even the candidate cells that are presently being researched have potential risks. They are often derived from pluripotent cells [pluri=many, potent=having the potential (to make many different cells)], which means cells that can be tweaked to become cells for neural repair, but that at the same time may also form undesired tumors.
Here at ICORD, we favour a cell type called Schwann cells. Schwann cells occur naturally in peripheral nerves of the body and can guide the regrowth of nerve fibres after an injury in the nerves. Schwann cells are not pluripotent, so their tumor-forming potential is minimal. The Miami Project to Cure Paralysis has started a human trial with Schwann cells to test their feasibility and safety. However, in order to obtain Schwann cells for spinal cord repair, a piece of nerve several inches long needs to be excised (typically from the leg). This is far from ideal, since it adds another surgery with the risk of infection and the risk of nerve injury leading to chronic pain.
Scientists at ICORD are pursuing another source of Schwann cells: the skin. Skin-derived Schwann cells were first discovered in the laboratory of Dr. Freda Miller in Toronto. We imagine that a thin sliver of skin could be harvested from the edges of the very same incision that is made by orthopedic spine surgeons a day or two after injury when they operate to stabilize the spinal column.
A recent study in the prestigious Journal of Neuroscience by Dr. Wolfram Tetzlaff and his team undertook a side-by-side comparison of these skin-progenitor cell derived Schwann cells (SKP-SCs) versus nerve-derived Schwann cells (N-SCs) after transplantation into the injured cervical spinal cord of rats. Interestingly, the SKP-SCs performed just as well, and in some parameters even better than, N-SCs cells, improving nerve fibre plasticity and functional outcome.
Taken together, these data favour the use of SKP-SCs over N-SCs. The next step is the assessment of human SKP-SC and their efficacy after chronic spinal cord injury. We know already that the SKP-SC from rats improve functional recovery when transplanted at 8 weeks after a spinal cord injury. If these experiments with human SKP-SCs are as successful as with the rat SKP-SCs, a trial in humans might be become warranted in future years. Until then, the challenge is to secure the funding for this journey of this new promising skin-derived cell type to human spinal cord repair.