Human cells patch up rat spinal cord -- 23 February 2001

Transplanted cells could open the door to spinal cord therapy.

Cells from human nerve tissue, when transplanted into rats, can repair damaged spinal cords and restore nerve impulse activity, scientists report¹. Their results open the door to possible therapies for the degenerative nerve disease multiple sclerosis (MS) and even paralysis.

To carry electrical impulses quickly through the body, nerve fibres must be coated with Schwann cells, which form a layer called a myelin sheath around the fibre. Although scientists do not know the exact cause of MS, in MS patients the myelin sheath in the brain and spinal cord gradually withers away and nerve impulses move sluggishly, or not at all. Symptoms of the disease range from numbness and loss of balance to paralysis.

As a model for MS, Ikuhide Kohama and his team from Yale University in Connecticut used rats with their spinal cords partially stripped of myelin. They removed Schwann cells from amputated human limbs and froze and stored them. The cells were then thawed and transplanted into the rats' spinal cord. To prevent them from rejecting the human cells, the animals' immune systems were suppressed with drugs.

The researchers found that not only did the grafted cells grow and fill in the gaps in the myelin sheath, but electrical measurements revealed that nerve impulse conduction improved to near-normal levels along the repaired spinal cords.

"This raises the possibility that a patient's own cells may be used to treat diseases that involve the loss of myelin," says Moses Chao, a neurobiologist studying the triggers for myelin formation at the New York University School of Medicine.

But researchers do not know whether Schwann-cell transplants will repair myelin in humans in the same way as in animals. They are therefore planning clinical trials to test the safety of transplanting an MS patient's own Schwann cells into their brain. Pending approval from a Yale University review board, the researchers expect the trial to start at Yale in the next few months.

Kohama's experiments mark the first time that human Schwann cells have been preserved by freezing and transplanted into an animal model, according to Naomi Kleitman of the Miami Project to Cure Paralysis, based at the University of Miami in Florida. Kleitman, who works on Schwann-cell transplantation, says researchers think that preservation by freezing will be an important step in human transplantation.

Schwann cells are multi-talented components of the nervous system. Animal studies have shown that not only do they cause myelin to regrow on the spinal cord and on nerves throughout the body, but they also promote the regeneration of spinal cord nerve fibres themselves -- a crucial step in curing paralysis.

Further work will be needed to test the movement and coordination of animals and humans after Schwann-cell transplantation, to see if the new cells actually reduce the physical symptoms of MS, the authors say.

1. Kohama, I., Lankford, K. L., Preiningerova, J., White, F. A., Vollmer, T. L. & Kocsis, J. D. Transplantation of cryopreserved adult human Schwann cells enhances axonal conduction in demyelinated spinal cord. Journal of Neuroscience 21, 944 - 950 (2001).