SPECIAL REPORT: The Miami Project to Cure Paralysis.

There is an unprecedented sense of optimism among scientists that restoring function by regrowing spinal nerve fibers will be possible. Scientists are overturning the conventional wisdom found at the start of almost any spinal cord regeneration article: Nerve fibers (axons) in the brain and spinal cord do not regenerate naturally, even though peripheral nerves can.

The new optimism centers on emerging strategies to overcome this natural obstinance; it is based on new success in achieving regrowth in the laboratory. How are the scientists achieving these successes, and how will they overcome the hurdles that remain?

Among the array of strategies being tested, the problem of bridging a gap in the spinal cord by grafting peripheral nerve helper cells (Schwann cells) into the site of injury has been a major interest of Miami Project researcher Mary Bartlett Bunge, Ph.D. Schwann cells are the support cells of the peripheral nerves, the nerves that course through our arms and legs, carrying messages to muscles or sensory information back toward the brain. They are well known to stimulate axon regeneration by making proteins that promote nerve growth either on contact, or at a distance (by secreting growth factors). Bunge is one of the world's foremost experts on the biology of Schwann cells. By bringing the cells that create the growth-promoting environment in nerves that support regeneration into the spinal cord, which does not, Bunge and her colleagues provide a scaffold for regrowing nerves and restoring communication between the brain and paralyzed regions of the body. A cable of Schwann cells grafted into the spinal cord inside a guidance channel stimulates thousands of nerve fibers to regenerate across the length of the bridge.

Early tests proved that Schwann cells are much more effective in eliciting the growth of distant nerve cells (located in the brain) if other growth-promoting proteins are added to the bridges. Specific growth factors (scientists have identified dozens of proteins that could be effective), used in combination with Schwann cell bridges or peripheral nerve grafts augment regeneration, and attract growth from nerve cells that modulate movements, affect autonomic functions and carry sensory messages. Studies from other laboratories, including a group in Sweden led by Lars Olson, M.D., support the significance of this approach. Scientists in California and Pennsylvania have used engineered skin cells to supply growth supportive proteins. Miami Project scientists have similarly engineered Schwann cells.

"The demonstration of growth from cells in the brainstem injured in the midthoracic (middle back) region of the spinal cord is very significant," Dr. Bunge stated. "This finding indicates that, as well as providing a route for axons to travel past the injury site, our cellular bridges must contain specific factors to stimulate distant nerve cells to respond."

Other experiments from this research team have increased regeneration by the administration of the neuroprotective steroid, methylprednisolone.