Saturday, June 12, 2004

New Nerve Cells

Every year, thousands of people end up paralyzed when their spinal cords are injured. Right now, these patients almost never fully recover. But, as this ScienCentral News video reports, one nanotechnologist says there may be a way to grow back injured nerve cells?and repair damaged spinal cords, so that paralyzed patients can leave their wheelchairs behind.

Tiny Scaffolding

Some of the 250,000 Americans who have been paralyzed by spinal cord injuries are pressing medical researchers for a cure. The most prominent is actor and director Christopher Reeve, who was paralyzed after a fall from his horse in 1995. At a symposium on spinal cord research at Rockefeller University, held on November 24, 2003, Reeve commented on "a certain frustration" that he and other paralyzed patients feel over the current pace of American research, which has been hampered by political debate over the use of stem cells. "I think that we need to inject more urgency into the whole process here," Reeve observed.

Another speaker at the Rockefeller symposium was Michael Di Scipio, 34, who was paralyzed after a diving accident in July 1999, when he was 29. A single father, he says his two young children have been injured, too?by what he can't do: "Not being able to run around and play with them, hold them, tickle them, tuck them in, give them a kiss good night. Things we're supposed to do as parents."

One reason that prospects for recovery are dim at present for patients with spinal cord injury is that unlike other cells, nerve cells, or neurons in the central nervous system (the brain and spinal cord) are unique in that they cannot replicate themselves in their mature state. So repairing spinal cords means finding a way to get nerve cells to grow back across the gap in a spinal cord that has been severed.

Some prominent nanotechnologists are hard at work on the problem. Samuel Stupp is professor of chemistry at Northwestern University, where he is director of the Institute for Bioengineering and Nanoscience in Advanced Medicine. He and his research team say they have engineered a nanoscale scaffold upon which new neurons can grow and bridge the gap in a damaged spinal cord.

Stupp starts out with a liquid made up of negatively-charged molecules, which normally would repel each other. "We started with a very simple concept," explains Stupp, "asking, can we design a material from the bottom up, that is made of nanostructures that assemble themselves?? When the negatively-charged liquid comes across positively-charged molecules found in living tissue, such as calcium or sodium ions, they instantly clump together into a gel. This gel forms into tiny fibers, or tubes, each about five nanometers wide and several hundreds of nanometers long. Gabriel Silva, a member of Stupp's research team, explains that each fiber has a hydrophilic, or water loving, core and a hydrophobic, or water-repelling, surface. In water, the fibers assemble themselves into miniature scaffolding. Molecules on the surface of each fiber that are capable of reacting when they come in contact with biological material like neural cells, promote the growth of neurons through and around the scaffolding. "In order to find ways or strategies to re-grow the spinal cord, we need to be able to give cells the right instructions," says Stupp. "We are able to induce neural cells to become neurons, instead of becoming another type of cell of the central nervous system."

When Stupp's team observes the growth of neurons on their scaffold through a microscope, Silva says the neurons they are looking for show as green areas, whereas a less desirable type of neural cell appears as red spots.

As they reported in the journal Science, the researchers were surprised by how much green they saw?in short, many new neurons they have been able to grow. That could mean hope for Reeve, Di Scipio and others like them, who one day may be able to leave their wheelchairs permanently.