Stem Cells Help Repair Rats’ Paralysis

By LAURAN NEERGAARD

WASHINGTON – Scientists have used stem cells and a potion of nerve-friendly chemicals to not just bridge a damaged spinal cord but actually re-grow the circuitry needed to move a muscle, helping partially paralyzed rats walk.

Years of additional research is needed before such an experiment could be attempted in people.

But the work marks a tantalizing new step in stem cell research that promises to one day help repair damage from nerve-destroying illnesses such as Lou Gehrig’s disease, or from spinal cord injuries.

"This is an important first step, but it really is a first step, a proof of principle that … you can rewire part of the nervous system," said Dr. Douglas Kerr, a neurologist at Johns Hopkins University who led the work being published Monday in the journal Annals of Neurology.

Perhaps most importantly, the experiment illustrates that if stem cells eventually live up to their promise, it won’t be a simple treatment – they can’t just be injected into a diseased body and figure out how to repair it on their own.

Instead, the new research details a complex recipe of growth factors and other chemicals that entice the delicate cells to form the right kind of tissue and make the right kind of connections. Miss a single ingredient, and the cells kind of wander aimlessly, unable to reach the muscle and make it move.

The study may bring "the appropriate tempering of expectations of stem cells," said Kerr, considered a leader in the field. "Some of my patients say, ‘Oh, I’m going to pull into the stem-cell station and get my infusion of stem cells,’ and it’s never going to be that."

Stem cells are building blocks that turn into different types of tissue. Embryonic stem cells in particular have made headlines recently, as scientists attempt to harness them to regenerate damaged organs or other body parts. They’re essentially a blank slate, able to turn into any tissue, given the right biochemical instructions.

The Hopkins experiment isn’t the first to use stem cells to help paralyzed rodents move. But previous efforts have succeeded only in bridging damage inside the spinal cord that blocked nerve cells from delivering their "move" messages to muscles, not in engineering an entire new circuit – the kind of repair that would be needed for degenerative nerve diseases.