Human stem cells help paralyzed rats, mice to walk
Johns Hopkins study could assist people, be a key to funding

Wednesday, July 25, 2001

By Michael Woods, Block News Alliance

BAR HARBOR, Maine -- Johns Hopkins University scientists yesterday reported using human stem cells to restore the ability to walk in rats and mice paralyzed by nerve damage like that found in several human diseases.

"So far as we know, this is the first time human stem cells have produced recovery from a disease in any animal, " said head researcher, Dr. John P. Gearhart.

Gearhart, an internationally known stem cell authority, said the achievement addresses one of the major objections to federal funding for stem cell research.

Human embryonic stem cells are "building block" cells that develop into every other kind of cell found in the body. Researchers believe they can make replacements for body tissue lost to disease or injury -- including whole new hearts, kidneys and other organs for transplantation.

Nevertheless, the federal government has refused to fund embryonic stem cell research because aborted fetuses are a major source of the cells. They can be obtained in other ways, one of which involves destroying human embryos stored in fertility clinics.

The Hopkins research was done with stem cells obtained from human fetuses aborted at 5-8 weeks of age.

One argument against federal funding, Gearhart noted, is that human stem cells have not yet been shown effective in treating a disease. The new findings weaken that argument, he said.

"It's one thing to see evidence that stem cells work in laboratory culture diseases, " Gearhart said at a renowned conference on genetics, this year's being the 42nd Short Course in Medical and Experimental Mammalian Genetics. "And it's quite another to see actual function restored in an animal."

Videos showed the reversal of paralysis in the laboratory animals to be dramatic. Researchers injected human neural stem cells into the spinal fluid of about 80 rats and mice paralyzed by a virus that attacks and destroys nerve cells that control muscle movement.

Normally, animals infected with the Sindbis virus permanently lose the ability to move their limbs, as neurons leading from the spinal cord to muscles deteriorate. Animals drag limp legs and feet behind them.

All of the animals treated with human embryonic stem cells recovered the ability to walk, although not with a normal gait.

Researchers believe the cells may have reversed paralysis in two ways. They may have grown into new rodent nerve cells that replaced the cells killed by the Sindbis virus or they may have produced chemicals that signaled the rodent nerve cells to start growing.

Rodents infected with Sindbis virus are used as a model for spinal motor atrophy. It is the most common inherited neurological disease and the most common inherited cause of infant death.

SMA affects as many as 1 in 6,000 infants, causing nerves leading from the spinal cord to the muscles to deteriorate. Children with SMA are born weak, have difficulty swallowing, breathing and walking. Most die in infancy, although some live into early childhood.

Gearhart said stem cell research may have its most immediate application in treating SMA and a related condition, amyotrophic lateral sclerosis, also called Lou Gehrig's disease.

ALS affects up to 20,000 adults, leading to whole-body paralysis and death as motor nerves linking the brain, spinal cord and muscles die.

Project ALS, a New York City organization that battles the disease, funded the Hopkins research. The treatment could be tested on humans within a few years, Gearhart said.

He predicted the ethical and religious concerns over stem cell research will vanish as scientists discover ways of making different kinds of cells without using embryos. But he emphasized that federal funding of embryonic stem cell research is essential to developing those alternative techniques -- a step that could take 10 years with ample funding and longer without it.