GALVESTON - For years, scientists have dreamed of using stem cells to replace neurons damaged by brain or spinal cord injury or such neurological disorders as Parkinson's disease, Alzheimer's disease or amyotrophic lateral sclerosis, or Lou Gehrig's disease.

But a major obstacle has always stood in the path of making such a therapy work: Whether derived from embryonic or adult tissue, only a few stem cells transform themselves into neurons when placed in most areas of the brain and spinal cord. Most simply fail to develop, or become support cells, not the neurons that need to be replaced.

Now researchers at the University of Texas Medical Branch have found a way to make the majority of human fetal stem cells implanted into rat brains and spinal cords develop into neurons.

Officials at UTMB described the development as a breakthrough with significance for the use of stem cells in central nervous system therapies.

A Nature Neuroscience paper on the work of UTMB researchers is being published
in the journal's December issue. It appears online today.

The paper describes experiments by Ping Wu, Yevgeniya Tarasenko, Yanping Gu, Li-Yen Huang, Richard Coggeshall and Yongjia Yu in which they pre-treated human fetal stem cells with a mixture of chemicals important to neuron development.

When injected into the prefrontal cortex, medial septum and spinal cord of adult rats - "non-neurogenic" regions that normally do not produce new nerve cells - the "primed" cells almost all differentiated into neurons.

Moreover, they developed into exactly the right kind of neurons for the central nervous system area into which they were implanted.

"This priming seems to get the cells into a plastic intermediate stage, and then after they're injected they acquire environmental cues and become specific kinds of neurons according to where they're located," said Wu, an assistant professor of anatomy and neurosciences at UTMB.

Wu has worked for two years to find a way to get fetal stem cells to develop into cholinergic motor neurons - nerve cells that release the neurotransmitter acetylcholine and also provide the link between the central nervous system and the muscles.

"Until now, nobody's been able to get a significant number of cholinergic neurons from primarily cultured stem cells, but using this primer we can get over 55 percent such neurons with transplanted stem cells," Wu said.

Wu's group is continuing to investigate the possibilities for stem cell implantation - extending the studies it has already conducted on healthy rats to those with spinal cord injury and motor neuron disease.