Sufferers from devastating neurodegenerative diseases have been given some hope by the results of recent research.
Researchers at the Burnham Institute for Medical Research in La Jolla, California, have found that a mixture of human stem cells taken from embryos and fetuses delayed a fatal brain and nerve disease in mice.
They believe their findings have implications for victims of diseases such as Parkinson's, Alzheimer's and amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig's disease.
The human embryonic stem cells were transplanted into the brains of mice bred with the equivalent of Sandhoff disease which causes children with it to have severe mental retardation and motor dysfunction; death usually occurs in infancy.
Dr. Evan Snyder and an international team of researchers have found the transplanted stem cells moved throughout the brain to take on the jobs of damaged neurons.
Sandhoff disease causes an inflammation that kills brain cells, and it is impossible to treat in part because of the blood-brain barrier, a molecular gateway that keeps many drugs out of the brain.
Mice typically develop symptoms by 90 days of age and die between 114 and 130 days, while children with Sandhoff rarely live beyond age 6.
Snyder's team used a mix of stem cells, taken from days-old human embryos left over at fertility clinics, and transplanted them into the brains of the mice and no tumours formed, the mice did not "reject" the foreign cells, and the treatment seemed to reduce inflammation.
The transplanted human cells migrated and integrated extensively throughout the brain, but did much more than replace brain tissue destroyed by the disease.
Some of the transplanted cells replaced damaged nerve cells and transmitted nerve impulses, offering the first evidence that stem cell-derived nerve cells may integrate electrically and functionally into a diseased brain.
They also boosted the brain's supply of the enzyme Hex, which is lacking in Sandhoff disease.
The researchers found in the treated mice that well-being and motor function was preserved and they lived 70 percent longer than untreated mice.
Although the disease ultimately returned, the researchers plan to try keeping the disease at bay by giving booster injections of the stem cells.