Studies released on Monday at a neuroscience conference in Prague concluded that stem cell therapy might improve the lives of patients suffering from traumatic brain injury and Huntington's disease.
One study by researchers in Singapore showed mental functions of brain-injured rats improved after they received injections of stem cells from human umbilical cord blood.
In a separate study, American researchers using rats found stem cells beneficial in treating human neurological diseases such as Huntington's.
The studies are among the latest to spotlight what medical experts say is the enormous potential of human embryo stem cells in treating disease and repairing damaged organs.
Harvesting of cells from embryos has sparked ethical debates
Stem cells can "differentiate", or turn into, specific types of cells when transplanted into organs. Scientists say they may be used to replace damaged or destroyed cells in human tissue, raising hope for better treatment of many ailments from muscular dystrophy to diabetes - and even ageing.
But the harvesting of cells from embryos has sparked ethical debates in many countries.
The European Union, for example, is currently rethinking a moratorium on funding for embryonic stem cell research. Last week the European Commission recommended new guidelines and lifting the moratorium, which expires at year's end. But the 15 EU countries are divided on the issue.
The studies released at the World Congress of Neuroscience, which ends on Tuesday, were conducted under the ethical guidelines enforced in Singapore and the United States. They were among more than a dozen stem-cell research papers outlined at the conference of neurologists.
Six scientists from Singapore's Defence Research Institute and two from the country's National Cancer Centre collaborated on the brain-injury study. Citing the ethical controversy, they said their stem cells came from umbilical cord blood in placentas obtained with the consent of the women.
Traumatic brain injury, the study said, is a common cause of death and disability among young people. But drug therapy "in general" has had "limited success" in treating the trauma without "serious side effects".
In contrast, brain-damaged rats injected with the stem cells had "improved neurological outcomes" in hearing, "startle response" and motor skills. The rats also did better in a water maze test.
The American researchers included four from Chicago's Rush Medical Centre and three from the University of Wisconsin's Waisman Centre.
Their study found human stem cell therapy improved the behavior of rats who had a Huntington's-like disorders. Stem cells obtained from foetal tissue differentiated into neurons and astrocytes, a type of nerve cell.
