U.S. study: Stem cells may cause brain tumors

Injecting human embryonic stem cells into the brains of Parkinson's disease patients may cause tumors to form, U.S. researchers reported on Sunday.

Steven Goldman and colleagues at the University of Rochester Medical Center in New York have for the first time essentially cured rats of a Parkinson's-like disease using human embryonic stem cells.

But 10 weeks into the trial, they discovered brain tumours had begun to grow in every animal treated.

The tumors found in the rats may have formed from stem cells that hadn't become neurons, Goldman said. Neurons don't normally divide.

The tumors may have been the result of the age of the stem-cell line used in the experiment, Goldman said. Labs funded by the U.S. Department of Health and Human Services can use only certain stem cells, which come from embryos obtained years ago.

While newer cells might create fewer tumors, "We don't know it and can't know it" under the current policy, he said.

Various types of cell transplants are being tried to treat Parkinson's disease, caused when dopamine-releasing cells die in the brain.

This key neurotransmitter, or message-carrying chemical, is involved in movement and Parkinson's patients suffer muscle dysfunction that can often lead to paralysis. Drugs can slow the process for a while but there is no cure.

The idea behind brain cell transplants is to replace the dead cells. Stem cells are considered particularly promising as they can be directed to form the precise desired tissue and do not trigger an immune response.

Parkinson's disease, with tremors and impaired balance, afflicts at least 500,000 Americans.

Source:Xinhua/Agencies