UK scientists are to trial a single injection therapy for stroke patients using stem cells next year.

The researchers hope the treatment will help restore brain function and any personality lost by the patients.

If successful, the scientists plan to develop similar approaches for treating Parkinson's disease and Alzheimer's.

Dr John Sinden, of ReNeuron Limited, told the British Association's Festival of Science: "The trial will involve a small number of patients but we expect that within six years we will have a drug on the market."

The injection will use neural stem cells, "master cells" that have yet to develop into specialised brain tissue.

The scientists have taken their stem cells from aborted foetuses.

"This is tissue that would otherwise be lost or wasted," he said. "Clearly we have sought and obtained ethical permission through the usual guidelines but we really need very little of this tissue. We bank cells from a single embryo - enough to treat a very large number of people."

Dr Sinden's team has introduced a genetic switch into the stem cells which makes them divide indefinitely when cultured at lower than normal body temperatures.

The raised temperature inside the body will "throw" the switch.

"As soon as we put the cells into the patient, the gene is actually turned off and the cells become 'mortal' again."

In the laboratory, ReNeuron has shown that the stem cells will develop into different and important brain cell types. When injected into the brain, the cells migrate to areas of damage and start to repair it.

"The damaged adult brain still retains the capacity to use stem cells. So what we've been doing is developing human neural stem cells that we can inject into the brain for the brain to then use for regeneration."