In the human body, stem cells divide to produce both copies of themselves and other, more specialized, cell types.

Until now, scientists were unable to sustain the ability of neural stem cells to produce copies of themselves when grown in a dish. This meant that the population of cells would always become mixed, with only a few stem cells and many more specialized cells.

By changing the growth conditions, the Edinburgh and Milan teams have for the first time established pure stem cell divisions, thus avoiding the unwanted differentiated cells.

Crucial Step Toward New Therapies

"We applied techniques developed to control the behavior of embryonic stem cells to our neural stem cells," says researcher Luciano Conti. "The knowledge we already have about embryonic stem cells helped us to understand and control these more specialized stem cells."

The scientists initially made their discovery using mouse cells, and then used human stem cells to replicate their findings.

The research teams made different cell types of the nervous system from the neural stem cells. All were in perfect working order, suggesting that the neural stem cells can be used to generate, and study in detail, the cells that are affected in such neurodegenerative disorders as Huntington’s and Parkinson’s disease.

Researchers then will be able to study the cellular and molecular processes that go wrong in disease -- a crucial first step in developing effective, safe therapies.

Damaged Tissue Replacement

Drugs that are being developed to interfere with the onset and/or progression of disease now may be tested on neural stem cells or on specific cell types made from them. Such an approach will reduce the number of animals used in this type of research, the scientists point out.

The researchers also feel that their work may represent a step in the right direction toward using stem cells to replace damaged tissue.

"The purity of the cells, and the fact that they do not make tumors, means they should be valuable for studying the potential of transplantation to repair damage," says Steve Pollard, one of the Edinburgh researchers.

Professor Austin Smith, who led the Edinburgh team, believes that sharing information and knowledge is critical to take stem cell research forward.

"Collaboration with our colleagues in Milan, through the EuroStemCell project, made our breakthrough possible. We have published in an open-access journal and included comprehensive practical protocols so that other researchers can replicate and advance this work," he said.