By Ewen Callaway of Nature magazine

Human embryonic stem cells that are potentially pure enough to be used in therapies have been deposited into the UK Stem Cell Bank, and will soon be available across Europe.

To make 'clinical-grade' cells, scientists produced them without the use of any of the animal cells or products typically needed, and did so under certified manufacturing conditions. They are the highest-quality cells of their kind publicly available, says Peter Braude, a stem-cell scientist at King's College London whose team derived them at an estimated cost of £3 million ($4.7 million). Much of the money went into infrastructure that will enable the creation of additional clinical-grade cell lines, he says.

"There are quite a few end users who would love to get their hands on these cells, and they will as soon as they are available," said Daniel Brison, a stem-cell scientist at the University of Manchester, UK, at a press briefing in London today. His own team expects to deposit a clinical-grade human embryonic stem-cell line into the UK Stem Cell Bank in 2012. Elsewhere in the United Kingdom, researchers at the University of Sheffield and Roslin Cells, a company based in Edinburgh, are also establishing clinical-grade lines.

Animal effects?

The new cells are not the first clinical-grade cells. Two small trials are already under way. One is using cells derived from human embryonic stem cells to treat spinal cord injury (although funding problems have stopped the trial enrolling new patients) and another is testing a treatment for age-related macular degeneration. Another macular degeneration trial will start soon. But these trials involve cells that were originally created using animal products for research . After a long vetting process, scientists converted them to clinical grade.

And a Singapore-based group created six clinical-grade cell lines in 2007, also using animal products. These lines are available for researchers funded by the US National Institutes of Health (NIH) and the California Institute for Regenerative Medicine (CIRM) in San Francisco, says Jeremy Crook, a stem cell biologist at the University of Melbourne, Australia, who led the team that made the lines.

But Braude says cells that have never touched the mouse 'feeder' cells or calf serum typically used to nourish human embryonic stem-cell lines are the safest source of cells for clinical trials. His team describes the creation of their cell lines in the journal Cytotherapy. Braude says his team has tested the cell lines for viral and mycoplasma infection, as well as for genetic abnormalities.

Quality assurance

The UK Stem Cell Bank, a government-funded repository, will begin distributing the cells once it has conducted additional quality tests, says Glyn Stacey, the bank's director. The two cell lines were created to ethical and quality standards spelled out in the EU Tissues and Cells Directives, so European researchers should get their hands on them soon.

Researchers further afield may have to wait longer, because ethical and quality-control standards for the cells vary between countries. The UK bank already has an agreement to share cells with CIRM-funded researchers, but it will take longer to get the new lines into the registry of lines approved for NIH funding, says Stacey.

The high quality of the new lines should make them appealing for clinical trials, says Braude, but it could take several years before the cells make their way into humans--if they ever do. Further testing could reveal genetic abnormalities or other problems with the cells that would prevent their use in therapies. Moreover, cell lines vary in their ability to make different tissues, such as heart muscle or cartilage, so a suite of clinical-grade lines is needed, Braude says.

By conducting basic research in the same cell lines that will be used in patients, researchers should also be able to speed the translation of their discoveries to treatments, says Crook. "The sooner clinically compliant stem cells can be introduced to research, the better."

This article is reproduced with permission from Nature magazine. It was first published on December 6, 2011.