Canadian researchers have discovered that embryonic stem cells produce a posse of supporting cells that keeps them immortal.
The work, led by Mick Bhatia at McMaster University in Hamilton, offers researchers a new way to control stem cells, and perhaps put them to work to repair the damage caused by diseases such as muscular dystrophy or Parkinson's.
Embryonic stem cells have so much potential because of their unlimited capacity for self-renewal. In the developing embryo, they give rise to the different types of cells that make up the body.
One day, they may be used to fix damaged hearts, kidneys or livers, or even to grow new organs for transplant.
But before researchers can harness their regenerative powers, they have to understand how stem cells work.
Dr. Bhatia and his team are the first to have shown that, in the laboratory, embryonic stem cells can build their own environment.
They create supporting cells that feed them growth factors they need to keep them in the unique state in which they can reproduce indefinitely and become skin, muscle, bone, heart, liver, kidney, brain or more than 250 other kinds of specialized cells.
"The idea that a stem cell has the power to make its own niche, its own environment, to feed itself, no one had ever looked at," says Dr. Bhatia, whose work was published in today's edition of the journal Nature.
The same process - stem cells building their own support network - probably takes place in human embryos as they grow, Dr. Bhatia says.
Scientists have known that the environment in which a stem cell lives is important - and appears to dictate what kind of cell it becomes. In adults, for example, stem cells found in muscle tissue produce muscle cells.
But until now, they didn't know that stem cells can build their own environment, Dr. Bhatia says.
"This means that the stem cells' decisions, at least in the embryonic stem cell, are self-programmed."
Their work could help researchers trying to grow and manipulate stem cells for use in experimental therapies.
"We have been spending all of our efforts in the past five or six years to try to make embryonic stem cells to turn into neurons or blood, so we could use them for regeneration," Dr. Bhatia says.
"The fact that these cells now have an environment, and that environment controls the stem cells, means that we should also be targeting the environment. ... We could alter the environment to make more nerve cells or more blood."
Alan Bernstein, president of the Canadian Institutes of Health Research, says the paper helps researchers understand what makes embryonic stem cells behave the way they do.
"This is important if we want to cure human disease or conditions," says Dr. Bernstein, who announced last month that he will be stepping down from the funding agency in October.
Dr. Bhatia says the work may also be important for better understanding cancer. Cancer cells act like stem cells, reproducing quickly and not dying like normal cells.
He says it may be the supporting cells around stem cells that trigger this abnormal growth.
