An interesting finding...
McMaster claims stem-cell breakthrough
Discovery important to cancer research, repairing damaged organs
Jul 11, 2007 01:15 PM
A landmark discovery by researchers at McMaster University could radically alter the way scientists can use embryonic stem cells to grow replacement tissues and treat cancer.
In a surprise revelation, a McMaster study found that human embryonic stem cells – “the great grandmothers” of all the other cells in our bodies – build themselves a nurturing cocoon that feeds them and directs their ability to transform into other types of tissues.
And by manipulating the products of this tiny, cellular placenta, it may be possible for scientists to prompt the stem cells to grow into desired tissues and organs, or to switch off tumour growth in cancers, says Mickie Bhatia, the lead study author.
The study will appear in an upcoming issue of the leading scientific journal Nature.
“We think we’ve introduced now a mechanism or a new approach to control stem cell fate,” says Bhatia, scientific director of the McMaster Stem Cell and Cancer Research Institute.
“I think-it opens up a completely new arena to now think about controlling the growth and differentiation of the human embryonic stem cells that we didn’t know existed until now,” he says.
The study shows that making replacement tissues to treat disease requires more than just the manipulation of the stem cell itself.
“You have to control the surrounding cells that govern this (transformation) process,” Bhatia says.
Bhatia says the major reason scientists study embryonic stem cells is for their potential to generate new types of tissues for transplant into damaged organs.
It is hoped, for example, that such stem cells might one day be used to grow new nerve cells in the damaged spinal cords of paraplegics, or to introduce insulin-producing cells into a diabetic pancreas.
Currently, however, researchers in regenerative medicine have been attempting to prompt this tissue transformation by targeting the stem cells themselves with various chemicals or technologies, Bhatia says.
Now, he says, scientists can turn their attention to the nurturing cells surrounding the embryonic stem cells, which appear to have a direct control over their ability to change into different things.
Bhatia say scientists have long thought that stem cells were coaxed to transform into other types of tissues by the environment or “niche” they found themselves in. Cardiac stem cells, for example develop heart tissue because that’s what they’re surrounded by.
It makes sense, then, that as the original cells present soon after conception, embryonic stem cells would need to create their own niche, Bhatia says.
“With this paper-we’re saying that controlling the stem cell happens not only in the stem cell itself, but also with (this newly discovered) niche,” he says.
This niche, Bhatia says, is made up of cells generated by the embryonic stem cells. These surrounding cells in turn feed and direct the parent stem cell via the production of special protein “growth factors”.
And some of the growth factors created by the niche cells direct the embryonic stem cell to do nothing but make copies of itself, Bhatia says.
To coax the stem cell to make other types of tissues, you have to stop this self-replication process, Bhatia says.
“The one thing we have to do first is we’ve got to draw their attention from making copies of themselves,” he says.
“Once we’ve done that, then we can draw their attention to making (different kinds) of cells.”
By blocking the growth factor proteins provided by the niche cells, the stem cells can proceed to create desired replacement tissues in the lab, Bhatia says.
Dr. Alan Bernstein, one of Canada’s top stem cell experts, called the study “very important.” explaining that the study shows the so-called niche cells seem to play an important role in determining the direction in which embryonic stem cells will choose to grow.
“Will they become neurons, will they become blood cells, will they become fat cells?” Bernstein says.
“We know that the niche to some extent influences their behaviour,” says Bernstein, president of the federal Canadian Institutes of Health Research.
The institute helped fund the Hamilton study, but Bernstein was not involved in the research.
He says the study’s suggestion that manipulating the stem cells’ niche to make it produce different tissues could become an important aspect of research in the field.
Bhatia says the study may also have far reaching implications for the treatment of cancers.
“We have a rising notion over the past few years that adult tumours come from stem cells,” he says.
As happens in healthy tissues, Bhatia says, the niche that controls their growth influences stem cells that generate malignant tumours.
“And so what we believe is that the niche that normally controls the stem cells is also part of what goes wrong when tumours grow,” he says.
“And so much like the (newly discovered) niche provides a new way of controlling differentiation for regenerative medicine, we believe it will also provide anew way of controlling cancer growth.”
Bhatia also says researchers should be able to use the growth factors produced by the niche cells to create more and better embryonic stem cells for continued laboratory research.