Researchers able to direct stem cells to create certain progeny

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Researchers able to direct stem cells to create certain progeny

Wed Aug 6, 6:12 PM

http://ca.news./s/capress/080806/health/health_directing_ste

m_cells

By Sheryl Ubelacker, The Canadian Press

TORONTO - Canadian researchers have found a way to control embryonic

stem cells so they give rise to only one category of cell, a first

step in medicine's quest to generate specific tissues to repair or

replace parts of the body that are diseased, damaged or just plain

worn out.

Embryonic stem cells are programmed to spawn all the different cells

of the body, from those that make up the brain or heart to those

that comprise the liver or skin. Scientists worldwide have been

trying to figure out the mechanisms that decide which cell becomes

what.

In Wednesday's issue of the journal Stem Cell, scientists at

Toronto's Hospital for Sick Children describe how they prodded stem

cells to generate a single category of cell. Called early-stage

endoderm cells, they give rise to only certain tissues in the body.

" By adding a gene, we've essentially been able to take embryonic

stem cells, which make everything, and push them a little bit down

one particular pathway, the endoderm pathway, " senior author Janet

Rossant, chief of research at Sick Kids Hospital, said in an

interview Wednesday.

" And that's the pathway of the cells that give rise to all the

tissues of the gut, to the lungs, to the liver, to the pancreas, to

very important cells that one day could be used for regenerative

medicine. "

" These cells themselves would not be used for transplantation, but

they're a tool to help us understand that process. "

Lead author Cheryle Sequin, a post-doctoral fellow in Rossant's lab,

said the researchers took existing embryonic stem cell lines and

manipulated their internal control mechanism by zeroing in on a

particular gene.

" So we created a new kind of stem cell, limited to making only one

cell type, " she said.

Having accomplished this first step, the next research endeavours

will involve determining what other steps are needed to coax the

stem cells into begetting specific offspring, as it were, from lung

cells to repair the damage of cystic fibrosis to pancreatic cells

that could be transplanted into diabetics to provide insulin.

" It's just really about controlling stem cells, is really what it

comes down to, " Seguin said. " We're one step closer to being able to

use these cells if we're one step closer to being able to control

what they can become. "

Mick Bhatia, scientific director of the Stem Cell and Cancer

Research Institute at McMaster University, called the work an

important advance because it demonstrates that stem cell

differentiation can be controlled or directed, a prerequisite for

their use in regenerative medicine.

While embryonic stem cells' ability to produce any cell in the body

is what gives them so much promise, the challenge for scientists is

how to make them become what is needed for specific patients, Bhatia

said from Hamilton.

" How do you get a cell that can become over 200 different things to

become one thing and not the other 199? " he said, noting that many

scientists have argued that such control is not possible, that other

mechanisms govern the decision to become one cell type versus

others.

Bhatia likened embryonic stem cells to students about to enter high

school, who have the option of taking courses to prepare for a

career in business, engineering or science, for instance. If they

choose engineering, they then have to decide what kind of

engineering - civil, industrial or electrical.

Continuing the analogy, he said the Sick Kids researchers have

directed the stem cells to take the endoderm (engineering) pathway;

the next step will be determining how to make them become lung cells

(civil engineering) or liver cells (electrical engineering).

" I think what they've done is establish a proof of principle that

stem cells can be directed in a very refined way, " said Bhatia, who

was not involved in the research.

" And that's important to what they've shown here, but it's more

important to the broader issue of people asking: 'Can stem cells be

controlled?' And I think this is showing yes, here's an example

where they can be controlled. "