Posted by: Thixia | January 1, 2009

Researchers able to direct stem cells to create certain progeny



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.”


Provided by:

The Canadian Press

Written by: Sheryl Ubelacker,





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