Embryonic stem cells are not the chameleon organ creators they were assumed to be, a major new study out of Hamilton’s McMaster University shows.

In a finding destined to significantly shift the field, researchers discovered that the so-called mother cells are not all alike and that each is preprogrammed to produce specific tissues, like blood or neurons.

“When you look over at them, there’s not some sort of white chameleon that is poised to do everything,” says Mick Bhatia, director of the school’s Stem Cell and Cancer Research Institute.

“You actually see a series of chameleons, ones that are red, green or yellow with very specific directions,” says Bhatia, the senior study author.

This newly discovered propensity for each embryonic cell to be dedicated to a specific body part will have a radical effect on attempts to create replacement tissues and organs for transplant, he says.

With the emerging ability to transform adult skin cells into embryonic-like versions, the creation of replacement organs from a patient’s own tissues has become a major focus in transplant research.

These efforts centre on taking the reprogrammed cells — known as induced pluripotent stem cells — and coaxing them with growth factors and other proteins to grow into desired tissues.

These replacement parts would not pose the risk of rejection that always accompanies donated tissues because they would be created from a patient’s own cells.

But Bhatia says his discovery suggests that these current tissue-growing efforts may be largely fruitless because they’re using stem cells that are determined to transform into something different.

He says recipes to grow neural cells, for example, might simply be killing the huge percentage of stem cells being used in the attempt that never had any intention to grow into that tissue type.

“There are embryonic stem cells there that already favour one (tissue) type versus another,” Bhatia says. “So all the growth factors and recipes we’ve been working on for years to make all the cells become neural or blood in fact might be quite wasted.”

But the study, released Thursday by the journal Cell Stem Cell, offers a new direction that could well make replacement tissue creation much more efficient, Bhatia says.

The McMaster team found that each embryonic stem cell had a different protein marker on its surface that identified it as being destined for one tissue type or another.

While they concentrated on stem cells that would eventually become neurons or blood, Bhatia says it is likely that such identifying markers exist for each of the embryonic cells that create all 226 tissue types in our bodies.

He says these distinctive markers will allow scientists to pluck out stem cells that are specific to the desired tissues and create those much more readily.

“The idea always was (that) all these cells were the same,” Bhatia says. “The fact that they have preferences means . . . you can grab cells that have these preferences and go back and revisit the recipe.”

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Bhatia also says the finding will allow scientists to select induced embryonic cells that are specific for the diseases a patient suffers.

“If you’re taking (the cells) from a patient with Alzheimer’s, you know you’re going to go neural.”