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How to turn your skin into bone
02 July 2005
From New Scientist Print Edition.
Andy Coghlan

The prospect of carrying out reconstructive surgery using bone, muscle and fat tissue grown from a patient's own cells has moved closer to reality. These tissues have now been grown from adult stem cells extracted from human skin.

It was shown three years ago that stem cells taken from the skin of mice can turn into a range of tissue types when injected into mouse embryos (New Scientist, 16 March 2002, p 12). But critics pointed out that, rather than forming normal new tissue, the stem cells might merely be fusing with existing cells, as has been shown to happen with some kinds of adult stem cell.

When it comes to skin stem cells from people, at least one team has managed to turn them into nerve cells in a dish. But what happens inside the body? To find out, Anthony Atala's team at the Wake Forest Institute for Regenerative Medicine in Winston-Salem, North Carolina, extracted mesenchymal stem cells from foreskin taken from 15 patients during routine circumcisions. Their ages ranged from 6 months to 24 years.

By treating the stem cells with various hormones and growth factors, Atala could drive them to develop into three tissue types: bone, fat and muscle. Next, he coated small, sponge-like scaffolds with cells of each tissue type and implanted them into mice.

A few weeks later, the cells had multiplied to form new tissue (Stem Cells and Development, vol 14, p 337). The scaffolds were implanted where no bone, fat or muscle was present, and the structures retrieved contained bone, muscle and fat, Atala says.

"Our research proves without a doubt that the cells are creating new tissue, not just annealing into existing tissue. That brings us much closer to clinical application," he says. "You could apply the technique wherever new tissue is needed, such as muscle injury or trauma, to correct congenital defects or acquired conditions like cancer where there's tissue loss following surgery which needs replacing."

Adult stem cells capable of growing into skin, bone, muscle and fat have usually been obtainable only from a patient's bone marrow, which requires a painful and expensive operation. Skin stem cells are easier to obtain. "You could use a little punch biopsy taken with a topical anaesthetic in the doctor's office, take the biopsy to the lab and grow the quantity needed, then inject the cells back into the patient," Atala says.

Because the tissue is grown from a patient's own cells, there would be no issue with rejection by the immune system. And there are no embryos involved, so the approach avoids the ethical objections some people have to embryonic stem cells.

Other researchers are enthusiastic about the findings. "This is a study that could translate into real therapies in the clinic," says Robert Lanza of Advanced Cell Technology, a company developing stem cell treatments in Worcester, Massachusetts. Embryonic stem cells "can certainly do more tricks", he says, but might be unnecessary for many clinical applications. "It's a reminder that you don't need to look very far to obtain a ready supply of immune-compatible cells and tissues."

From issue 2506 of New Scientist magazine, 02 July 2005, page 16

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