Reprogrammed Adult Cells Not an Alternative to Embryonic Stem Cells

July 20, 2010— -- Adult tissues that are reprogrammed to become stem cells may not be the blank slate that researchers find in other stem cell types, further questioning whether adult cells can be considered a reliable alternative for embryonic stem cells, according to a two new studies published Monday in Nature and Nature Biotechnology.

In one study, researchers at Children's Hospital in Boston, genetically engineered adult tissues in mice to imitate embryonic stem cells. They found these reprogrammed cells, known as induced pluripotent stem cells, meant to act as blank cells, actually retained characteristics of the tissue that it once was.

"We're finding that there's a subtle memory of where the [adult] cells came from," said Dr. George Daley, director of the stem cell transplantation program at Children's Hospital and lead researcher of one of the studies.

Stem cells are heralded as a tabula rasa that can be fashioned into healthy organs and other tissues to potentially treat diseases. Adult cells are often used to reproduce cells of its origin, while embryonic stem cells are not limited to a specific tissue type.

However, both studies suggest that induced pluripotent stem cells made from reprogrammed adult cells may not be equivalent to embryonic stem cells, as many researchers once thought.

"We thought we could reset [blood cells] so we can make a bone tissue or other tissue types, and realized it not make a bone tissue as well. But it did well going back to a blood cell," said Daley.

Researchers currently use adult stem cells to treat genetic diseases. For example, adult blood cells are used to treat genetic blood diseases such as leukemia, and skin cells may be used to regenerate skin tissue and heal otherwise fatal wounds.

"It's an advantage when you want to make the same tissue type, but not if you're looking at making something new," said Daley.

While induced pluripotent stem cells are not yet used in practice, researchers are exploring ways that any adult cell can be reprogrammed into stem cells and refashioned into any type of tissue in the body, regardless of where it was originally taken.