[Bloomberg] — Potent stem cells derived from reprogramming skin or other adult body tissues may have limits on their usefulness as an alternative to cells from human embryos, researchers said.

The study found that induced pluripotent stem cells, or IPS cells, retain a “memory” of their original adult tissue, making it more difficult to turn them into other cell types for medical treatment, according to authors from Harvard University and Johns Hopkins University. The study was published online today in the journal Nature. Similar results from other Harvard researchers were published in the journal Nature Biotechnology.

The findings may pose a challenge to previous research that suggested reprogrammed adult body cells may be substituted for embryonic stem cells, which have the ability to grow into all tissue types in the body. Researchers are already developing ways to get around the limits identified in today’s study, so the IPS cells may still be used to treat illnesses such as Parkinson’s disease or diabetes.

“It’s a challenge to be understood and overcome,” George Daley, a researcher at the Harvard Stem Cell Institute and Children’s Hospital in Boston and lead author of the Nature study, said today in a telephone interview. “We already have strategies for overcoming this.”

Still, the study results are a setback for the field of regenerative medicine, in which stem cells are used to grow new body tissues aimed at repairing or replacing body parts damaged from injury or illness.

All Applications

“These findings cut across all clinical applications people are pursuing and whatever diseases they are modeling,” Daley said.

Embryonic stem cells are derived from days-old human embryos, which are destroyed in the process. The technique has generated ethical debate. IPS cells, derived from reprogramming adult stem cells, have been viewed as an alternative to the embryonic stem cells.

While the reprogrammed stem cells may not be as versatile as embryonic stem cells at growing into all body cell types, the research released today found they are still useful.

“This study in no way challenges the usefulness of IPS cells” for research and drug discovery, Daley said in a telephone interview today. “They remain enormously valuable.”

A second study also published today showed similar results, with IPS cells retaining biological memory of its origins from adult cells. That restricted the capacity of the reprogrammed cells to differentiate into other kinds of cells, according to the research from Harvard-affiliated Massachusetts General Hospital.

Technique Breakthrough

Four years ago, a Japanese research team headed by Shinya Yamanaka pioneered the technique to reprogram adult skin cells into the working equivalent of embryonic stem cells.

Daley and colleagues earlier this month reported they were able to make human IPS cells from adult blood cells in a process they said was faster than the method of using adult skin cells. IPS cells made from blood were easier to turn back into blood than IPS cells made from skin or brain cells, he said in the interview.

While thousands of patients around the world have been treated with adult stem cells in research studies and have shown mixed results, no humans have been given cells derived from embryos in an approved trial.

Geron Corp., a Menlo Park, California-based company, said Oct. 30 it had reached an agreement with the U.S. Food and Drug Administration that may allow the company to proceed later this year with the first embryonic stem-cell study in humans. The study will test Geron’s therapy for injured spinal cords.

–With assistance from Rob Waters in San Francisco. Editors: Donna Alvarado, Andrew Pollack

To contact the reporter on this story: David Olmos in San Francisco at dolmos@bloomberg.net

To contact the editor responsible for this story: Reg Gale at Rgale5@bloomberg.net