Researchers from the Harvard Stem Cell Institute (HSCI) and Mass. General Hospital (MGH) are one step closer to reprogramming adult stem cells and making them capable of creating tissues for all parts of the body without the use of viruses or cancer-causing genes.

Harvard Medical School professor Konrad A. Hochedlinger recently discovered how long adult mouse stem cells need to be exposed to reprogramming factors before they convert to a pluripotent, embryonic-like state, at which point they can be potentially used for medical treatments.

According to Hochedlinger, his lab set out to unveil the mysteries of the reprogramming process a little more than six months ago.

“Nobody knew which genes were involved in the reprogramming process or whether it occurs randomly,” said Nimet A. Maherali, who works in Hochedlinger’s laboratory and is a teaching fellow for Molecular and Cellular Biology 125: “Stem Cells and Cloning.” “It was a big task to accomplish.”

Hochedlinger’s discovery could potentially have therapeutic applications.

“We now know the conditions for replacing genes of viruses with small compounds and proteins to make safer stem cells,” said Hochedlinger, whose findings were published on the Web site of the journal Cell Stem Cell earlier this month. “From what I hear from unpublished reports, I think that we will be able to do this in the near future.”

Currently, most researchers are using cancer-causing genes and retroviruses to reprogram adult stem cells, a technique that eliminates the ability to use the converted cells in medical treatments.

Hochedlinger said that his lab is now researching whether human adult stem cells will behave differently from the mouse cells used in the experiments.

“There may be slight differences in timing and molecular cornerstones,” Hochedlinger said.

Despite the discovery—and other ones regarding adult stem cells at the University of Wisconsin and Kyoto University—researchers at Harvard have pledged to continue pursuing embryonic stem cell research.

Embryonic research has come under fire from those who consider the destruction of embryos to be immoral. Federal funding for embryonic research is currently constrained by a 2001 order by President Bush.

“Everybody who is doing important stem cell research at this point believes that embryonic stem cell research has to continue,” Harvard science spokesman B.D. Colen said. “We are still in an early stage, and we need to continue down all avenues.”

—Staff writer June Q. Wu can be reached at junewu@fas.harvard.edu.