Chemical found to simplify production of stem cells
Harvard team hopes technique cuts tumor risk
WASHINGTON - Researchers trying to find ways to transform human skin cells into stem cells said yesterday that they found a shortcut by adding a chemical to the cells.
The chemical allowed the team at the Harvard Stem Cell Institute to use just two genes to transform skin cells into more powerful induced pluripotent stem cells, or iPS cells.
"This study demonstrates there's a possibility that instead of using genes and viruses to reprogram cells, one can use chemicals," said Dr. Doug Melton, who directed the study published in the journal Nature Biotechnology. That could reduce the risk of tumors developing in the cells.
Melton said Danwei Huangfu, a postdoctoral researcher in his lab, developed the new method.
"The exciting thing about Danwei's work is you can see for the first time that you could sprinkle chemicals on cells and make stem cells," said Melton, a researcher at the Howard Hughes Medical Institute.
Huangfu tried treating the cells first with valproic acid. After she did this, she found it took only two of the four usual genes to reprogram the human skin cells into iPS cells, which resemble embryonic stem cells.
Huangfu said the valproic acid unraveled the chromatin - the physical structure of the chromosomes - making it possible to get in and alter the DNA more easily.
"We may need two types of chemicals, one to loosen the chromatin structure, and one to reprogram. We are looking for that reprogramming chemical, and it should be possible to find it eventually," she said.
Stem cells are the body's master cells, giving rise to all the tissues, organs, and blood. Embryonic stem cells are considered the most versatile kinds of stem cells.
Doctors hope to someday use stem cells to transform medicine. Melton, for instance, wants to find a way to regenerate the pancreatic cells destroyed in type 1 diabetes and perhaps cure that disease.
But embryonic stem cells are difficult to make, requiring the use of an embryo or cloning technology. Many people also object to their use, and several countries, including the United States, limit funding for such experiments.
In the past year, several teams of scientists have reported finding a handful of genes that can transform ordinary skin cells into iPS cells.
To get these genes into the cells, they have had to use retroviruses, which integrate their own genetic material into the cells they infect. This can be dangerous and can cause tumors.