September 26, 2008
Safer Stem Cells Research?
Researchers claim they developed a safer way to make powerful stem cells from ordinary skin cells, improving research focused on so-called regenerative medicine.
They used a common cold virus to carry transformative genes into ordinary mouse cells and made them look and act like embryonic stem cells.
If it can be replicated with human cells, it may offer a safe way to test cell therapy to treat diseases such as sickle cell anemia or Parkinson's,
Konrad Hochedlinger of Massachusetts General Hospital and Harvard Medical School in Boston reported in the journal Science.
Experts say stem cells are the body's master cells that give rise to all the tissues, like organs and blood.
Doctors consider embryonic stem cells the most powerful kinds of stem cells, because they can give rise to any type of tissue.
Many people object to their use, and several countries, including the United States, limit funding for such experiments.
During the past few months, several teams of scientists say they have found a handful of genes that can transform ordinary skin cells into induced pluripotent stem cells, or iPS cells. These cells look and act like embryonic stem cells.
Scientists used retroviruses to turn genes into cells. This can be dangerous and can cause tumors and perhaps other effects.
Hochedlinger's team used a much more harmless virus, called an adenovirus, to carry into the cells the four transformative genes, called Oct4, Sox2, Klf4 and c-Myc.
Researchers used both mouse skin cells and liver cells from fetal mice and made types to look and act like iPS cells.
"The nice thing about adenoviruses in contrast with retroviruses is they deliver proteins inside the cells but they will never, ever integrate their DNA into the cells," said Hochedlinger.
He said, as the cells divide, they dilute the virus until it disappears but the genetic changes remain.
To test the cells, scientists made chimeras --- a blend of two separate animals.
They injected these cells into mouse embryos and when the pups were born, they showed evidence that the cells had indeed transformed them.
"It results in this stripy pattern of brown fur that comes from the iPS cells and black fur which comes from the host embryo tissue," Hochedlinger said.
According to researchers, these chimeric mice have yet to develop tumors.
"We are in the process already of trying to make integration-free iPS cells in human cells," Hochedlinger said.
"It is a little more tricky because human reprogramming takes a little while longer than mouse reprogramming."
Doctors believe some day, they may be able to make tailor-made transplants to treat diseases in people by removing a few cells, transforming them in the lab and transplanting the new tissue or organs back in.
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