With the introduction of just four factors, researchers have successfully induced differentiated cells taken from mouse embryos or adult mice to behave like embryonic stem cells. The researchers reported their findings in an immediate early publication of the journal Cell.
The cells--which the researchers designate "induced pluripotent stem cells" (iPS)--exhibit the physical, growth, and genetic characteristics typical of embryonic stem cells, they reported. "Pluripotent" refers to the ability to differentiate into most other cell types.
"Human embryonic stem cells might be used to treat a host of diseases, such as Parkinson's disease, spinal cord injury, and diabetes," said Shinya Yamanaka of Kyoto University in Japan. "However, there are ethical difficulties regarding the use of human embryos, as well as the problem of tissue rejection following transplantation into patients."
Those problems could be circumvented if pluripotent cells could be obtained directly from the patients' own cells.
"We have demonstrated that pluripotent stem cells can be directly generated from fibroblast cultures by the addition of only a few defined factors," Yamanaka said. Fibroblasts make up structural fibers found in connective tissue.
Pluripotent stem cells can become any type of cell in the body. Adult stem cells are not as flexible. But currently the only way to get pluripotent stem cells is from embryonic cells. That raises ethical opposition in some quarters. Pluripotent stem cells created from adult cells would avoid most of the political resistance and at the same time be more immunologically compatible.
If this approach works for humans as well then some day we'll be able to have pluripotent stem cells made from our own cells. Then those cells could be used to grow replacement parts such as internal organs or injected into joints to supply joint material to those suffering from arthritis.
The researchers chose factors to introduce into adult cells by looking at which genes are turned on in embryonic stem cells. Note that advances in biotechnology in recent years have made it a lot easier to measure the levels of activity of many genes at once.
The researchers selected 24 genes--all previously found to play a role in early embryos and embryonic stem cell identity--as candidate factors that might give body cells the ability to become other cell types.The researchers found that four of those factors, known as Oct3/4, Sox2, c-Myc, and Klf4, could lend differentiated fibroblast cells taken from embryonic or adult mice the pluripotency normally reserved for embryonic stem cells.
They further reported that transplantation of the iPS cells under the skin of mice resulted in tumors containing a variety of tissues representing the three primary types found in mammalian embryos. Those primary "germ layers" in embryos eventually give rise to all an animal's tissues and organs.
The researchers still need to repeat this experiment with human cells to find out if this method will work for human cells as well. If they succeed then this discovery could open the gates for much higher levels of research funding for pluripotent stem cells.
|Share |||Randall Parker, 2006 August 10 11:38 PM Biotech Stem Cells|