Simple recipe turns human skin cells into embryonic stem cell-...(nile diabetes and spinal cord injury. ...)

The use of human embryos, however, faces ethical controversies that hinder the applications of human embryonic stem cells, they continued. In addition, it is difficult to generate patient or disease-specific embryonic stem cells, which are required for their effective application. One way to circumvent these issues is to induce pluripotent status in other cells of the body by direct reprogramming, Yamanaka said.

Last year, his team found that four 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. Fibroblasts make up structural fibers found in connective tissue. Those four factors are transcripton factors, meaning that they control the activity of other genes. They were also known to play a role in early embryos and embryonic stem cell identity.

The researchers have now shown that the same four factors can generate iPS cells from fibroblasts taken from human skin. From about 50,000 transfected human cells, we obtained approximately 10 iPS cell clones, Yamanaka said. This efficiency may sound very low, but it means that from one experiment, with a single ten centimeter dish, you can get multiple iPS cell lines.

The iPS cells were indistinguishable from embryonic stem cells in terms of their appearance and behavior in cell culture, they found. They also express genetic markers that are used by scientists to identify embryonic stem cells. Human embryonic stem cells and iPS cells display similar patterns of global gene activity.

They showed that the converted human cells could differentiate to form three germ layers in cell culture. Those primary germ layers in embryos eventually give rise to all the bodys tissues and organs. They further showed that the human iPS cells could give rise to neurons using a method earlier demonstrated for human embryonic
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