WASHINGTON, Nov. 20 (Xinhua) -- Two separate team of researchers from the United States and Japan announced Tuesday that they successfully converted human skin cells into cells that resemble embryonic stem cells, a breakthrough that might sidestep the ethical stumbling blocks of stem cells obtained from human embryos.

The research papers by the U.S. team led by James Thomson from University of Wisconsin-Madison will be published in the Nov. 22 edition of journal Science. Japanese research team led by Shinya Yamanaka of Kyoto University will publish their papers in the Nov.30 edition of journal Cell.

The two teams both make use of the "cell genetic reprogramming" technique to introduce some new genetic elements into the human skin cells to create cells indistinguishable from embryonic stem cells, without having to create and destroy any human embryo in the process.

The two teams choose different skin cells as the suppliers. Yamanaka reprogrammed skin cells from the face of an unidentified 36-year-old woman, and Thomson's team worked with human fibroblasts, skin cells that are easy to obtain and grow in culture.

Then they did basically the same thing: introducing a different set of four genes into the different skin cells. The new genes reprogrammed the ordinary cells and converted them into the so-called "induced pluripotent stem (iPS) cells", which are similar, not identical to embryonic stem cells. "Pluripotent" refers to the ability to differentiate into most other cell types.

"The induced cells do all the things embryonic stem cells do," explains Thomson. "It's going to completely change the field."

Their work is considered as a significant breakthrough in the stem cell field. However, the researchers noted that more study of the newly-made cells is required to ensure that the "cells do not differ from embryonic stem cells in a clinically significant or unexpected way." So it is hardly time to discontinue embryonic stem cell research, they said.

It would be "premature to conclude that iPS cells can replace embryonic stem cells," said the Japanese research team.

The successful isolation and culturing of human embryonic stem cells in 1998 sparked a huge amount of scientific and public interest, as stem cells are capable of becoming any of the cells or tissues that make up the human body. Scientists, as well as patients all over the world, hope to use stem cell to treat diseases including diabetes, Parkinson's disease and spinal injuries.

But embryonic stem cells also sparked significant controversy as embryos were destroyed in the process of obtaining them. In the United States, President Bush had twice vetoed legislation to pave the way for taxpayer-funded embryo research.

So the new findings, without involving any human embryos, seem to be opening a new window to stem cell-related therapies. "These methods should be useful for developing disease models and for drug development," said the journal Science.