Chinese scientists have reported an important advance in the characterization of certain stem cells by creating live mice through reprogrammed skin cells.

In an online paper published Thursday in the US journal Cell Stem Cell, the scientists reported that a specific iPS cell line gave an unusually high level of chimerism when injected into blastocysts (an early embryo) and thus might have unique characteristics not found in many other iPS cell lines.

Scientists working with the iPS cells, or induced pluripotent stem cells, have been eager to find out if they are fully pluripotent, as that would tell to what extent they have been truly reprogrammed and resemble the versatile embryonic stem cells (ESCs), said Dr. Shaorong Gao of the National Institute of Biological Sciences in Beijing.

"Although these findings are an important proof of principle, it would be premature to make claims about whether iPS cells in general are functionally equivalent to normal ESCs," Gao said.

The findings offer added hope, however, that the process of reprogramming may indeed one day overcome the need for embryo destruction in order to derive pluripotent cells for research and potential therapies, he said.

The same findings were also made by another team led by Professor Zhou Qi from the Chinese Academy of Sciences and Professor Fanyi Zeng from Shanghai Jiao Tong University. They published their findings in the British journal Nature.

The generally accepted "gold standard" for determining whether a mouse iPS cell line has been

fully reprogrammed is to show that when injected into a blastocyst, the iPS cells can, like bona fide ESCs, develop into different tissues in the resulting chimeric mouse, Gao told Xinhua.

However, until now mouse iPS cells have not been able to pass a more stringent test of true pluripotency termed "tetraploid complementation," which uses a hybrid embryo method to generate full-term mice entirely comprised of ESC-derived cells.

(Xinhua News Agency July 25, 2009)