On July 23^rd 2009, the research report “iPS cells produce viable mice through tetraploid complementation” was published online in Nature (doi:10.1038/nature08267). This report answers the lingering question about the developmental potential of the iPS cells.

This research was led by Dr. Qi Zhou of the Institute of Zoology in Beijing and Fanyi Zeng of Shanghai Jiao Tong University, and was accomplished by their research group. In this research, they used viral vectors to introduce four genes into mouse fibroblast cells to reprogram these somatic cells into pluripotent cell in order to create iPS cells. After carrying out a standard set of tests to check whether the reprogramming had worked, the research group confirmed that they have generated 37 iPS cell lines. Then they tested the pluripotency of these iPS cell lines by tetraploid complementation and 6 of 37 iPS cell lines generated 27 live mice. 12 mice that were mated produced healthy offspring and for now, they have got hundreds of second generation, and more than 100 third-generation mice which were healthy and viable.

Since this report published online in Nature, the media worldwide gave the quake tremendous covers. Nature, Science, Times, Reuters, Economist, Wall Street Journal, Scientific American, Washington Post, ABC News, Boston Globe, Fox News, Los Angeles Times, Time Magazine, USA Today, Daily Telegraph, Independent, have published the comments on this report.

Numbers of stem cell researchers valued this work. "These investigators have, for the first time, unequivocally demonstrated that the iPS lines they have generated are truly pluripotent," wrote Andrew Laslett, group leader of Human Embryonic Stem Cell Technology at the Australian Stem Cell Centre in Melbourne, Australia. "Most research progresses in small steps. Xiao Xiao represents a jump forward," said Bruce Whitelaw, head of the Division of Developmental Biology at the Roslin Institute, and editor-in-chief of the journal Transgenic Research. Whitelaw also said, "The world must now believe that iPS cells can be truly pluripotent". "Yes, Xiao Xiao received the torch lit by Dolly," Whitelaw commented while reviewing the history of clone.

And for the ethical concern, Zhou said he hopes that researchers will take advantage of the technology as "an important model for understanding reprogramming". He added: "It is not intended to be a first step towards using iPS cells to create a human being."

In all, this is the first time that scientists have demonstrated that iPS cells can pass the gold standard for pluripotency and generated live mouse. The first iPS mouse was named Tiny, in the hope that the Tiny mouse and a small step could move the field of stem cell research forward, and the research could translate into great promises for future therapeutic interventions. (Written by: Qing Li)