Mice from Skin Cells
Reprogrammed cells develop into live animals.

Source: “iPS cells produce viable mice through tetraploid complementation”
Qi Zhou et al.
Nature 461: 86-90

“iPS cells can support full-term development of tetraploid blastocyst-­complemented embryos”
Shaorong Gao et al.
Cell Stem Cell 5: 135-138

Results: Researchers in China grew viable mice from induced pluripotent stem cells, which are made by modifying adult cells. Some of the mice went on to produce a second generation of offspring.

Why it matters: The research proved that induced pluripotent stem (iPS) cells, like embryonic stem cells, can differentiate into any cell type in the body. It suggests that iPS cells can be used for the same scientific purposes as embryonic stem cells–for example, to develop treatments that replace diseased cells.

Methods: Researchers transferred iPS cells generated from mouse fibroblasts (a type of skin cell) into specialized embryos that lacked the ability to develop on their own. Introducing the iPS cells triggered the embryos to begin developing. The embryos were then transplanted into surrogate mothers.

Next steps: Although the scientists’ achievement was impressive, only 1 to 3 percent of the embryos developed into live mice. In addition, many of those mice had physical abnormalities or died soon after birth. Scientists want to understand how the differences between iPS cells and embryonic stem cells might lead to these abnormalities. They also want to increase the rate of live births.