Researchers in China are reporting that they have found a way to determine which somatic cells -- or differentiated body cells -- that have been reprogrammed into a primordial, embryonic-like state are the most viable for therapeutic applications.
In a paper published online last week by the Journal of Biological Chemistry, two collaborating teams from institutes at the Chinese Academy of Sciences point to a marker they found in induced-pluripotent stem cells, or iPS cells, taken from mice. That marker is a cluster of small RNA whose expression appears strictly correlated with levels of pluripotency, or "stemness." (The more pluripotent, the more likely a stem cell will develop into the desired tissue, organ or being.)
"We identified a genomic region encoding several genes and a large cluster of microRNAs in the mouse genome whose expression is high in fully pluripotent embryonic stem cells and iPS cells but significantly reduced in partially pluripotent iPS cells, indicating that the Dlk1-Dio3 region may serve as a marker," said Qi Zhou, a researcher at the CAS Institute of Zoology and co-author of the paper. "No other genomic regions were found to exhibit such clear expression changes between cell lines with different pluripotent levels."
After the creation of the first iPS cells in Japan in 2006, Zhou and others set out to determine whether the reprogrammed adult cells are versatile enough to generate an entire mammalian body, as embryonic stem cells can.
Then, last summer, Zhou announced that his team had reprogrammed somatic cells of mice, injected them into embryos and created 27 live offspring, which clearly demonstrated that iPS cells can, like embryonic stem cells, produce healthy adults. Though lauded as a huge step forward, they also found not all iPS cells were perfect: Many of the iPS cell lines used did not produce mice, and some of the mice that were produced had abnormalities.
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