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takyon writes:

Researchers at Michigan State University have discovered a new type of stem cell. Induced extraembryonic endoderm (iXEN) stem cells were discovered while looking at cells thought to be defective, cancerous, or waste byproducts:

Researchers at Michigan State University say they have discovered a new kind of stem cell, one that could lead to advances in regenerative medicine as well as offer new ways to study birth defects and other reproductive problems. [...] Prior to the discovery of reprogramming, scientists developed pluripotent stem cells from embryos. However, the embryo produces not only pluripotent stem cells, but also XEN cells, a stem cell type with unique properties. While pluripotent stem cells produce cells in the body, XEN cells produce extraembryonic tissues that play an essential but indirect role in fetal development.

Parenti and his team speculated that if the embryo produces both pluripotent and XEN cells, this might also occur during reprogramming. The eureka moment came when Parenti discovered colonies of iXEN cells popping up like weeds in his iPSC cultures. Using mice models, the team spent 6 months proving that these genetic weeds are not cancer-like, as previously suspected, but in fact, a new kind of stem cell with desirable properties. Even more surprising, the team found that by inhibiting expression of XEN genes during reprogramming, they could decrease production of iXEN cells and increase production of iPSCs. "Nature makes stem cells perfectly, but we are still trying to improve our stem cell production," Parenti said. "We took what we learned by studying the embryo and applied it to reprogramming, and this opened up a new way to optimize reprogramming."

OSKM Induce Extraembryonic Endoderm Stem Cells in Parallel to Induced Pluripotent Stem Cells (open, DOI: 10.1016/j.stemcr.2016.02.003)

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