Prior to the discovery of reprogramming cells into induced pluripotent stem cells , 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 iPS cell cultures. Using mice models, the team spent six 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 iPS cells.
"iXEN cells can shed light on reproductive diseases. If we can continue to unlock the secrets of iXEN cells, we may be able to improve induced pluripotent stem cell quality and lay the groundwork for future research on tissues that protect and nourish the human embryo.”
MSU discovers a new kind of stem cell