One of the obstacles to employing human embryonic stem cells for medical use lies in their very promise: They are born to rapidly differentiate into other cell types. Until now, scientists have not been able to efficiently keep embryonic stem cells in their pristine stem state. The alternative that has been proposed to embryonic stem cells – reprogrammed adult cells called induced pluripotent stem cells (iPS cells) – have similar limitations. Though these can differentiate into many different cell types, they retain signs of “priming,” – commitment to specific cell lineages.
A team at the Weizmann Institute of Science has now taken a large step toward removing that obstacle: They have created iPS cells that are completely “reset” to the earliest possible state and maintained them in that state. Among other things, this research may, in the future, pave the way toward the ability to grow transplant organs to order.
Since they were first created in 2006, iPS cells have been touted as an ethical and practical substitute for embryonicstem cells. They are made by inserting four genes into the genomes of suchadult cells as skin cells. This turns back the developmental clock almost all the way – but not completely – to an embryonic-stem-cell-like state. Dr. Jacob Hanna of the Institute’s Molecular Genetics Department and his team, including research students Ohad Gafni and Leehee Weinberger and researchers in the Israel National Center for Personalized Medicine, realized that inserting genes to reset the stem cells was not enough. One also has to put the cells’ drive to differentiate on hold.