The first induced pluripotent stem cells were created in 2007 by Shinya Yamanaka's team at Kyoto University in Japan, which inserted extra copies of four known stem cell genes, including OCT4 and SOX2, into human skin cells. Those genes began expressing proteins that changed the skin cells back to a more pluripotent state. This technique, which has since been repeated by other labs and refined to the point were fewer additional genes are needed to achieve reprogramming, was a major scientific breakthrough. Its potential for use in human therapies is limited, however, because inserting new genes into adult cells, either directly or by using viruses to carry the genetic payload, can cause a host of problems.
In the current study, the team at WPI and CellThera turned on the existing, yet dormant, stem cell genes OCT4, SOX2 and NANOG already in the skin cells by lowering the amount of atmospheric oxygen the cells were exposed to, and by adding a protein called fibroblast growth factor 2 (FGF2) to the culture medium. (FGF2 is a naturally occurring protein that is known to be vital for maintaining the pluripotency of embryonic stem cells.)
Furthermore, once the stem cell genes were activated and began expressing proteins, the team found those proteins migrated back into the nucleus of the skin cells, precisely as would occur in induced pluripotent stem cells. "This was an exciting observation," said Raymond Page, PhD, research assistant professor of biology and biotechnology at WPI and lead author on the paper. "Having these proteins localize to the nucleus is the first step of reprogramming these cells."
Even more surprising, the team found that the stem cell genes OCT4, SOX2 and NANO
|Contact: Michael Cohen|
Worcester Polytechnic Institute