"It takes a long time to generate iPS cells and then differentiate them into tissue-specific functional cell types," said Ding, "and it's a tedious process. Also, what you generate is not ideal."
Specifically, it takes some two to four weeks for scientists to create iPS cells from skin cells and the process is far from efficient, with only one cell out of thousands making the complete transformation. Furthermore, once scientists obtain iPS cells, they then have to go through the tricky procedure of inducing the iPS cells to differentiate into desired types of cells, which takes an additional two to four weeks.
In addition, the process of generating mature cells from iPS cells is not foolproof. When, for example, scientists induce iPS cells to become heart cells, the resulting cells are a mix of heart cells and some lingering iPS cells. Scientists are concerned that giving these new heart cells (along with the remaining pluripotent cells) to patients might be dangerous. When pluripotent cells are injected in mice, they cause cancer-like growths.
Because of these concerns, Ding and colleagues decided to try to tweak the process by completely bypassing the iPS stage and going directly from one type of mature cell (a skin cell) to another (a heart cell).
Bypassing the Stem Cell Stage
The team introduced the same four genes initially used to make iPS cells into adult skin fibroblast cells, but instead of letting the genes be continuously active in cells for several weeks, they switched off their activities just after a few days, long before the cells had turned into iPS cells. Once the four genes were switched off, the scientists gave a signal to the cells to make them turn into heart cells.
"In 11 days, we went from skin cells to beating heart cells in a dish," said Ding. "It was phenomenal to see."
Ding points out the protocol is fundamentally di
|Contact: Mika Ono|
Scripps Research Institute