In the most recent face-off between Induced pluripotent stem cells (iPSCs) and embryonic stem cells (ES cells), ES cells came out ahead; iPSCs aren’t the same as ES cells even when they carry the same mutation. That’s according to work published in the May 7 issue of Cell Stem Cell.

Induced versus embryonic

First, some background. Embryonic stem cells come from 5-6 day old embryos left over after in vitro fertilization. These primitive cells can become any cell in the body. iPSCs come from adult cells — most often the skin — that are reprogrammed to act like embryonic stem cells. They can also form all cell types in the body. When Shinya Yamanaka first created iPS cells in 2007, the prevailing wisdom was that they might one day completely replace ES cells, but only if they were safe and truly equivalent to their embryonic counterparts.

That “but” has driven ongoing experiments, many by CIRM-funded researchers, who have found that the two cell types express different genes (see this blog entry). In this latest work, European and Israeli researchers found that when they created iPS and ES cells both carrying a mutation that causes fragile X syndrome, the two cell groups behaved very differently, with the iPS cells not even activating the mutated gene.

Disease in a dish

This finding raises questions about whether iPSCs will be the best choice for mimicking diseases in a dish.

In an article in Medical News Today, Nissim Benvenisty, director of the Stem Cell Unit at the Hebrew University of Jerusalem and a leading author of the study, says:

“Until we understand better the differences between these two types of cells, the optimal approach might be to model human genetic disorders using both systems, whenever possible”

That said, when Stefan Heller of Stanford University created ear hair cells from both ES and iPSCs lls he found no difference in their functionality.