Hopes have been high since induced pluripotent stem cells (IPSCs) were first produced four years ago that these cells would be sufficiently like embryonic stem cells (ESCs) that they could fill the same roles in research and therapeutic applications. Initial indications were very promising. But more recently, subtle differences have come to light. And even worse, recent research has shown that differentiated cells produced from IPSCs created from adult cells of a specific mouse could be rejected by the immune system of the same mouse – indicating that there are enough differences that the immune system could not be deceived.
However, the latest study seems to show that whatever differences may exist must be pretty subtle. IPSCs were compared with actual ESCs with respect to the messenger RNA present, the quantities of each of more than 6000 different proteins in the cell, and the epigenetic modifications present in those proteins. The study claims to show that the IPSCs and the ESCs were “99 percent similar”.
Ever since human induced pluripotent stem cells were first derived in 2007, scientists have wondered whether they were functionally equivalent to embryonic stem cells, which are sourced in early stage embryos.
Both cell types have the ability to differentiate into any cell in the body, but their origins — in embryonic and adult tissue — suggest that they are not identical.
Although both cell types have great potential in basic biological research and in cell- and tissue-replacement therapy, the newer form, called IPS cells, have two advantages. They face less ethical constraint, as they do not require embryos. And they could be more useful in cell-replacement therapies: growing them from the patient’s own cells would avoid immune rejection.
But until IPS cells are proven to have the same traits as embryonic stem cells, they cannot be considered to be identical.
In a study published today (Sept. 11), researchers at the University of Wisconsin-Madison report the first full measurement of the proteins made by both types of stem cells. In a study that looked at four embryonic stem cells and four IPS cells, the proteins turned out to be 99 percent similar