MADISON 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 (Sunday, 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, says Joshua Coon, an associate professor of chemistry and biomolecular chemistry who directed the project.
"We looked at RNA, at proteins, and at structures on the proteins that help regulate their activity, and saw substantial similarity between the two stem-cell types," he says.
Proteins are complex molecules made by cells for innumerable structural and chemical purposes, and the new study measured more than 6,000 individual proteins using highly accurate mass spectrometry, a technique that measures mass as the first step of identifying proteins.
The study in Nature Methods, published online, is the first comprehensive comparison of proteins in the two stem cell types, says Doug Phanstiel, who is now at Stanford University, an
|Contact: Joshua Coon|
University of Wisconsin-Madison