There is considerable enthusiasm for the use of “reprogrammed” pluripotent stem cells, or iPSCs, for use in the laboratory and as possible cellular treatment for people with certain injuries or diseases. This enthusiasm is warranted; human iPSCs (hiPSCs) are readily obtained, and without the destruction of a human embryo as is needed to obtain a “natural” human embryonic stem cell (hESC). Therefore, iPSCs are often described as the “ethical” stem cells.
Just how dissimilar iPSCs may be to “natural” ESCs has been controversial, however. A recent publication in the journal Nature Biotechnology strongly suggests that while not identical, it may well be that they can be treated interchangeably in the lab or for possible clinical use.
In the paper (journal subscription or $32 online article purchase required), scientists from Harvard, MIT, Johns Hopkins, and other major research institutes in the U.S. and Italy describe an elegant experiment. They took two previously established hESCs—derived from two different human embryos, to be sure—and let them differentiate into a specific type of adult cell called a fibroblast. Then they took the fibroblasts and reprogrammed them into hiPSCs using a technique that avoids the risk of making the cells malignant—a risk associated with some other reprogramming methods. To put it another way, they let the hESCs mature and then “back-translated” them, as it were, to a pluripotent state with the reprogramming step. (Recall that a “pluripotent” cell is capable of becoming many different adult cell types.) They did the appropriate experimental controls.
They looked specifically at whether the expression—or transcription into messenger RNA—of the hESCs and the hiPSCs differed. And the answer was yes, but not very much—only 49 genes, they counted, out of a total of about 30,000 in the genome, when they compared the hiPSCs with the hESC (the one of the two cell lines) it originally came from. There were greater differences between hiPSCs that came from one of the two hESCs, and the other hESC. Gene modifications called “epigenetic” changes, that turn genes on or off, were also so similar as to be virtually identical.
The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.