Tuesday, June 7, 2011

Setback for Induced Pluripotent Stem Cells

Ever heard of induced pluripotent stem cells (iPSCs)? They were supposed to be the answer to the politically-charged issue of the use of embryonic stem cells in research or disease treatment. The idea has always been that if fully differentiated somatic cells could somehow be induced to return to an undifferentiated state (i.e. become pluripotent stem cells), then they could replace embryonic stem cells altogether. In addition, since iPSCs could be derived from the patient for which they would be used, it was presumed that they would not induce an immune response in the patient.

That presumption now is in doubt. A recent paper reports that iPSCs derived from mouse cells cause an immune response when injected back into genetically identical mice, leading ultimately to rejection of the iPSCs.

Scientists generally were surprised by these findings, since iPSCs were not supposed to be immunogenic in genetically identical animals. But further analysis revealed that these iPSP’s may be over-expressing certain genes, leading to the production of proteins seen as foreign by the immune systems of the recipient mice. Whatever the reason, the finding casts doubt on the idea that iPSPs could replace embryonic stem cells any time soon.

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