Reprieve for reprogrammed stem cells

What could have been a stumbling block for using reprogrammed stem cells in the clinic may barely be a bump in the road. A study published in 2011 in Nature found that stem cells produced by reprogramming mouse skin cells get attacked when transplanted back into mice. Stem cells derived from embryos didn’t similarly rile the immune system. The finding was unexpected because reprogrammed stem cells, also known as induced pluripotent stem cells, or iPS cells, come from the mouse or person into whom they are transplanted, so the immune system shouldn’t recognize them as foreign. Now Masumi Abe of the Japanese National Institute of Radiological Sciences in Chiba and colleagues have performed a more expansive version of the earlier study, examining 10 different types of iPS cells and seven types of embryonic stem cells to address the potential problem. Neither embryonic stem cells nor iPS cells provoked the immune system to attack to any significant degree when transplanted into mice, the researchers report online January 9 in Nature. However, heart muscle cells grown from iPS cells in a lab dish did stir up the immune system, which may be cause for concern.