Chimeras are one of the more controversial and fascinating areas of human stem cell and early embryo research. The notion of a chimera traces back thousands of years to creatures that were mixtures of various animals including humans in some cases.
What about a real human chimera embryo?
Today, chimera research has the potential to make major advances in our knowledge and even biomedical treatments such as through human organ creation within animal chimeras. However, human chimera research is intensely divisive amongst society more generally.
A few weeks ago the NIH announced that it will no longer be funding research on chimeras, pending an ethics and policy review (a big HT to Gretchen Vogel at Science; I recommend that you also read her piece on this as well.)
This development at the NIH means the suspension of federal funding for specific chimera projects involving human stem or germ cells. Other work such as that supported by CIRM continues in this area. Chimeras do not have to involve human cells and much interesting research has been done in this narrowed area including mouse-rat chimeras (see image above from Dr. Hiromitsu Nakauchi).
It will be important to carefully watch what NIH decides on human stem cell chimeras, as this will have a great influence on the extent to which this research moves forward even if in principle some studies such as those of Dr. Nakauchi can continue with non-federal funding sources.
Is human chimera research ethical? What if it could lead to major advances in biomedicine such as generating new organs including livers that are now in short supply for donors? Does that change the equation and dow do we balance the risks and potential benefits?
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