As described in my post of February 25, and at other times on this blog, efforts are proceeding to apply “mitochondrial replacement techniques” (MRTs) to prevent severe, maternally-inherited mitochondrial disease from being passed on to children of affected women. MRTs involve attempting to put the nucleus of an egg or embryo from an affected woman into a cell or embryo from an unaffected mom, so that the latter’s healthy mitochondria would be passed on to offspring. This is still at the research stage but as I commented on February 25, expert reviews in the U.K. and the U.S. have recommended trying to proceed.
There are many technical challenges, among them that the transfer is not 100% perfect. Some of the abnormal mitochondria may “come along for the ride” in the transfer. One might think that wouldn’t matter if there are only a few.
But research suggests that the sort of “oops” that can happen in complex biology may indeed happen. Nature has a news item this week reporting that in some research, the abnormal mitochondria may not only survive the transfer, but their genes may be replicated faster than the normal mitochondria, sort of like weeds growing back faster than the grass in your lawn, and taking over. How much of an impediment would this be to creating an unaffected embryo to try to bring to term? That’s not clear, but the laboratory finding has researchers saying that efforts to have an unaffected baby born after MRT should slow down a bit until things are worked out.
Like the research that yielded the new finding, working things out means creating some number of new human embryos solely for research, and destroying them in the process. These embryos are of course nascent human beings that current law and regulation—and substantial public opinion—do not afford any human rights. And one expert says that the research can’t just use very early embryos, or embryonic stem cells derived from them, but to really understand what’s going on, embryos have to be created and grown up in the lab for up to two weeks—before being destroyed.
So human embryos will continue to be the raw materials of reproductive medical technology, not just the patients who eventually might benefit from the results.