A new effort at “somatic” gene editing in China is reported this week. The key summary:
“As the researchers report in the New England Journal of Medicine,
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they transplanted [blood stem] cells that had undergone CRISPR-based editing [of a gene that encodes for a receptor, or “docking station”] into a patient with HIV and acute lymphoblastic leukemia. While [the edited cells lasted for a long time in the bloodstream of the HIV-infected recipient], they only made up between 5 percent and 8 percent of blood cells. A higher percentage is needed for this to be an HIV cure…”
In “somatic” gene editing, mature cells, such as “adult stem cells” or diseased tissues, are gene edited for the purples of treating a fully-formed individual with a disease. That is what appears to be in view here. Similar efforts are in progress to treat sickle cell anemia and other genetic diseases. The ethical issues are relatively well-understood, and fit within the regime of regulating cells-as-medicines in clinical trials of humans, under the ethical and regulatory regime that governs the latter.
That’s in contrast to “heritable” gene editing, which attempts to edit genes in embryos, fertilized eggs (zygotes), or gametes (sperm or eggs) with changes that would be passed on through the generations, as recent entries on this blog have been addressing. The Chinese twin girls who were reported to have undergone gene editing late in 2018 are examples of an attempt at “heritable” gene editing.
A second report from Nature describes efforts to use human “reprogrammed” stem cells, aka pluripotent stem cells, to make human “embryo-like structures.” This is distinct from making a human embryo, for example in IVF, then removing cells, likely destroying it, for use in research or to develop medical treatments. In conservative commentaries in recent years, these “reprogrammed” stem cells are considered the “ethical embryonic stem cells,” because they can’t form a full individual and they don’t require creation and destruction of an embryo, that would under normal circumstances form a full individual.
Thing is, these “embryo-like structures” can still form something called a “primitive streak,” which, in normal embryos, is the first sign of formation of a nervous system. The primitive streak usually forms 14 days after fertilization, so, to try to avoid concerns about research on embryos, scientists who think such research is ethical in limited circumstances have operated under a “14-day rule”–voluntary in the US, mandated by law in the UK–after which embryos would not be destroyed for research. These “embryo-like structures” may form a primitive streak, it appears. The situation is similar to “synthetic human entities with embryo-like features,” or “SHEEFs,” which may bypass the primitive streak but raise similar issues of whether something too like a natural human being is being engineered by this work for it to be ethical.
A developmental biologist at Caltech says, the California Institute of Technology in Pasadena. “We will have to confront ourselves with the question of what is a human embryo, and whether these models really have the potential to develop into one.” The researchers making these synthetic embryos argue that they lack a placenta and other cells needed for development, so could not develop into a person.
At least for now.