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Over the years that scientists have been inserting human cells into the embryos of mice, causing the furry creatures to grow Mini Me versions of human tissues and even brain structures, none of the animals have ever looked up in a panic and screamed, “What am I doing in this body?!” But the prospect of something going sci-fi-ishly wrong in experiments that create “chimeras” — creatures containing cells and even organs from another species — has long made scientists and bioethicists uneasy, enough so that in September the National Institutes of Health announced that it would no longer fund some chimera research.
Now comes the backlash.
In an emphatic letter published in Science, 11 researchers argue that NIH should reverse its decision against funding studies in which scientists implant human stem cells into early, nonhuman embryos. By bailing on such experiments, the letter argues, NIH “poses a threat to progress,” strangling research that “has tremendous promise” for developmental biology (understanding how embryos develop) and regenerative medicine (providing cells, tissues, or organs to treat diseases).
Research with chimeras (named for the lion-goat-serpent mashup of Greek mythology) is not new. In 1984 scientists melded cells from goat and sheep embryos, producing a “geep.” A human-mouse chimera called SCID-hu (human thymus, liver, or lymph nodes; mouse everything else) has been a workhorse of studies in AIDS, cancer, and other diseases for nearly 30 years. Few objected. Then scientists turned to brain cells.
Read full, original post: Human-animal chimeras face new ethical scrutiny