Human-Animal Chimeras Are Gestating on U.S. Research Farms

[Clark]

http://www.technologyreview.com/news/545106/human-animal-chimeras-are-gestating-on-us-research-farms/

Human-Animal Chimeras Are Gestating on U.S. Research Farms
A radical new approach to generating human organs is to grow them inside pigs or sheep.
      By Antonio Regalado

Braving a funding ban put in place by America’s top health agency, some U.S. research centers are moving ahead with attempts to grow human tissue inside pigs and sheep with the goal of creating hearts, livers, or other organs needed for transplants.
The effort to incubate organs in farm animals is ethically charged because it involves adding human cells to animal embryos in ways that could blur the line between species.
Last September, in a reversal of earlier policy, the National Institutes of Health announced it would not support studies involving such “human-animal chimeras” until it had reviewed the scientific and social implications more closely.
The agency, in a statement, said it was worried about the chance that animals’ “cognitive state” could be altered if they ended up with human brain cells.
The NIH action was triggered after it learned that scientists had begun such experiments with support from other funding sources, including from California’s state stem-cell agency. The human-animal mixtures are being created by injecting human stem cells into days-old animal embryos, then gestating these in female livestock.
Based on interviews with three teams, two in California and one in Minnesota, MIT Technology Review estimates that about 20 pregnancies of pig-human or sheep-human chimeras have been established during the last 12 months in the U.S., though so far no scientific paper describing the work has been published, and none of the animals were brought to term.
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