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Panel: Use Caution in Stem Cell Study of Monkey Brains

Posted on: Friday, 15 July 2005, 06:06 CDT

A panel of scientists, concerned about the remote possibility of instilling human traits in animals, has recommended caution in efforts to implant embryonic stem cells in the brains of monkeys and apes.

In its recommendations, released in today's Science, the panel raises the possibility that the human cells might transfer qualities to the animals and change the "moral" dimension of experimenting on them.

The recommendations follow National Academies of Science guidelines on stem cell research released in April.

"Our brains are ourselves, the brain is what makes us human," says panel member Hank Greely of Stanford University. "Appropriately, there is more concern about putting human cells into non-human brains."

Scientists hope to grow embryonic stem cells into replacement brain cells to treat neurological disorders such as Parkinson's and Huntington's disease. Safety tests of these treatments would require first implanting the cells in animals, perhaps including primates. However, whether implanting such cells might raise the consciousness of the animals to a higher level, changing the ethics of experimentation, raises some awkward questions, Greely says.

Only a few experiments have tried such implantation. In 2001, Harvard researchers transplanted human brain stem cells into the brains of fetal bonnet monkeys. The researchers found that the human stem cells formed into the appropriate brain cell varieties and became part of the primates' brains. However, it wasn't clear whether the human cells truly contributed to the monkeys' brain activity.

"It's a bit out there, but the fact this discussion is taking place is significant," says psychologist Dan Weiss of Penn State University, who was not part of the panel. Weiss, who studies animal thought processes, notes that no good measures for animal consciousness can presently answer the questions raised by the panel.

Despite the uncertainty, the panel, which was headed by biologist Ruth Faden of Johns Hopkins University in Baltimore, would limit experiments based on six factors: the number of implant cells; the age of the primate; the species; the size of the brain; the location in the brain of the implant; and any neurological ailments suffered by the primate. Implanting a large number of human stem cells into a healthy, developing chimp, a species closely related to humans, would raise a red flag, for example.

The panel was a two-year ad-hoc effort by biologists, legal experts and ethicists, who came together to hash out these issues after publication of the Harvard research alerted them to concerns about primate experiments.

The panel called for case-by-case review of all such brain experiments in primates. A co-chairman of the stem cell guidelines panel at the National Academies of Science, Richard Hynes of the Massachusetts Institute of Technology, called the Science article recommendations sensible.

Source: USA TODAY

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