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Research Mingling Human, Animal Cells Continues to Evolve

Posted on: Sunday, 1 May 2005, 03:00 CDT

RENO, Nev. - On a farm about six miles outside this gambling town, Jason Chamberlain looks over a flock of about 50 smelly sheep, many of them possessing partially human livers, hearts, brains and other organs.

The University of Nevada-Reno researcher talks matter-of-factly about his plans to euthanize one of the pregnant sheep in a nearby lab. He can't wait to examine the effects of the human cells he had injected into the fetus' brain about two months ago.

"It's mice on a large scale," Mr. Chamberlain says with a shrug.

As strange as his work might sound, it is firmly within the new ethics guidelines the influential National Academies issued this past week for stem cell research.

In fact, the academies' report endorses research that co-mingles human and animal tissue as vital to ensuring that experimental drugs and new tissue replacement therapies are safe for people.

Doctors have transplanted pig valves into human hearts for years, and scientists have injected human cells into lab animals for even longer. But the biological co-mingling of animal and human is evolving into even more exotic and unsettling mixes of species

In the past two years, scientists have created pigs with human blood, fused rabbit eggs with human DNA and injected human stem cells to make paralyzed mice walk.

Particularly worrisome to some scientists are the nightmare scenarios that could arise from the mixing of brain cells: What if a human mind somehow got trapped inside a sheep's head?

The "idea that human neuronal cells might participate in 'higher order' brain functions in a nonhuman animal, however unlikely that may be, raises concerns that need to be considered," the academies' report warned.

In January, an informal ethics committee at Stanford Uni-versity endorsed a proposal to create mice with brains nearly completely made of human brain cells. Stem cell scientist Irving Weissman said his experiment could provide unparalleled insight into how the human brain develops and how degenerative brain diseases such as Parkinson's progress.

The academies' report recommends that each institution involved in stem cell research create a formal, standing committee to specifically oversee the work, including experiments that mix human and animal cells.

Few human-animal hybrids are as advanced as the sheep created by stem cell scientist Esmail Zanjani and his team at the University of Nevada-Reno. They want to one day turn sheep into living factories for human organs and tissues and along the way create cutting-edge lab animals to more effectively test experimental drugs.

Source: Augusta Chronicle, The

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