They look like ordinary baby rhesus macaques, but Hex, Roku and Chimero are the world's first chimeric monkeys, each with cells from the genomes of as many as six rhesus monkeys.

Until now research on so-called chimeric animals, or those that have cells with different genomes, has been limited to mice; a recent procedure produced mice using cells from two dads.

The researchers turned to monkeys for more insight into the capabilities of embryonic stem cells. Most experiments on stem cell therapies are based on mice, and the researchers wanted to understand whether primate embryonic stem cells respond the same way as those of mice do.

To create the chimeric monkeys, researchers essentially glued together cells from individual rhesus monkey embryos and then implanting these mixed embryos into mama monkeys.

The key was mixing cells from very early-stage embryos, or blastocysts, that consisted of just two to four cells – each one of the cells still totipotent, capable of transforming into a whole animal as well as the placenta and other life-sustaining tissues. (This is in contrast to pluripotent stem cells, which can differentiate into any tissue type in the body, but not certain embryonic tissues or entire organisms.)

"The cells never fuse, but they stay together and work together to form tissues and organs," said Shoukhrat Mitalipov of the Oregon National Primate Research Center at Oregon Health & Science University. "The possibilities for science are enormous." [Images of the Chimeric Monkeys]

Try, try again

The researchers first tried creating chimeric monkeys using the process for chimeric mice. In this procedure, embryonic stem cells are injected into a host embryo after they have been cultured for as long as decades. These stem cells will mix with the host embryo's cells to produce tissues and organs and ultimately offspring. When these offspring are mated, the resulting offspring have cells derived solely from the implanted stem cells. If you were to pluck two cells from a chimeric mouse's body, you could get two different genomes  –  complete sets of chromosomes and genetic information.

But the methods that work to create chimeric mice failed in rhesus monkeys, leading to offspring with cells only from the host embryo.

"Unfortunately that didn't work," Mitalipov told LiveScience in a telephone interview. "We produced offspring that way and they didn't show any contribution of stem cells." The stem cells seemed to have gotten lost somewhere, he said.

The researchers guessed that the culturing somehow had changed these embryonic stem cells. So they recovered stem cells from an embryo's inner cell mass (rather than from the freezer after being cultured) and, without culturing them, injected the stem cells into a host embryo.

Rather than one chimeric monkey infant, the result was two separate fetuses — twins.

Finally, the researchers hit on a successful method, using early blastocysts that had split into no more than four separate cells. They took individual cells out of these clumps and aggregated them back together, mixing and matching between three and six individuals to create 29 new blastocysts. The researchers picked the 14 strongest-looking of them and implanted them in five surrogate mother monkeys. 

12 Comments

1. 1. payitfwd 08:52 PM 1/6/12

   What a beautiful story. It's heart-warming to see that these baby monkeys are being "cared for" by researchers in rubber gloves rather than their mothers in the wild. I'm sure living their lives in metal cages while being constantly experimented on is a delightful experience. I love the human race and the suffering we enjoy inflicting on other humans and the "lesser" animals.

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2. 2. lilolme 11:27 PM 1/6/12

   I agree. Seven billion people. Are we an endangered species?
   

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3. 3. Eduuu in reply to payitfwd 12:42 AM 1/7/12

   I agree, the extent of the exploitation is daunting. It's a brutal industry.

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4. 4. IAMCRAIG in reply to payitfwd 02:19 AM 1/7/12

   If you don't grow your food and raise your own livestock (while treating it well throughout their lifespan), you're a gigantic hypocrite. You're also a hypocrite if you're using the majority of any technology today (take a look at some of the wars being fought in Africa over various metals and the atrocities that arise from such conflicts)
   
   
   This is a great discovery that will help further the human race, no matter what we do, we're going to have a negative impact on everything around us unless we all regress into farmers or hermits, though even then, other living beings will still suffer one way or another from our actions. At least any discomfort these animals feel will be for good reason.

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5. 5. timbosta 05:02 AM 1/7/12

   Ok, reduce it to it's simplest form: Is an individual important? Is the species more important than the individual? Which species are more important than others? Is an individual of one species more important than the whole of another species? The whole question of the ethics of vivisection is just quicksand. Seems to me if you eat meat or wear leather or kill spiders from fear, you'd better shut up.

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6. 6. tharriss 10:49 AM 1/7/12

   I don't think it helps to make it black and white, it has to be picking a spot on a spectrum... and people from different backgrounds with different views will all choose a different spot on the curve as the optimum spot. That's why these ethical discussions go round and round and round and never end or solve anything... there is no one exactly right solution.
   
   Personally I think the answer is to try and minimize suffering overall... sometimes it is better that individuals suffer to limit the suffering of others... sometimes the knowledge that we won't throw an individual under the bus, even to help the majority, ends up limiting the suffering of the majority in the macro sense.
   
   Society benefits if we all feel secure that society values us as individuals, and society can benefit if we sometimes sacrifice and individual for the good of everyone else... but usually the benefit of the sacrifice is less than the feeling of security everyone gets from knowing they won't be sacrificed. The same ethic that protects indivual humans from being exploited for the good of everyone else, can be applied to animals... and if we break it too much for animals, it can feel like a step towards breaking it for people, which then harms everyone... but of course animals aren't humans, so that link between throwing them under the bus and throwing one of us under a bus isn't as strong. How do you choose which and when? Heh, everyone argues and disagrees and tells everyone else they are idiots, but I'd prefer some calm application of reason whenever possible.
   
   I'd always tend to side with whoever seems to have really thought it all through, and did their best to balance all the conflicts in terms of least overall suffering for everyone... the answer may never be perfect, but siding with thinking carefully, over with knee-jerk emotional reactions, tends to be a winning rule of thumb for me.
   
   

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7. 7. priddseren 08:15 PM 1/7/12

   Kinda Dr. Mengeleish or Frankensteinish to me. At one point do scientists draw a line on what is just too much with minimal benefit. Really these guys are not discovering anything, they are just goofing around with stuff, in this case stem cells and embryos and seeing what happens. What happens when one of these guys does make a human/cat/monkey chimera. Eventually one of these scientist will try.

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8. 8. Shoe9 11:53 PM 1/7/12

   It is scary, daring stuff. Makes me uncomfortable. But if we can help heal the suffering of hundreds of thousands of people, maybe millions (thinking of childhood diabetes, Parkinson's disease...) maybe it is worth it.

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9. 9. indeseo 06:33 PM 1/10/12

   there are some people here who purport to read (and understand) these articles, but it is evident they do not understand very much at all. No one is asking them to run headlong 'over-the-cliff' (although, judging from their writings, they are already over the edge and on the way down), and no one is telling some tear-jerk story( (although one can almost hear these folks blow their nose because of the tears brought on by their imagination [and inner lack]), but these pseudo-science-readers are a real detriment to the useful purposes of research and progress.
   Please, some of you, go back to your soap-operas and romance novels, and please, please, don't have children
   in fact, some of you really should do your duty and volunteer for some experiment to be conducted upon yourself; you have benefited enough and given too little in return - why? because you have lapped up the benefits of a good education, and the understanding you demonstrate does credit to no one
   

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10. 10. postfuture 06:04 PM 1/12/12

    So, when we are going to create half-animal-half-human ancient gods? How long to wait for a date with a mermaid, Pan or Anubis? Is not it our ultimate goal? And what's the price?

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11. 11. dtran822 02:07 AM 1/26/12

    It is basic research like this one which have developed all of the vaccines, medications, surgical procedures that exist today. A scientist must justify their use of any model in their study in order to get the funding in the first place. The use of animals is a price we have to pay. Maybe you should write to our lawmakers to ease up on the use of human subjects or you should volunteer yourself to get tested on. Why bother reading this journal If you don't even support the work that these scientists spend years on.

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12. 12. checkmate4u 10:04 PM 4/27/12

    Indeseo, you are quite right, these pseudo- scientists have no clue what the implications for these stem cell experiments are. One day this research will provide numerous health benefits, and possibly to the ones who commented on this article. Same thing happened with biotech, which developed through cancer, and other disease research. This in turn has led to advances in stem cell experiments.

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