Retrospectacle: A Neuroscience Blog

i-16f6f0afa66a0a0684ca68e4a024160f-thumb_rooster.gifRemember Bush’s speech last year where he denounced “human-animal hybrids“? Well, I don’t know about you, but I about fell off the couch laughing. But now it looks like his worst fear has come to pass: a chimeric sheep with 15% human cells, engineered with the hope of animal organs one day being used for human transplants. A University of Nevada scientist, Dr. Esmail Zanjani, has developed the technique which involves integrating human stem cells into a sheep blastocyst.

He has already created a sheep liver which has a large proportion of human cells and eventually hopes to precisely match a sheep to a transplant patient, using their own stem cells to create their own flock of sheep.

The process would involve extracting stem cells from the donor’s bone marrow and injecting them into the peritoneum of a sheep’s foetus. When the lamb is born, two months later, it would have a liver, heart, lungs and brain that are partly human and available for transplant.

Using a couple of ounces of bone marrow from a donor (no small amount really), scientists could isolate enough stem cells to inject into 10 sheep fetuses. According to the article, which is from a UK source, over 7,000 people are awaiting organ transplants and more than two-thirds of them will die before that transplant is made available. Therefore this new technique, if proven successful, could drastically reduce the reliance on human transplant organs and help to save thousands of lives.

i-340cef1aa8abe109cb700618ea56b594-hybrid sheep.bmp
Like, totally, Baaah.

I was also thinking that the availability of more organs may help to save the lives of people who would never have made it on the organ recipient list in the first place (because they are too old, sick, etc). In addition, people who have unusual immunological or blood profiles would not have to wait longer for the right match to come along. Organs tailored to the donor can be produced to be a perfect match, which will reduce the likelihood of rejection by the body.

Hat tip Bob Abu.


  1. #1 Dave
    March 26, 2007

    Gads! The Manimals have finally arrived?!?! Hide the children!

  2. #2 Spirula
    March 26, 2007

    I oppose transpecies transplants or fusions, but not for stem cell or manimal reasons. I think it opens the dangerous door of trans-species viral jumps that previously could not be made.

  3. #3 factician
    March 26, 2007

    I second the comment made by Spirula. There’s a lot of reasons to think that increased contact between human and animal cells will increase the frequency of movement of viruses across species. Of course, the only way to be sure is to actually make the human-animal hybrids…

  4. #4 Shelley Batts
    March 26, 2007

    Actually, that would require fusion of the cells. As stated in the article, the state at which the stem cells are injected make that impossible.

  5. #5 factician
    March 26, 2007

    Species jumping by viruses doesn’t require cell fusions at all. Take the bird flu, for example. Most of the cases in humans so far occurred in people who work with birds for a living.

    In the case of growing human organs in animals (or vice versa – some folks are trying to engineer pig organs to make them less likely to be rejected by people) you’re putting animal cells right next door to human cells. Normally, mutations that allow viruses to jump the species barrier never do that because any mutation that changes specificity to allow infection of a new host would decrease the ability of said variant to infect the original host. Said variant dies out, never having infected anyone. But put target cells next door, and your variant can pass freely from one cell type to another. Granted, a certain amount of this is just hand-waving because you can’t demonstrate that this will occur until you actually make human/animal hybrids. And one would still expect it to be a relatively rare event. But rare doesn’t mean never. And the consequences of creating new human zoonoses is something to be concerned about (I know that the IRBs responsible for approving these types of experiments generally demand that the material used be virus-free – but how do you demonstrate that, really?).

    As a side note, people have modelled this sort of things with bacteriophages and various species of bacteria.

  6. #6 bsci
    March 26, 2007

    The press release seems suspiciously well timed for the release of:

  7. #7 Shelley Batts
    March 26, 2007

    Well in that case, factician, I suppose it should be demonstrated in vivo and then, if proven a viable threat, we’d have to consider whether its worth it. But, couldn’t these animals be grown in specific pathogen free condidtions (SPF)? I do adenoviral vector work, and acquiring animals which are free of virus as well as maintained free of outside virus is a necessity. If the sheep/human hybrid is never exposed to a virus in the first place, one can’t mutate. Sure, every now and then someone might forget to don a glove, etc and a virus is transmitted, but keeping it rare and infrequent is the goal. This would be necessary anyway to preclude the donor from being infected with a virus upon transplantation, wouldn’t it?

    Raising them in SPF conditions would probably be far more safe than continuing animal husbandry on a mass scale (ie, raising cattle, chickens, sheep, etc). As you mentioned, bird flu was likley transmitted by close contact with birds…so why isn’t there more “hand waving” in their direction, when its already been proven to be true?

  8. #8 Kagehi
    March 26, 2007

    Personally, I can’t wait for the first wacko to get a transplant from something like this and start babbling about how, “Ever since I got that new lung I have had a strange craving for grass!” lol Happens in normal transplants, why should we expect any less wacky results from this sort?

  9. #9 factician
    March 26, 2007

    Getting and maintaining animals that are virus free is easier said than done. After all, it merely depends on your assay for virus free. An associate of mine works at a company that isolates viruses from serum sold to labs as virus-free. One of these viruses is currently being developed as a tumor treatment. My point is, unless you have a PCR assay or an immunoassay to find the virus, you won’t see it – so any viruses that haven’t been studied extensively won’t be found. And there are many, many viruses that no one has ever studied (see Craig Venter’s recent paper in PLoS Biology for an idea of how much is out there that we haven’t looked at). Anyone who thinks the serum in their lab is truly “virus-free” is kidding themselves. It’s free of the most notorious and tissue-culture damaging viruses.

    The problem with trans-species virus movement is that once it’s happened, you’ve created a new human disease. I.e. demonstrating that it can happen will be a sad day, indeed. Granted, there is much human suffering that can be taken care of by increasing our organ supply. Weigh that against a hypothetical risk of creating a new disease that could kill millions (or just give us all a mild rash). In my view, it’s a pretty difficult cost/benefit analysis to make, given that the risks will be rare, but potentially devastating.

  10. #10 dan dright
    March 26, 2007

    Look at the upside: We could grow a brain for W, a heart for Cheney, and some testicles for the democratic party!

  11. #11 Spirula
    March 27, 2007

    The additional point regarding a how pathogen free a SPF facility can be, is that they can only screen for known or symptomatic pathogens. For example, it would be unlikely that anyone working with African green monkeys 30 years ago would be at all suspect that they might be harboring HIV. Asymmtomatic viruses would be my greatest concern.

  12. #12 Black Knight
    March 29, 2007

    Life imitates art! Story at 10!

    Baa-aaaa. . .

  13. #13 fred
    August 4, 2007

    the think i dont trust in all that its:how much time the transplant organ will live? because we all know that the animal didnt have the same life time then an human they should do another test with 50% human ,is this sheep will live much longer than a real sheep?

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