Why use pig organs in transplants? Wouldn’t a chimp organ work better, since we are more closely realted to chimps.
Even if it did, people generally find it more ethically acceptable to kill a pig in order to save a human being (we kill pigs in order to eat them, too, after all) than to kill a chimp. Also a chimp can carry diseases that are transferrable to humans more readily than a pig will, although AFAIK the organs are pretty well sterilized before use.
Plus they breed and mature faster. And pig organs are pertty much the same size as humans. I have no idea if there is a “stronger” rejection reaction to pig organs than to chimp organs. Interesting question. The plan is to genetically engineer pigs so that their organs apear “human” to our immune system. That’s the “plan”, anyway. I don’t know how far along we are in getting there.
There’s a handful of reasons.
1)Pig hearts are very similar to humans in their design and size.
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Pigs are not an endangered species
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Pigs reproduce more quickly and have larger litters than primates, meaning they are more easily manipulated through breeding.
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Pigs are generally healthier, hardier animals than primates
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A primate’s close genetic relation to humans actually increases the risk of a transplanted organ carrying over some kinds of pathogens that would also affect humans (AIDS, anyone?), which is not as true with pigs.
Are chimps endangered?
So a pig’s heart is more closely related in design and size than chimp’s heart?
They’re actually about equally “compatable”, give or take a few details either way. And yes, chimps are endangered but baboons are not, and their heart design is about the same as a chimp. So the choice is usually posed as baboon vs. pig because of the endangered status of chimps.
Primate organs do pose a bit lower rejection risk, but it’s all the other factors combined–in addition to the actual physical similarities–that make Pig’s hearts the more acceptable choice. We already use their valves to replace damaged ones in humans with quite a bit of sucess. One of the main problems with pig hearts, however, is that in the pig the heart is on the same level as the brain. But in a human, the heart has to pump against gravity to make it the foot and a half or so up to the brain. It remains to be seen if this is something that doctors will be able to counteract or if the transplanted hearts will naturally strengthen up enough that it isn’t an issue.
This is all still very new technology, you understand. Animal-to-human heart transplants have been attempted since the '60s, but it wasn’t until the mid '80s that a transplantee lived more than a few days (baboon heart, survived about 20 days). And in the mid 90’s they had a patient who survived with a pig heart for a little over a month. Right now, the main focus is on breeding “transgenic” pigs, meaning that they’ll have enough in common with human immune systems that their organs won’t be immediately rejected by us.
So a primate heart will be rejected less often, but a pig heart is close enough that the increased rejection rate is not a major concern?
Why are the differences is structure that make a pig heart more like a human heart?