Why do we use pigs for donor tissue? What is in their DNA that is so compatible to ours? Why can’t we use bears or other animals?
Vona
Mostly because pig parts (like heart valves, ect.) are about the right size, and there are a lot of pigs available.
Do you want to hunt down a grizzly, just so you can steal its atrial valve? Not that it would fit, anyway.
No, but my first question was about the commonality between pigs and bears. I’ve read that they are related phylogenically.
Vona
Can’t be true- even amongst people there is donor incompatibility and rejection. What is it about pigs that makes them safe for tissue transplact???
Everything is related, it’s just a matter of how distantly. As noted above, bears are more closely related to humans than pigs are, but only slightly.
Pigs are used for potential transplants for several reasons:
- Pig organs are about the same size as human organs.
- There are lots of pigs around.
- You don’t run into ethical issues like you would with, say, chimps.
- Pigs breed pretty quickly and have large litters.
Currently there is a progam to breed a strain of pigs that have been genetically modified (with human DNA) to better match human tissue. Without getting into a lot of detail, this means modifying certain structures on the outside of cells that vary by species. The goal would be to make pig tissue about as compatible as human tissue is, although it still won’t be like having your own tissue (or that of an identical twin) available.
Pigs aren’t safer. You still have rejection issues. Pig parts are just much cheaper and common.
Gahhh! That was not noted above, because it’s wrong. Bears are more closely related to pigs than to humans, but only slightly. Sorry about that. I’m better with Lions and Tigers and Bears. 
Oh, my.
O.K., just how closely are bears related to pigs vis a vis humans? Where did the pig and bear ancestors separate? And where were we (us huimans) when this happened?
And why all this concern with pigs and bears? Reading a lot of fairy tales lately?
The original question was phylogenetically, how close are pigs and bears and if, as humans, we’re not close to them, why do we use pigs as donors?
According to wikipedia :
“The Euarchontoglires probably split from the Laurasiatheria sister group about 85 to 95 million years ago during the Cretaceous. This hypothesis is supported by fossil as well molecular evidence.”
My sister had a pig valve in her heart for just over 25 years. When one of my many detractors heard that he said, “It figures.”
See my post in your other thread (although I didn’t talk about timeline of separation). And see post #6 in this thread for why we use pigs for transplants.