When you do experiments about organ transplantation, do you use human organs or an animal organs?

Question: When you do experiments about organ transplantation, do you use human organs or an animal organs?
- Keywords:
  animal,
  human,
  organ,
  organ transplantation
Asked by 454sysb37 to Noel on 9 Mar 2015.
- Noel Carter answered on 9 Mar 2015:
  
  A mixture. We have done work with rats, mice and pigs. But ultimately what we are trying to achieve are improvements in treating humans.

Question: When you do experiments about organ transplantation, do you use human organs or an animal organs?