Man has dreamt of this for centuries. https://en.wikipedia.org/wiki/Human–animal_hybrid
"In a remarkable—if likely controversial—feat, scientists announced today that they have created the first successful human-animal hybrids. The project proves that human cells can be introduced into a non-human organism, survive, and even grow inside a host animal, in this case, pigs.
This biomedical advance has long been a dream and a quandary for scientists hoping to address a critical shortage of donor organs.
Every ten minutes, a person is added to the national waiting list for organ transplants. And every day, 22 people on that list die without the organ they need. What if, rather than relying on a generous donor, you could grow a custom organ inside an animal instead?"