Why would it matter WHERE the new cells are grown?
The article given by the OP proposed putting these human induced pluripotent cells and parts into different species, with scientists admitting they don’t know what will happen to them. They hope they become livers or kidneys, but they could also become parts of brains of the animals:
Why would that matter? Genetically human brain cells could exist in the brain of a pig, but it would still be the brain of a pig, animated by a non-rational soul.
They also said these pigs should not be bred together or there may be even more chance human cells could be involved in the brains of the pigs. But they said they wouldn’t breed them. What if the next researchers decide to breed the pigs together anyway even if the first researchers said they wouldn’t?
The moral fault would be in the breeding, not in the use of the cells. Much like how a chemist can morally work with toxic chemicals. But if he dumps the chemicals in a lake, that would be a moral fault. The working with the chemicals is not.
What if these cells transplanted into pigs develop into human kidneys? If they are implanted back into humans, then they may have pig tissue which would include DNA. Would you then keep those humans from reproducing? What if the patients don’t obey the rules?
If the pigs reproduce, what of it. They are still pigs. They are bodies animated by non-rational, sensitive souls. They would still be pigs.
I don’t always know the philosophical and theological language for this argument. In a way it is simple and yet profound. We already know we should not kill human embryos. There are other things that go beyond our comprehension and we should know at least enough to keep our hands off.
The reason we do not kill human embryos is because they are human. The ‘humanness’ of the embryo is NOT a function of the genetics, it is a function of the soul that God created and unified with the body.
It is God who chooses if the creature is human, not any human. And that is true regardless of the genetic makeup.
A pig is a pig regardless of how much of it’s genetics, or the genetics of it’s parts. It is so because God gave it an animal soul, one that can empower the Senses ( sensitive soul), but cannot Reason.