On a general note, I never thought about this issue. My first instinct was that, because this is an organism that could not survive outside it’s laboratory environment, there is no ethical issue because there should be independent life in order for ethical concerns to attach.
However, how complex does the organism have to be before it does become unethical to kill it – what if taking this to the extreme we can grow entire people but make them completely dependent on the lab environment for life such that they could never have been produced in nature?
I feel like this is complicated, however, by the issue that because the heart is dependent on science for life, unless it is placed in an animal host it will have to die when the science is cut off. What if it could be kept alive indefinitely in the lab (no tissue degradation)? It would have to be “killed” eventually in that case – putting it in a person (unless also immortal) would be sentencing it to death oddly.
I strongly disagree with the analogy with sentience. We always get into the issue of defining sentience (mice? dogs? bacteria?). Too many issues if we get it wrong – I think we should stick to living here.
Finally – we are JUST addressing ethical issues at this point, correct? We are not collapsing ethics and morals here…are we?