I think there are a few issues here.
In this case, the “meat” was grown from stem cells, not from nothing. I’d assume the stem cells need to be from an animal that is kosher, and was properly shechted. If it’s not, wouldn’t that make the meat treif?
The thought of buttel b’shishim occurred to me. However, doesn’t the rule only apply when the small amount doesn’t affect the taste of the final product? In this case, the entire product is based off of the small amount, so it definitely has an affect on it. Would we say buttel b’shishim applies here?