Presumably they culture more, but obviously the first cells would have had to. Some of these companies have been very particular about sourcing their starting cells non-lethally from sanctuary animals or whatever, because why not.

Generally stem cell cultures these days are sourced once then replicated forever.

Likely, but stem cell harvesting is not as horrible for pigs and doesn't require thousands of them either. It's certainly a massive improvement.

That's kinda the point‽