Cloning provides another potential solution, scientists could eliminate the sugar molecule before using the pig cells to create clones.
With a chimera, the organ transplanted from the pig would primarily be composed of human cells, not pig cells.
As the human cells grow alongside the pig cells, the growing embryo learns to treat them as its own, and thereby not reject them.
The reason, Dr. Logan said, is that pig cells are studded with a sugar molecule, galactose alpha 1-3 galacthat, thet thumanman immune system immediately attacks.
In most cases they are outcompeted by the pig embryo's own cells but in the case of the pancreas there are no pig cells to compete with.
Diacrin recently suspended its trials on stroke victims after two of five patients suffered seizures, though the company does not think the pig cells were the cause.
Earlier attempts to make human organs by this method have, however, failed, because human cells tend to be outcompeted by pig cells in pig embryos; the organs remain stubbornly porcine.
But transplanting pig cells into people is still controversial, since it brings the risk of transplanting pig diseases (which may be contagious) at the same time.
(When I say fake meat, I don't mean the much publicized laboratory simulacrum from Maastricht University that combines pig cells and horse fetal serum, a mixture that's then "fed" sugar, fat, amino acids and so on, to produce translucent strips. We'll tackle that when and if it becomes marketable).
Only 30 patients tested positive, and of the 23 who were investigated further, the vast majority also had pig DNA coursing through their veins, leading the researchers to conclude that the PERV they detected was actually lodged within rogue pig cells that had escaped from the therapeutic tissue.
