Silence descends on the operating theatre and the tension builds until it’s almost a physical presence in the room.
Surgeons have just connected a pig’s kidney to a human body. The clamps have been released and human blood is now flowing into the pig organ.
“You could have heard a pin drop,” says transplant surgeon Dr Jayme Locke.
Success or failure will be determined in moments and there is now just a single question on everyone’s minds: “Pink or black?”
Using animal organs in the human body is an old idea, and has ranged from “zest for life” chimpanzee testicle implants to replacement kidneys and hearts taken from our primate relatives. The latter often ended in death soon afterwards. The problem is, our immune system treats the transplanted organ like an infection and attacks.
The focus these days is on pigs, as their organs are roughly the right size and we have centuries of experience farming them.
But the challenge of hyperacute rejection – keeping organs pink, not black – is the same. You can’t just pop down to the farm, choose a pig and transplant its organs. It’s taken huge advances in genetic engineering to alter pigs’ DNA so their organs are more compatible with our immune systems.
If the body unleashes a horrendous assault on the foreign organ – holes will be ripped in every cell in the pig tissue and the organ will clot from the inside out. It will go splotchy, then blue, then completely black within minutes.
If “hyperacute rejection” is avoided, the organ will blush pink with the flow of blood and oxygen.
“It turned beautiful and pink… the sense of relief, the sense of joy and hope just filled the room. We might have high-fived as well,” said Dr Locke, from the University of Alabama at Birmingham, in the US.
This operation was just one of a series of medical breakthroughs that have renewed interest in the field of xenotransplantation.