Perhaps it was the extravagant display of deadly weaponry that prompted Xi Jinping and Vladimir Putin to mull on mortality at this week’s military parade in Beijing.
It was more banter than serious discussion, but with both aged 72, the Chinese president and his Russian counterpart may feel the cold hand on the shoulder more than Kim Jong-un, the 41-year-old North Korean leader who strolled beside them.
Speaking through a interpreter, Xi told Putin that 70 is considered young today, prompting Putin to claim that human organs can now be repeatedly transplanted, potentially allowing people to “stave off old age indefinitely”. “This century,” Xi responded, “it might be possible to live to 150.”
It was breezy talk, but have advances in organ transplantation reached the stage where the procedures can extend the lives of healthy humans as well as save those with terminal illness?
For particular patients, the case for transplantation is clear. “When you’ve got end-stage kidney, liver or heart disease, transplantation adds years of life on the whole,” says Reza Motallebzadeh, a professor of renal transplantation at UCL. “It is absolutely life-saving.”
A long list of organs and tissues can now be transplanted, including heart, lungs, kidneys, pancreas, liver, small bowel, skin, bone, heart valves and corneas. And more organs are being added. Earlier this year, a woman became the first in the UK to give birth after receiving a womb donated by her sister.
Around the world, demand for organ transplants outstrips supply. In Britain, the waiting list for life-saving organ transplants has never been higher. With a limited supply, what organs exist go to those who stand to benefit the most – typically young and terminally ill people.
But what if we had a plentiful supply of organs? Would it make sense to offer them to older people to keep them well? Motallebzadeh is sceptical. “Having an organ transplant is a massive operation and you’ve got to be robust enough physiologically to get through that,” he says.
And that is not the only consideration, says Motallebzadeh. “The three main causes of death in transplant recipients are cancer, infection and cardiovascular disease. And many of the anti-rejection therapies have side-effects that lead to this.”
In short, having multiple rounds of surgery and continual doses of powerful anti-rejection drugs, which raise the risk of cancer, cardiovascular disease and lethal infections, could reduce lifespan rather than extend it.
Major efforts are afoot to solve the organ shortage problem. One route involves using organs from pigs. The procedure, xenotransplantation, remains experimental but doctors in New York have performed pig kidney and pig lung transplants into brain-dead people to see how they fare.
In the past year, two living patients have received genetically modified pig kidneys. The edits removed harmful pig genes, inactivated viruses lurking in the pig genome that could reawaken and cause infections and, crucially, added human genes to make them more compatible.
The organs were supplied by eGenesis, a biotech company co-founded by the Harvard University geneticist George Church. He said both patients were “healthy and happy” and not on kidney dialysis any more.
The company has approval from the US Food and Drug Administration for a clinical trial in 33 patients. “If those 33 do as well as the first two, then it’ll be scaled up for the whole population,” Church said. “The number of pigs we would have to make is a tiny fraction of the number consumed each year for bacon and pork chops.”
For now, the company is focusing on kidneys, liver and heart, but Church anticipates providing every organ and tissue that is normally transplanted from human to human.
Farming pigs for organs is a practice that will have its critics, but far more radical and ethically fraught proposals are on the table. Earlier this year, researchers said advances in stem cell biology and artificial womb technology could enable scientists to create spare human bodies.
The process is convoluted, but involves making an embryo from a patient’s cells, disabling genes needed for it to form a brain, and growing it in an artificial womb. The result is a brainless human body, made to supply organs to its genetic parent.
“There’s an ick factor,” says Carsten Charlesworth, a postdoctoral researcher at Stanford University. “For a lot of people, an arm’s fine, a liver’s fine and a kidney’s fine. But when you have everything except a brain, it feels more human-like and people worry.”
Church has high hopes for another approach. The liver and other organs could be genetically modified, in or out of the body, to be resistant to infection and release anti-ageing compounds such as proteins that help the body maintain good health. “You’re turning the organ into an anti-ageing therapy,” he says. If done in situ, it avoids the need for major surgery, risky anti-rejection medicines and headless humans.
So might people born this century live to 150? “Probably somebody reading your article is going to be the last person to not have the option of living to 150,” Church says. “It would be sad to be the person who just misses the cut, and I have the feeling I’m one of those people.”