An Italian neuroscientist promised in recent weeks that a new type of surgery—wait for it, a human head transplant—will be ready to try on real, live patients in the next two years. Unfortunately, according to many other neurosurgeons and transplant specialists, that’s an absurd claim. We won’t be swapping out our bodies for younger, fitter models for at the minimum decades, if not centuries—or ever.
Still, some people have their heads frozen after death in the hope that future scientific advances may be able to bring them back, plop their heads on a new body—biological or robotic—and let them live forever. Baseball hall of famer Ted Williams did it. (Walt Disney did not—sorry.) Yet eliminating ice damage to hundreds of billions of brain cells—only one of a multitude of challenges to achieve that goal—makes such a feat nothing more than a futuristic fantasy, biologists say.
The prospect of preserving any organ, even a lesser one than the brain, remains a daunting challenge—yet targeting a heart or liver for cold storage may be achievable. The effort to cryopreserve organs was recently buoyed by the Department of Defense (DoD), which in January announced the first-ever government grants for research on organ banking: three programs awarding up to $3.5 million per team to some 20-plus research teams.* And this past weekend scientists from around the world gathered in Palo Alto, Calif., for a three-day summit on organ cryobanking, the first in over three decades. The event marks the beginning of a “modern-day Apollo Program” for organ banking, proclaimed Sebastian Giwa, CEO of the Organ Preservation Alliance, a small nonprofit that organized the summit.
Today freezing, thawing and transplanting organs has only been successfully carried out with a rabbit kidney and a few rat hearts. If human organs could be cryopreserved, hospitals could create organ banks where hearts, lungs, kidneys and more would be available for surgeons and patients anytime: no long transplant waiting lists, no unnecessary deaths.
Using current technologies, transplanted organs cannot be stored long; lungs last only 12 hours outside the body, a heart only four to five. Because organs cannot be stored, or even transported long distances in many cases, an estimated 21 people die each day awaiting a transplant, according to the U.S. Department of Health and Human Services.
It is already possible to freeze single cells, such as eggs and sperm, but ice crystals and other effects of freezing wreak havoc on large tissues; they splinter, break, bruise and die. “What we’re asking a system to do is to tolerate fantastically abnormal conditions,” said Gregory Fahy, chief scientific officer at 21st Century Medicine, who has studied organ cryopreservation for over 30 years, during a presentation at the summit. Because of that, he admitted, “successes have been few.” Yet attendees were optimistic based on the new DoD funding, and research teams presented noteworthy advances against the two of the most difficult problems of freezing organs: cryoprotectant toxicity and thawing.
Cryoprotectants are chemicals used during the freezing process to prevent or contain ice formation and mitigate cell damage. Unfortunately, the most common cryoprotectants are toxic to human tissues at high concentrations. At the summit, scientists from the University of Ottawa and the University of Alberta described the creation of synthetic cryoprotectants that inhibit ice formation with less toxicity. The team synthesized and evaluated 225 different molecules, each a slightly different version of a naturally occurring antifreeze protein isolated from Antarctic fish. One of the resulting molecules enabled them to successfully freeze and quickly thaw human red blood cells. Because the synthetic molecules are small and can be customized, “they stand a really good shot at working in tissues,” says Robert Ben, a synthetic chemist at Ottawa who led the work.
Freezing may seem like the hard part but the real headache is thawing an organ. Imagine dropping an ice cube into a glass of warm water—it splinters and cracks. The same is true for an organ during thawing due to uneven heating. A team led by John Bischof at the University of Minnesota unveiled a new way to uniformly thaw a tissue, a technique they call “nanowarming.” The concept is to either enclose or infuse a tissue with biocompatible, magnetic nanoparticles. (Nanoparticles have been demonstrated as safe in several U.S. Food and Drug Administration–approved human therapies.) The scientists then expose it to radio waves to excite the nanoparticles, which generate heat throughout the tissue. “We’re using the nanoparticles as little warmers,” says Bischof. “We’re controlling where the heat is.” The team used the particles in a proof-of-concept experiment to uniformly thaw solutions of cells and will next test the procedure in arteries and heart valves.
So will we be freezing our heads anytime soon? Don’t bet on it. One of the most difficult parts of freezing and thawing an organ is preserving structure, and the brain has the most complex and least understood structure of all our organs, plus numerous different cell types that would freeze at different rates.
Still, with more time and money, donated organs could eventually be in a hospital freezer near you. “I’m more optimistic than ever,” Fahy says. “There’s a lot of energy here. It’s the right time.”
*Correction (3/12/15): This sentence was edited after posting; the original erroneously stated the amount and distribution of Department of Defense funding.