Immortal Jellyfish Offers Clues, Not a Human Cure

The jellyfish Turritopsis dohrnii can reverse its life cycle, but scientists remain far from turning that trick into a treatment for people. Researchers are studying how its cells change state, hoping the biology might one day help repair human tissue or treat age-related disease. No one’s proposing to turn elderly people into babies; that idea belongs to science fiction.

A body that starts over

When the jellyfish faces stress, it stops moving and sinks to the bottom of its tank. Its umbrella-shaped adult body, called a medusa, transforms into a ball of cells. Within one to three days, a polyp buds from the ball and grows into a colony that can produce new medusae.

“From one jellyfish that doesn’t die, then you get this colony that can form hundreds more,” said marine biologist Maria Miglietta of Texas A&M University at Galveston. Each new jellyfish can, in principle, rejuvenate in the same way.

Miglietta has cut, boiled and starved the animals, overloaded their tanks with salt, and placed them in fresh water. They’ve repeatedly appeared to evade death. But some jellyfish in her laboratory seem unable to rejuvenate, and researchers don’t know whether those that can eventually reach a limit and die of old age.

The ability was first reported in 1992, after an Italian scientist who kept the jellyfish in a laboratory forgot to feed them over a weekend. He expected to find dead animals. Instead, he found new polyps in the container, Miglietta said.

What the cells can do

Biologist Stefano Piraino of Italy’s University of Salento studied how the reversal might work. During the process, some medusa tissues undergo “transdifferentiation”: adult cells return to a stem-cell-like state and then specialise into other cell types. “Adult cells become ‘undifferentiated’ and become something else that is needed to form the polyp,” Miglietta said.

A 2022 study compared Turritopsis dohrnii genes with those of a related species not known to rejuvenate. Molecular biologist and bioinformatician Victor Quesada of the University of Oviedo in Spain cautioned that researchers can’t be sure the other species lacks the ability; many jellyfish remain understudied.

The study found that Turritopsis dohrnii had more copies of genes that produce proteins helping repair mutations and other DNA damage. It also had more copies of genes involved in maintaining telomeres, the caps at the ends of DNA strands that protect genetic material. Telomeres normally shorten with age. The jellyfish’s ability to maintain them could be one factor in its longevity, Quesada said.

Miglietta’s research in 2019 and 2021 found increased activity in genes involved in DNA repair and telomere maintenance, along with mysterious genes whose functions remain unknown. A separate preliminary study found some overlap between genes overactivated during the cyst stage and genes linked to human longevity.

A long way from human use

Miglietta is working with pediatric oncologist and physician-scientist Michael Koldobskiy of Johns Hopkins to investigate the process and eventually test whether it can be induced in human cells. Scientists have induced rejuvenation-like processes in mammalian cells, but applying them to human tissues has proved difficult.

Possible applications include healing wounds or tissue injured by strokes or heart attacks, and reversing damage associated with age-related vision loss or Alzheimer’s disease. Koldobskiy said researchers would first need to identify the molecular “switch” behind the process and determine whether humans have the same one. “We’re a long way away from harnessing that for human benefit,” he said. “At the organ and tissue level, I think it’s very much a possibility.”

The jellyfish lives across oceans from the Mediterranean to the Caribbean and Japan, but its apparent resilience doesn’t make it invulnerable. Changing plankton availability, predators and algae that smother colonies may kill it in the wild. Maria Pascual-Torner of Spain’s Institute of Marine Sciences called it “an extremely vulnerable organism.” The animal’s cells may offer clues, but its survival still depends on conditions researchers don’t fully understand.