The Greenland shark, which can live for centuries, uses a variety of tactics to avoid the typical declining health that comes with age.
dotted zebra/Alamy
Greenland sharks are spilling new secrets about antiaging.
In the deep, dark waters of the Arctic and North Atlantic, these ghostly giants — which can live for centuries — have hit upon a few tricks for surviving long-term. Some of their organs may be resistant to the ravages of age, while others seem resilient to tissue damage that accrues over time, recent studies suggest.
The findings offer some glimmers into how these sharks manage to live longer than all other vertebrates on the planet. It’s work that could one day lead to therapies for treating aging organs in people, says Lily Fogg, a biologist at the University of Basel in Switzerland. That’s the “ultimate dream goal,” she says.
Scientists estimate that Greenland sharks (Somniosus microcephalus) may survive for upward of four hundred years. “They’re these huge, ancient grandpa sharks,” Fogg says. But it’s unclear how exactly their bodies keep on cruising decade after decade.
Fogg’s team studied the animals’ eyeballs. No one knew if the sharks had much vision, let alone if that vision degraded over time. The common thinking was that the sharks were either severely visually impaired or completely blind, Fogg says. She and her colleagues examined eye tissue from 10 Greenland sharks, some up to about 150 years old. The animals had all the cellular and molecular tools in place for seeing in the deep sea’s dim light, the team reported January 5 in Nature Communications.
The tissue also looked like it had avoided the typical wear and tear of aging. That may be due to dialed-up activity of DNA repair machinery in the eyes, Fogg says. This machinery fixes damage that can lead to cell death and tissue degeneration. An earlier investigation of the Greenland shark’s genome also pointed to enhanced DNA repair function, reported physiologist Alessandro Cellerino and his colleagues.
The antiaging strategy at work in the eyeballs may not occur in all the Greenland shark’s organs, however. Researchers studying the animal’s heart found that it appears to collect the typical scars and stresses that time tattoos on our tissues, scientists reported December 23 on bioRxiv.org. “We were expecting the opposite,” says Cellerino, of the Scuola Normale Superiore in Pisa, Italy.
His team dissected and examined the hearts of six Greenland sharks. The researchers discovered organs peppered with tough scars that built up as the animals aged. In humans, this scar tissue is a sign of cardiovascular disease. It stiffens the heart, making it harder to pump blood efficiently. The sharks’ hearts also showed evidence of cellular damage, such as energy-producing mitochondria, broken-down and stuffed into the cells’ recycling centers.
Yet somehow, Cellerino says, despite the scarring and other damage, the sharks’ hearts still appear to work. They can keep on pumping even with damage that would make other animals’ hearts give out. Researchers don’t know exactly why, though they speculate the sharks’ tissue may produce protective hormones that help the heart deal with age-related injury.
Ecologist Catherine Macdonald says she’s not surprised by the two papers’ results. “Any animal with such a long life span is going to need the ability both to repair and to maintain,” says, Macdonald, of the University of Miami. She wants to learn more about how the sharks’ eyes and hearts function in living animals. That’s hard to study in a shark that can dive as deep as 2,200 meters below the ocean’s surface. But a better understanding of what underpins these animals’ extended life spans could offer clues to the mysteries of aging in people, she says.
Still, Macdonald doesn’t see immediate applications for human health. And the new work definitely doesn’t mean consumers should hop on shark-based antiaging trends, she says. “We don’t need to go out and start drinking Greenland shark blood.”
