Greenland sharks survive for centuries with diseased hearts

Greenland sharks are thought to live between 250 and 500 years, but their hearts show signs of serious age-related diseases even when sharks are only 150 years old.

Some parts of the shark’s body, such as the eyes, appear immune to aging and cancer, which could suggest that the marine predator’s heart is also protected from age-related decline. But an analysis found that Greenland sharks (Somniosus microcephaly) actually show signs of serious heart disease – and yet there is no apparent loss of function or reduction in the species’ lifespan.

Alessandro Cellerino, of the Scuola Normale Superiore in Pisa, Italy, a member of the team that carried out the research, said he found the results of the analysis of six Greenland sharks – four females and two males, all measuring more than 3 meters long – “truly astonishing”.

Based on their length, the team estimates that the six specimens were between 100 and 150 years old. The team performed a series of microscopy tests on the animals’ hearts, including high-resolution fluorescence and electron microscopy.

“We discovered that the heart of the Greenland shark is highly fibrous and full of the aging markers lipofuscin and nitrotyrosine,” says Cellerino.

In humans, a high level of fibrosis, or scarring of heart tissue, is a common indicator of age-related heart disease and potential heart failure.

However, Cellerino says, the “massive accumulation” of lipofuscin linked to mitochondrial damage and other markers of aging does not appear detrimental and “does not alter the lifespan of the Greenland shark.”

The presence of high levels of nitrotyrosine, another indicator of heart disease signifying inflammation and oxidative stress, suggests that the Greenland shark may have evolved strategies to tolerate chronic oxidative damage “rather than simply minimizing it.”

“The first time I looked through a microscope, I assumed that what I was seeing was a technical artifact or experimental error,” he says.

For comparison, the researchers also studied another deep-sea fish, the velvet-bellied lanternshark (Etmopterus spinax), whose lifespan is estimated at 11 years, as well as the turquoise killifish (Nothobranchius furzeri), which is an extremely short-lived species, with a lifespan of only a few months, and which lives in seasonal pools of the African savannah.

Elena Chiavacci, also from the École Normale Supérieure, says that Greenland sharks have highly fibrous hearts, while the other two species show no fibrosis.

“When it comes to nitrotyrosine, the Greenland shark shows massive accumulation, while the lantern shark shows none,” says Chiavacci.

Despite its extremely short lifespan, the killifish also exhibits some of the same nitrotyrosine-based aging markers as the Greenland shark, she says.

Cellerino says the Greenland shark has extraordinary resilience in the face of aging, particularly cardiac aging. “The fact that there is a creature on this planet whose heart can coexist with the aging process without apparent decline is remarkable,” he says. “Together, these results highlight the exceptional resilience of the Greenland shark heart and highlight its potential to inform future strategies to promote healthy aging.” »

Joao Pedro Magalhaes, of the University of Birmingham in the United Kingdom, says the study highlights that scientists don’t really understand the molecular and cellular mechanisms of aging, or even which aging-related molecular changes are detrimental and which are beneficial.

Another conclusion is that researchers need to diversify the animals used to study aging and longevity, says Magalhaes.

“Most scientists, myself included, employ short-lived animals like worms, mice and rats, but it is clear that we have amazing long-lived species, like the Greenland shark and the bowhead whale, which can live much longer than humans and hold the secrets to longevity,” he says.