Scientists Find Groundbreaking Potential for Tissue Regrowth and Immortality in the Ocean

Scientists Find Groundbreaking Potential for Tissue Regrowth and Immortality in the Ocean

From the revived corpse of Frankenstein's monster to the disembodied hand, "Thing," in the Addams Family, reanimated tissue is one of the most enduring images in science fiction. It turns out, that image has some basis in nature, according to the recent discovery of a mysterious creature that lives on the seafloor that scientists are calling a "real-life zombie."

In a new study, researchers documented the continued viability of amputated tissue from a sea cucumber for over three years in natural seawater. It's the first known report of the long-term survival - and continued growth - of discarded tissue outside of a highly controlled, sterilized environment.

The finding challenges assumptions of what's possible for tissue immortality and opens up exciting possibilities in the biomedical field. It could also be used as an experimental model for biological research that is more widely accessible, without the ethical and logistical challenges of many existing cell lines.

Featuring Bigelow Laboratory for Ocean Sciences Senior Research Scientist Rachel Sipler, the study was led by scientists at Memorial University of Newfoundland and was recently published in the journal Science Advances.

"We haven't grown a new, complete sea cucumber yet, but we are seeing pretty stunning growth and diversification of cells literally years after this tissue was removed," Sipler said. "It's like a lizard that loses its tail. We know some lizards can grow new tails; we're talking about whether the tail can grow a new lizard."

Since the mid-20th century, scientists have made significant breakthroughs with "immortal" cell lines, like the famous HeLa cells, that can be grown in a lab and proliferate indefinitely for long-term research. In earlier studies, though, tissue cultures have only been maintained under "axenic" conditions that are tightly controlled, rigorously maintained, and lack any bacteria or other organisms. Even then, they have not demonstrated signs of actual healing and growth, nor retained the ability to independently move.

Many echinoderms, the phylum that includes sea cucumbers, are known to display impressive regeneration capacity and negligible cell aging. Lost tissue, though, was always assumed to eventually decay or die. Yet, in what Sipler calls a product of "keen observation," the researchers noticed that some discarded tissue from a tube foot of a sea cucumber hadn't decayed after a number of weeks. In fact, it seemed to be growing.

The researchers ran a number of experiments in flowing seawater with tissue removed from the feet, main body, and tentacles of three individuals of Psolus fabricii, a cold-water species of sea cucumber.

They found evidence of diversifying cells, immune activity, and tissue reorganization in the explanted tissue. And in the absence of a mouth, the cells appeared to be getting nutrients by absorbing amino acids dissolved in the seawater. Even after three years, when the researchers stopped the experiments in order to publish, the tissue was still active. This ability to survive in a complex, stressful environment, Sipler says, makes this cell line unique compared to other tissue cultures

"Natural seawater is just about the most microbially diverse, least clean approach we could take experimentally," she said. "Yet, that rich environment full of bacteria and all this organic matter was actually feeding them and allowing this tissue to heal and grow."

The implications for biomedical sciences and engineering, the authors say, are profound, with potential applications in everything from tissue regrowth to anti-microbial healing.

It also opens up new opportunities for biological research and education more broadly. The tissue they've preserved not only shows an unprecedented ability to maintain its structural integrity and complexity in culture. It can also be grown more easily in the lab and, as an invertebrate, isn't subject to as many research restrictions, making it useful in contexts where there are legal obstacles or limited biosafety infrastructure for using human-based or other vertebrate cell lines.

"This discovery highlights that the ocean holds profoundly unexpected biological innovations," said Gloucester Marine Genomics Institute Science Director Andrea Bodnar, who was not involved in the study. "The fact that tissue explants from a sea cucumber can heal, reorganize, and survive independently for years in natural seawater suggests an entirely new model for biological resilience and tissue regeneration."

As an oceanographer, Sipler adds, the exciting discovery drives home the incredible untapped potential of ocean life.

"The best advances in science are made when you find a natural analog for what you're studying," she said. "Here is this species that has this groundbreaking ability, and we had no idea. It's a reminder how much is yet to be discovered in the marine environment, and how important it is to protect these resources that may hold really valuable knowledge for us."

Photo Captions

Photo 1: A progression of tube foot tissue one year (left) versus several years (right) after excision showing increasing wound closure and healing at the wound site over time. Shifting colors from red to lighter white and pink reflects pigmented cells forming and consolidating aggregates of healthy tissue and the progression of transparent connective tissue (Credit: Sara Jobson).

Photo 2: Microscopy image of an excised tube foot stained with 5-bromo-2′-deoxyuridine showing cell differentiation, with denser green coloring reflecting areas of more active cellular processes (Credit: Sara Jobson).