At first glance, it might seem that jellyfish and humans don’t have a lot in common. But we’ve learned a lot from these marine creatures.
In 1991, NASA sent baby jellyfish into space to study human development in zero gravity, and the so-called ‘immortal jellyfish’ is being studied for the way its cells can regenerate into an earlier life stage.
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But there’s another way that scientists are trying to unlock their secrets – and it’s to do with how they heal wounds.
Jocelyn Malamy (who works at the Marine Biological Laboratory in Massachusetts, US) has spent the last 10 years observing how medusae of the species Clytia hemisphaerica heal wounds.
As this species is transparent, researchers can watch its cells move in real time.
And unlike with humans, no scar tissue is formed. Instead, Malamy says that “healing in the jellyfish looks more like embryonic healing, which is scar-free.”
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Stitching up wounds
Epithelial cells cover the body’s surface, making up skin and lining the inside of tissues such as the gut. These cells form a monolayer on the upper surface of Clytia hemisphaerica, and researchers can observe these cells stitching damaged tissue back together.
And according to the researchers, smaller wounds can heal within minutes, and larger wounds heal in under an hour.
“A lot of the processes that we see in Clytia’s wound healing are really similar to what you see in all other systems, including mammalian systems,” Malamy explains.
“When you’re staring at these epithelial cells, you wouldn’t know this was a jellyfish. It could be any kind of squamous epithelial cell sheet, and that’s nice, because it means that hopefully what we learn in jellyfish can give us insights into other animals as well.”
Now, Malamy’s latest paper, published in the journal Molecular Biology of the Cell, explains the sequence of how these wounds close.
When a wound occurs, lamellipodia (which she describes as “foot-like feelers”) extend out of the cells at the edge of a wound and ‘crawl’ across the basement membrane, which is a “protein sheet that’s underneath all epithelial cells in all systems”.
As they move, they drag forward the cells that produced them and stretch the cell body over a wound, closing it.
While the lamellipodia move forward, an actomyosin cable forms at the back. When the lamellipodia cover the basement membrane, the cable contracts.
This is particularly important if the lamellipodia reach debris or a tear in the membrane, as the cable pulls them over the damage, expelling wound debris as it does.
However, if the wound in the basement membrane is too big, the lamellipodia won’t be able to reach each other. When this occurs, Malamy explains that the whole sheet of epithelium “lifts itself up and starts walking.” Once the lamellipodia can reach each other, the wound starts to close.
More research is needed on basement membrane repair. “It’s great that you can heal a wound by dragging the cells over it,” Malamy explains, “but at some point, a damaged basement membrane has to get fixed.”
It’s currently unclear how this repair happens in any system, so it’s hoped that this research could inform future clinical innovations for tissue repair.
Read the full paper here: The basement membrane determines the choice of wound healing mechanism across wound scales in the basal eukaryote Clytia hemisphaerica
Top image: side view of Clytia hemisphaerica. Credit: Jccardenas13; Elizabeth Lee, PhD, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
