The jellyfish Cladonema pacificum exhibits branched tentacles that can robustly regenerate after amputation. Credit: Sosuke Fujita, The University of Tokyo
Key points:
- Although scientists have long been aware of some animals’ regenerative abilities, the how has remained a mystery.
- Now, researchers in Japan have identified a specific set of cells that appear at the site of an injury to help form the blastema needed to quickly boost regeneration.
- The cellular origins are still unclear but researchers think the data could eventually help improve humans’ own regenerative abilities.
At about the size of a pinkie nail, the jellyfish species Cladonema can regenerate an amputated tentacle in two to three days—but how? Scientists have long known that jellyfish, along with other cnidarians such as corals and sea anemones, exhibit high regeneration abilities, but how they form the critical blastema has remained a mystery until now.
In a new study published in PLoS Biology, a Japanese research team has revealed that stem-like proliferative cells—which are actively growing and dividing but not yet differentiating into specific cell types—appear at the site of injury and help form the blastema.
“Importantly, these stem-like proliferative cells in blastema are different from the resident stem cells localized in the tentacle. The resident stem cells are responsible for generating all cellular lineages during homeostasis and regeneration, meaning they maintain and repair whatever cells are needed during the jellyfish’s lifetime. Repair-specific proliferative cells only appear at the time of injury. Together, resident stem cells and repair-specific proliferative cells allow rapid regeneration of the functional tentacle within a few days,” said corresponding author Yuichiro Nakajima, lecturer at the University of Tokyo.
This finding informs how researchers understand how blastema formation differs among different animal groups. Salamanders, for example, are bilaterian animals—those that form left to right during embryonic development—capable of regenerating limbs. Their limbs contain stem cells restricted to specific cell-type needs, a process that appears to operate similarly to the repair-specific proliferative cells observed in the jellyfish.
“Given that repair-specific proliferative cells are analogues to the restricted stem cells in bilaterian salamander limbs, we can surmise that blastema formation by repair-specific proliferative cells is a common feature independently acquired for complex organ and appendage regeneration during animal evolution,” said first author Sosuke Fujita, a postdoctoral researcher in the same lab as Nakajima.
The cellular origins of the repair-specific proliferative cells observed in the blastema remain unclear, though, and the researchers say the currently available tools to investigate the origins are too limited to elucidate the source of those cells or to identify other different stem-like cells.
“It would be essential to introduce genetic tools that allow the tracing of specific cell lineages and the manipulation in Cladonema,” Nakajima said. “Ultimately, understanding blastema formation mechanisms in regenerative animals, including jellyfish, may help us identify cellular and molecular components that improve our own regenerative abilities.”