The Cladonema jellyfish species can regenerate an amputated tentacle in two to three days, but how exactly does it do so? It’s roughly the size of a pinkie nail. Insects and salamanders alike rely on the capacity to develop a blastema, a collection of undifferentiated cells that can grow into the missing appendage and repair damage, in order to regenerate functioning tissue. Jellyfish and other cnidarians, like corals and sea anemones, have significant capacities for regeneration; yet, it is still unclear how they create the essential blastema.
According to a Japanese study team, stem-like proliferative cells help generate the blastema by appearing at the site of damage and aggressively expanding and dividing without yet differentiating into specific cell types.
The results were released in the peer-reviewed journal PLOS Biology.
“Importantly, these stem-like proliferative cells in blastema are different from the resident stem cells localised in the tentacle,” Yuichiro Nakajima, corresponding author and lecturer at the University of Tokyo’s Graduate School of Pharmaceutical Sciences, stated.
“Repair-specific proliferative cells mainly contribute to the epithelium — the thin outer layer — of the newly formed tentacle.”
According to Nakajima, resident stem cells found in and around the tentacle are in charge of producing all cellular lineages during homeostasis and regeneration, which means they uphold and fix any cells that are required for the jellyfish to survive.
Only at the moment of injury do proliferative cells specific to repairs emerge.
Nakajima stated that jellyfish use their tentacles for hunting and feeding. “Together, resident stem cells and repair-specific proliferative cells allow rapid regeneration of the functional tentacle within a few days,” she said.
According to first author Sosuke Fujita, a postdoctoral researcher in Nakajima’s lab at the Graduate School of Pharmaceutical Sciences, this finding helps researchers understand how blastema production varies among different animal taxa.
According to Fujita, the work may offer insight from an evolutionary standpoint. “In this study, our aim was to address the mechanism of blastema formation, using the tentacle of cnidarian jellyfish Cladonema as a regenerative model in non-bilaterians, or animals that do not form bilaterally — or left-right — during embryonic development,” Fujita stated.
For instance, salamanders are bilaterian creatures with the ability to regenerate limbs.
The Life Cycle Of A Jellyfish
Their limbs are home to stem cells that are confined to meet the needs of particular cell types; this process seems to work similarly to the proliferative cells in jellyfish that are specific to repair.
“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,” Fujita stated.
The researchers note that the instruments currently available to explore the origins are too limited to clarify the source of those cells or to identify other, distinct stem-like cells. The cellular origins of the repair-specific proliferative cells detected in the blastema are still unknown.
“It would be essential to introduce genetic tools that allow the tracing of specific cell lineages and the manipulation in Cladonema,” Nakajima stated. “Ultimately, understanding blastema formation mechanisms in regenerative animals, including jellyfish, may help us identify cellular and molecular components that improve our own regenerative abilities.”
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