About the size of a pinky fingernail, the jellyfish type Cladonema can regenerate a mutilated tentacle in two to three days -; but how? Regeneration of functional tissue in all species, including salamanders and insects, relies on the ability to form a blast, a clump of undifferentiated cells that can repair damage and grow into the missing limb. Jellyfish, along with other cnidarians such as corals and sea anemones, exhibit high regenerative abilities, but how they form the critical flora has remained a mystery until now.
A research group based in Japan has revealed that germ proliferative cells -? which are actively growing and dividing but not yet differentiated into specific cell types – appear at the site of injury and help form the blastema.
The findings were published in the scientific journal PLOS Biology.
Importantly, these stem proliferative cells in the blastema are distinct from the resident stem cells found in the tentacle. Repair-specific proliferative cells contribute mainly to the epithelium -? the thin outer layer -? of the newly formed tentacle”.
Yuichiro Nakajima, corresponding author, lecturer at the Graduate School of Pharmaceutical Sciences at the University of Tokyo
Resident stem cells present in and near the tentacle are responsible for generating all cell lineages during homeostasis and regeneration, meaning they maintain and repair as many cells as are needed throughout the life of the jellyfish, according to Nakajima. Repair-specific proliferative cells appear only at the time of injury.
“Together, resident stem cells and repair-specific proliferative cells enable the rapid regeneration of a functional tentacle within days,” Nakajima said, noting that jellyfish use their tentacles to hunt and feed.
This finding informs how researchers understand how blastema formation differs between different animal groups, according to first author Sosuke Fujita, a postdoctoral researcher in the same lab as Nakajima at the Graduate School of Pharmaceutical Sciences.
“In this study, our aim was to address the mechanism of blastema formation, using the tentacle of the cnidarian jellyfish Cladonema as a regenerative model in non-bilateral, or non-bilaterally – or left-right – forming animals; during embryonic development,” Fujita said, explaining that the work may provide insight from an evolutionary perspective.
Salamanders, for example, are bipedal animals capable of regenerating limbs. Their extremities contain stem cells restricted to specific cell-type needs, a process that appears to function similarly to the repair-specific proliferative cells seen in jellyfish.
“Given that repair-specific proliferative cells are analogous to restricted stem cells in salamander bilateral limbs, we can hypothesize that blastema formation by repair proliferative cells is a shared feature independently acquired for the regeneration of complex organs and appendages during the evolution of animals,” Fujita said. he said.
The cellular origin of the repair-specialized proliferative cells seen in the blastoma remains unclear, however, and researchers say the tools currently available to investigate the origin are too limited to elucidate the source of these cells or identify other , different stem cells.
“It would be important to introduce genetic tools that allow specific cell lineages to be traced and manipulated Cladonema“Ultimately, understanding the mechanisms of blastema formation in regenerative animals, including jellyfish, may help us identify cellular and molecular components that enhance our own regenerative abilities.”
Financing:
The research is supported by grants from the Japan Society for the Promotion of Science KAKENHI, the Japan Science and Technology Agency, the Japan Medical Research and Development Agency, and the cooperative research program of the National Institute of Basic Biology of Japan.
Source:
Journal Reference:
Fujita, S., et al. (2023). Distinct stem cell-like populations facilitate functional regeneration of the Cladonema medusa tentacle. PLOS Biology. doi.org/10.1371/journal.pbio.3002435.
