Among the animals that can regenerate after a limb is amputated, cnidarians — a family of corals, sea anemones and jellyfish — are relatively easy organisms to study in the laboratory.
For this reason, a team led by scientists from the University of Tokyo decided to conduct their radioactive cell labeling experiments (“pulse-chase” analysis) on the jellyfish Cladonema pacificum, in which a severed tentacle regrows in just two to three days can.
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The key element in this ultra-rapid healing is the “blastem,” a collection of undifferentiated cells that can repair the damage sustained and grow into the missing appendix. But the exact way in which this crucial structure forms has remained a mystery.
Two types of cells connecting
The Japanese researchers published their results in the journal PLOS Biology (December 21, 2023). According to their article, the precious blastema is created by connecting two cell types: repair-specific proliferative cells (RSPC) on the one hand and resident stem cells on the other.
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“It is important to note that these proliferative cells, which are specifically responsible for repair in the blastema, are different from the resident stem cells in the tentacle,” emphasizes Professor Yuichiro Nakajima, a lecturer at the Graduate School of Pharmaceutical Sciences at the University of Tokyo supervised the study.
RSPC-type cells “contribute primarily to the epithelium – the thin outer layer – of the newly formed tentacle,” explains the researcher. However, they only appear at the time of injury, unlike resident stem cells, which, as the name suggests, are always present and allow for the continuous renewal of animal tissue.
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Elucidating the origin of repair cells
“Together, resident stem cells and repair-specific proliferative cells enable rapid regeneration of the functional tentacle within a few days,” summarizes Professor Nakajima. A process that is all the more important because jellyfish absolutely need their tentacles to hunt and eat.
Dr. Sosuke Fujita, lead author of the study, compares this functionality with the regeneration of amputated limbs in the salamander, an animal with bilateral symmetry. According to him, this property was acquired independently by several groups of animals during evolution. The authors now hope to elucidate the origin of these amazing RSPC cells.
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“Ultimately, understanding the mechanisms of blastema formation in regenerative animals, including jellyfish, may help us identify the cellular and molecular components that enhance our own regenerative capabilities,” notes Dr. Fujita.
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