2023-12-29 20:11:00
Among the animals capable of regenerating after the amputation of part of their body, cnidarians – a family of corals, sea anemones and jellyfish – are relatively easy organisms to study in the laboratory.
This is the reason why a team led by scientists from the University of Tokyo chose to carry out its radioactive labeling experiments on cells (analysis “pulse-chase”) on the jellyfish Cladonema pacificumof which a severed tentacle can grow back in just two or three days.
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The key element of this ultra-rapid healing is the “blastema”, a cluster of undifferentiated cells capable of repairing damage and growing to form the missing appendix. But the exact way in which this crucial structure forms has remained a mystery until now.
Two types of cells that combine
Japanese researchers published their results in the scientific journal PLOS Biology (December 21, 2023). According to their article, the precious blastema is formed thanks to the association of two types of cells: on the one hand, proliferative cells specific to repair (“repair-specific proliferative cells” or RSPC) and on the other, the resident stem cells (“resident stem cells”).
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“It is important to note that these repair-specific proliferative cells in the blastema are different from the resident stem cells located in the tentacle”underlines in a communiqué Professor Yuichiro Nakajima, lecturer at the Graduate School of Pharmaceutical Sciences at the University of Tokyo, who supervised the study.
RSPC type cells “contribute mainly 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 their name suggests, are present at all times and allow animal tissues to be continually renewed.
72 hours after amputation under anesthesia, the jellyfish tentacle is fully functional. 2023 Sosuke Fujita, The University of Tokyo
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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 days”, summarizes Professor Nakajima. A process that is all the more crucial as jellyfish absolutely need their tentacles to hunt and feed.
Dr. Sosuke Fujita, first author of the study, compares this mode of operation to the regeneration of amputated limbs in the salamander, an animal with bilateral symmetry. According to him, this characteristic was acquired independently by several groups of animals during evolution. The authors now hope to elucidate the origins of these astonishing 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”note le Dr Fujita.
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