Built-in Memory in the Cells Is Secret of Hydra's Powers of Regeneration, Technion Team Shows

Zafrir Rinat
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Hydra.Credit: Coveredinsevindust at English Wikipedia
Zafrir Rinat

A study conducted at the Technion-Israel Institute of Technology in Haifa has shed new light on the ability of the hydra, a tiny fresh-water animal, to regenerate itself. The hydra’s cells have a built-in memory that enables it to regenerate, according to the results of the study, and these findings might be able to be applied in the future to better understand cell and tissue regeneration in human beings as well.

The hydra is a tiny predator about a centimeter in length. It lives in fresh water and hunts for its prey using tentacles around its mouth. Scientists have long been fascinated by its ability to regenerate an entire animal from small pieces of tissue or clusters of cells. This quality gave the hydra its name, which is a reference to the mythological Greek serpent, which according to legend had many heads and regenerated them when they were lopped off.

The findings of the study, which was carried out through the Technion Physics Department by Profs. Kinneret Keren and Erez Braun and a group of students, were published this week in the journal Cell Reports.

Up to now, it was thought that the real-life hydra’s ability to regenerate itself from pieces of tissue was based on chemical signals that guided the tissue on how to generate a head, tentacles and a foot, but the new study links the capacity to a built-in mechanical memory in its cells. This is all based in thin protein fibers, Prof. Keren explained. The skeleton of the protein fibers can survive and instruct cells on how to arrange themselves to create an adult hydra, she said.

The pieces of tissue severed from the body of the hydra fold themselves into a small ball at first. This process forces the protein fibers to balance the preservation of the old skeleton structure and adaptation to the new ball. New body parts develop based on the pattern information about which is stored in the skeleton. The ball sprouts a mouth and tentacles and ultimately results in a complete animal.

The Technion researchers discovered that they could interfere with the process in a way that alteres the shape of the regenerated hydra, and even created one with two heads. Through their experimentation with tissue, they concluded that the response from the tissue is what is responsible for the structure of the developing organism.

“Hydras are simpler organisms than most of their relatives,” Keren said, “but the basic pattern of orderly skeleton fibers is also common in many of the organs of the human body, in the muscles, the heart and the intestines, and also in certain tissue such as skin and hair that undergoes the process of regeneration. Similar mechanisms are at work in the development of many organisms from the stage of the embryo to a mature animal. Therefore in-depth understanding of the process of regeneration of the hydra may shed light on the mechanical processes involved, in addition to chemical signals, in the biological development.”

“It’s still distant, but it’s possible that in the future, this research will be able to assist in understanding the regeneration of organs of human beings,” Keren added.