Secret of the ‘immortal’ hydra’s regenerating ability uncovered
The hydra, a relative of jellyfish and coral, can regrow its whole body from a small piece of tissue in a few days.
Who wants to live forever? A tiny freshwater creature called the hydra can, and scientists at the University of California have revealed the source of its remarkable healing ability.
The hydra is named after the serpent monster from Greek myth, which regrows two heads each time one is cut off. But freshwater hydras have an even more impressive regenerating ability: an entire hydra can regrow from a small piece of tissue in only a few days.
Biologists are particularly excited by this ability, since many of the networks involved in the healing process developed early in the process of evolution, meaning that they are shared among many animals, including humans.
“In other organisms, like humans, once our brain is injured, we have difficulty recovering because the brain lacks the kind of regenerative abilities we see in hydra,” said researcher Abby Primack.
If hydra’s healing ability can be fully understood, it could potentially be harnessed to heal brain injuries or degenerative disease. When a hydra is damaged, it grows new tissue from stem cells. These are the same type of cell found in human embryos and adult bone marrow. They are a basic form of cell which can do something no other type of animal cell can do: they can reproduce to create a different type of cell with a specific function, such as brain cells or skin cells.
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The team analysed molecules known as RNA to study the processes that turned hydra stem cells into different specialised cells. RNA, or Ribonucleic acid, is the molecule that reads DNA and carries out its instructions. By studying the RNA, they could deduce which particular genes were being activated in the process.
“The beauty of single-cell sequencing and why this is such a big deal for developmental biologists is that we can actually capture the genes that are expressed as cells differentiate from stem cells into their different cell types,” said assistant professor Celina Juliano.
Hydra has not just one type of stem cell, but three. The researchers tracked how each type of stem cell could develop into different cell types. They were surprised to learn that one path branched out to create either neurons or gland cells, as though the cell hadn’t made a decision when the process began.
In future studies, the team want to understand what genes determine this decision.