Stem cell map shows how immortal invertebrate regenerates itself
Our bodies do a decent enough job of repairing themselves, able to patch up wounds, fight off infections and even heal broken bones. But that only applies up to a certain point – lose a limb, for example, and it's not coming back short of a prosthesis. Other creatures have mastered this skill though, and now scientists at the University of California Davis (UC Davis) and Harvard have sequenced the RNA transcripts for the immortal hydra and figured out how it manages to do just that.
The hydra is a tiny freshwater invertebrate, which is related to jellyfish and corals. Measuring a few millimeters long, these little critters kind of resemble a soft stick with tentacles on one end. While they're not particularly exciting at a glance, the hydra has a hidden talent – it's basically immortal. These things don't seem to age at all, with their lifespan basically indefinite until killed by predators or environmental factors.
Even more amazing, they can perfectly regenerate their entire bodies. Cut a hydra in half and pretty soon you have two hydra, as the critters can regrow all tissue types and even a new central nervous system. Humans, on the other hand, struggle to repair any tissue without some kind of scarring, and the nervous system is particularly resistant to patch-jobs.
The researchers on the new study set out to investigate how the hydra does it, in the hopes of maybe learning something about ourselves. Hydra use three different lines of stem cells to renew their cells, and the researchers sequenced the messenger RNA transcripts of 25,000 individual hydra cells to figure out what all those cells are doing.
Next, they used that data to build a decision tree that shows how each type of stem cell differentiates into the new cells and tissues. For example, the team found that interstitial stem cells produce nerve cells, gland cells and the stinging cells that adorn the hydra's tentacles. This allowed the team to basically create a complete map of the stem cell developmental lineages, and identify which genes may be controlling this "decision-making process."
While it might seem pointless to study the biology of such a distantly-related creature, importantly, the regulatory gene networks at work in the hydra arose early in the evolution process, meaning they're still present in humans. It's unlikely that we'll be able to directly mimic these healing superpowers any time soon, but in understanding them – as well as similar processes at work in animals like axolotls, newts, worms, geckos and salamanders – we could uncover some new healing treatments.
"All organisms share the same injury response pathway but in some organisms like hydra, it leads to regeneration," says Abby Primack, co-author of the study. "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."
The research was published in the journal Science.
Source: UC Davis