In Brief

The acorn worm, an invertebrate, has an incredible ability to regenerate. Humans and the acorn worm share many genes, and scientists are studying the acorn worm in hopes of someday being able to stimulate regeneration in humans.

A Human Regrowth Industry?

The ability to regenerate body parts has always been a fascinating prospect, inspiring characters like Wolverine who can instantly heal themselves and regrow body parts they’ve lost — and now regeneration has inspired scientific research.

Many species in the animal kingdom can regenerate: arthropods (like scorpions) can regrow appendages, some annelids (like worms) can regenerate from only a few segments of their body, echinoderms (like starfish) can both self-amputate and re-grow limbs, amphibians (like salamanders and newts) can regenerate a limb in as little as a month, and some reptiles can regenerate their tails.

Scorpion

The aquatic acorn worm, a small coral reef dweller that burrows in the sand and one of the closest invertebrate relations to the human, can regenerate any part of its body that has been cut off, even its nervous system and head. Cutting an acorn worm in half simply results in two complete, indistinguishable specimens within fifteen days. They are also unusually similar in body structure to humans. Researchers wondered: since humans have most of the same genes, shouldn’t we be able to do the same thing?

... Juvenile Acorn worm (Saccoglossus kowalevskii)

“I really think we as humans have the potential to regenerate, but something isn’t allowing that to happen,” biology professor Billie Swalla commented in a University of Washington (UW) press release describing his recent work. Swalla is the Director of Friday Harbor Laboratories and part of a research team, along with Shawn Luttrell, that’s focused on the study of regeneration in invertebrates. “I believe humans have these same genes, and if we can figure out how to turn on these genes, we can regenerate.”

Although it may sound like only the most fanciful science fiction, many research scientists believe that the regeneration of human body parts is achievable. We already regenerate skin, pieces of other organs, and nails; we also have many of the necessary genes. “We share thousands of genes with these animals, and we have many, if not all, of the same genes they are using to regenerate their body structures,” says Luttrell. “This could have implications for central nervous system regeneration in humans if we can figure out the mechanism the worms use to regenerate.”

Reverse Engineering Worms

The human roadmap that is contained in our DNA is present in every cell in our bodies, and it should also contain enough information to build or regenerate the body. However, access to that part of the plan is not accessible in humans for some evolutionary reason. One possible reason for this is that regeneration may take too much energy in a large, complex organism like a human. Another could be that our highly developed immune system actually stops the process with responses such as scar formation.

The UW team has been investigating which gene expression patterns take place when regeneration begins in acorn worms. Since regeneration follows precisely the same steps in every worm once it starts, the researchers believe that a “master control” gene may exist. If such a gene is what starts the process, it may be able to trigger regeneration in humans.

They are also attempting to identify which kinds of cells function as the building blocks of regeneration. Stem cells are an obvious possibility, but there may be other types of cells which could be repurposed for regeneration. Eventually, the team hopes to use gene activation or editing to start the process in other animals, including humans.

Ultimately, this would change the face of medicine. Burn victims could regenerate their skin, people would no longer need to wait for organ transplants, and if limbs were lost in an accident, they could be regrown. This technology, if it is possible, is not happening anytime soon. The challenges are complex, and so is the duplication of working human nervous systems, brains, and internal organs that would need to be mastered. Genetically we are in a favorable position, and our progeny may see human regeneration as part of our medical reality in 100 years or so.