Scientists have successfully grown a flatworm with two heads – one at each end – by rewiring its bioelectricity.
Planarian flatworms are fascinating creatures. They have an extraordinary ability to regenerate lost body parts. If you cut them in two (lengthways or crosswise), they will regenerate into two separate flatworms. They are one of several species, including lizards and sponges, that have some sort of memory for lost limbs that can be used to regrow body parts when they are removed.
But now scientists at Tufts University in Medford, Massachusetts, have found that by changing the electrical current in the cells of the planaria all at once, they will either grow a head or a tail to replace the lost body part.
This led the team to conclude that bioelectrical patterns can determine what the flatworms will become after they've regenerated – rather than stem cells.
For the study, published in Biophysical Journal, Michael Levin and his team used the chemical octanol to block the channels that electrical signals travel through in the worms.
After this, they split the worms. Twenty-five percent of the worms regenerated into double-headed forms, while 72 percent were normal (with the remaining 3 percent not growing properly).
Once the worms had regenerated, the team then repeated the amputation experiment on them, without giving them a second treatment. They found that, again, the flatworms regenerated the wrong part 25 percent of the time.
The researchers also found that the worms they thought were unaffected by the treatment – as they had regrown normally after the initial treatment – still regenerated the wrong part around 25 percent of the time.
It seems the flatworms’ pattern memory had been altered, although this was not apparent in their intact state and was revealed only upon regeneration. The researchers concluded that the worms had morphological memory traces coded into their bioelectric patterns, which had been permanently altered by their treatment.
“With this work, we now know that bioelectric properties can permanently override the default body shape called for by a genome, that regenerative target morphology can be edited to diverge from the current anatomy, and that bioelectric networks can be a control point for investigating cryptic, previously unobservable phenotypes," said Levin.
Levin, who previously showed it was possible to make a planarian grow the head of a seperate species of flatworm, is hopeful that this latest research will help develop our understanding of regenerative mechanisms.
He added: “Bioelectricity has a powerful instructive role as a mediator in the reprogramming of anatomical structure, with many implications for understanding the evolution of form and the path to regenerative therapies."