Whitehead Institute researchers study planarians, a type of flatworm that can regenerate its
whole body, in order to figure out how the regeneration process works.
The hope is to eventually use this knowledge to guide the development of regenerative medicine.
When you cut the head, the animal, all of a sudden, needs to make a completely new brain.
That means the planarian has to rebuild all of the circuits for its nerve cells with precisely
the right wiring patterns for the nervous system to work again.
For a glimpse at how this process works, Scimone and her colleagues in Whitehead Institute
Member Peter Reddien’s lab zeroed in on planarians’ eyes—and how they reconnect
to the brain after injury.
With small surgeries, you can remove the eye—and only the eye.
So that makes this system very powerful, because it’s not that you are injuring the whole
brain, you are only removing the eye.
You can also transplant them.
And you can try to see how the system is wired into the brain.
And if that happens, which mechanisms it requires to do so.
The researchers found that a small group of muscle cells in the head, called guidepost
cells, are able to attract developing nerve cells and point them in the right direction.
Just as in humans, nerve cells from the planarian’s eyes have to cross over each other to reach
the opposite side of the brain.
At two places called choice points, the guidepost cells are able to direct growing nerve cells
from the eye to the correct side of the brain.
Planarian muscle is also necessary for structure and movement—
But also providing other types of information that are essential for the animal to regenerate.
With the cues from the guidepost muscle cells, planarians are able to rebuild new eyes and
wire them to a functional brain in just few days.
I think it’s fascinating how they can again assemble all the neuron circuits.
Usually that doesn’t happen in other species.
Most of the neuronal circuits are wired during embryonic development.
By exploring how regeneration works in other species and finding surprising roles for cell
types like muscle, this research could help reveal a path forward for regenerative medicine.