Planaria sp. are barely larger than apple seeds, yet they have got unique regenerative capabilities that might be the envy of quite a few animals. It turns out that it is one protein that is responsible for the process. In the near future, it will be possible to make use of the discovery.
On paper, an insignificant part of Planaria sp. may become "reborn" as a fully functional specimen - the regenerative capabilities of these organisms are extensive and almost unheard of in the animal world. Scientists have managed to single out a specialised protein that initiates those regenerative processes."This discovery is groundbreaking for science", highlights Ricardo Zayas, a developmental biologists at San Diego State University in California who did not participate in the research effort but recognises its potential.
It has been known for decades that a group of unspecialised stem cells, known as neoblasts, facilitates the regenerative processes within Planaria sp. However, it has been unknown until now which particular type of neoblasts is accountable for the phenomenon. Alejandro Sánchez Alvarado, a developmental biologist of Stower Institute for Medical Research in Kansas City, Missouri, used new techniques for the isolation of single cells, also aimed at characterising their gene ability. The research led both him and his team to 12 potential types of regenerative cells whose surfaces contained a curious protein. Making a fluorescent tag enabled the researchers to isolate a single cell type named "neoblast subtype no. 2" (Nb2), aimed to be subject to further tests. After the team had intentionally damaged Planaria, the number of Nb2 cells has risen rapidly, eventually resulting in the healing of the wound. In another experiment, a single Nb2 cell was not capable of multiplication and diversification in order to sustain the life of Planaria, having previously been exposed to a lethal dose of radiation.
In the case of humans, the same protein affects the spreading of cancer cells. Due to the activity of the antibody that allows for isolating Nb2 cells, Sánchez Alvarado and others are able to examine the action of so-called tetraspanins in a more detailed way. Other researchers are also making progress in terms of discoveries concerning the molecular details of regeneration.
"It is too early to say how those findings will translate into therapies to restore body parts in humans", highlights Peter Reddien, a developmental biologist at the Massachusetts Institute of Technology in Cambridge. "But discovering the mechanisms that allow natural regeneration to occur is a good start".