The Lund University team collected wild planarians from a pond in Pildammsparken, Malmö, because these flatworms are known to be masters of regeneration. According to the researchers, a single planarian can produce up to 200 new individuals from a tiny fragment. In the lab, the worms, roughly five millimeters long, were cut in half to release exosomes. Rakel Bjurling described that after nine days, the rear part had already developed eyes, and within two weeks both halves had grown back to their original size.
Exosomes are small vesicles that carry signaling molecules between cells, influencing growth, gene expression, and immunity, the researchers explained. They pointed out that earlier work has established exosomes as key players in planarian tissue repair. For the first time, the Lund group isolated exosomes from wild rather than laboratory-cultured planarians, a move that Bjurling said was meant to capture the organism's natural biology. Because the exosomes are roughly the size of viruses, isolating them was extremely fiddly, she added.
The researchers applied these exosomes to human skin models of the type used in cosmetics testing. They found that adding the signaling molecules made the skin thicker. When the skin was damaged, wounds closed faster. In burn injuries, blood vessels healed more rapidly with the help of the planarian exosomes. According to Rakel Bjurling, until now it was unknown whether these planarian exosomes could affect cells from other species. Martin Hjort stated that the study suggests planarian signaling molecules can accelerate the body’s own healing processes, representing the first time anyone has shown that regeneration from a planarian can be used in another organism. The team cautioned that the specific molecules involved and their interaction with human cells remain unclear, and safety assessments are needed; it is also unknown whether wild planarians are more effective than laboratory-cultured ones. Comprehensive safety testing is required before any therapeutic application, and clinical use is likely years away.