Can the cut-off eye regenerate? Science today reveals the secrets of this magical creature.

Planarian is a kind of magical creature. Its most well-known feature is its super regenerative ability: its head is cut off, and the rest of its body can grow a new head, which is amazing.} the true planarian has a very strong regeneration ability (photo source: reference [2]). In fact, the regeneration ability of this magical creature has high accuracy.scientists have found that if you don't simply and roughly cut off its whole head, but just cut off its eyes, after a few days, the eyes of the true planarian can grow back again, and the new eyes still have normal functions.this phenomenon has puzzled scientists.after all, it is not enough to grow photosensitive cells in order to make the eye function normally.these animals also have to connect the photoreceptor cells and the brain with nerves.in the process of embryonic development, a kind of "guidepost cells" will tell nerve cells how to walk through the complex three-dimensional anatomical environment, when to stretch, when to turn, when to stop, and finally to open the neural pathway of vision.however, many of these landmark cells only appear briefly during embryonic development and soon disappear.so, what are the secrets that adult true planarians have mastered to regenerate their eyes? In a science paper published today, a team from the Whitehead Institute in Massachusetts answered the question.using fluorescence in situ hybridization (FISH), researchers found a small number of new cells near the visual system of the true planarian.these cells have a high degree of coincidence with the nerve. They are either located near the eye, near the position where the photoreceptor cells protrude from the axon, or they are distributed along the path of the axon.surprisingly, in the newly found "landmark cells", according to the characteristics of gene expression, researchers found that two of them were actually muscle cells! "In most animals, muscle cells don't do this."said Dr. M. Lucila scimone, the first author of the study.in other animals, most of them are neurons and glial cells.} under microscope, do these muscle cells affect the distribution of new nerves? To test this hypothesis, the researchers developed an "eye transplant" technique, in which the eye of one true planarian is transplanted onto the head of another.the study found that these new eyes are sure to extend neurons towards these muscle cells, and adjust their forward direction after touching these muscle cells, and finally connect with the brain to perform normal visual function.interestingly, if the researchers transplanted these eyes to other parts of the body of the true planarian worm (lacking this special muscle cell), the photoreceptor neurons would not find their way to the brain. similarly, if these muscle cells are removed before transplantation, the same result will occur. } two types of muscle cells help to pave the neural pathway for the transplanted eyes (photo source: reference [1]). How do these magical muscle cells know where to appear and guide the distribution of nerves? Subsequent studies have found that special signaling molecules are secreted in muscles to tell the cells where to go. if these signaling molecules are interfered with, the guiding cells will lose their way, go to the wrong place, and lead the nerve to the wrong place. "this is an exciting new direction in the future," said Professor Peter w. reddien, co-author of the study. "We now know the transcriptome of these cells, which means that we can know all the genes expressed in these cells. this will allow us to list interesting genes, explore their function, and see what affects the function of these cells. "} miraculous planarias may hide the secret of treating human nerve injury (photo sources: Holger Brandl, HONGKEE moon, Miquel, Vila Farr é, Shang Yun Liu, Ian Henry, and Jochen C. rink / cc by(), a special review of this paper was made in science. In the end, it is pointed out that this work has brought a new direction for human nerve regeneration. one day, we may be able to mimic the function of these landmark cells and guide the formation of axons. this is a good news for patients with nerve damage caused by various reasons. References: [1] m. Lucila scimon et al. (2020), music and neural guidepost like cells facility planar visual system registration, science, DOI: 10.1126/ science.aba3203 [2] Guide cells help navigate axon regeneration, Retrieved June 25, 2020, From these muscle cells are guideposts to help recurrent flatforms grow back their eyes, retrieved June 25, 2020, from. if you need guidance on treatment plan, please go to a regular hospital.