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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
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    Scientists discover clues to aging and healing from a squishy sea   
   creature    
    A relative of jellyfish and corals regrows its entire body with help from   
   'aging' cells.    
      
     Date:   
         June 30, 2023   
     Source:   
         NIH/National Human Genome Research Institute   
     Summary:   
         Insights into healing and aging by those who studied how a tiny sea   
         creature regenerates an entire new body from only its mouth. The   
         researchers sequenced RNA from Hydractinia symbiolongicarpus,   
         a small, tube-shaped animal that lives on the shells of hermit   
         crabs. Just as the Hydractinia were beginning to regenerate new   
         bodies, the researchers detected a molecular signature associated   
         with the biological process of aging, also known as senescence.   
      
      
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   FULL STORY   
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   Insights into healing and aging were discovered by National Institutes   
   of Health researchers and their collaborators, who studied how a tiny   
   sea creature regenerates an entire new body from only its mouth. The   
   researchers sequenced RNA from Hydractinia symbiolongicarpus, a small,   
   tube-shaped animal that lives on the shells of hermit crabs. Just as the   
   Hydractinia were beginning to regenerate new bodies, the researchers   
   detected a molecular signature associated with the biological process   
   of aging, also known as senescence.   
      
   According to the study published in Cell Reports, Hydractiniademonstrates   
   that the fundamental biological processes of healing and aging are   
   intertwined, providing new perspective on how aging evolved.   
      
   "Studies like this that explore the biology of unusual organisms reveal   
   both how universal many biological processes are and how much we have   
   yet to understand about their functions, relationships and evolution,"   
   said Charles Rotimi, Ph.D., director of the Intramural Research Program at   
   the National Human Genome Research Institute (NHGRI), part of NIH. "Such   
   findings have great potential for providing novel insights into human   
   biology."  Untangling the evolutionary origins of fundamental biological   
   processes, such as aging and healing, is essential to understanding   
   human health and disease.   
      
   Humans have some capacity to regenerate, like healing a broken bone or   
   even regrowing a damaged liver. Some other animals, such as salamanders   
   and zebrafish, can replace entire limbs and replenish a variety of   
   organs. However, animals with simple bodies, like Hydractinia, often   
   have the most extreme regenerative abilities, such as growing a whole   
   new body from a tissue fragment.   
      
   A regenerative role for senescence stands in contrast to findings in human   
   cells. "Most studies on senescence are related to chronic inflammation,   
   cancer and age-related diseases," said Andy Baxevanis, Ph.D., senior   
   scientist at NHGRI and an author of the study. "Typically, in humans,   
   senescent cells stay senescent, and these cells cause chronic inflammation   
   and induce aging in adjacent cells. From animals like Hydractinia, we can   
   learn about how senescence can be beneficial and expand our understanding   
   of aging and healing."  Previously, researchers found that Hydractinia has   
   a special group of stem cells for regeneration. Stem cells can transform   
   into other types of cells, and are therefore useful for creating new   
   body parts. In humans, stem cells mainly act in development, but highly   
   regenerative organisms like Hydractiniause stem cells throughout their   
   lifetimes. Hydractinia stores its regeneration-driving stem cells   
   in the lower trunk of its body. However, when the researchers remove   
   the mouth -- a part far from where the stem cells reside -- the mouth   
   grows a new body. Unlike human cells, which are locked in their fates,   
   the adult cells of some highly regenerative organisms can revert into   
   stem cells when the organism is wounded, though this process is not well   
   understood. The researchers therefore theorized that Hydractinia must   
   generate new stem cells and searched for molecular signals that could   
   be directing this process.   
      
   When RNA sequencing pointed to senescence, the researchers scanned the   
   genome of Hydractinia for sequences like those of senescence-related   
   genes in humans.   
      
   Of the three genes they identified, one was "turned on" in cells near   
   the site where the animal was cut. When the researchers deleted this   
   gene, the animals' ability to develop senescent cells was blocked, and   
   without the senescent cells, the animals did not develop new stem cells   
   and could not regenerate.   
      
   The researchers tracked the senescent cells in Hydractinia to find how   
   this animal circumvents the harmful effects of senescence. Unexpectedly,   
   the animals ejected the senescent cells out of their mouths. While humans   
   can't get rid of aging cells that easily, the roles of senescence-related   
   genes in Hydractinia suggest how the process of aging evolved.   
      
   We humans last shared an ancestor with Hydractinia -- and its close   
   relatives, jellyfish and corals -- over 600 million years ago, and these   
   animals don't age at all. Because of these factors, Hydractinia can   
   provide crucial insights about our earliest animal ancestors. Therefore,   
   the researchers theorize that regeneration may have been the original   
   function of senescence in the first animals.   
      
   "We still don't understand how senescent cells trigger regeneration or   
   how widespread this process is in the animal kingdom," said Dr. Baxevanis.   
      
   "Fortunately, by studying some of our most distant animal relatives,   
   we can start to unravel some of the secrets of regeneration and aging --   
   secrets that may ultimately advance the field of regenerative medicine   
   and the study of age- related diseases as well."   
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Biotechnology # Biology #   
                   Biotechnology_and_Bioengineering # Genetics   
             o Earth_&_Climate   
                   # Rainforests # Ice_Ages # Environmental_Policy #   
                   Geography   
       * RELATED_TERMS   
             o Hermit_crab o Crab o Molecular_biology o   
             Calorie_restricted_diet o Animal_shell o Eustachian_tube o   
             Gastropod_shell o Fertilisation   
      
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   Story Source: Materials provided by   
   NIH/National_Human_Genome_Research_Institute. Original written by Anna   
   Rogers. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Miguel Salinas-Saavedra, Febrimarsa, Gabriel Krasovec, Helen   
      R. Horkan,   
         Andreas D. Baxevanis, Uri Frank. Senescence-induced cellular   
         reprogramming drives cnidarian whole-body regeneration. Cell   
         Reports, 2023; 112687 DOI: 10.1016/j.celrep.2023.112687   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230630123210.htm   
      
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