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 ========================================================================== 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

========================================================================== 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.


========================================================================== 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 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230630123210.htm

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