Spongy sea creature rewrites science

Researchers discovered a link between healing and aging by studying the regenerative abilities of a small sea creature called Hydractinia Symbiolongicarpus. The creature, which can grow an entirely new body from just its mouth, revealed that senescence, commonly associated with aging, may play a role in its extreme regenerative abilities.

A cousin of the jellyfish and coral, it can regenerate its entire body with the help of “senescent” cells.

Researchers from the National Institutes of Health and their partners have discovered new findings about healing and aging by studying a small sea creature capable of regenerating its entire body using only its mouth. They analyzed RNA sequence Hydractinia Symbiolongicarpusa small, tube-shaped animal creature that lives in the shells of hermit crabs.

Just as Hydractinia As they began to regenerate new bodies, the researchers discovered a molecular signature linked to the biological process of aging, also known as senescence. According to the study published in Cell reports, Hydractinia It shows that the fundamental biological processes of healing and aging are intertwined, providing a new perspective on how aging develops.

“Studies like these that explore the biology of unusual organisms reveal how universal many biological processes are and how much we still have to understand about their functions, relationships and evolution,” said Charles Rotimi, director of the Intramural Institute. A research program at the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health. “Such findings have great potential to provide new insights into human biology.”

Anatomy of hydractinia

Hydractinia’s regeneration-driving stem cells are stored in the lower trunk of the animal’s body, away from the mouth. Credit: Darryl Lyga, National Human Genome Research Institute (NHGRI)

Untangling the evolutionary origins of fundamental biological processes, such as aging and healing, is essential to understanding human health and disease. Humans have some regenerative capacity, such as healing broken bones or even regrowing a damaged liver. Some other animals, such as salamanders and zebrafish, can replace entire limbs and regenerate a variety of organs. However, simple-bodied animals, e.g Hydractiniaoften has extreme regenerative capabilities, such as growing an entire new body from a piece of tissue.

The regenerative role of aging contrasts with findings in human cells. “Most studies on aging are related to chronic inflammation, cancer, and age-related diseases,” said Andy Paxivanis, Ph.D., senior scientist at NHGRI and author of the study. “Normally, senescent cells remain in humans, and these cells cause chronic inflammation and induce senescence in neighboring cells. From animals such as HydractiniaWe can learn how aging can be beneficial and expand our understanding of aging and healing.

Previously, researchers discovered this Hydractinia It contains a special group of stem cells for regeneration. Stem cells can turn into other types of cells and are therefore useful in creating new parts of the body. In humans, stem cells mainly function in development, but highly regenerative organisms love them Hydractinia Use stem cells throughout their lives. Hydractinia It stores its regeneration-driving stem cells in its lower body.

However, when researchers remove the mouth — a part far from where the stem cells are located — the mouth grows a new body. Unlike human cells, which control their own fate, adult cells in some highly regenerative organisms can revert to stem cells when the organism is injured, although this process is not well understood. Therefore, the researchers assumed this Hydractinia New stem cells must be generated and molecular signals that can direct this process sought.

When RNA sequences indicated aging, researchers scanned the genome Hydractinia For sequences such as those of genes associated with aging 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. Without senescent cells, the animals did not develop new stem cells and were unable to regenerate.

The researchers tracked the senescent cells in it Hydractinia To find out how this animal circumvents the harmful effects of aging. Unexpectedly, the animals expelled the senescent cells from their mouths. While humans cannot get rid of senescent cells so easily, the roles of genes associated with aging in them do Hydractinia Suggests how the aging process has evolved.

We humans shared an ancestor last time Hydractinia – and their relatives, jellyfish and corals – are more than 600 million years old, and these animals never age at all. Because of these factors, Hydractinia It can provide crucial insights into our early animal ancestors. Therefore, the researchers suggest that regeneration may have been the original function of aging in early animals.

“We still do not understand how senescent cells trigger regeneration or how widespread this process is in the animal kingdom,” Dr. Paxivanis said. “Fortunately, by studying some of our distant animal relatives, we can begin to unravel some of the secrets of regeneration and aging — secrets that may eventually advance the field of regenerative medicine and the study of age-related diseases as well.”

Reference: “Aging-induced cellular reprogramming leads to whole-body rejuvenation” by Miguel Salinas Saavedra, Gabriel Febremarsa, Helen R. Krasovec, Andreas D. Horkan, and Uri Paksevanis, June 30, 2023, Cell reports.
doi: 10.1016/j.celrep.2023.112687

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