Aging cells may be key to allowing healthy cells to regenerate
Two new studies from the animal kingdom may offer insight into the biological function of aging in humans. Both studies focused on senescent cells, or cells that have stopped dividing in response to stress but remain alive. The presence of senescent cells is seen as a marker of aging (we develop more senescent cells as we age). Additionally, senescent cells cause inflammation in surrounding cells and have been connected to a number of diseases such as cancer. But new research indicates that far from being throwaway or harmful cells, senescent cells may have originally evolved to allow the body to regenerate itself better.
The first study, published in Cell Reports, explored senescent cells in a simple-celled, tube-like creature called Hydractinia. Hydractinia species live on hermit crab shells and are distantly related to jellyfish, sharing a similarly squishy body and waving arms. Hydractinia are normally able to regenerate themselves if cut in half or injured using stem cells. But scientists discovered that when their senescent cells were blocked from developing, the animals could not create new stem cells or regenerate. While researchers are still investigating, it appears that senescent cells may be vital in helping rejuvenation happen. Scientists also observed that normal Hydractinia were able to avoid the harmful effects of senescent cells by ejecting them from their mouth before they caused damage.
The second study, published in Aging Cell, also explores a possible connection between senescent cells and regeneration, but focuses instead on salamanders. Salamanders are able to regrow entire limbs and organs, and display no signs of aging or age-related diseases such as cancer. Scientists had already noticed that senescent cells were present during key parts of the limb regeneration process in salamanders. The research team was able to regulate how many senescent cells were present in a salamander’s wound, and discovered that by increasing senescent cells, a larger “regeneration bud” developed and limb regeneration happened more quickly. Through further research, the scientists discovered that senescent cells secrete molecules that provoke nearby muscle tissue to regenerate and produce new muscle. It appears that senescent cells provide key signals in the regeneration process for healthy cells to multiply and differentiate into new muscle cells.
Both studies point to a more nuanced understanding of the purpose of aging. It is entirely possible that aging, senescent cells are actually crucial to how the body regenerates itself. While humans only have limited regenerative capacities such as mending broken bones, these studies on creatures with extreme regenerative abilities highlight the importance of senescent cells. Right now, there are numerous studies focused on how to limit the creation of senescent cells in the human body and thus prevent aging. But perhaps the secret to anti-aging lies not in banishing senescent cells entirely, but instead harnessing them to prompt greater regeneration. More research in the field is needed to fully understand the implications and potential health uses of senescent cells.
