The hydra is a unique multicellular organism. What makes it so special is that it is essentially immortal and shows no signs of aging either at the cellular or organism level. It preferentially reproduces asexually, rather than mating it forms buds which break off into progeny. The animal is able to do this by maintaining a continuous robust and unending supply of stem cells.
One theory as to the cause of human aging is the progressive loss of stem cells. Tissue in the body can recover from damage, be it internal or external, through the generation of fresh new cells from division of stem cells residing in niches in those tissues. However with advancing age, eventually these stem cell niches become depleted and the organism, in this case people, reach the end of life.
In the current landmark study, researchers looked to find which genes in hydra are responsible for a never ending supply of stem cells.
They discovered this characteristic depends specifically on a gene called FoxO, a fork-head box O transcription factor. This gene is a master genetic switch that when active allows for the expression of many genes involved in cell cycling.
When FoxO activity was reduced in hydra they exhibited signs of aging and cell senescence.
These findings are quite interesting because is has already been shown that a FoxO gene is involved in human aging as well. There is a specific variant of the FoxO3a human gene that has been linked to extreme human lifespan. It is more commonly found in centenarians.
The authors write:
Taken together, studies of FoxO in Hydra have several important implications. They not only reveal FoxO as a molecular factor that has contributed to the early evolution of stem cells, but also highlight intriguing similarities between Hydra and other multicellular organisms including humans, in the mechanisms
that maintain stemness and control life span. Thus, the work furthers our understanding of stem cell self-renewal at the beginning of animal evolution and also has implications for regenerative medicine and cellular aging.
Now that we have very strong evidence that enhancing FoxO activity may increase stem cell regeneration, it is conceivable that drugs might be developed to enhance or amplify FoxO activity and thus stem cell robsutness in humans.