Immortal animals have already cured aging. Immortal animals use stem cells to repair damage indefinitely, so damaged cells are cleared out and replaced with new ones. The organism is maintained, nothing essential breaks and the organism keeps on living. With aging, regeneration is switched off and the organism declines until something essential breaks. Humans have wound healing, which is a diminished version of regeneration. Elucidate and adapt the same technique, one to one to other organisms and ultimately as therapy to humans. It is not simply a matter of injecting stem cells.
While human regeneration is generally thought of as limb regeneration and research uses limb regeneration, we are interested with cell turnover regeneration and regeneration in wound healing, not just superficial wounds but the micro-damage that is not felt by the person such as damage to the extracellular matrix by ultraviolet rays, muscle and bone remodeling when lifting weights in the gymnasium, or perhaps damage to stomach lining or blood vessels during a meal. Unlike limb regeneration, we define "human" regeneration, generally as embryonic resynthesis. The physical process of you giving rise to you again (self renewal), rather than giving rise to offspring. As it is often stated the every 7 years the body replaces itself, resynthesis occurs, but the therapy is to make the resynthesis source embryonic components.
This includes, tissue maintenance in model organisms such as the planarian, salamander, immortal jellyfish, zebrafish and several others. It includes an event in which the oocyte undergoes an age-reversal process. It includes anecdotal observation where a fetus has a stroke and fully repairs themselves, and it also may include the zygote growing into a fetus, where if a fetal limb were amputated during this period it would regenerate similar to the salamander.
These examples of regeneration have to be adapted to humans and made into a therapy.
If the tissue does not grow younger with cell turnover, aging continues, the decline in tissue maintenance with aging is possibly the primary cause of aging and mortality.
According to Alexei Terman, of Linkoping University in Sweden, "Clearly, if all damaged structures were renewed with perfect accuracy, aging would not occur. But the inevitability of aging suggests that the biological mechanisms of removal and re-synthesis are not perfect. Of these two processes, the one most suspect in the progression of aging is that of inefficient removal."
We sway towards imperfect re-synthesis as the cause of aging because the breakdown of the extracellular matrix by ultraviolet rays, photoaging resulting in wrinkles is not caused by inefficient removal, instead caused by imperfect re-synthesis. This aging associated inhibition of re-synthesis has system-wide deleterious consequence. Planaria shows and even proves that perfect re-synthesis cures aging.
We cannot cure dementia, Parkinson's, Alzheimer's until we can activate neurogenesis in situ, obviously.
- Stem cells are the core of the repair system. Stem cells must be young and kept young. They must be abundant, the more abundant theoretically the more maintenance, the less abundant results in maintenance foregone. There is not enough stem cells in the human body to fully participate in the extensive tissue regeneration, and scars or fibrosis is the fallback. With enough stem cells scars do not form.
- Chemical signalling, there is a complex chemical signalling process that orchestrates tissue maintenance. Growth factors, micro-environment. Telomerase and maintenance of telomeres.
- Electrical signalling, there is also an electrical signalling process that orchestrates tissue maintenance. See Dr. Robert O. Becker and Dr. Michael Levin
- Mechanical load, nerve health.