Abstract
Longevity: The Disposable Soma?
From the first alchemist's elixir of life to J.K. Rowling's Harry Potter and the Sorcerer's Stone, people have fantasized about immortality. Strictly speaking, one might argue that the body needs to exist only long enough to procreate. The soma (all of the body's cells except for the sex cells) is disposable once genes have been passed to the next generation. Nevertheless, the human desire for somatic survival, coupled with scientific development, has resulted in an ever-lengthening human life span. It is interesting to consider whether we are getting closer to an indefinitely lengthened life span.
While most of us have considered death inevitable, is that presumption a scientific certainty? People age and die by having their components wear out and break down. If we were cars, those parts could be replaced, and we might be kept on the road almost indefinitely. Aging science (and philosophy) may be moving us closer and closer to the point at which our bodily destruction can be delayed, prevented, or even repaired.
One controversial, visionary proponent of antiaging technology is Aubrey de Grey, PhD. He is editor-in-chief of the peer-reviewed academic journal Rejuvenation Research, which publishes articles on aging intervention. Dr. de Grey has published widely, and his writings include an interesting book written for the general public entitled Ending Aging: The Rejuvenation Breakthroughs That Could Reverse Human Aging in Our Lifetime that provides an overview of aging science. 1 Dr. de Grey is an engineer, and his biotechnologic vision of aging is interesting and provocative, if somewhat troublesome for traditional biologists.
Dr. de Grey has developed Strategies for Engineered Negligible Senescence (SENS). With his engineer's eye, he has divided aging into seven components: cell loss, apoptosis-resistance (the tendency of cells to resist dying when they are supposed to die), gene mutation in the cell nucleus, gene mutation in the mitochondria, the accumulation of “junk” inside cells, the accumulation of “junk” outside cells, and the accumulation of inappropriate chemical links in the material that supports cells. 1 While the challenges of defeating aging are formidable, this divides the problem into distinct components that do not seem quite so daunting.
The two primary approaches to these problems are to ameliorate and slow the normal wear and tear, masking its consequences, or to “service” the body at regular intervals to replace parts that have worn out.
Oxidation is a common factor in the final five items on de Grey's list of the seven components of aging. Mainstream science recognizes that mitochondria are important in bodily wear and tear. Sugars are broken down into mitochondria, where they react with oxygen and release energy into cells. They also produce free radicals that oxidize other molecules, including DNA and proteins, causing damage.
There has been extensive research on the use of antioxidants to combat free radicals and slow the process of bodily damage, and other concomitants of aging. Whether one addresses oxidative injury through newly developed antioxidants, vitamins, diet modification, or other means, the importance of addressing oxidative injury is established for a variety of disease states, including some cancers. Its contribution to the aging process does not seem farfetched.
Replacing worn-out parts also is not inconceivable science fiction. Stem-cell research has already demonstrated that stem cells may develop into virtually any body component. It is likely that science will learn how to harness, direct, and utilize the potential of stem cells to repair disease or injury. For example, in otolaryngology, there has been discussion about using stem cells to regenerate the superficial layer of lamina propria of vocal folds to treat patients with vocal fold scar. It is quite conceivable that stem-cell science, or as yet unforeseen similar developments, eventually will permit us to repair or replace worn-out bodily cells and organs.
There are other interesting approaches to address aging. For example, one is to find a way to overcome the Hayflick limit on cell reproduction. The Hayflick limit, named after Leonard Hayflick, is the limit on the number of times a given cell can divide. While this varies among species, once the cell reaches its Hayflick limit, it stops dividing (except for stem cells, which do not have a Hayflick limit). The problem with overcoming the Hayflick limit and getting cells to start dividing again is that the process sounds a lot like cancer, and researchers worry (quite reasonably) that malignancy might result from this approach.
Another strategy is starvation. For reasons that are not entirely clear, decreased dietary intake prolongs life. Unfortunately, starvation also has undesirable consequences, such as shutting down ovulation, since survival trumps reproduction as a biological priority. If the body could be led to think it is experiencing the beneficial effects of starvation without actually starving, that might be another approach to increasing longevity. Such manipulation may involve the genes for sirtuins, for example, which are proteins that have been shown to extend life in simpler organisms than humans.
The likelihood of our living indefinitely is low. However, while we otolaryngologists are busy combating aging through rhinoplasties, face lifts, and other cosmetic interventions, it behooves us to recognize that there are scientists who dedicate their careers to the problems of aging, and there are provocative thinkers such as Aubrey de Grey who challenge us to hypothesize that aging changes and the disposability of the soma can be overcome. Accepting that hypothesis might lead to interesting and creative research.
Dr. de Grey is one of the few researchers who believe that there are some people currently living who might see their lives extended indefinitely. He bases that extraordinary concept on the hope that further discoveries in life-extending technologies will be made before all of us die, a journey that he refers to as achieving “longevity escape velocity.” While de Grey's pronouncements seem fantastic, accepting them may be an interesting challenge to research. Certainly, accepting that “death is inevitable” is not likely to inspire us to think outside the box. However, believing that death is not inevitable might lead us to develop creative approaches to address aging, longevity and, immortality—topics that should be fascinating to us all.