Rejuvenation is a medical discipline focused on the practical reversal of theaging process.[1]
Rejuvenation is distinct fromlife extension. Life extension strategies often study the causes ofaging and try to oppose those causes to slow aging. Rejuvenation is thereversal of aging and thus requires a different strategy, namely repair of thedamage that is associated with aging or replacement of damaged tissue with new tissue. Rejuvenation can be a means of life extension, but most life extension strategies do not involve rejuvenation.
Various myths tell the stories about the quest for rejuvenation. It was believed thatmagic or intervention of asupernatural power can bring back youth and many mythical adventurers set out on a journey to do that, for themselves, their relatives or some authority that sent them anonymously.
An ancient Chinese emperor sent out ships of young men and women to find a pearl that would rejuvenate him. This led to a myth among modern Chinese that Japan was founded by these people.
In some religions, people were to be rejuvenated after death prior to placing them inheaven.
The stories continued well into the 16th century. The Spanish explorerJuan Ponce de León led an expedition around theCaribbean islands and intoFlorida to find theFountain of Youth. Led by the rumors, the expedition continued the search and many perished. The Fountain was nowhere to be found as locals were unaware of its exact location.
Since the emergence ofphilosophy,sages and self-proclaimedwizards always made enormous efforts to find the secret of youth, both for themselves and their noblepatrons andsponsors. It was widely believed that somepotions may restore the youth.
Another commonly cited approach was attempting to transfer theessence of youth from young people to old. Some examples of this approach were sleeping withvirgins orchildren (sometimes literally sleeping, not necessarily having sex),[2] bathing in or drinking their blood.
The quest for rejuvenation reached its height withalchemy. All around Europe, and also beyond, alchemists were looking for thePhilosopher's Stone, the mythical substance that, as it was believed, could not only turn lead into gold, but also prolong life and restore youth. Although the set goal was not achieved, alchemy paved the way to thescientific method and so to the medical advances of today.[citation needed]
Serge Abrahamovitch Voronoff was a French surgeon born in Russia who gained fame for his technique of grafting monkey testicle tissue on to the testicles of men while working in France in the 1920s and 1930s. This was one of the first medically accepted rejuvenation therapies (before he was proved to be wrong around 1930–1940). The technique brought him a great deal of money, although he was already independently wealthy. As his work fell out of favor, he went from being a highly respected surgeon to a subject of ridicule. By the early 1930s, over 500 men had been treated in France by his rejuvenation technique, and thousands more around the world, such as in a special clinic set up inAlgiers.[3] Noteworthy people who had the surgery includedHarold McCormick, chairman of the board ofInternational Harvester Company,[4] and the aging premier ofTurkey.[5]
Rejuvenation technology and its effects on individuals and society have long been a subject of science fiction. TheMisspent Youth andCommonwealth Saga byPeter F. Hamilton are among the most well known examples of this, dealing with the short- and long-term effects of a near perfect 80-year-old to 20-year-old body change with mind intact. The less perfect rejuvenation featured in theMars trilogy byKim Stanley Robinson results in long-term memory loss and sheer boredom that comes with extreme age. The post-mortal characters in theRevelation Space series have long-term or essentially infinite lifespans, and sheer boredom induces them to undertake activities of extreme risk.
Aging is the accumulation ofdamage tomacromolecules,cells,tissues andorgans in and on the body which, when it can no longer be tolerated by anorganism, ultimately leads to itsdeath. If any of that damage can be repaired, the result is rejuvenation.
There have been many experiments which have been shown to increase themaximum life span oflaboratory animals,[citation needed] thereby achievinglife extension. A few experimental methods such as replacinghormones to youthful levels have had considerable success in partially rejuvenating laboratory animals and humans. A 2011 experiment involved breeding genetically manipulated mice that lacked an enzyme called telomerase, causing the mice to age prematurely and suffer ailments. When the mice were given injections to reactivate the enzyme, it repaired the damaged tissues and reversed the signs of aging.[6] There are at least eight important hormones that decline with age: 1.human growth hormone (HGH); 2. the sexual hormones: testosterone or oestrogen/progesterone; 3.erythropoietin (EPO); 4. insulin; 5.DHEA; 6. melatonin; 7. thyroid; 8. pregnenolone. In theory, if all or some of these hormones are replaced, the body will respond to them as it did when it was younger, thus repairing and restoring many body functions. In line with this, recent experiments show that heterochronicparabiosis, i.e. connecting the circulatory systems of young and old animal, leads to the rejuvenation of the old animal, including restoration of proper stem cell function. Similar experiments show that grafting old muscles into young hosts leads to their complete restoration, whereas grafting young muscles into old hosts does not. These experiments show that aging is mediated by systemic environment, rather than being an intrinsic cell property.[citation needed] Clinical trials based on transfusion of young blood were scheduled to begin in 2014.[7] Another intervention that is gaining popularity is epigenetic reprogramming.[8] Through the use ofYamanaka factors, aged cells can revert to a younger state. It has been demonstrated that reprogramming induces a youthful epigenetic state and can restore vision after injury.[9] Only through reprogramming were stochastic epigenetic variations, which accumulate with age, successfully reversed, as demonstrated by a stochastic data-based clock.[10]
Most attempts atgenetic repair have traditionally involved the use of aretrovirus to insert a newgene into a random position on achromosome. But by attachingzinc fingers (which determine wheretranscription factors bind) toendonucleases (which breakDNA strands),homologous recombination can be induced to correct and replace defective (or undesired) DNA sequences. The first applications of this technology are to isolatestem cells from thebone marrow of patients havingblood diseasemutations, to correct those mutations inlaboratory dishes using zinc finger endonucleases and to transplant the stem cells back into the patients.[11] More recent efforts leverage CRISPR-Cas systems or adeno-associated viruses (AAVs).
EnhancedDNA repair has been proposed as a potential rejuvenation strategy.[12] SeeDNA damage theory of aging.
Stem cellregenerative medicine uses three different strategies:
Asalamander can not only regenerate alimb, but can regenerate thelens orretina of aneye and can regenerate anintestine. For regeneration the salamander tissues form ablastema byde-differentiation ofmesenchymal cells, and theblastema functions as a self-organizing system to regenerate the limb.[13]
Yet another option involves cosmetic changes to the individual to create the appearance of youth. These are generally superficial and do little to make the person healthier or live longer, but the real improvement in a person's appearance may elevate their mood and have positive side effects normally correlated withhappiness.Cosmetic surgery is a large industry offering treatments such as removal of wrinkles ("face lift"), removal of extra fat (liposuction) and reshaping or augmentation of various body parts (abdomen,breasts,face).
There are also, as commonly found throughout history, many fake rejuvenation products that have been shown to be ineffective. Chief among these are powders, sprays, gels, andhomeopathic substances that claim to contain growth hormones. Authentic growth hormones are only effective when injected, mainly due to the fact that the191-amino acid protein is too large to be absorbed through themucous membranes, and would be broken up in the stomach if swallowed.
TheMprize scientific competition is under way to deliver on the mission of extending healthy human life. It directly accelerates the development of revolutionary new life extension therapies by awarding two cash prizes: one to the research team that breaks the world record for the oldest-ever mouse; and one to the team that develops the most successful late-onset rejuvenation. Current Mprize winner for rejuvenation is Steven Spindler. Caloric restriction (CR), the consumption of fewer calories while avoiding malnutrition, was applied as a robust method of decelerating aging and the development ofage-related diseases.[14]
The biomedicalgerontologistAubrey de Grey has initiated a project, strategies for engineered negligible senescence (SENS), to study how to reverse the damage caused by aging. He has proposed seven strategies for what he calls the seven deadly sins of aging:[15]
In 2009, Aubrey de Grey co-founded theSENS Foundation to expedite progress in the above-listed areas.
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