Biological immortality

Not to be confused with immortalised cell line.

Biological immortality refers to a stable or decreasing rate of mortality from cellular senescence as a function of chronological age. Various unicellular and multicellular species may achieve this state either throughout their existence or after living long enough. A biologically immortal living being can still die from means other than senescence, such as through injury or disease.

This definition of immortality has been challenged in the new Handbook of the Biology of Aging,[1] because the increase in rate of mortality as a function of chronological age may be negligible at extremely old ages, an idea referred to as the late-life mortality plateau. The rate of mortality may cease to increase in old age, but in most cases that rate is typically very high.[2] As a hypothetical example, there is only a 50% chance of a human surviving another year at age 110 or greater.

The term is also used by biologists to describe cells that are not subject to the Hayflick limit.

Cell lines

Biologists chose the word "immortal" to designate cells that are not subject to the Hayflick limit, the point at which cells can no longer divide due to DNA damage or shortened telomeres. Prior to Leonard Hayflick's theory, Alexis Carrel hypothesized that all normal somatic cells were immortal.[3]

The term "immortalization" was first applied to cancer cells that expressed the telomere-lengthening enzyme telomerase, and thereby avoided apoptosis—i.e. cell death caused by intracellular mechanisms. Among the most commonly used cell lines are HeLa and Jurkat, both of which are immortalized cancer cell lines. HeLa cells originated from a sample of cervical cancer taken from Henrietta Lacks in 1951.[4] These cells have been and still are widely used in biological research such as creation of the polio vaccine,[5] sex hormone steroid research,[6] and cell metabolism.[7] Normal stem cells and germ cells can also be said to be immortal (when humans refer to the cell line).

Immortal cell lines of cancer cells can be created by induction of oncogenes or loss of tumor suppressor genes. One way to induce immortality is through viral-mediated induction of the large T‑antigen,[8] commonly introduced through simian virus 40 (SV-40).[9]

Organisms

According to the Animal Ageing and Longevity Database, the list of organisms with negligible aging (along with estimated longevity in the wild) includes:[10]

Tardigrades

Tardigrade

Tardigrades, also known as "water bears", are highly resilient microscopic animals. They are capable of surviving extremes such as heat, radiation, drought, and the vacuum of space by going into a "tun"—essentially a shrivelled blob—a type of suspended animation (Cryptobiosis) where their metabolism slows to near zero and they simply wait out the harsh conditions until the environment is more favorable.

However they are not "immortal".[11] It has been estimated that a tardigrade would have a life span of less than a year if it never entered the cryptobiotic state. However, one that alternates active with cryptobiotic periods might survive for as long as sixty years - though more typically up to 10 years. The maximum known was a museum specimen of moss that had been kept dry for one hundred and twenty years which yielded a number of tardigrades. When the animals were moistened, a few of them revived, but all died within a few minutes.

Bacteria and some yeast

Many unicellular organisms age: as time passes, they divide more slowly and ultimately die. Asymmetrically dividing bacteria and yeast also age. However symmetrically dividing bacteria and yeast can be biologically immortal under ideal growing conditions.[12] In these conditions, when a cell splits symmetrically to produce two daughter cells, the process of cell division can restore the cell to a youthful state. However, if the parent asymmetrically buds off a daughter only the daughter is reset to the youthful state - the parent isn't restored and will go on to age and die. In a similar manner stem cells and gametes can be regarded as "immortal".

Hydra

Hydra

Hydras are a genus of the Cnidaria phylum. All cnidarians can regenerate, allowing them to recover from injury and to reproduce asexually. Hydras are simple, freshwater animals possessing radial symmetry and no post-mitotic cells. All hydra cells continually divide. It has been suggested that hydras do not undergo senescence, and, as such, are biologically immortal. In a four-year study, 3 cohorts of hydra did not show an increase in mortality with age. It is possible that these animals live much longer, considering that they reach maturity in 5 to 10 days.[13] However, this does not explain how hydras are consequently able to maintain telomere lengths.

Jellyfish

Turritopsis dohrnii, or Turritopsis nutricula, is a small (5 millimeters (0.20 in)) species of jellyfish that uses transdifferentiation to replenish cells after sexual reproduction. This cycle can repeat indefinitely, potentially rendering it biologically immortal. This organism originated in the Caribbean sea, but has now spread around the world. Similar cases include hydrozoan Laodicea undulata[14] and scyphozoan Aurelia sp.1.[15]

Lobsters

Further information: Lobster § Longevity

Research suggests that lobsters may not slow down, weaken, or lose fertility with age, and that older lobsters may be more fertile than younger lobsters. This does not however make them immortal in the traditional sense, as they are significantly more likely to die at a shell moult the older they get (as detailed below).

Their longevity may be due to telomerase, an enzyme that repairs long repetitive sections of DNA sequences at the ends of chromosomes, referred to as telomeres. Telomerase is expressed by most vertebrates during embryonic stages but is generally absent from adult stages of life.[16] However, unlike vertebrates, lobsters express telomerase as adults through most tissue, which has been suggested to be related to their longevity.[17][18][19] Contrary to popular belief, lobsters are not immortal. Lobsters grow by moulting which requires a lot of energy, and the larger the shell the more energy is required.[20] Eventually, the lobster will die from exhaustion during a moult. Older lobsters are also known to stop moulting, which means that the shell will eventually become damaged, infected, or fall apart and they die.[21] The European lobster has an average life span of 31 years for males and 54 years for females.

Planarian flatworms

Polycelis felina, a freshwater planarian

Planarian flatworms have both sexually and asexually reproducing types. Studies on genus Schmidtea mediterranea suggest these planarians appear to regenerate (i.e. heal) indefinitely, and asexual individuals have an "apparently limitless [telomere] regenerative capacity fueled by a population of highly proliferative adult stem cells". "Both asexual and sexual animals display age-related decline in telomere length; however, asexual animals are able to maintain telomere lengths somatically [ie during reproduction by fission or when regeneration is induced by amputation], whereas sexual animals restore telomeres by extension during sexual reproduction or during embryogenesis like other sexual species... homeostatic telomerase activity observed in both asexual and sexual animals is not sufficient to maintain telomere length, whereas the increased activity in regenerating asexuals is sufficient to renew telomere length... "[22]

Lifespan: For sexually reproducing planaria: "the life span of individual planarian can be as long as 3 years, likely due to the ability of neoblasts to constantly replace aging cells.". Whereas for asexually reproducing planaria: "individual animals in clonal lines of some planarian species replicating by fission have been maintained for over 15 years"[23]

Attempts to engineer biological immortality in humans

Although the premise that biological aging can be halted or reversed by foreseeable technology remains controversial,[24] research into developing possible therapeutic interventions is underway.[25] Among the principal drivers of international collaboration in such research is the SENS Research Foundation, a non-profit organization that advocates a number of what it claims are plausible research pathways that might lead to engineered negligible senescence in humans.[26]

In 2015, Liz Parrish, CEO of BioViva, treated herself using gene therapy, with the goal of not just halting, but reversing aging.[27] She has since reported feeling more energetic, but long-term study of the treatment is ongoing.

For several decades,[28] researchers have also pursued various forms of suspended animation as a means by which to indefinitely extend mammalian lifespan. Some scientists have voiced support[29] for the feasibility of the cryopreservation of humans, known as cryonics. Cryonics is predicated on the concept that some people considered clinically dead by today's medicolegal standards are not actually dead according to information-theoretic death and can, in principle, be resuscitated given sufficient technological advances.[30] The goal of current cryonics procedures is tissue vitrification, a technique first used to reversibly cryopreserve a viable whole organ in 2005.[31][32]

Similar proposals involving suspended animation include chemical brain preservation. The non-profit Brain Preservation Foundation offers a cash prize valued at over $100,000 for demonstrations of techniques that would allow for high-fidelity, long-term storage of a mammalian brain.[33]

Immortalism and immortality as a political cause

In 2012 in Russia, and then in the United States, Israel, and the Netherlands, pro-immortality transhumanist political parties were launched.[34] They aim to provide political support to anti-aging and radical life extension research and technologies and want to ensure the fastest possible—and at the same time, as least disruptive as possible—societal transition to radical life extension, life without aging, and ultimately, immortality. They aim to make it possible to provide access to such technologies to the majority of people alive today.[35]

Other life extensionists

Biogerontologist Marios Kyriazis suggested that biological immortality in humans is an inevitable consequence of natural evolution.[36][37] His theory of extreme lifespans through perpetual-equalising interventions (ELPIs) proposes that[38] the ability to attain indefinite lifespans is inherent in human biology, and that there will come a time when humans will continue to develop their intelligence by living indefinitely, rather than through evolution by natural selection.[39][40]

See also

References

  1. ↑ Masoro, E.J. (2006). Austad, S.N., ed. Handbook of the Biology of Aging (Sixth ed.). San Diego, CA: Academic Press. ISBN 0-12-088387-2.
  2. ↑ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (Nov–Dec 2005). "Late life: a new frontier for physiology". Physiological and Biochemical Zoology 78 (6): 869–878. doi:10.1086/498179. PMID 16228927.
  3. ↑ Shay, J. W. and Wright, W. E. (2000). "Hayflick, his limit, and cellular ageing" (PDF). Nature Reviews Molecular Cell Biology 1 (1): 72–76. doi:10.1038/35036093. PMID 11413492.
  4. ↑ Skloot, Rebecca (2010). The Immortal Life of Henrietta Lacks. New York: Crown/Random House. ISBN 978-1-4000-5217-2.
  5. ↑ Smith, Van (2002-04-17). "The Life, Death, and Life After Death of Henrietta Lacks, Unwitting Heroine of Modern Medical Science.". Baltimore City Paper. Retrieved 2010-03-02.
  6. ↑ Bulzomi, Pamela. "The Pro-apoptotic Effect of Quercetin in Cancer Cell Lines Requires ERβ-Dependant Signals." Cellular Physiology (2012): 1891-898. Web.
  7. ↑ Reitzer, Lawrence J.; Wice, Burton M.; Kennel, David (1978), "Evidence That Glutamine, Not Sugar, Is the Major Energy Source for Cultured HeLa Cells" (PDF), The Journal of Biological Chemistry 254 (April 25): 26X9–2676, retrieved 2013-04-03
  8. ↑ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (1983). "Expression of the Large T Protein of Polyoma Virus Promotes the Establishment in Culture of "Normal" Rodent Fibroblast Cell Lines". PNAS 80 (14): 4354–4358. doi:10.1073/pnas.80.14.4354. PMC 384036. PMID 6308618.
  9. ↑ Irfan Maqsood, M.; Matin, M. M.; Bahrami, A. R.; Ghasroldasht, M. M. (2013). "Immortality of cell lines: Challenges and advantages of establishment". Cell Biology International 37 (10): 1038–45. doi:10.1002/cbin.10137. PMID 23723166.
  10. ↑ Species with Negligible Senescence. AnAge: The Animal Ageing and Longevity Database
  11. ↑ Facts and Fiction about long-term survival in tardigrades J. Zool., Lond. (2001) 255:121-123 http://www.academia.edu/4858666/Facts_and_fiction_about_long-term_survival_in_tardigrades
  12. ↑ Current Biology: Volume 23, Issue 19, 7 October 2013, Pages 1844–1852 "Fission Yeast Does Not Age under Favorable Conditions, but Does So after Stress." Miguel Coelho1, 4, Aygül Dereli1, Anett Haese1, Sebastian Kühn2, Liliana Malinovska1, Morgan E. DeSantis3, James Shorter3, Simon Alberti1, Thilo Gross2, 5, Iva M. Tolić-Nørrelykke1
  13. ↑ Martínez, Daniel E. (1998). "Mortality patterns suggest lack of senescence in Hydra" (PDF). Experimental Gerontology (Elsevier Science Inc) 33 (3): 217–225. doi:10.1016/S0531-5565(97)00113-7. PMID 9615920.
  14. ↑ De Vito; et al. (2006). "Evidence of reverse development in Leptomedusae (Cnidaria, Hydrozoa): the case of Laodicea undulata (Forbes and Goodsir 1851)". Marine Biology 149: 339–346. doi:10.1007/s00227-005-0182-3. Retrieved 2015-12-31.
  15. ↑ He; et al. (2015-12-21). "Life Cycle Reversal in Aurelia sp.1 (Cnidaria, Scyphozoa)". PLOS ONE 10: e0145314. doi:10.1371/journal.pone.0145314. PMID 26690755. Retrieved 2015-12-31.
  16. ↑ Cong YS (2002). "Human Telomerase and It's Regulation". Microbiology and Molecular Biology Reviews 66 (3): 407–425. doi:10.1128/MMBR.66.3.407-425.2002. PMC 120798. PMID 12208997.
  17. ↑ Wolfram Klapper, Karen Kühne, Kumud K. Singh, Klaus Heidorn, Reza Parwaresch & Guido Krupp (1998). "Longevity of lobsters is linked to ubiquitous telomerase expression". FEBS Letters 439 (1–2): 143–146. doi:10.1016/S0014-5793(98)01357-X.
  18. ↑ Jacob Silverman. "Is there a 400 pound lobster out there?". howstuffworks.
  19. ↑ David Foster Wallace (2005). "Consider the Lobster". Consider the Lobster and Other Essays. Little, Brown & Company. ISBN 0-316-15611-6.
  20. ↑ http://www.lobsters.org/tlcbio/biology3.html
  21. ↑ http://www.smithsonianmag.com/science-nature/dont-listen-to-the-buzz-lobsters-arent-actually-immortal-88450872/?no-ist
  22. ↑ Thomas C. J. Tan, Ruman Rahman, Farah Jaber-Hijazi, Daniel A. Felix, Chen Chen, Edward J. Louis, and Aziz Aboobaker (February 2012). "Telomere maintenance and telomerase activity are differentially regulated in asexual and sexual worms" (PDF). PNAS 109 (9): 4209–4214. doi:10.1073/pnas.1118885109.
  23. ↑ http://www.geochembio.com/biology/organisms/planarian/#dev_stages
  24. ↑ Holliday, Robin (April 2009). "The extreme arrogance of anti-aging medicine". Biogerontology 10 (2): 223–228. doi:10.1007/s10522-008-9170-6. PMID 18726707. Retrieved 1 June 2013.
  25. ↑ "Rejuvenation Research". Mary Ann Liebert, Inc.
  26. ↑ "A Reimagined Research Strategy for Aging". SENS Research Foundation. Retrieved 1 June 2013.
  27. ↑ "A Tale of Do-It-Yourself Gene Therapy".
  28. ↑ Smith, Audrey U (1957). "Problems in the Resuscitation of Mammals from Body Temperatures Below 0 degrees C". Proceedings of the Royal Society of London. Series B, Biological Sciences 147 (929): 533–44. doi:10.1098/rspb.1957.0077. JSTOR 83173.
  29. ↑ "Scientists Open Letter on Cryonics". Retrieved 2013-03-19.
  30. ↑ "Alcor: Cryonics Myths". Retrieved 1 June 2013.
  31. ↑ "Plenary Session: Fundamentals of Biopreservation". CRYO 2005 Scientific Program. Society for Cryobiology. July 24, 2005. Archived from the original on 2006-08-30. Retrieved 2006-11-08.
  32. ↑ Fahy GM, Wowk B, Pagotan R, Chang A, Phan J, Thomson B, Phan L (2009). "Physical and biological aspects of renal vitrification". ORGANOGENESIS 5 (3): 167–175. doi:10.4161/org.5.3.9974. PMC 2781097. PMID 20046680.
  33. ↑ "Brain Preservation Foundation: Technology Prize". Retrieved 1 June 2013.
  34. ↑ "The Longevity Party - Who Needs it? Who Wants it?". Retrieved 4 April 2014.
  35. ↑ "A Single-Issue Political Party for Longevity Science". Fight Aging!. July 27, 2012. Retrieved January 31, 2013.
  36. ↑ https://acrobat.com/#d=MAgyT1rkdwono-lQL6thBQ Archived December 24, 2010 at the Wayback Machine
  37. ↑ Kyriazis, Marios (March 4, 2011). "Indefinite Lifespans: A Natural Consequence of the Global Brain". H+. Humanity+. Retrieved January 31, 2013.
  38. ↑ Llewellyn-Smith, Julia (October 25, 2011). "Has the fountain of youth been found?". The Daily Telegraph.
  39. ↑ The ELPIs Theory. Retrieved January 31, 2013.
  40. ↑ "Achieving Human Biological Immortality - Marios Kyriazis". YouTube. Retrieved January 31, 2013.

Bibliography

External links

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