Biological immortality

Source: Wikipedia, the free encyclopedia.

Biological immortality (sometimes referred to as bio-indefinite mortality) is a state in which the rate of mortality from

chronological age. Various unicellular and multicellular species, including some vertebrates, 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, poison, disease, predation, lack of available resources, or changes to environment
.

This definition of immortality has been challenged in the 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]

The term is also used by biologists to describe cells that are not subject to the Hayflick limit on how many times they can divide.

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.[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] Embryonic stem cells and germ cells have also been described as immortal.[8][9]

Immortal cell lines of cancer cells can be created by induction of

large T-antigen,[10] commonly introduced through simian virus 40 (SV-40).[11]

Organisms

According to the Animal Aging and Longevity Database, the list of animals with negligible aging (along with estimated longevity in the wild) includes:[12]

In 2018, scientists working for Calico, a company owned by Alphabet, published a paper in the journal eLife which presents possible evidence that Heterocephalus glaber (Naked mole rat) do not face increased mortality risk due to aging.[13][14][15]

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.[16] 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 is not restored and will go on to age and die. In a similar manner stem cells and gametes can be regarded as "immortal".

Hydra

Hydra

mitotic cells (cells that will never divide again) only in the extremities.[17] All hydra cells continually divide.[18] 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.[19] However, this does not explain how hydras are subsequently able to maintain telomere
lengths.

Jellyfish

Caribbean sea, but has now spread around the world.[citation needed] Key molecular mechanisms of its rejuvenation appear to involve DNA replication and repair, and stem cell renewal, according to a comparative genomics study.[20][21]

Similar cases include hydrozoan

Lobsters

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

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 (i.e. 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... "[30]

For sexually reproducing planaria: "the lifespan 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".[31][32]

See also

References

  1. .
  2. .
  3. .
  4. .
  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. Archived from the original on 2004-08-14. 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. PMID 429309
  8. ^ University of Cologne (7 March 2018). "On the immortality of stem cells". ScienceDaily. Retrieved 17 September 2020.
  9. ^ Surani, Azim (1 April 2009). "Germ cells: the route to immortality". University of Cambridge. Retrieved 17 September 2020.
  10. PMID 6308618
    .
  11. .
  12. ^ Species with Negligible Senescence Archived 2015-04-17 at the Wayback Machine. AnAge: The Animal Ageing and Longevity Database
  13. ^ "Calico Scientists Publish Paper in eLife Demonstrating that the Naked Mole Rat's Risk of Death Does Not Increase With Age". Calico. 25 January 2018. Archived from the original on 27 January 2018. Retrieved 27 January 2018.
  14. ^ "Naked mole rats defy the biological law of aging". Science Magazine - AAAS. 26 January 2018. Archived from the original on 26 January 2018. Retrieved 27 January 2018.
  15. PMID 29364116
    .
  16. ^ 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
  17. PMID 26136619
    .
  18. .
  19. (PDF) from the original on 2016-04-26.
  20. ^ Greenwood, Veronique (6 September 2022). "This Jellyfish Can Live Forever. Its Genes May Tell Us How". The New York Times. Retrieved 22 September 2022.
  21. PMID 36037356
    .
  22. .
  23. .
  24. .
  25. .
  26. from the original on 2011-07-27.
  27. on October 12, 2010.
  28. ^ "Biotemp". Archived from the original on 2015-02-11. Retrieved 2015-02-10.
  29. ^ Koren, Marina. "Don't Listen to the Buzz: Lobsters Aren't Actually Immortal". Archived from the original on 2015-02-12.
  30. from the original on 2012-03-06.
  31. ^ "Schmidtea , model planarian". www.geochembio.com. Archived from the original on 2010-12-30.
  32. ^ Archived at Ghostarchive and the Wayback Machine: "What Bodies Think About: Bioelectric Computation Outside the Nervous System - NeurIPS 2018". YouTube.

Bibliography