Biological immortality
Encyclopedia
Biological immortality refers to a stable rate of mortality as a function of chronological age. Some individual cells and entire organisms in some species achieve this state either throughout their existence or after living long enough. This requires that death occur from injury or disease rather than deterioration, i.e., the absence of cellular senescence
. However, this definition of immortality has been challenged in the new Handbook of the Biology of Aging, because the increase in rate of mortality as a function of chronological age may be negligible at extremely old age
s, also 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. As a hypothetical example, there is only a 50% chance of a human surviving another year at age 110 or greater. The fact that some multi-cellular organisms do not experience senescence implies that aging is not an Aristotelian inevitability and refutes the prior hypothesis that aging follows a Gompertz model.
No actual organism
or individual cell
is inviolably immortal
(i.e. "invincible" or "indestructible"). Biologically immortal living
things die, for example, upon receiving sufficient injury or otherwise having its body destroyed or diseased.
s have chosen the word immortal to designate cells that are not limited by the Hayflick limit
(where cells no longer divide because of DNA damage
or shortened telomere
s). Prior to Leonard Hayflick
, Alexis Carrel
hypothesized that all normal somatic
cells are immortal.
The term immortalization was first applied to cancer
cells that expressed the telomere-lengthening enzyme
telomerase
, and thereby avoided apoptosis
(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. Normal stem cell
s and germ cell
s 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 gene
s. One way to induce immortality is through viral-mediated induction of the large T-antigen
, commonly introduced through simian virus 40
(SV-40).
to study the scientific theory of panspermia.
are said to be biologically immortal, but only at the level of the colony
. An individual bacterium can easily die. The two daughter bacteria resulting from cell division
of a parent bacterium can be regarded as unique individuals or as members of a biologically "immortal" colony. The two daughter cells can be regarded as "rejuvenated
" copies of the parent cell because damaged macromolecule
s have been split between the two cells and diluted. In the same way stem cells and gamete
s can be regarded as "immortal".
are a genus
of simple, fresh-water animals possessing radial symmetry and no post-mitotic cells. The fact that all cells continually divide allows defects and toxins to be "diluted". It has been suggested that hydras do not undergo senescence
(aging), and as such are biologically immortal. However, this does not explain how hydras are consequently able to maintain telomere
lengths.
is a small (5 millimetre (0.196850393700787 in)) species of jellyfish
which uses transdifferentiation
to replenish cells after sexual reproduction
. This cycle can repeat indefinitely, potentially rendering it biologically immortal. It originated from the Caribbean sea, but has now spread around the world.
ists, such as those who practice cryonics
, have the hope that humans may someday become biologically immortal.
Biogerontologist Marios Kyriazis
suggested that biological immortality in humans is an inevitable consequence of natural evolution
. . His ELPIs (Extreme Lifespans through Perpetual-equalising Interventions) theory proposes that 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 and sophistication by living indefinitely, rather than through Darwinian evolution.
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
. However, this definition of immortality has been challenged in the new Handbook of the Biology of Aging, because the increase in rate of mortality as a function of chronological age may be negligible at extremely old age
Old age
Old age consists of ages nearing or surpassing the average life span of human beings, and thus the end of the human life cycle...
s, also 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. As a hypothetical example, there is only a 50% chance of a human surviving another year at age 110 or greater. The fact that some multi-cellular organisms do not experience senescence implies that aging is not an Aristotelian inevitability and refutes the prior hypothesis that aging follows a Gompertz model.
No actual organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
or individual cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
is inviolably immortal
Immortality
Immortality is the ability to live forever. It is unknown whether human physical immortality is an achievable condition. Biological forms have inherent limitations which may or may not be able to be overcome through medical interventions or engineering...
(i.e. "invincible" or "indestructible"). Biologically immortal living
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...
things die, for example, upon receiving sufficient injury or otherwise having its body destroyed or diseased.
Cell lines
BiologistBiologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...
s have chosen the word immortal to designate cells that are not limited by the Hayflick limit
Hayflick limit
The Hayflick limit is the number of times a normal cell population will divide before it stops, presumably because the telomeres reach a critical length....
(where cells no longer divide because of DNA damage
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1...
or shortened telomere
Telomere
A telomere is a region of repetitive DNA sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos "end" and merοs "part"...
s). Prior to Leonard Hayflick
Leonard Hayflick
Leonard Hayflick , Ph.D., is Professor of Anatomy at the University of California, San Francisco, School of Medicine, and was Professor of Medical Microbiology at Stanford University School of Medicine. He is a past president of the Gerontological Society of America and was a founding member of the...
, Alexis Carrel
Alexis Carrel
Alexis Carrel was a French surgeon and biologist who was awarded the Nobel Prize in Physiology or Medicine in 1912 for pioneering vascular suturing techniques. He invented the first perfusion pump with Charles A. Lindbergh opening the way to organ transplantation...
hypothesized that all normal somatic
Somatic
The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...
cells are immortal.
The term immortalization was first applied to cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
cells that expressed the telomere-lengthening enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
telomerase
Telomerase
Telomerase is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. This region of repeated nucleotide called telomeres contains non-coding DNA material and prevents constant loss of important DNA from...
, and thereby avoided apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
(cell death caused by intracellular mechanisms). Among the most commonly used cell lines are HeLa
HeLa
A HeLa cell is a cell type in an immortal cell line used in scientific research. It is the oldest and most commonly used human cell line. The line was derived from cervical cancer cells taken on February 8, 1951 from Henrietta Lacks, a patient who eventually died of her cancer on October 4, 1951...
and Jurkat
Jurkat cells
Jurkat cells are an immortalized line of T lymphocyte cells that are used to study acute T cell leukemia, T cell signaling, and the expression of various chemokine receptors susceptible to viral entry, particularly HIV. Jurkat cells are also useful in science because of their ability to produce...
, both of which are immortalized cancer cell lines. Normal stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
s and germ cell
Germ cell
A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate near the gut of an embryo and migrate to the developing gonads. There, they undergo cell division of two types, mitosis and meiosis, followed by...
s 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 gene
Tumor suppressor gene
A tumor suppressor gene, or anti-oncogene, is a gene that protects a cell from one step on the path to cancer. When this gene is mutated to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes.-Two-hit hypothesis:Unlike...
s. One way to induce immortality is through viral-mediated induction of the large T-antigen
SV40 Large T-antigen
SV40 large T antigen is a hexamer protein that is a proto-oncogene derived from the polyomavirus SV40 which is capable of transforming a variety of cell types. The transforming activity of TAg is due in large part to its perturbation of the retinoblastoma and p53 tumor suppressor proteins...
, commonly introduced through simian virus 40
SV40
SV40 is an abbreviation for Simian vacuolating virus 40 or Simian virus 40, a polyomavirus that is found in both monkeys and humans...
(SV-40).
Organisms
Immortality may not be desirable for multi-cellular organisms, as the main controls over cancer are the apoptotic mechanisms.Tardigrades
Tardigrades, otherwise known as "water bears", are highly resilient microscopic animals. Capable of surviving extremes such as heat, radiation, drought, and even the vacuum of space by going into suspended animation, where their metabolism slows to near zero and they simply wait out the harsh conditions until the environment is more favorable. The Russian Space Administration is planning a mission to launch water bears at PhobosPhobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...
to study the scientific theory of panspermia.
Bacteria
BacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
are said to be biologically immortal, but only at the level of the colony
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
. An individual bacterium can easily die. The two daughter bacteria resulting from cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
of a parent bacterium can be regarded as unique individuals or as members of a biologically "immortal" colony. The two daughter cells can be regarded as "rejuvenated
Rejuvenation (aging)
Rejuvenation is the hypothetical reversal of the aging process.Rejuvenation is distinct from life extension. Life extension strategies often study the causes of aging and try to oppose those causes in order to slow aging...
" copies of the parent cell because damaged macromolecule
Macromolecule
A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...
s have been split between the two cells and diluted. In the same way stem cells and gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s can be regarded as "immortal".
Hydra
HydrasHydra (genus)
Hydra is a genus of simple fresh-water animal possessing radial symmetry. Hydras are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions and can be found by...
are a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of simple, fresh-water animals possessing radial symmetry and no post-mitotic cells. The fact that all cells continually divide allows defects and toxins to be "diluted". It has been suggested that hydras do not undergo senescence
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
(aging), and as such are biologically immortal. However, this does not explain how hydras are consequently able to maintain telomere
Telomere
A telomere is a region of repetitive DNA sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos "end" and merοs "part"...
lengths.
Jellyfish
Turritopsis nutriculaTurritopsis nutricula
Turritopsis nutricula, the immortal jellyfish, is a hydrozoan whose medusa, or jellyfish, form can revert to the polyp stage after becoming sexually mature. It is the only known case of a metazoan capable of reverting completely to a sexually immature, colonial stage after having reached sexual...
is a small (5 millimetre (0.196850393700787 in)) species of jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
which uses transdifferentiation
Transdifferentiation
Transdifferentiation in biology takes place when a non-stem cell transforms into a different type of cell, or when an already differentiated stem cell creates cells outside its already established differentiation path...
to replenish cells after sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
. This cycle can repeat indefinitely, potentially rendering it biologically immortal. It originated from the Caribbean sea, but has now spread around the world.
Lobsters
Older lobsters are more fertile than younger lobsters. Some scientists have claimed that they could effectively live indefinitely, barring injury, disease, capture, etc. See Lobster longevityLife extensionists
Some life extensionLife extension
Life extension science, also known as anti-aging medicine, experimental gerontology, and biomedical gerontology, is the study of slowing down or reversing the processes of aging to extend both the maximum and average lifespan...
ists, such as those who practice cryonics
Cryonics
Cryonics is the low-temperature preservation of humans and animals who can no longer be sustained by contemporary medicine, with the hope that healing and resuscitation may be possible in the future. Cryopreservation of people or large animals is not reversible with current technology...
, have the hope that humans may someday become biologically immortal.
Biogerontologist Marios Kyriazis
Marios Kyriazis
Marios Kyriazis is a medical doctor and gerontologist who helped launch and formalise the concept of ‘Anti-aging medicine’ worldwide...
suggested that biological immortality in humans is an inevitable consequence of natural evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
. . His ELPIs (Extreme Lifespans through Perpetual-equalising Interventions) theory proposes that 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 and sophistication by living indefinitely, rather than through Darwinian evolution.
See also
- ImmortalityImmortalityImmortality is the ability to live forever. It is unknown whether human physical immortality is an achievable condition. Biological forms have inherent limitations which may or may not be able to be overcome through medical interventions or engineering...
- DNA damage theory of agingDNA damage theory of agingThe DNA damage theory of aging proposes that aging is a consequence of unrepaired DNA damage accumulation. Damage in this context includes chemical reactions that mutate DNA and/or interfere with DNA replication. Although both mitochondrial and nuclear DNA damage can contribute to aging, nuclear...
- American Academy of Anti-Aging MedicineAmerican Academy of Anti-Aging MedicineThe American Academy of Anti-Aging Medicine is a United States registered 501 nonprofit organization that promotes the field of anti-aging medicine and trains and certifies physicians in this specialty. As of 2011, approximately 26,000 practitioners had been given certificates...
- Strategies for Engineered Negligible Senescence (SENS)
- Immortality Institute
- Maximum lifespan
- Methuselah FoundationMethuselah FoundationThe Methuselah Foundation studies methods of extending lifespan. It is a non-profit 501 volunteer organization, co-founded by Aubrey de Grey and David Gobel, which is based in Springfield, Virginia, United States...
- Reliability theory of aging and longevityReliability theory of aging and longevityReliability theory of aging and longevity is a scientific approach aimed to gain theoretical insights into mechanisms of biological aging and species survival patterns by applying a general theory of systems failure, known as reliability theory.-Overview:...
- CryptobiosisCryptobiosisCryptobiosis is an ametabolic state of life entered by an organism in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair...
- Negligible senescenceNegligible senescenceNegligible senescence refers to the failure of a few select animals to display symptoms of aging. More specifically, negligibly senescent animals do not have measurable reductions in their reproductive capability with age, or measurable functional decline with age. Death rates in negligibly...
External links
- Biological Immortality Slide show by Michael R. Rose
- Cellular Senscence and Apoptosis in Aging
- Cellular Senescence Information Center
- Geron Announces Launch of Telomerase-Immortalized Cell Line Geron Corporation
- Late Life: A New Frontier for Physiology study indicates biological immortality in humans late in life
- No Limit to Lifespan if We're Machines (pdf) - Betterhumans, August 26, 2004
- More on human biological immortality