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Spore-like cells were proposed to be
pluripotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
cells that lie dormant in animal tissue and become active under stress or injury as
adult stem cells Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek σωματικóς ...
, exhibiting behavior characteristic of
spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
. They were proposed in 2001 by brothers
Charles Charles is a masculine given name predominantly found in English and French speaking countries. It is from the French form ''Charles'' of the Proto-Germanic name (in runic alphabet) or ''*karilaz'' (in Latin alphabet), whose meaning was ...
and Martin Vacanti and colleagues. Further work in collaboration with Japanese researchers led to the apparent discovery of
STAP cells Stimulus-triggered acquisition of pluripotency (STAP) was a proposed method of generating pluripotent stem cells by subjecting ordinary cells to certain types of stress, such as the application of a bacterial toxin, submersion in a weak acid, or p ...
, in which the pluripotent cells were newly created by stress or injury. This work was published in 2014, but soon found to be due to fraudulent work by Haruko Obokata.


Characteristics

Spore-like cells were said to be a specific class of
stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of ...
s in adult organisms, including humans, which are small, versatile, and most frequently remain in a
dormant Dormant, "sleeping", may refer to: Science *Dormancy Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps ...
"spore-like" state as the rest of the cells of the organism divide, grow, and die. Despite their dormancy, they apparently retain the ability to grow, divide, and differentiate into other cell types expressing characteristics appropriate to the tissue environment from which they were initially isolated, if some external stimulus should prompt them to do so. This capacity to continue to regenerate new cells has been shown in
in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology and ...
conditions for some animals in which all other cells have died, especially if the animal died from exposure to cold elements. Spore-like cells were said to remain viable in unprepared tissue (using no special preservation techniques), frozen at -86 °C and then thawed, or heated to 85 °C for more than 30 minutes. This has led researchers to try to revitalize spore-like cells from tissue samples of frozen carcasses deposited in
permafrost Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surfac ...
for decades (frozen walrus meat more than 100 years old, and mammoth and bison in Alaska estimated to be 50,000 years old). Vacanti et al. believed that these unique cells lie dormant until activated by injury or disease, and that they have the potential to regenerate tissues lost to disease or damage. Because the cell-size of less than 5 micrometers seems rather small as to contain the entire human
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...
the authors speculate on the "concept of a minimal genome" for these cells.


Later work

Charles Vacanti continued to work on these cells when he moved to Harvard, including with thoracic surgeon Koji Kojima who identified them in lung tissue. Working with a graduate student Haruko Obokata in his lab at Harvard from 2008, Vacanti later refined this theory to suggest that stress or injury could actually trigger the development of pluripotency in somatic cells. He first proposed this to Obokata and Masayuki Yamato at a conference in Florida in 2010; Yamato had independently come to the same conclusion. Obokata returned to Japan and continued this work at RIKEN. Vacanti presented these results in July 2012 at the Society of Cardiovascular Anesthesiologists conference, and then in January 2014 the journal ''
Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans ar ...
'' published two articles suggesting that a simple acid treatment could cause mouse blood cells to become
pluripotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
. The ''Boston Globe'' reported that "His discovery is a reminder that as specialized as science is, sometimes, a little ignorance may be a virtue. A stem-cell expert would probably never have even bothered to try the experiment Vacanti has been pursuing, on and off, since the late 1990s." Both STAP articles were retracted in July 2014 after an investigation by RIKEN concluded that the data were fabricated. Researcher Mariusz Ratajczak has linked spore-like cells to his idea of Very small embryonic-like stem cells, also proposed to be very small adult stem cells.


See also

*
Stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of ...
*
Adult stem cell Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek σωματικóς ...
*
Spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...


References


External links


La planète des clones (french) - ARTE documentation about spore-like cells (among other topics)


{{DEFAULTSORT:Spore-like cells Stem cells