In vitro

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Studies that are in vitro (Latin: in glass; often not italicized in English[1][2][3]), colloquially called "test tube experiments", are studies in biology and its sub-disciplines traditionally done in test-tubes, flasks, petri dishes etc., but which now involve the full range of techniques used in molecular biology and larger commercial applications.

Examples of in vitro studies include: the isolation, growth and identification of microorganisms; cells derived from multicellular organisms (cell culture or tissue culture); subcellular components (e.g. mitochondria or ribosomes); cellular or subcellular extracts (e.g. wheat germ or reticulocyte extracts); purified molecules (often proteins, DNA, or RNA, either individually or in combination); and the commercial production of antibiotics and other pharmaceutical products. Studies that are conducted using components of an organism that have been isolated from their usual biological surroundings permit a more detailed or more convenient analysis than can be done with whole organisms. In contrast, in vivo studies are those conducted in animals including humans, and whole plants. These may involve investigations into the pathogenesis of infections using live bacteria or their toxins, or the effects of antibiotics or drugs etc.

Viruses, which only replicate in living cells, are studied in the laboratory in cell or tissue culture, but many animal virologists refer to such work as being 'in vitro' to distinguish it from 'in vivo' work on whole animals.

Advantages[edit]

Living organisms are extremely complex functional systems that are made up of, at a minimum, many tens of thousands of genes, protein molecules, RNA molecules, small organic compounds, inorganic ions and complexes in an environment that is spatially organized by membranes and, in the case of multicellular organisms, organ systems.[4] For a biological organism to survive, these myriad components must interact with each other and with their environment in a way that processes food, removes waste, moves components to the correct location, and is responsive to signalling molecules, other organisms, light, sound, heat, taste, touch, and balance.

Top view of a module base (lid removed) looking into the four separated wells where cell culture inserts would usually sit and be exposed to tobacco smoke, for an in-vitro study of the effects.

This extraordinary complexity of living organisms is a great barrier to the identification of individual components and the exploration of their basic biological functions. The primary advantage of in vitro work is that it permits an enormous level of simplification of the system under study, so that the investigator can focus on a small number of components.[5][6] For example, the identity of proteins of the immune system (e.g. antibodies), and the mechanism by which they recognize and bind to foreign antigens would remain very obscure if not for the extensive use of in vitro work to isolate the proteins, identify the cells and genes that produce them, study the physical properties of their interaction with antigens, and identify how those interactions lead to cellular signals that activate other components of the immune system.[7]

Cellular responses are often species-specific, making cross-species analysis problematic. Newer methods of same-species-targeted, multi-organ studies are available to bypass live, cross-species testing.[8]

Disadvantages[edit]

The primary disadvantage of in vitro experimental studies is that it can sometimes be very challenging to extrapolate from the results of in vitro work back to the biology of the intact organism. Investigators doing in vitro work must be careful to avoid over-interpretation of their results, which can sometimes lead to erroneous conclusions about organismal and systems biology.[9]

For example, scientists developing a new viral drug to treat an infection with a pathogenic virus (e.g. HIV-1) may find that a candidate drug functions to prevent viral replication in an in vitro setting (typically cell culture). However, before this drug is used in the clinic, it must progress through a series of in vivo trials to determine if it is safe and effective in intact organisms (typically small animals, primates and humans in succession). Typically, most candidate drugs that are effective in vitro prove to be ineffective in vivo because of issues associated with delivery of the drug to the affected tissues, toxicity towards essential parts of the organism that were not represented in the initial in vitro studies, or other issues.[10]

Examples[edit]

  • Protein purification involves the isolation of a specific protein of interest from a complex mixture of proteins, often obtained from homogenized cells or tissues.
  • In vitro fertilization is used to allow spermatozoa to fertilize eggs in a culture dish before implanting the resulting embryo or embryos into the uterus of the prospective mother.
  • In vitro diagnostics refers to a wide range of medical and veterinary laboratory tests that are used to diagnose diseases and monitor the clinical status of patients using samples of blood, cells or other tissues obtained from a patient.

See also[edit]

Notes[edit]

  1. ^ Merriam-Webster, Merriam-Webster's Collegiate Dictionary, Merriam-Webster. 
  2. ^ Iverson, Cheryl, et al. (eds) (2007). "12.1.1 Use of Italics". AMA Manual of Style (10th ed.). Oxford, Oxfordshire: Oxford University Press. ISBN 978-0-19-517633-9. 
  3. ^ American Psychological Association (2010), "4.21 Use of Italics", The Publication Manual of the American Psychological Association (6th ed.), Washington, DC, USA: APA, ISBN 978-1-4338-0562-2. 
  4. ^ Alberts, Bruce (2008). Molecular biology of the cell. New York: Garland Science. ISBN 0-8153-4105-9. 
  5. ^ Vignais, Paulette M.; Pierre Vignais (2010). Discovering Life, Manufacturing Life: How the experimental method shaped life sciences. Berlin: Springer. ISBN 90-481-3766-7. 
  6. ^ Jacqueline Nairn; Price, Nicholas C. (2009). Exploring proteins: a student's guide to experimental skills and methods. Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-920570-1. 
  7. ^ Sunshine, Geoffrey; Coico, Richard (2009). Immunology: a short course. Wiley-Blackwell. ISBN 0-470-08158-9. 
  8. ^ "Existing Non-animal Alternatives". Source: AltTox.org. 8 September 2011. 
  9. ^ Rothman, S. S. (2002). Lessons from the living cell: the culture of science and the limits of reductionism. New York: McGraw-Hill. ISBN 0-07-137820-0. 
  10. ^ De Clercq E (October 2005). "Recent highlights in the development of new antiviral drugs". Curr. Opin. Microbiol. 8 (5): 552–60. doi:10.1016/j.mib.2005.08.010. PMID 16125443.