Animal Disease Model

An Animal Disease Model is a Disease Model that is used to study the progression of diseases and to test new treatments before they are given to humans.

• Context:
  • It can be based on a model organism.
• Example(s):
  • Baker's Yeast Disease Model,
  • Fruit fly Disease Model,
  • Guinea Pig Disease Model,
  • Mouse Disease Model,
  • Zebra Fish Disease Model,
  • …
• Counter-Example(s):
  • Biomedical Model,
  • Cellular Model,
  • Recovery Model.
• See: Xenograft Model, Model Organism, Disease, Developmental Biology, Xenotransplantation, Clinical Trial.

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References

2021b

• (Wikipedia, 2021) ⇒ https://en.wikipedia.org/wiki/Animal_disease_model Retrieved:2021-11-14.
  • An animal model (short for animal disease model) is a living, non-human, often genetic-engineered animal used during the research and investigation of human disease, for the purpose of better understanding the disease process without the risk of harming a human. Although biological activity in an animal model does not ensure an effect in humans, many drugs, treatments and cures for human diseases are developed in part with the guidance of animal models. Animal models representing specific taxonomic groups in the research and study of developmental processes are also referred to as model organisms. There are three main types of animal models: Homologous, Isomorphic and Predictive.

    Homologous animals have the same causes, symptoms and treatment options as would humans who have the same disease.

    Isomorphic animals share the same symptoms and treatments, only.

    Predictive models are similar to a particular human disease in only a couple of aspects. However, these are useful in isolating and making predictions about mechanisms of a set of disease features.

2021b

• (Wikipedia, 2021) ⇒ https://en.wikipedia.org/wiki/Glossary_of_clinical_research Retrieved:2021-11-14.
  • Animal model
  • An animal with a disease either the same as or like a disease in humans. Animal models are used to study the development and progression of diseases and to test new treatments before they are given to humans.

2021c

• (NIH/NCI, 2021) ⇒ https://www.cancer.gov/publications/dictionaries/cancer-terms/def/animal-model Retrieved:2021-11-14.
  • QUOTE: An animal with a disease either the same as or like a disease in humans. Animal models are used to study the development and progression of diseases and to test new treatments before they are given to humans. Animals with transplanted human cancers or other tissues are called xenograft models.

2021d

• (Nature, 2021) ⇒ https://www.nature.com/subjects/animal-disease-models Retrieved:2021-11-14.
  • QUOTE: Animal disease models are non-human animals bearing pathologies that share features with a human disease. Disease models can either exist naturally or be induced artificially and are used for studying human disease with an experimental system.

2021e

• (Wikipedia, 2021) ⇒ https://en.wikipedia.org/wiki/Model_organism#Disease_models Retrieved:2021-11-14.
  • Animal models serving in research may have an existing, inbred or induced disease or injury that is similar to a human condition. These test conditions are often termed as animal models of disease. The use of animal models allows researchers to investigate disease states in ways which would be inaccessible in a human patient, performing procedures on the non-human animal that imply a level of harm that would not be considered ethical to inflict on a human.

    The best models of disease are similar in etiology (mechanism of cause) and phenotype (signs and symptoms) to the human equivalent. However complex human diseases can often be better understood in a simplified system in which individual parts of the disease process are isolated and examined. For instance, behavioral analogues of anxiety or pain in laboratory animals can be used to screen and test new drugs for the treatment of these conditions in humans. A 2000 study found that animal models concorded (coincided on true positives and false negatives) with human toxicity in 71% of cases, with 63% for nonrodents alone and 43% for rodents alone. In 1987, Davidson et al. suggested that selection of an animal model for research be based on nine considerations. These include "1) appropriateness as an analog, 2) transferability of information, 3) genetic uniformity of organisms, where applicable, 4) background knowledge of biological properties, 5) cost and availability, 6) generalizability of the results, 7) ease of and adaptability to experimental manipulation, 8) ecological consequences, and 9) ethical implications.” Animal models can be classified as homologous, isomorphic or predictive. Animal models can also be more broadly classified into four categories: 1) experimental, 2) spontaneous, 3) negative, 4) orphan. Experimental models are most common. These refer to models of disease that resemble human conditions in phenotype or response to treatment but are induced artificially in the laboratory. Some examples include:

    • The use of metrazol (pentylenetetrazol) as an animal model of epilepsy.
    • Induction of mechanical brain injury as an animal model of post-traumatic epilepsy.
    • Injection of the neurotoxin 6-hydroxydopamine to dopaminergic parts of the basal ganglia as an animal model of Parkinson's disease.
    • Immunisation with an auto-antigen to induce an immune response to model autoimmune diseases such as Experimental autoimmune encephalomyelitis.
    • Occlusion of the middle cerebral artery as an animal model of ischemic stroke.
    • Injection of blood in the basal ganglia of mice as a model for hemorrhagic stroke.
    • Sepsis and septic shock induction by impairing the integrity of barrier tissues, administering live pathogens or toxins.
    • Infecting animals with pathogens to reproduce human infectious diseases
    • Injecting animals with agonists or antagonists of various neurotransmitters to reproduce human mental disorders
    • Using ionizing radiation to cause tumors
    • Using gene transfer to cause tumors.
    • Implanting animals with tumors to test and develop treatments using ionizing radiation
    • Genetically selected (such as in diabetic mice also known as NOD mice)
    • Various animal models for screening of drugs for the treatment of glaucoma * The use of the ovariectomized rat in osteoporosis research
    • Use of Plasmodium yoelii as a model of human malaria
  • Spontaneous models refer to diseases that are analogous to human conditions that occur naturally in the animal being studied. These models are rare, but informative. Negative models essentially refer to control animals, which are useful for validating an experimental result. Orphan models refer to diseases for which there is no human analog and occur exclusively in the species studied.

    The increase in knowledge of the genomes of non-human primates and other mammals that are genetically close to humans is allowing the production of genetically engineered animal tissues, organs and even animal species which express human diseases, providing a more robust model of human diseases in an animal model.

    Animal models observed in the sciences of psychology and sociology are often termed animal models of behavior. It is difficult to build an animal model that perfectly reproduces the symptoms of depression in patients. Depression, as other mental disorders, consists of endophenotypes that can be reproduced independently and evaluated in animals. An ideal animal model offers an opportunity to understand molecular, genetic and epigenetic factors that may lead to depression. By using animal models, the underlying molecular alterations and the causal relationship between genetic or environmental alterations and depression can be examined, which would afford a better insight into pathology of depression. In addition, animal models of depression are indispensable for identifying novel therapies for depression.

2008

• (Simmons, 2008) ⇒ Danielle Simmons (2008)."The Use of Animal Models in Studying Genetic Disease: Transgenesis and Induced Mutation". In: Nature Education 1(1):70.
  • QUOTE: Except in the case of highly controlled and regulated clinical trials, geneticists and scientists do not use humans for their experimental investigations because of the obvious risk to life. Instead, they use various animal, fungal, bacterial, and plant species as model organisms for their studies(...)

    When animal models are employed in the study of human disease, they are frequently selected because of their similarity to humans in terms of genetics, anatomy, and physiology. Also, animal models are often preferable for experimental disease research because of their unlimited supply and ease of manipulation(...)

     Rodents are the most common type of mammal employed in experimental studies, and extensive research has been conducted using rats, mice, gerbils, guinea pigs, and hamsters. Among these rodents, the majority of genetic studies, especially those involving disease, have employed mice, not only because their genomes are so similar to that of humans, but also because of their availability, ease of handling, high reproductive rates, and relatively low cost of use. Other common experimental organisms include fruit flies, zebra fish, and baker's yeast.

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