Methods

Overview of Animal Models in Research

  • Importance of animal models in scientific studies regarding diseases

  • Discussion on variability in human populations and its implications for research

Human Variability in Research

  • Genetic variability among humans:

    • Significant variability exists even among healthy individuals.

    • Implications for studying pathogenesis (causes of disease) due to inherent differences in genetics and health.

  • Challenges in human studies:

    • Ethical considerations limit the use of human subjects; certain studies (e.g., pathogenesis over a long period) are not feasible.

    • Recruiting sufficient human participants is difficult.

    • Incentives: Researchers typically need to provide rewards (e.g., gift cards) to encourage participation.

Use of Animal Models in Research

  • Preference for animal studies:

    • More commonly accepted and feasible to use animals for research purposes compared to human subjects.

  • Historical Example:

    • The Tuskegee syphilis study exemplifies unethical use of human subjects for prolonged observation of untreated disease.

    • Current ethical guidelines prevent similar studies on humans, emphasizing the need for treatment.

  • Advantages of animal models:

    • Scientists can infect animals with pathogens to observe disease progression and symptoms over time.

    • Ethical guidelines mandate humane treatment; severe suffering leads to euthanasia of the animal if necessary.

  • Specific example:

    • Research conducted at FDA on pertussis in animal models—monkeys observed over 30 days. If they became severely ill, euthanasia was necessary.

  • IACUC (Institutional Animal Care and Use Committee):

    • Review board overseeing animal research to ensure humane treatment and ethical standards are met.

Common Animal Models in Research

  • Various animal models used in research across different sizes and types:

    • Mice: One of the most common research animals.

    • Tadpoles: Used for specific biological studies.

    • Yeast: Though not an animal model, it is used in various biological experiments.

    • C. elegans: A type of small nematode worm used in genetic and developmental biology studies.

Criteria for Choosing an Animal Model

  • Factors influencing the selection of a model organism for research:

    • Genetic similarity: Comparing proteins/enzymes in animals to those in humans to predict human responses.

    • Lifespan: Understanding how long the organism lives after infection.

    • Genetic considerations: Homologous genes or pathways that are similar to human biology.

    • Ease of use and availability: Facilities may be limited to specific types of animals; housing for nonhuman primates is less common compared to mice.

    • Research question: The specific question dictates the model; smaller animals can sometimes provide adequate information for smaller questions.

    • Sample size considerations:

    • Minimum of three replicates is often needed in experiments to ensure reliability and avoid issues with outliers in data.

    • Having only one or two animals would not provide enough comparison to yield reliable scientific results.

Conclusion

  • Importance of ethical considerations in selecting animal models vs. human subjects for research.

  • The ongoing balance between scientific inquiry and humane treatment of research subjects.

  • Each research question requires careful consideration of the model and methods used to ensure accurate, humane, and ethical research outcomes.