Taking a Closer Look at "Replacement"


As we continue to look more closely at each of the 3 R’s as they relate to preclinical research, lets take a look at what Russell and Burch determined to be the first R to consider – Replacement. Again, Replacement is the attempt to find alternative methods that do not use laboratory animals, such as in vitro or in silico approaches. Additionally, it is the consideration of using non-sentient models than those that are believed to have a higher perception of pain.

When considering any of the 3 R’s however, it is important to weigh the potential benefits of the study being performed, and the knowledge or information to be obtained, as it relates to the wellbeing of others. In some situations, no replacement options exist, it is then that the other two R’s – Reduction, and Refinement – are considered.

Where Replacement is an option, scientists often consider:

In Vitro Assays

  • Cell culture models – for example to study drug toxicity, study the effects of gene function, or to begin studying underlying disease mechanisms.
  • Isolated tissues – for example isolated tissues or organs, so that one animal can be used to harvest tissues for a number of studies; used to study physiological functions or disease processes that involve more than one type of cell from the body.
  • Bioprinted tissues – complex tissue structures, such as skin, can now be bioprinted using advanced systems; these tissues may be used again to study physiological or disease processes that involve more complex tissue, without having to be harvested from an animal
  • Microfluidic devices – such as organs on a chip, can be used to create miniature environments that mimic the complexity of living systems. These devices can be used to study the effects of drugs or other interventions on cells or tissues.

In Situ Assays 

  • Computer models can be used to simulate complex biological processes and predict the effects of drugs or other interventions. This approach is particularly useful for testing the safety of new drugs before they are tested further in animals.

Taking a deeper look at Bioprinting, for example, this is a rapidly growing field that has the potential to Replace some of the need for the use of laboratory animals in preclinical research. Bioprinting is a technology that involves the use of 3D printing to create functional biological tissues, which can be used to replace animal testing in some cases.

  • Bioprinting can be used to create functional tissue models that accurately mimic the structure and function of specific organs, such as the myocardium, liver, and alveolar walls. These tissue models can be used to test the toxicity and efficacy of new drugs.
  • Bioprinting can be used to create functional models of diseases, such as cancer, which in some studies can be used to replace the use of these models in vivo. For example, bioprinted cancer models can be used to study the progression and treatment of cancer, prior to moving into a mouse model of the disease.
  • The tissues and models created using a bioprinter can also be used for drug screening, allowing researchers to test the efficacy and toxicity of new drugs on functional tissue models, without the need for animal testing.

Bioprinting, along with the other options discussed previously should all be considered as Replacement options before considering the use of laboratory animals in any study. These alternative methods can be used alone or in combination with one another, depending on the specific research question being addressed. By using these methods, researchers can reduce or eliminate the use of animals in preclinical research while still generating valuable data to advance our understanding of biology and disease.