Module 03 - The Three Rs of Humane Animal Experimentation

Satisfying the Replacement Principle

In this section, we will consider replacement as it pertains to three different areas of research, teaching and testing.

General Principles Concerning Replacement in Research and Testing

Cell cultures, bacteria and inanimate models cannot be used to study processes as they would occur within the context of a whole, live organism. Thus a culture of heart cells is not comparable to heart cells in situ, as it cannot reveal the interactions between all the various heart cells as they are normally situated within a whole heart, nor those with the nervous, endocrinologic and immune systems that normally affect them, nor the effects of blood flow and pressure and of the many other factors and signals that exist in a live, whole organism.

Behavioral responses cannot be studied in simple cultures of cells. The behavior of simple organisms (e.g., bacteria, nematodes) could be studied, however it would be very difficult to extrapolate the relevance to more complex organisms. Along the same line, it would be impossible to study species specific and sex specific phenomena.

In cases where specific processes, either cellular or molecular, need to be looked at or used in isolation, replacement alternatives such as cell/tissue/organ cultures or bacterial cultures become excellent tools. Some of the variability factors that complicate intact animal research are reduced when cell cultures, bacteria, etc., are used. These include factors such as light, sound, latent infections, etc. Of course, if totally inanimate alternatives are used, variability of this type should not be a factor at all.

Where fresh cell lines are required, it should be possible to get many more cultures and therefore experiments from each animal than if the whole animal was used for the study. If the alternative is inanimate (e.g., a computer) there may still be a need to use a small number of animals to get data to feed into the computer. The quality of that data needs to be excellent or it becomes a case of garbage in and garbage out.

Biological systems are known for their complexity and their ability to behave in an unexpected manner with the production of artefacts. A much simpler system such as a cell line is not so likely to produce artefacts, as long as the cells are maintained in the appropriate milieu.

A corollary to the artefact problem is the simplicity with which the environment of the cells may be altered and in a manner that could not be repeated in the intact animal. It is easy for example, to alter the pH, the ion content, the oxygen level etc. of the growth medium to study the effect of these changes. The repeatability of the studies should be much greater when there is good control of all the potential variables.

The cost of using alternatives is likely to be less than the cost of using intact animals although this may not be inevitable. The costs of computers, software, cell/tissue/organ culture equipment, etc., may exceed the costs of animals.

Replacement in Research

The alternatives. The use of lower, less sentient animals, particularly invertebrates is considered to be an acceptable means of replacing higher animals as research subjects. The nematode, Caenorhabditis elegans, is widely used to study basic neuronal function. This organism has 302 neurons in its nervous system and so it is reasonable to study the function of each neuron and its interaction with other neurons. In a similar vein, geneticists have used fruit flies for many years.

There are other important replacement alternatives in research: one of the most common and useful ones is the replacement of rodent-based methods by in vitro methods for monoclonal antibody production.

Replacement in Safety and Efficacy Testing

The use of animals for safety and efficacy testing new products has increased greatly over the past forty years or so. Companies producing the products, regulatory agencies and consumers want to be sure that the products are safe to use. While medical treatments make up the greatest bulk of these products, just about anything we use must be proven to be safe, for example, the cars we drive and the products we use, including household cleaners, pesticides, cosmetic products, etc. Once upon a time baboons were used in crash tests. The alternatives, instrumented mannequins (crash test dummies), provide much more precise information than did the animal model.

Public concerns for safety of products drove the need for increased testing, and public concerns about how animals are used in safety testing are now driving the need to seek alternatives.

One of the major challenges for the proponents of alternative methodologies for testing new compounds has been to prove that they are as effective as the animal based tests they are intended to replace. Two organizations created to ensure sound scientific validation and subsequent acceptance by regulatory agencies of proposed alternatives to animals in testing are the European Centre for the Validation of Alternative Methods (ECVAM) in Italy and the Interagency Coordinating Committee for the Validation of Alternative Methods (ICCVAM) in USA.

Although regulatory agencies throughout the world have been cautious about accepting these alternatives, progress continues to be made. As of 2002, there are three in vitro tests accepted by the European regulatory agencies and three by the USA regulatory agencies and there are several more being evaluated.

Replacement in Education and Training

Practical Skills Training

Learning skills, from simple techniques such as blood sampling to complicated surgical procedures such as laparoscopic surgery, are an important part of the training of medical and veterinary personnel. Animals continue to be used in this training. However, some skills such as suturing techniques may be developed without using animals. Discarded placentas may be used to practice microsurgery techniques.

The alternatives. There are now inanimate models that can be used to practice procedures. The Koken rat, for example, will allow a student to practice tail vein injections many times before it is attempted on a live animal. Mannequins and computer-based technologies are available to allow surgeons to practice laparoscopic surgeries. The acceptance of these inanimate objects for training comes when the touch and feel of the training is similar to that experienced when using a living organism.

Education

Animals have been used extensively for teaching and demonstration of biological principles. In recent years, there has been a significant reduction in the numbers of animals due to the adoption of alternatives.