"There's more to life than rats and flies"
~Dr. Pam Osenkowski, Director of Science Programs
November 12, 2012
The science journal Nature recently featured an interesting article entitled “There’s more to life than rats and flies” (November 1, 2012, Vol. 491, p. 31-33) that discussed the consequences of scientists relying so heavily on a small subset of model organisms to carry out their research. The author of the article, an associate professor of zoology, identified many problems with commonly used animal models, the same kinds of scientific problems that NAVS has reported on over the years to show that other species are inherently inadequate to model what happens in people. The conclusions and recommendations of the author, however, illustrate how over-reliant the scientific community is on the use of animal models. When considering what to do when an animal model poorly represents aspects of human health and disease, the author suggested simply accounting for their limitations in the study design or using other kinds of animals. NAVS has instead advocated that scientists turn to more human-relevant alternatives as better solutions.
I’m sure it will come as no surprise to you that scientists commonly use mice and rats in the lab. Millions of them. But have scientists really thought about or justified whether or not they make relevant models for studies of human health and disease? What about the “shortlist” of other favored animal models: the roundworm C. elegans, the fruit fly D. melanogaster, and the zebrafish D. rerio for instance? Why are scientists relying so heavily on these select species when carrying out experiments? While it is true that many biological principles are shared among species, these organisms have been selected mainly because they are easy to breed, they can reproduce rapidly, they have short life cycles, and they are small and easy to handle. These are not exactly human-like characteristics. So are these animals necessarily the best models? No. The most convenient models? Perhaps. Also over the course of time, scientists have become familiar with these species and they are easily accessible to researchers. And interestingly, because funding agencies are also familiar with this handful of organisms, it seems that researchers may be steered away from selecting a nontraditional model to address a scientific question, in part, because that choice may require a longer explanation in a grant application, one that would not be required with a well-established model.
The article does a nice job reminding researchers that they need to spend more time critically thinking about whether or not their models accurately represent specific facets of human health and disease and to select models purposefully because they are a good fit for the research topic – not just because they are convenient and traditional. Selection of a scientific model can be a challenging process, as it is difficult to predict which model will generate the most useful information in a given study. Valid models of human health and disease should be relevant to and predictive of what happens in the human condition and limit additional variables that can complicate interpretation of data. They are also ones in which researchers have a very clear understanding of the underlying biological properties and mechanisms. Since it has been repeatedly demonstrated that animal models are poorly predictive of what happens in people, one can only ask if today’s scientists choose to work with animal models because they are good models, or simply because they are available to use and have been used historically.
The author of this article suggested that scientists consider expanding the range of animal models to include such animals as Antarctic icefish, comb jellies, cichlids, dune mice and finches to develop alternative ways to study human disease. Is this the best solution? Wouldn’t the use of additional animal species take researchers further and further away from the animal at the center of the study – humans? Because animal models have inherent limitations, researchers will always struggle to interpret data from any animal model and have difficulty extrapolating that information to people. Continued reliance on any animal model only diverts resources away from the development of new and innovative technologies that can find answers to today’s medical mysteries.
I agree with the author’s analogy that overreliance on a small number of model organisms “comes with the same trade-off as a high-magnification lens: a reduced field of view.” However, researchers will have a much better “view” overall when priority is placed with developing and using human-relevant models to study human health and disease. As toxicologist Thomas Hartung, Director of the Center for Alternatives to Animal Testing at Johns Hopkins Bloomberg School of Public Health said, “we are not 70 kilogram rats.” As long as that is the case, the dangers of extrapolating data from animals to people will continue. Because clinical failure can be explained in part by the inadequacies of animal models to fully represent human disease, and because some models are chosen out of convenience rather than careful planning, researchers need to be more honest about the limitations of the models they are working with and do more to move research into the species of interest -- humans-- in the first place.
For more information see:
Bolker, J. “There’s more to life than rats and flies.” Nature, November 1, 2012, Vol. 491, p 31-33.