Animal advocates object to the use of animals in research and science. These objections can be divided many ways but for the purposes of this essay, I will divide them into two groups. First, animal advocates object to the use of intact whole animals as surrogates for humans. Intact whole animals are routinely used for, among other things, toxicology testing and are used to predict human response to medications and chemicals. This use of animals is not scientifically valid as we prove in Animal Models in Light of Evolution, therefore I will have nothing further to say about it at this time.
The second objection is quite different, as it does not involve intact whole animals but rather animal parts, for examples cells, that are used in assays and so forth. Such uses of animal parts are scientifically legitamate as long as prediction is not asserted. If cells from animals are used in basic science, for example to study some process of the cell, then the researchers can rightly claim that she is using these cells, not as surrogate human cells but merely as cells per se in order to study whatever process she wants to study. So far so good.
But animal cells are frequently used as surrogate human cells and therein lies a problem. An article in Nature about using tissues on a computer chip to test for toxicity stated:
Either animal or human cells can be put on the chips. Shuler and Baxter began to incorporate the latter into some of their chips back in 2000. Toxicologists and drug developers typically work with rats because they need a living system that roughly matches human physiology. But in the end, notes Robert Freedman, chief executive of Hµrel, "a rat liver is not a human liver". (1)
Liver cells from rats are not human cells either.
Regenberg et al.:
The recent US Food and Drug Administration (FDA) decision to place on clinical hold the first application for a trial of a CBI-NC [cell-based interventions for neurologic conditions] using cells derived from embryonic stem cells suggests that there is substantial uncertainty about the ability of these animal models to accurately predict safety and efficacy of CBI-NCs in human trials (http://www. nature.com/news/2008/080519/full/news.2008.842. html) . . . Preclinical studies rely heavily upon animal models of human disease. To provide a sound basis for making determinations about reasonable safety and efficacy, these animal models must provide accurate information about how a medical intervention will perform in human clinical trials. The ability of animal model studies to accurately predict clinical trial outcomes can be termed predictive validity. Animal models for human disease never have perfect predictive validity. Poor predictive validity can result in outcomes for human clinical trials that differ significantly from the results of preclinical data . . . In some cases, particularly in studies involving genetically distinct strains of mice, the extreme genetic homogeneity may even lead to intraspecific failures of predictive validity (i.e., the results are confounded by a unique genetic variant within a particular mouse strain and cannot be generalized beyond that strain) . . . an expert interdisciplinary working group on safety issues in CBI trials concluded, ‘(g)iven that the processes of culturing and differentiating cells are idiosyncratic and successful methods vary from one species to the next, the extent to which it is reasonable to extrapolate from the results with mouse cell lines to human cell lines is unclear’ (Dawson et al, 2003). (2) (Emphasis added.)
A panel of American cell culture experts, writing in the journal Cytotechology, 1992:
Although most toxicologists are concerned with solving problems that affect humans, most research is conducted in nonhuman species because techniques for studying responses in vivo with human subjects are obviously limited. The significant differences among species in cellular regulatory and metabolic processes and in responses to specific cytotoxic perturbations make it difficult to predict the susceptibility of human cells to toxic chemicals. (3)
Using cells from animals to study how cells from animals work and to generate hypotheses about human cells that can then be tested using human cells is viable. But putting rat cells on a computer chip to test for human responses to drugs is not.
Furthermore there is no reason to use cells from animals as cells from humans can be easily obtained. There are assays that work better with animal cells, or so I have been told, and researchers thus justify using the animal cells. The problem with this self-evident, however. If there are differences between human cells and animal cells that result in the assay being different, then it is not unlikely that some of those differences will also influence the response of the cell to whatever process the scientist is studying. Such difference might underlie why a drug does not harm the animal the cells came from but does harm humans.
Before animal advocates spend a lot of time pleading for more money to spent on alternatives to using cells or tissues or other parts from animals, they might want to determine whether the assays currently using animal parts are viable in the first place. Some are and alternatives should be sought but other uses are not viable and hence should just be abandoned.
No doubt some will respond to this by saying the above is controversial (these days what isn’t) thus attempting to create doubt. In his book Doubt is Their Product: How Industry's Assault on Science Threatens Your Health, David Michaels quotes a memo from the tobacco industry:
Doubt is our product since it is the best means of competing with the body of fact that exists in the minds of the general public. It is also the means of establishing a controversy. (4)
(For a detailed look at what research methods should be used in biomedical research, I refer the reader to our book: What Will We Do If We Don’t Experiment On Animals?)
1. R. Khamsi, Nature 435, 12 (May 5, 2005).
2. A. Regenberg et al., J Cereb Blood Flow Metab 29, 1 (Jan, 2009).
3. Cytotechnology 8, 129 (1992).
4. D. Michaels, Doubt is Their Product: How Industry's Assault on Science Threatens Your Health. (Oxford University Press, New York, 2008).