P h y s i c i a n s c o m m i t t e e f o r r e s P o n s i b l e m e d i c i n e

5 1 0 0 W i s c o n s i n A v e., n. W., s u i t e 4 0 0 • W A s h i n g t o n, D c 2 0 0 1 6p h o n e ( 2 0 2 ) 6 8 6 - 2 2 1 0 • F A x ( 2 0 2 ) 6 8 6 - 2 2 1 6 • p c r m @ p c r m . o r g • W W W . p c r m . o r g

Problems Associated with Animal Experimentation

iSTOCKPHOTO

011513

Humane and effective research

Currently, an estimated 115-127 million animals are usedin experimental research worldwide each year, and these

numbers are considered conservative estimates.1,2 Meanwhile, independent opinion surveys have shown that public support for animal experimentation has declined significantly over the last 50 years, and that the public would welcome the replacement of animals in research.3-5 The association of animal experimentation with serious adverse physical and behavioral effects on animals is no longer subject to dispute,6 and it is increasingly acknowledged in the research community that “humane animal research” is not possible.

Further, there is growing opinion among scientists that animal experimentation is scientifically flawed for physiological, genetic, and procedural reasons. Many scientifically and ethically superior replacements for the use of animals have already been developed, and many more are in development. Therefore, rapid replacement of animal experimentation with nonanimal and human-based methods is a scientific and ethical imperative.

Poor extrapolation for human diseases and treatments

Because of vast anatomical, physiological, and genetic differences between humans and nonhuman animals, results from experiments on animals are often irrelevant to human health.

Specific diseases almost always differ among species in prevalence, manifestations, natural history, and responses to treatments, so researchers are routinely forced to create diseases in animal “models” that attempt to approximate certain aspects of the human disease but do not translate well among species. That is, the same “disease”—whether natural or “created”—typically manifests differently among common experimental animals such as mice, rats, dogs, and monkeys, between closely related species such as mice and rats, and even within the same species. There is little wonder that translation to humans is unreliable and potentially hazardous.

As stated by Irwin Bross, Ph.D., after retiring from 24 years as director of biostatistics at Roswell Park Memorial Institute for Cancer Research: “Among experienced public health officials, it is well known that you can 'prove' anything with animal studies. This is because there are so many different animal model systems and each system gives different results.”7

Animal experiments for studying human diseasesNumerous reports demonstrate the unreliability of animal experimentation for predicting human clinical outcomes and the suitability of nonanimal methods to replace them.8-14 Persistence of many scientists’ belief in the animal experimentation paradigm, and their resistance to change, has been attributed to “technological and institutional lock-in” (inflexible pathways).15

Unknown to most of the public, entire fields of medical discovery have produced little or nothing of value to humans from decades of animal experimentation. Although at least

85 HIV/AIDS vaccines have been successful in nonhuman primate studies, as of 2008 every one of nearly 200 preventive and therapeutic vaccine trials has failed to demonstrate benefit to humans.16 Every one of at least two dozen animal diabetes cures has failed in humans, and the traditional mouse diabetes model has now been discredited.17 The entire field of mouse immunology research is tainted by the recent discovery that, unlike humans, mice have a second thymus gland.18

The use of animal models for traumatic brain injury research19 and regenerative research in neurological diseases20 has produced no effective treatments and has been discredited. Every one of 10 randomized prospective controlled trials and many other clinical trials of treatments for acute spinal cord injury successful in animals has failed to confirm benefits for humans.21 Similarly, every one of more than 150 stroke treatments successful in animal studies has failed in human testing.22 Much the same story of animal research failure prevails for nearly all chronic neurological and autoimmune diseases, including but not limited to Alzheimer’s disease, Parkinson’s disease, muscular dystrophies, rheumatoid arthritis, multiple sclerosis, lupus erythematosus, and other connective tissue diseases.

Many years of kitten vision research showing that congenital blindness could not be cured was recently disproved in humans, suggesting that many people were denied the gift of sight because of incorrect animal research.23 The cause of sudden infant death syndrome (SIDS; crib death) went undetermined despite many years of animal research, but was identified from brainstem autopsies in children who died of SIDS.24 One of the most glaring and dangerous errors of animal research was the widespread acceptance of estrogen-progestin hormone replacement therapy (HRT) for postmenopausal women as a preventive measure for cardiovascular disease, based on research using nonhuman primates. The Women’s Health Initiative subsequently reported that HRT reduces the risks for heart disease and atherosclerosis in monkeys, but increases these risks in women.25

Decades of animal experimentation have failed to cure or substantially ameliorate a very high percentage of chronic diseases, including cancers. John Bailar III, M.D., Ph.D., former editor-in-chief of the Journal of the National Cancer Institute, stated that no substantial progress was made after

a quarter century of effort focused on animal-modeled drug development.26 The traditional mouse models for cancer have been widely discredited,27-30 as has the entire field of cancer vaccine immunology.31 Human cancer cell lines are more accurate than animals for identifying effective cancer drugs, and in fact the traditional mouse allograft model is not predictive at all.30 The U.S. National Cancer Institute (NCI) developed the DTP Human Tumor Cell Line Screen, a panel of 60 human tumor cell lines, to replace unreliable animal testing for identification of compounds with anti-tumor effects.32 According to former NCI Director Richard Klausner, M.D., “We have cured mice of cancer for decades, and it simply didn’t work in humans.”33

Finally, the renaissance in medical science promised from the use of genetically modified (GM) animals, predominantly rodents, has not occurred. To the contrary, it has been demonstrated that purported gene links to diseases are often not valid,34 that species-specific epigenetic influences often trump gene associations, and that identical genes often function differently in mice and humans,35 undermining the very premise on which GM animal science is based.

Further befuddling attempts at interspecies (and even intraspecies) extrapolation are the findings that genetically identical rats can give different research results,36 and that identical human twins have gene expression differences that increase with age.37 It is thus to be expected that using nonhuman animals to study and treat human diseases is destined to fail because of these and other immutable genetic determinants.

Animal suffering

There are two sources of suffering for animals living in laboratories: experimental procedures and confinement in the laboratory environment. Additionally, animals suffer from premature maternal separation, loss or lack of normal social bonds, the inability to express natural behaviors, and stressors associated with transportation and culling. Animals in laboratories are subjected to numerous invasive and painful procedures, including exposures to toxic drugs and chemicals,

011513

011513

force-feeding, invasive surgeries, burns, traumatic injuries, injections, blood draws, biopsies, prolonged restraint, food and water deprivation, dart gun sedation (“takedowns”), and psychological manipulation. When not subjected to experimental procedures, animals frequently suffer social deprivation in small, often barren cages enclosed in windowless rooms.

Some inhumane laboratory procedures to which animals are subjected include the following:

Creating heart attacks, heart failure, abnormal heart rhythms, strokes, and other cardiovascular traumas in monkeys, dogs, pigs, and other animals

Dropping weights onto rodents to produce spinal cordinjuries and paralysis

Producing often fatal burn injuries in dogs to study burntreatments

Using pigs, goats, and monkeys in civilian and militarytrauma research and training; injuries include shooting,blunt and sharp traumas, burns, amputations, emergencysurgery procedures, and administration of toxic drugs

Inducing a state of “learned helplessness” in rodents, dogs,primates, and other animals by subjecting them to aninescapable source of fear or frustration, such as electricshock, forced swimming to exhaustion, or hanging bytheir tails, until the animals despair and stop resisting theirritant

Implanting electrodes into the brains and eyes of monkeysand cats to conduct neurological and vision experiments

Implanting electrodes into the intestines of dogs to inducemotion sickness and vomiting

Inducing symptoms of migraines in cats and primates through brain stimulation and manipulation with chemicals

There is also substantial evidence that ordinary features of life in the laboratory environment cause pain and distress. For instance, routine laboratory procedures, such as handling, blood collection, and drug dosing, cause animals in laboratories to experience marked and prolonged physiological stress.6 This stress often accumulates over the duration of an animals life and parallels between traumatic conditions for humans and laboratory conditions for animals have been noted.38 Laboratory cages are an unnatural environment and are insufficient to meet animals’ complex psychological, social, and behavioral needs. Nonhuman primates are regularly housed in small, solitary cages, leading to self-injury, mutilation, and psychological distress. In one study of a colony of rhesus macaques, 89 percent were observed engaging in abnormal behaviors including self-injury, self-mutilation, and stereotypies (repetitive, purposeless behaviors indicative of distress).39 Other laboratory animals also show signs of pain and distress as a result of ordinary laboratory conditions. For instance, 50 percent of mice in laboratories exhibit stereotypies.40

Replacements for animal use

Great strides have already been made in the development of nonanimal research methods, including computational models, bioinformatics, systems biology, in vitro techniques, tissue engineering, microfluidics (organ-on-a-chip), stem cell methods, epidemiology, human tissue studies, genetic methods, advanced imaging technologies, and other approaches.Epidemiology (the study of human populations), has been instrumental to many advances in our understanding of risks to human health. For example, epidemiological studies have led to the discovery of the dangers of cigarette smoking, environmental and industrial toxic exposures, and the hazards of pollution and poor public hygiene, as well as identifying the major risk factors for heart disease and stroke, cancers, infectious diseases, and many other human diseases. In vitro and human cell and tissue cultures have proven superior to animal tests for a multitude of investigative purposes, including screening potential cancer treatments, testing drugs with biochips,41,42 and replicating human skin for research.43,44

Human tissue banks now make this field of research prolific and clinically relevant. Computer-based methods produce computational disease and treatment models, collect and manage millions of human research data points, and carry out virtual human clinical trials. Genetic methods are not only identifying and characterizing the dizzying array of factors influencing genetic expression (gene homology and copy number, epigenetic factors, RNA interference), but contributing to the development of disease risk profiles and treatments based on individual genetic determinants. Imaging technologies such as computed tomography (CT), magnetic resonance imaging (MRI and fMRI), magnetoencephalography (MEG), diffusion tensor imaging (DTI), accelerator mass spectroscopy (AMS), ultrasonography, and various nuclear imaging techniques combine the benefits of replacing unreliable animal studies and producing human-specific results. Replacements for animal use in research are increasingly available and, more importantly, they will replace all manner of animal use as research emphasis and funding shift from the failed animal research paradigm to development and implementation of better research methods.

011513

References1. Taylor K, Gordon N, Langley G, Higgins W. Estimates for worldwide

laboratory animal use in 2005. ATLA. 2008;36:327-342. 2. Knight A. 127 million non-human vertebrates used worldwide for

scientific purposes in 2005. ATLA. 2008;36:494-496.3. Humane Society of the United States (2001). Poll shows Americans

disapprove of animal research when it causes the animals to suffer. Accessed June 11, 2008 at: http://www.hsus.org/press_and_publications/press_releases/poll_shows_americans_disapprove_of_animal_research_when_it_causes_the_animals_to_suffer.html

4. Plous S. Opinion research on animal experimentation: areas of support and concern. Accessed June 11, 2008 at http://altweb.jhsph.edu/meetings/pain/plous.htm.

5. Sky News (2006). Accessed May 2006 at http://news.sky.com/skynews. Link is no longer available, but poll data are available.

6. Balcombe JP, Barnard ND, Sandusky C. Laboratory routines cause animal stress. Contemporary Topics. 2004;43, 42-51.

7. Bross I. How animal research can kill you. The AV Magazine. November 1983.

8. Hackam DG, Redelmeier DA. Translation of research evidence from animals to humans. JAMA. 2006;296:1731-1732.

9. Horrobin DF. Modern biomedical research: an internally self-consistent universe with little contact with medical reality? Nat Rev Drug Discov. 2003;2:151-154.

10. Ioannidis JPA. Evolution and translation of research findings: from bench to where? PLoS Clin Trials 2006;1:e36.

11. Langley G, Evans T, Holgate ST, Jones A. Replacing animal experiments: choices, chances, and challenges. BioEssays 2007;29:918-926.

12. Perel P, Roberts I, Sena E, et al. Comparison of treatment effects between animal experiments and clinical trials: systematic review. BMJ 2006;334, 197 (doi:10.1136/bmj.39048.407928.BE).

13. Pound P, Ebrahim S, Sandercock P, Bracken MB, Roberts I. Where is the evidence that animal research benefits humans? BMJ 2004;328:514-517.

14. Watts G. Alternatives to animal experimentation.BMJ 2007;334:182-184.

15. Frank J. Technological lock-in, positive institutional feedback, and research on laboratory animals. Structural Change and Economic Dynamics. 2005;16:557-575.

16. Bailey J. An assessment of the role of chimpanzees in AIDS vaccine research. ATLA. 2008;36:381-428.

17. Cabrera O, Berman DM, Kenyon NS, Ricordi C, Berggren P-O, Caicedo A. The unique cytoarchitecture of human pancreatic islets has implications for islet cell function. Proc Natl Acad Sci. 2006;103:2334-2339.

18. Terszowski G, Müller SM, Bleul CC, et al. Evidence for a functional second thymus in mice. Science. 2006;312:284-287.

19. Beauchamp K, Mutlak H, Smith WR, Shohami E, Stahel PF. Pharmacology of traumatic brain injury: where is the “golden bullet?” Molecular Medicine. 2008;14:731-740.

20. Regenberg A, Mathews DJH, Blass, DM, et al. The role of animal models in evaluating resonable safety and efficacy for human trials of cell-based interventions for neurologic conditions. J Cerebral Blood Flow & Metabolism. 2009;29:1-9.

21. Tator CH. Review of treatment trials in human spinal cord injury: issues, difficulties, and recommendations. Neurosurgery. 2006;59:957-987.

22. Macleod M. What can systematic review and meta-analysis tell us about the experimental data supporting stroke drug development? Intl J Neuroprotection and Neuroregeneration. 2005;1:201.

23. Ostrovsky Y, Andalman A, Sinha P. Vision following extended congenital blindness. Psychological Science. 2006;17:1009-1014.

24. Paterson DS, Trachtenberg FL, Thompson EG, et al. Multiple serotonergic brainstem abnormalities in sudden infant death syndrome. JAMA. 2006;296:2124-2132.

25. Writing group for the Women’s Health Initiative investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA. 2002;288:321-333.

26. Bailar JC III, Gornick HL. Cancer undefeated. N Engl J Med. 1997;336:1569-1574.

27. Garber K. Realistic rodents? Debate grows over new mouse models of cancer. J Natl Cancer Inst. 2006;98:1176-1178.

28. Editorial. The end of the beginning? Nat Rev Drug Discov. 2006;5:705.

29. Sausville EA, Burger AM. Contributions of human tumor xenografts to anticancer drug development. Cancer Res. 2006;66:3351-3354.

30. Voskoglou-Nomikos T, Pater JL, Seymour L. Clinical predictive value of the in vitro cell line, human xenograft, and mouse allograft preclinical cancer models. Clin Cancer Res. 2003;9:4227-4239.

31. Rosenberg SA, Yang JC, Restifo NP. Cancer immunotherapy: moving beyond current vaccines. Nat Med. 2004;10:909-915.

32. Shoemaker RH. The NCI60 human tumour cell line anticancer drug screen. Nat Rev Cancer. 2006;6:813-823. Also see the NCI DTP Human Tumor Cell Line Screen home page at http://dtp.nci.nih.gov/branches/btb/ivclsp.html.

33. Cimons M, Getlin J, Maugh TH III. “Cancer drugs face long road from mice to men; medicine: doctors downplay excitement over report. Questions raised about how media handle such advances.” Los Angeles Times, May 6, 1998: page A1.

34. Morgan TM, Krumholz HM, Lifton RP, Spertus JA. Nonvalidation of reported genetic risk factors for acute coronary syndrome in a large-scale replication study. JAMA. 2007:297:1551-1561.

35. Liao B-Y, Zhang J. Null mutations in human and mouse orthologs frequently result in different phenotypes. Proc Natl Acad Sci. 2008;105:6987-6992.

36. Rohde CM, Wells DF, Robosky LC, et al. Metabonomic evaluation of Schaedler altered microflora rats. Chem Res Toxicol. 2007;20:1388-1392.

37. Fraga MF, Ballestar E, Paz MF, et al. Epigenetic differences arise during the lifetime of monozygotic twins. Proc Natl Acad Sci. 2005;102:10604-10609.

38. Ferdowsian and Merskin. Parallels in sources of trauma, pain, distress, and suffering in humans and nonhuman animals. J Trauma Dissociation. 2012;13:448-468.

39. Lutz C, Well A, Novak M. Stereotypic and self-injurious behavior in rhesus macaques: a survey and retrospective analysis of environment and early experience. Am J Primatol. 2003;60:1-15.

40. Mason GJ, Latham NR. Can’t stop, won’t stop: is stereotypy a reliable animal welfare indicator? Animal Welfare. 2004;13:57-69.

41. Lee M-Y, Park CB, Dordick JS, Clark DS. Metabolizing enzyme toxicology assay chip (MetaChip) for high-throughput microscale toxicity analyses. Proc Natl Acad Sci. 2005;102:983-987.

42. Lee M-Y, Kumar RA, Sukumaran SM, Hogg MG, Clark DS, Dordick JS. Three-dimensional cellular microarray for high-throughput toxicology assays. Proc Natl Acad Sci. 2008;105:59-63.

43. Merali Z. Human skin to replace animal tests. New Scientist 25. July 2007. Accessed June 12, 2009 at http://www.newscientist.com/article/mg19526144.100-human-skin-to-replace-animal-tests.html.

44. CORROSITEX, EPISKIN, EpiDerm, and SkinEthic assays (see validation studies at http://ecvam.jrc.it).