Institutional Animal Care and Use Committee Considerations for Animal Models of Peripheral Neuropathy

Abstract

Peripheral neuropathy and neuropathic pain are debilitating, life-altering conditions that affect a significant proportion of the human population. Animal models, used to study basic disease mechanisms and treatment modalities, are diverse and provide many challenges for institutional animal care and use committee (IACUC) review and postapproval monitoring. Items to consider include regulatory and ethical imperatives in animal models that may be designed to study pain, the basic mechanism of neurodegeneration, and different disease processes for which neuropathic pain is a side effect. Neuropathic pain can be difficult to detect or quantify in many models, and pain management is often unsuccessful in both humans and animals, inspiring the need for more research. Design of humane endpoints requires clear communication of potential adverse outcomes and solutions. Communication with the IACUC, researchers, and veterinary staff is also key for successful postapproval monitoring of these challenging models.

What Is Peripheral Neuropathy

The peripheral nervous system is comprised of the motor and sensory nerves that connect the brain and spinal cord to the soft tissues of the limbs, trunk, and head, as well as those that innervate the thoracic and abdominal organs. Peripheral neuropathy is any disorder that affects the sensory and/or motor function of the peripheral nerve through an effect on the nerve axon or the myelin coating. Often both motor and sensory dysfunction occurs, but symptoms of one predominate, depending on the nerve fiber type affected (Netter et al. 2012). Symptoms may be acute or chronic, and solitary nerves or multiple nerves may be affected, including nerves in a specific geographic location, such as distal symmetric peripheral neuropathy (Bierhaus and Nawroth 2012; Netter et al. 2012).

Neuropathic pain is a sporadic but potentially devastating outcome of peripheral neuropathy in the human population and is an area of intense interest in biomedical research (Bridges et al. 2001). Neuropathic pain has been defined as “pain initiated or caused by a primary lesion or dysfunction in the nervous system” (Merskey and Bogduk 1994) and “pain arising as a direct consequence of a lesion or disease affecting the somatosensory system” (Treede et al. 2008). Neuropathic pain is difficult to predict in human patients, has been described by these patients as more intense than other types of chronic pain, and tends to respond to medication differently than other types of pain (Bridges et al. 2001; Eaton 2003; Grubb 2010a; Haanpaa et al. 2009). Nonsteroidal anti-inflammatory drugs and opioid analgesics are often less effective for neuropathic pain, and some anticonvulsive drugs and antidepressants may be more effective in cases of neuropathic pain (Bridges et al. 2001; Grubb 2010a; Haanpaa et al. 2009; Mizoguchi et al. 2009; Torrance et al. 2007).

Animal Models of Peripheral Neuropathy

As with any animal model of disease, careful attention must be paid to selection of the appropriate model in peripheral neuropathy and neuropathic pain studies. Peripheral neuropathy models can be divided into sensory models, motor models, autonomic models, or combinations of these, such as models of diseases involving both sensory and motor neuropathy, such as Charcot-Marie-Tooth disease (Eaton 2003; Lee et al. 2013). Conversely, models can be divided into spontaneous, chemically induced, or surgically induced models (Eaton 2003). In addition, peripheral neuropathy and the resulting neuropathic pain can develop in some models as a side effect of the primary disease process and not as a main area of research. Finally, some investigators are studying neuropathic pain, whereas others are focused on mechanisms of the induction of peripheral neuropathy, such as the genetics of neurodegenerative diseases or the development of autoimmune responses to different nervous system components. Therefore each research project has a unique combination of research goals, animal models, and potential outcomes that influence institutional animal care and use committee (IACUC) considerations. Given the ethical concerns relating to withholding pain medications or causing pain that may not be effectively treated, the IACUC needs to be well informed of the goal of the research and how that goal influences model selection, as well as the potential outcomes of these models, intended or otherwise.

Sensory and Motor Neuropathy

Most biomedical research that involves peripheral neuropathy targets important human diseases associated predominantly with symptoms of sensory neuropathy, including diabetic neuropathy, chemotherapy-associated peripheral neuropathy, and HIV-associated sensory neuropathy (Hoke 2012). The bulk of this work is performed in rodent models, although Drosophila have been used in chemotherapy-associated neuropathy studies (Bhattacharya et al. 2012), and macaques and neonatal cats, in addition to rodents, are used in HIV-associated sensory neuropathy studies (Burdo et al. 2012; Hoke 2012). Atypical animal models are occasionally used, such as the nine-banded armadillo for leprosy-associated sensory neuropathy studies (Sharma et al. 2013). Animal models of diabetic neuropathy in rodents include the use of spontaneously diabetic BKS-db/db or B6-ob/ob mice or the induction of diabetes by administration of streptozotocin in a high single dose or consecutive daily lower doses (Bierhaus and Nawroth 2012). Animal models of chemotherapy-associated peripheral neuropathy typically involve infusions of vinka alkaloids (vincristine), taxanes (paclitaxel and docetaxel), and platinum compounds (oxaliplatin) over days to weeks (Authier et al. 2009).

Surgical models of neuropathic pain include partial or complete sciatic nerve or spinal nerve transection or ligation (Bridges et al. 2001). Currently the most commonly used methods in rodents include the Chung model (spinal nerve ligation), the Seltzer model (partial sciatic nerve ligation), the Bennett model (chronic constriction injury of the sciatic nerve), and the Decosterd and Woolf model (spared nerve injury with selective ligation) (Bridges et al. 2001; Dowdall et al. 2005; Taneja et al. 2012). Complete sciatic nerve ligation is used less commonly and is more likely to be associated with self-mutilation, as discussed further below (Bridges et al. 2001).

Autonomic Neuropathy

Animal models of primary autonomic neuropathy are uncommon, although autonomic dysfunction is reported in both human diabetics and in animal models of diabetic neuropathy (Canda 2011; Mabe and Hoover 2011) and in animal models of chemotherapy-induced neuropathy (Vera et al. 2011). Autonomic neuropathy can also occur secondary to autoimmune peripheral neuropathy models (Evliyaoglu et al. 2012; Soliven 2012). With autonomic neuropathy, sympathetic and/or parasympathetic dysfunction may occur. Autonomic dysfunction can cause cardiac arrhythmia and changes in heart rate or blood pressure, dysuria and incontinence, and altered gastrointestinal motility, resulting in vomiting, diarrhea, and/or constipation (Hoke 2012; Netter et al. 2012).

Ethics

The Ethical Challenge

There are general ethical challenges surrounding the IACUC review of protocols involving peripheral neuropathy and neuropathic pain that are not significantly different than those involving other studies. Specifically, the committee must determine if the general principles outlined in Public Health Service (PHS) policy have been met, including the use of sound research design and scientific practices that will yield scientifically valid and valuable results that have relevance to human or animal health ([NRC] National Research Council 2011). However, unique aspects of this area of study are the development of neuropathic pain and the challenges that surround protocols involving potentially unrelieved pain.

Laboratory animals are at risk of neuropathic pain as a direct attempt to model it in them but also as an unwanted side effect in other research projects. Scientists intentionally induce pain in animals to study the pain or to study its treatment; if they cannot induce measureable pain, they may not be sure the pathways they examine are relevant or know whether the treatments they are studying are effective. At other times, neuropathic pain may develop, but it is not the object of the research and may even interfere with the study. A hybrid possibility exists as well—that even in direct studies of neuropathic pain, there can be “unwanted” pain and other health effects resulting from the pain under study. For example, if neuropathy secondary to knee arthritis affects animals' ability to feed themselves or results in allodynia (sensitivity to mechanical or thermal stimuli that usually do not cause pain) that makes movement on some substrates uncomfortable, then the knee-related pain under study has whole-body ramifications beyond what the study is designed to investigate.

The investigator, veterinarian, and IACUC share the ethical challenge of addressing animal pain and welfare balanced against the exigencies of collecting quality data (Carbone 2011). They must reduce animal pain to the minimum and strongly justify leaving any pain unalleviated. There are real concerns about how drugs will affect the data. Moreover, chronic neuropathic pain is refractory to treatment in humans (Backonja 2012; Boswell et al. 2006; Bridges et al. 2001; Tranquilli et al. 2007)—hence the efforts to model it in the laboratory and to seek treatments—and it is likewise likely refractory to treatment in animals (Grubb 2010a). In the worst-case scenario, animals receive medications that skew data without effectively treating their pain.

Regulatory and Professional Guidance

For all animal studies, pain studies included, regulations, guidelines, and policies require that animal pain be treated unless withholding treatment is “justified for scientific reasons” (9 C.F.R. §3 [1991]; Office of Laboratory Animal Welfare 2002). The US Department of Agriculture (USDA) provides some guidance on what degree of untreated pain crosses a threshold and requires special IACUC attention (USDA 2011; USDA n.d.). The Guide for the Care and Use of Laboratory Animals is much less clear on how the IACUC should evaluate studies in which expected animal pain is left untreated (Carbone 2012; NRC 2011).

Beyond regulation and policy, there is some professional guidance on how the scientist or IACUC evaluates whether withholding pain medications is appropriate. The International Association for the Study of Pain has issued statements on the IACUC's responsibility to evaluate the protocol and a more extensive 30-year-old position statement on pain in laboratory animals (International Association for the Study of Pain n.d.; Zimmermann 1983). The American College of Laboratory Animal Veterinarians and the Institute for Laboratory Animal Research provide some technical guidance that can also be read as steps toward establishing a normative standard of care (American College of Laboratory Animal Medicine 2006; NRC 2009).

The IACUC's Task

The IACUC must review the investigator's plans for minimizing animal pain and distress. This includes assurance that the attending veterinarian has been consulted. Regardless of whether pain medications will be administered or withheld, the IACUC must review humane endpoints (see “Adverse Outcomes and Endpoints”) that signal when to terminate a painful stimulus or to remove the animal from study (possibly through euthanasia).

Russell and Burch (1959) proposed a framework for managing laboratory animal suffering (or “inhumanity”), starting by cataloging it as either direct or contingent. Diabetes research illustrates the distinction. Diabetic neuropathy, as noted above, is a serious human health concern that can be modeled in diabetic mice (Sima 2000). The pain of the neuropathy is the object of study; it is directly induced, and without it there is no research project. On the other hand, the great majority of diabetes studies in animals are not pain focused. They may review pathogenesis of the disease, transplantation or stem cell therapies to cure it, or other questions. Pain is contingent. If there is neuropathy, it is largely irrelevant to whether an intervention under study can prevent islet cell rejection, so the pain serves no purpose. If it could be treated without disrupting the research, it would be. The IACUC must be attentive to both direct pain and the possibility of contingent pain.

Normative decisions about what pain is ethical to allow require answering both questions of values (e.g., How much potential new knowledge justifies how much pain?) and questions of facts (e.g., How much untreatable pain does this model cause? How severe is it? Will this experiment produce the desired information?). Often the fact questions are probabilistic and quantitative rather than either/or certainties (e.g., What is the likelihood this experiment will produce the desired information?). The Guide for the Care and Use of Laboratory Animals calls for some assessment of justification: “the IACUC is obliged to weight the objectives of the study against potential animal welfare concerns” (NRC 2011). This new requirement will develop as institutions gain experience addressing it. Will that mean that seeking cures for some types of pain justify certain experiments but other types of pain, perhaps rarer or less urgent, do not?

Fact questions the IACUC might ask are presented in Table 1. Benefit and harm must both be assessed to determine justification and approvability. Benefit may be assessed generally by the IACUC, but benefit is not just about whether a particular project is worth doing; it is also about whether the project is likely to produce the desired information. The latter is generally best assessed by experts in the field.

In neuropathic pain research, the important harm questions are related to pain, including that related to surgery to induce a condition, as well as any ensuing, chronic pain induced. Although concern for severe, ongoing, untreatable neuropathic human pain drives the urgency of the research, not all models produce severe, ongoing, untreatable pain in the animals. Some produce an allodynia that is only mildly painful unless specific tests (e.g., cold-plate exposure or mechanical tests) are applied, and even those analgesiometric tests are terminated when the animal signals a response.

It is essential to take stock of each step in the model. The “spared nerve” model of neuropathic pain involves an initial surgery, with nerve manipulations, that could be acutely painful for a few days. The chronic pain that then develops must be carefully assessed. For example, is it continuously, significantly painful, or is it only painful when the animal is subjected to a noxious stimulus or is forced to move? This model depends on late events days or weeks subsequent to the surgical manipulations. It is reasonable to question whether untreated pain or use of pain-modulating drugs will affect development of the neuropathy, and if so, whether the effect will be strong enough to significantly affect data collected. Weeks or months before the animals undergo the spared nerve surgery, they may have been genotyped and identified by invasive means (e.g., tail-tip amputation, ear-notching). The investigator and IACUC should consider whether pain of tissue sampling procedures should be treated with anesthetics and analgesics and whether nociceptive insults in the developing animal (and/or the drugs used to manage these) affect the outcomes of the experiments later on.

Pain Management

Pain Detection

According to the Recognition and Alleviation of Pain in Laboratory Animals, “although spontaneous pain may be associated with [neuropathic pain] models, this is not readily apparent and is certainly difficult to document. There is rarely any significant change in behavior or weight loss that might indicate ongoing pain” (NRC 2009). Sensory neuropathy typically has no clinical manifestations in many species other than changes in electrophysiologic parameters and behavioral testing in response to thermal, mechanical, and chemical stimuli (Bierhaus and Nawroth 2012; Eaton 2003; Hoke 2012). This behavioral testing used in rodents and other models tests allodynia and hyperalgesia (Hoke 2012). Allodynia, as defined previously, is sensitivity to mechanical or thermal stimuli that usually does not cause pain, whereas hyperalgesia is increased sensitivity to a stimulus that is typically painful (Bridges et al. 2001; Grubb 2010a). Allodynia and hyperalgesia are often measured by response to thermal (e.g. tail flick, hot/cold plate test), mechanical (e.g., von Frey's), or chemical (e.g., formalin) stimulation (Barrot 2012; Eaton 2003; Hoke 2012). Although these measurements provide outcomes in response to treatment paradigms or genetic modifications, they are difficult to adapt for clinical cases because some tests require acclimation of the subject (mechanical and thermal tests) whereas other tests are invasive and cause significant pain themselves (chemical tests). In addition, although hyperalgesia and allodynia are commonly associated with neuropathic pain, they do not provide a clear indication of the amount of pain an individual is currently experiencing (Tranquilli et al. 2007).

Clinical signs of peripheral neuropathy vary from model to model as well as from species to species. Neuropathy causing weakness is well recognized in cats and dogs with diabetes; however, primary sensory clinical signs have not been reported in these species, although subclinical sensory and motor dysfunction is most likely present (Cuddon 2002). Similarly, chemotherapy-associated peripheral neuropathy has been described in the dog, but motor dysfunction and not sensory dysfunction was described in this report (Hamilton et al. 1991). Models that affect both sensory and motor nerves make interpretation of clinical signs difficult. In one study of mice with chronic constriction injury, a blinded observer could not confirm any changes in licking, guarding, or limping of the affected side, despite injuries that produced clear differences in gait analysis and provoked testing (allodynia and hyperalgesia) (Mogil et al. 2010). At doses of analgesics sufficient to eliminate the responses in the evoked tests, the gait analysis did not change, demonstrating that motor changes were affecting gait as much as pain (Mogil et al. 2010), and a study in rats after nerve injury found similar results (Piesla et al. 2009). Facial grimace scores in mice are not useful for detection of neuropathic pain, although they have been used to track painful responses in other types of pain (Langford, Bailey, et al. 2010). In one study, ultrasonic vocalization was shown to be associated with neuropathic pain (Kurejova et al. 2010), but this indicator must be used carefully as it can be confounded by fear, novelty, and anxiety; therefore, results have been mixed in other reports (Koplovitch et al. 2012). Another study has used conditioned place preference to demonstrate that animals with peripheral neuropathy show a preference for locations where they receive analgesics (King et al. 2009), suggesting this method could be used to detect pain. In addition to these methods, varied effects on sleep, anxiety-like behavior, and depression-like behavior have been shown in a variety of pain models (reviewed in Urban et al. 2011). Yet another study examined the “daily activity” of mice after three chronic neuropathic pain models using video monitoring and found no consistent alterations (Urban et al. 2011). The authors argue that the particular models studied do not reflect the life-altering chronic neuropathy seen in humans because even if the animals do feel chronic pain, there are no reliable measures of that pain (Urban et al. 2011). Finally, intense focused ultrasound has recently been used to quantify pain after nerve injury and may show promise as a quantitative method of assessing pain (Garcia et al. 2013).

Self-mutilation, or autotomy, is a sequela seen most commonly in complete sciatic nerve transection and other similar models. In one study, 9 of 14 rats undergoing complete sciatic transection were euthanized before the planned endpoint because of autotomy, compared with one rat (out of 10) each in the spinal nerve ligation and chronic constriction injury groups and no rats in the partial sciatic transection groups (Dowdall et al. 2005). The etiology of autotomy is debated (Kauppila 1998; Mogil et al. 2010). Many individuals believe that this behavior is due to unrelieved neuropathic pain similar to “phantom limb pain” in humans with amputations (Coderre et al. 1986; Kauppila 1998). Others believe that autotomy is due to a loss of sensation or “numbness” and does not indicate pain, although currently this argument is less supported (Koplovitch et al. 2012; Rodin and Kruger 1984). Still, some authors have maintained that partial sciatic transection protocols are more humane because they cause less autotomy and potentially less pain (Bridges et al. 2001; Dowdall et al. 2005). This argument has been refuted by one researcher who used sequential surgeries to suggest that severe pain is present in the partial nerve transection models and autotomy is avoided because sensation is retained, making it more painful to chew on the limb than to not chew on the limb (Koplovitch et al. 2012). In support of this, their data demonstrated that when sensation was taken away with the second surgery (transection of the saphenous and sural nerves), self-mutilation commenced rapidly. These researchers stated, “An ethical imperative of pain research is to be aware of, and to minimize, discomfort experienced by experimental animals and not just to minimize its outwardly observable signs” (Koplovitch et al. 2012).

If there are not effective ways to detect neuropathic pain in clinical situations, determining appropriate treatments, treatment courses, and the effectiveness of preemptive pain relief is even more difficult. In addition to the neuropathic pain that results from the neuropathy, the methods used to induce the model may cause pain before the development of neuropathic pain. For example, surgical models of peripheral neuropathy are likely to be associated with postoperative pain from soft tissue damage, and nerve constriction by sutures will be associated with acute inflammation in addition to chronic neuropathic pain (Bridges et al. 2001). Yet, the acute inflammatory response is important to create neuropathic pain, and anti-inflammatory treatment has been shown to adversely affect the subsequent development of neuropathic pain in these models (Wagner et al. 1998). Thus, this provides a difficult and controversial problem. Few studies have been done to demonstrate that preemptive pain relief will interfere with peripheral neuropathy models; however, the premise that they would is logical based on the known physiology. Still, relying on administration of pain relief only when clear clinical signs of pain are detected is not likely to be fruitful in preventing pain because studies have shown (see above) that neuropathic pain is difficult to detect in companion animals and in research animals. Therefore, during IACUC review, preemptive pain relief should be considered for those studies in which the IACUC determines it will not interfere with the research goals.

Pain Treatment

Preemptive pain relief for neuropathic pain is easy to propose but more difficult to determine. Treatment of neuropathic pain in clinical veterinary medicine is based on some animal studies and guidelines from human medicine, although many guidelines from human medicine cannot be directly adapted to animals (Grubb 2010a). For effective pharmacologic treatment of neuropathic pain, multimodal analgesia is generally required (Grubb 2010a; Mathews 2008; O'Connor and Dworkin 2009). First-tier treatment involves the use of certain anticonvulsant drugs (e.g., gabapentin, pregabalin) and tricyclic antidepressants (e.g., imipramine, amitriptyline) (Grubb 2010a; Grubb 2010b; O'Connor and Dworkin 2009). Topical lidocaine has also been used (Grubb 2010a), although most species will promptly remove topical medications by grooming. Second tier medications, which are often less effective in cases of neuropathic pain, include opioid analgesics, tramadol, and nonsteroidal anti-inflammatory drugs (Eaton 2003; Grubb 2010a; O'Connor and Dworkin 2009). Opioid receptors are typically downregulated in chronic neuropathic pain, which may partially explain why treatment of neuropathic pain requires other drugs in addition to opioids (Bridges et al. 2001; Mizoguchi et al. 2009). As previously mentioned, anti-inflammatory drugs may negatively affect development of the model by decreasing inflammation, but their role in decreasing inflammation commonly makes them part of the multimodal approach to the clinical treatment of neuropathic pain (Bridges et al. 2001; Grubb 2010a).

Nonpharmacologic approaches that may affect neuropathic pain include selection of bedding texture (long particle vs. short particle), diet (decreased soy, increased taurine), and social interaction (group vs. solitary housing) (Belfer et al. 1998; Langford, Tuttle et al. 2010; Robinson et al. 2004; Shir et al. 1998). It may be possible to incorporate alternate bedding textures into the protocol, and unless scientifically justified, rodents and other social species should be group housed. Still, it must be remembered that changes in these parameters will likely change the outcome of the study and should be kept as constant as possible throughout the study. Other nonpharmacologic approaches that may be difficult to incorporate into the care of rodents but that could be considered in larger species include massage, thermotherapy, and, potentially, acupuncture (Grubb 2010a).

Adverse Outcomes and Endpoints

Adverse outcomes and endpoints can be difficult to distinguish in peripheral neuropathy models. IACUC review should include clear lists of the possible adverse outcomes and appropriate planned interventions. Endpoint criteria should also be well delineated so the IACUC can understand what each animal will experience.

Motor/Autonomic Dysfunction

Adverse effects in peripheral neuropathy models can broadly be divided into two categories: motor/autonomic dysfunction and pain. Motor dysfunction can cause weakness of one or more limbs, which could impair a rodent's ability to hang from a wire top to get to food and water. Disuse of a limb and inability to hold the limb in an anatomically correct position can lead to soft tissue damage and contracture, which further impairs mobility (Sackley et al. 2009). Motor dysfunction also may render an animal less able to groom itself normally and to move away from feces and urine, with resulting skin ulceration and infection. If innervation to the bladder is involved (autonomic dysfunction), dysuria may occur, and regular bladder expression may be required (Lane 2000). Dysuria can also render the animal more susceptible to bladder infections (Lane 2000).

Interventions need to be specific and appropriate for each complication. For example, if dragging of the limb or contracture is possible, antibiotic therapy for skin wounds or infection, bandaging of wounds, or physical therapy to prevent and treat contracture should be considered during the protocol development process. Veterinary involvement in the implementation of these treatments is essential. If dysuria is likely, frequency of bladder expression and prophylactic antibiotic administration should be delineated.

Endpoint criteria associated with motor and autonomic dysfunction will vary with the protocol and model used but may include inability to obtain food and water, limb paralysis, skin lesions that are refractory to treatment, or symptoms of urinary tract infection.

As described above, clinical signs of pain are difficult to detect in peripheral neuropathy models; thus, they are unlikely to be viable components of adverse outcome endpoint criteria. Often signs such as licking the affected wound, guarding, vocalizing, limping, weight loss, or failure to eat or drink are listed as possible indicators of pain in IACUC protocols, despite clear evidence that these signs are rarely displayed by animals presumed to have neuropathic pain (Blackburn-Munro 2004). The absence of these signs, depending on the species, does not indicate the absence of pain, and the presence of such signs may suggest a complication (e.g., illness, infection, inability to reach food and water effectively) other than pain.

Although there is not universal agreement that autotomy develops in response to pain, self-mutilation is disturbing to caregivers and is commonly listed as an adverse outcome and as a component of the endpoint criteria. If treatment interventions (e.g., pain relievers, topical mixtures with bitter taste) will be used, they should be delineated. For autotomy, many researchers use a scale and scoring system (see Figure 1) describing the extent of self-mutilation to arrive at an endpoint. The development of autotomy can be very consistent for some models, although it can develop sporadically in others (Dowdall et al. 2005; Koplovitch et al. 2012).

Model-Specific Adverse Outcomes

Other adverse outcomes to consider may be side effects of the model itself rather than specific clinical signs of motor or sensory nerve dysfunction. For example, diabetic rodents may develop systemic illness, including urinary tract disease, and associated clinical signs, such as weight loss and diarrhea (Fox et al. 1999). Also, monkeys with simian immunodeficiency virus –associated neuropathy in some studies are preselected to have encephalitis and may show signs of forebrain dysfunction (Burdo et al. 2012). Chemotherapy agents can be associated with gastrointestinal signs of illness, soft tissue damage from extravascular administration routes, and blood dyscrasias (Looney 2010). Focus on the pain model can sometimes allow these other, equally serious, complications to be less clearly delineated.

Postapproval Monitoring—Collaborative Effort Between the Researcher, the Veterinary Staff, and the IACUC

Regulatory Requirements

As interpreted by Oki et al. (1996), the PHS policy and USDA regulations regarding continuing review of IACUC approved activities include three main purposes (i.e., “to inform the IACUC of the current status of the project; to ensure continued compliance with PHS, USDA and institutional requirements; and to provide for re-evaluation of the animal activities at appropriate intervals”). These reviews usually take place at the time of PHS-required protocol de novo reviews (i.e., 3-year renewals) and USDA-required protocol annual reviews. Some institutions require annual review of all protocols and may include such information at that time for all species.

Regulatory requirements also make the IACUC responsible for assuring that animal activities are being conducted as approved. DeHaven (2002) included this issue in an article on IACUC best practices. He noted that a procedure for monitoring of ongoing animal-related activities could help assure that specific practices are being conducted compliantly, including, for example, frequency of monitoring and use of analgesia. He suggested that this aspect of postapproval monitoring “might be performed independent of, or as part of, required ACC facility inspections and program reviews.”

Regular Monitoring

The Guide for the Care and Use of Laboratory Animals (NRC 2011, 33–34) explicitly addresses postapproval monitoring and acknowledges that such monitoring occurs in many ways for all studies involving animals, such as during daily health checks by animal care staff, veterinary observations, and semiannual inspections by the IACUC. Monitoring of animals by research staff is also an important part of postprocedure monitoring. However, additional or more intense monitoring may be advisable in studies that are expected to result in animal pain. In all cases, postapproval monitoring is a shared responsibility and should be a collaborative effort between all parties, especially the researcher, the veterinary staff, and the IACUC.

Communication

Collaboration requires good communication, which should begin during the IACUC protocol review process as the researcher, veterinarians, and IACUC members work together to determine animal monitoring plans and endpoint criteria. Once the protocol is approved, the final plan is put into action. At the University of Washington, this sometimes includes assignment of the protocol to our Protocol Monitoring Program. This involves assignment of a specific veterinarian to the project. The IACUC approval notification to the researcher includes this assignment and initiates the formal postapproval communication between the assigned veterinarian and the research group. At this point, it is important to also clearly communicate the veterinarian's role in the project and the particulars and expectations related to the interactive efforts. For example, the IACUC may require the veterinarian's presence during certain procedures and/or some level of joint health observations of the animals with the researcher or his/her staff.

Reporting

Once the experiments begin, the animal monitoring plan is initiated. Record keeping is extremely important so that reviews of postprocedure observations/measurements are adequate not only to identify whether special care or endpoint criteria have been reached but also to identify unexpected events that may necessitate adjustments to the monitoring plan, endpoints, or even to the experimental design.

For example, if the monitoring plan includes pain scoring, it is critical that the scoring be conducted according to the approved parameters but adjusted collaboratively with veterinarians and the IACUC. This collaborative effort will help assure the balance between reaching research goals and protection of animal welfare and will also help assure that regulatory requirements are met. Depending on the specific adjustments that need to be made in the plan, a significant change may need review and approval by the IACUC, while keeping in mind, of course, that the veterinary staff can prescribe immediate changes to protect the welfare of animals in ongoing studies.

If monitoring reveals other issues, such as animals reaching endpoint criteria earlier than expected and before research goals can be met, then the researcher may need to adjust the actual experiment plan. Likewise, modifications may be necessary if the planned endpoints are not being reached at all or are not being reached within the desired time frame. In either case, collaboration and consultation are important. The researcher may want to consult with research colleagues regarding the experiment design and certainly with the veterinary staff and the IACUC regarding specific changes that need to be made to the IACUC protocol.

Conclusions

Animal models of peripheral neuropathy are diverse. Clear understanding of the model, potential complications, anticipated pain, ethical considerations, and experimental endpoints is needed by members of the IACUC, veterinary staff, and researchers when performing research where peripheral neuropathy is a target of the research or an unwelcome sequela to the disease process under study.

References

Author notes