Severity assessment of complex and repeated intracranial surgery in rats

Introduction Evidence-based grading of the impact of intracranial surgery on rat’s well-being is important for ethical and legal reasons. We assessed the severity of complex and repeated intracranial surgery in a 6-hydroxydopamine (6-OHDA) Parkinson’s rat model with subsequent intracranial electrode implantation, and in an intracranial tumor model with subsequent resection. Methods Stereotactic surgery was performed in adult male rats with the same general anesthesia and perioperative pain management. In the Parkinson’s model, Sprague Dawley (SD) rats received unilateral injection of 6-OHDA (n=11) or vehicle (n=7) into the medial forebrain bundle as first operation. After four weeks, neural electrodes were implanted in all rats as second operation. For tumor formation, BDIX/ UlmHanZtm (BDIX) rats (n=8) received frontocortical injection of BT4Ca cells as first operation, followed by tumor resection as second operation after one week. Multiple measures severity assessment was done two days before and four days after surgery in all rats, comprising clinical scoring, body weight and detailed behavioral screening. To include a condition with a known burden, rats with intracranial tumors were additionally assessed up to a predefined humane endpoint that has previously been classified as "moderate". Results After the first operation, only 6-OHDA injection resulted in transient elevated clinical scores, a mild long-lasting weight reduction and motor disturbances. After the second surgery, body weight was transiently reduced in all groups. All other parameters showed variable results. Principal Component Analysis showed a separation from the preoperative state driven by motor-related parameters after 6-OHDA injection, while separation after electrode implantation and more clearly after tumor resection was driven by pain-related parameters, although not reaching the level of the humane endpoint of our tumor model. Conclusion Overall, cranial surgery of different complexity only transiently and rather mildly affects rat’s well-being. Multiple measures assessment allows the differentiation of model-related motor disturbances in the Parkinson’s model from potentially pain-related conditions after tumor resection and electrode implantation.

Automated monitoring of respiratory rate as a novel humane endpoint: A refinement in mouse metastatic lung cancer models

In oncology research, while xenograft tumor models are easily visualized and humane endpoints can be clearly defined, metastatic tumor models are often based on more subjective clinical observations as endpoints. This study aimed at identifying objective non-invasive criteria for predicting imminent distress and mortality in metastatic lung tumor-bearing mice. BALB/c and C57BL/6 mice were inoculated with CT26 or B16F10 cells, respectively. The mice were housed in Vium smart cages to continuously monitor and stream respiratory rate and locomotion for up to 28 days until scheduled euthanasia or humane endpoint criteria were met. Body weight and body temperature were measured during the study. On days 11, 14, 17 and 28, lungs of subsets of animals were microCT imaged in vivo to assess lung metastasis progression and then euthanized for lung microscopic evaluations. Beginning at day 21, most tumor-bearing animals developed increased respiratory rates followed by decreased locomotion 1–2 days later, compared with the baseline values. Increases in respiratory rate did not correlate to surface tumor nodule counts or lung weight. Body weight measurement did not show significant changes from days 14–28 in either tumor-bearing or control animals. We propose that increases in respiratory rate (1.3–1.5 X) can be used to provide an objective benchmark to signal the need for increased clinical observations or euthanasia. Adoption of this novel humane endpoint criterion would allow investigators time to collect tissue samples prior to spontaneous morbidity or death and significantly reduce the distress of mice in the terminal stages of these metastatic lung tumor models.

Reston virus causes severe respiratory disease in young domestic pigs

Reston virus (RESTV), an ebolavirus, causes clinical disease in macaques but has yet only been associated with rare asymptomatic infections in humans. Its 2008 emergence in pigs in the Philippines raised concerns about food safety, pathogenicity, and zoonotic potential, questions that are still unanswered. Until today, the virulence of RESTV for pigs has remained elusive, with unclear pathogenicity in naturally infected animals and only one experimental study demonstrating susceptibility and evidence for shedding but no disease. Here we show that combined oropharyngeal and nasal infection of young (3- to 7-wk-old) Yorkshire cross pigs with RESTV resulted in severe respiratory disease, with most animals reaching humane endpoint within a week. RESTV-infected pigs developed severe cyanosis, tachypnea, and acute interstitial pneumonia, with RESTV shedding from oronasal mucosal membranes. Our studies indicate that RESTV should be considered a livestock pathogen with zoonotic potential.

Defining body-weight reduction as a humane endpoint: a critical appraisal

In many animal experiments scientists and local authorities define a body-weight reduction of 20% or more as severe suffering and thereby as a potential parameter for humane endpoint decisions. In this study, we evaluated distinct animal experiments in multiple research facilities, and assessed whether 20% body-weight reduction is a valid humane endpoint criterion in rodents. In most experiments (restraint stress, distinct models for epilepsy, pancreatic resection, liver resection, caloric restrictive feeding and a mouse model for Dravet syndrome) the animals lost less than 20% of their original body weight. In a glioma model, a fast deterioration in body weight of less than 20% was observed as a reliable predictor for clinical deterioration. In contrast, after induction of chronic diabetes or acute colitis some animals lost more than 20% of their body weight without exhibiting major signs of distress. In these two animal models an exclusive application of the 20% weight loss criterion for euthanasia might therefore result in an unnecessary loss of animals. However, we also confirmed that this criterion can be a valid parameter for defining the humane endpoint in other animal models, especially when it is combined with additional criteria for evaluating distress. In conclusion, our findings strongly suggest that experiment and model specific considerations are necessary for the rational integration of the parameter ‘weight loss’ in severity assessment schemes and humane endpoint criteria. A flexible implementation tailored to the experiment or intervention by scientists and authorities is therefore highly recommended.

Therapeutic targeting of polyamines in malignant pleural mesothelioma xenograft models.

e20060 Background: Although the use of asbestos has been restricted, the incidence of malignant pleural mesothelioma (MPM) is still rising. The US FDA approved a combination of pemetrexed with cisplatin for treatment of unresectable MPM. And development of novel adjuvant therapeutic options for resected early-stage disease is also urgently needed. From our preliminary data, ornithine decarboxylase (ODC) is highly expressed in MPM xenografts and clinical tumor samples. Upregulation of ODC increases polyamines production and enhances tumor growth. a-difluoromethylornithine (DFMO) is a specific ODC inhibitor. This study aims to disclose the adjuvant (minimal residual disease setting) and therapeutic (metastatic setting) effects of DFMO in MPM xenografts. Methods: In adjuvant therapy setting, nude mice were fed with DFMO in drinking water 7 days before subcutaneous inoculation of 200,000 tumor cells. In therapeutic setting, 107 corresponding cells were injected subcutaneously into nude mice which were randomized for treatment after established tumor growth. Mice with tumor size > 600mm3 were considered reaching humane endpoint. Spermidine levels, protein expression, cytokines concentration, and apoptosis were investigated by Dot plot, Western blot, ELISA, and TUNEL assay respectively. Results: In adjuvant therapy setting, DFMO suppressed tumor growth and increased median survival in both 211H and H226 xenografts. In H226 xenografts, 43% of treated mice have not yet reached humane endpoint, mimicking long-term survival. Upon DFMO treatment, decrease in spermidine level, increase in nitrotyrosine content, and activation of apoptosis were observed in both xenografts. In addition, increase in nitrosocysteine level, intratumoral IL-6, keratinocyte chemoattractant and TNFα, DNA lesions and inhibition of Akt/mTOR pathway were induced by DFMO in H226 xenografts, which may explain higher potency of DFMO in these xenografts. In therapeutic setting, DFMO also suppressed tumor growth in both xenografts with similar mechanisms. Conclusions: DFMO may have a potential role as adjuvant therapy in MPM especially epithelioid mesothelioma.

Humane endpoint in mice by Brazilian researchers in the vaccine sector

ABSTRACT The application of a humane endpoint (HE) for mice in vaccine trials and further challenging tasks with lethal samples is necessary to reduce or prevent pain and suffering in these animals, and is a refinement of the 3R policy enforced for animal testing in both national and international scenarios. In order to investigate the application of HE in Brazil, researchers from the vaccine sector have answered a questionnaire about their research profile, their usage of HE and their knowledge of its defining criteria, monitoring of animals, staff training, and euthanasia methods employed. The main results revealed that researchers failed to recognise the very concept of HE as well as when to apply it. In addition, the Institutional Animal Care and Use Committees (IACUCs) failed upon giving their approval to the trials. HE is an important refinament of animal testing policy, and these results highlight the need for a clear pre-established definition of when and how it should be implemented in order to ensure more effective application. Furthermore, it is important to clarify the ethics involved and the commitment of both the research teams and IACUCs to animal welfare.

Preexisting Simian Immunodeficiency Virus Infection Increases Susceptibility to Tuberculosis in Mauritian Cynomolgus Macaques

ABSTRACT Tuberculosis (TB), caused by Mycobacterium tuberculosis, is the leading cause of death among human immunodeficiency virus (HIV)-positive patients. The precise mechanisms by which HIV impairs host resistance to a subsequent M. tuberculosis infection are unknown. We modeled this coinfection in Mauritian cynomolgus macaques (MCM) using simian immunodeficiency virus (SIV) as an HIV surrogate. We infected seven MCM with SIVmac239 intrarectally and 6 months later coinfected them via bronchoscope with ∼10 CFU of M. tuberculosis. Another eight MCM were infected with M. tuberculosis alone. TB progression was monitored by clinical parameters, by culturing bacilli in gastric and bronchoalveolar lavages, and by serial [18F]fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging. The eight MCM infected with M. tuberculosis alone displayed dichotomous susceptibility to TB, with four animals reaching humane endpoint within 13 weeks and four animals surviving >19 weeks after M. tuberculosis infection. In stark contrast, all seven SIV+ animals exhibited rapidly progressive TB following coinfection and all reached humane endpoint by 13 weeks. Serial PET/CT imaging confirmed dichotomous outcomes in MCM infected with M. tuberculosis alone and marked susceptibility to TB in all SIV+ MCM. Notably, imaging revealed a significant increase in TB granulomas between 4 and 8 weeks after M. tuberculosis infection in SIV+ but not in SIV-naive MCM and implies that SIV impairs the ability of animals to contain M. tuberculosis dissemination. At necropsy, animals with preexisting SIV infection had more overall pathology, increased bacterial loads, and a trend towards more extrapulmonary disease than animals infected with M. tuberculosis alone. We thus developed a tractable MCM model in which to study SIV-M. tuberculosis coinfection and demonstrate that preexisting SIV dramatically diminishes the ability to control M. tuberculosis coinfection.