Animal models and conserved processes

Modeling Heart Diseases on a Chip: Advantages and Future Opportunities

Heart disease is a significant burden on global health care systems and is a leading cause of death each year. To improve our understanding of heart disease, high quality disease models are needed. These will facilitate the discovery and development of new treatments for heart disease. Traditionally, researchers have relied on 2D monolayer systems or animal models of heart disease to elucidate pathophysiology and drug responses. Heart-on-a-chip (HOC) technology is an emerging field where cardiomyocytes among other cell types in the heart can be used to generate functional, beating cardiac microtissues that recapitulate many features of the human heart. HOC models are showing great promise as disease modeling platforms and are poised to serve as important tools in the drug development pipeline. By leveraging advances in human pluripotent stem cell-derived cardiomyocyte biology and microfabrication technology, diseased HOCs are highly tuneable and can be generated via different approaches such as: using cells with defined genetic backgrounds (patient-derived cells), adding small molecules, modifying the cells' environment, altering cell ratio/composition of microtissues, among others. HOCs have been used to faithfully model aspects of arrhythmia, fibrosis, infection, cardiomyopathies, and ischemia, to name a few. In this review, we highlight recent advances in disease modeling using HOC systems, describing instances where these models outperformed other models in terms of reproducing disease phenotypes and/or led to drug development.

Lighting Up Ca2+ Dynamics in Animal Models

Calcium (Ca2+) signaling coordinates are crucial processes in brain physiology. Particularly, fundamental aspects of neuronal function such as synaptic transmission and neuronal plasticity are regulated by Ca2+, and neuronal survival itself relies on Ca2+-dependent cascades. Indeed, impaired Ca2+ homeostasis has been reported in aging as well as in the onset and progression of neurodegeneration. Understanding the physiology of brain function and the key processes leading to its derangement is a core challenge for neuroscience. In this context, Ca2+ imaging represents a powerful tool, effectively fostered by the continuous amelioration of Ca2+ sensors in parallel with the improvement of imaging instrumentation. In this review, we explore the potentiality of the most used animal models employed for Ca2+ imaging, highlighting their application in brain research to explore the pathogenesis of neurodegenerative diseases.

An organ-on-a-chip model for pre-clinical drug evaluation in progressive non-genetic cardiomyopathy

Angiotensin II (Ang II) presents a critical mediator in various pathological conditions such as non-genetic cardiomyopathy. Osmotic pump infusion in rodents is a commonly used approach to model cardiomyopathy associated with Ang II. However, profound differences in electrophysiology and pharmacokinetics between rodent and human cardiomyocytes may limit predictability of animal-based experiments. This study investigates the application of an Organ-on-a-chip (OOC) system in modeling Ang II-induced progressive cardiomyopathy. The disease model is constructed to recapitulate myocardial response to Ang II in a temporal manner. The long-term tissue cultivation and non-invasive functional readouts enable monitoring of both acute and chronic cardiac responses to Ang II stimulation. Along with mapping of cytokine secretion and proteomic profiles, this model presents an opportunity to quantitatively measure the dynamic pathological changes that could not be otherwise identified in animals. Further, we present this model as a testbed to evaluate compounds that target Ang II-induced cardiac remodeling. Through assessing the effects of losartan, relaxin, and saracatinib, the drug screening data implicated multifaceted cardioprotective effects of relaxin in restoring contractile function and reducing fibrotic remodeling. Overall, this study provides a controllable platform where cardiac activities can be explicitly observed and tested over the pathological process. The facile and high-content screening can facilitate the evaluation of potential drug candidates in the pre-clinical stage.

Comparison of Neonatal and Adult Fibrin Clot Properties between Porcine and Human Plasma

BACKGROUND

Recent studies suggest that adult-specific treatment options for fibrinogen replacement during bleeding may be less effective in neonates. This is likely due to structural and functional differences found in the fibrin network between adults and neonates. In this investigation, the authors performed a comparative laboratory-based study between immature and adult human and porcine plasma samples in order to determine if piglets are an appropriate animal model of neonatal coagulopathy.

METHODS

Adult and neonatal human and porcine plasma samples were collected from the Children's Hospital of Atlanta and North Carolina State University College of Veterinary Medicine, respectively. Clots were formed for analysis and fibrinogen concentration was quantified. Structure was examined through confocal microscopy and cryogenic scanning electron microscopy. Function was assessed through atomic force microscopy nanoindentation and clotting and fibrinolysis assays. Lastly, novel hemostatic therapies were applied to neonatal porcine samples to simulate treatment.

RESULTS

All sample groups had similar plasma fibrinogen concentrations. Neonatal porcine and human plasma clots were less branched with lower fiber densities than the dense and highly branched networks seen in adult human and porcine clots. Neonatal porcine and human clots had faster degradation rates and lower clot stiffness values than adult clots (stiffness [mmHg] mean ± SD: neonatal human, 12.15 ± 1.35 mmHg vs. adult human, 32.25 ± 7.13 mmHg; P = 0.016; neonatal pig, 10.5 ± 8.25 mmHg vs. adult pigs, 32.55 ± 7.20 mmHg; P = 0.015). The addition of hemostatic therapies to neonatal porcine samples enhanced clot formation.

CONCLUSIONS

The authors identified similar age-related patterns in structure, mechanical, and degradation properties between adults and neonates in porcine and human samples. These findings suggest that piglets are an appropriate preclinical model of neonatal coagulopathy. The authors also show the feasibility of in vitro model application through analysis of novel hemostatic therapies as applied to dilute neonatal porcine plasma.

Acute and Subchronic Toxicity Profile of a Polyherbal Drug Used in Sri Lankan Traditional Medicine

A polyherbal drug composed of leaves of Murraya koenigii L. Spreng, cloves of Allium sativum L., fruits of Garcinia quaesita Pierre, and seeds of Piper nigrum L. is a popular drug which has been used by indigenous practitioners in Sri Lanka for the treatment of diabetes mellitus and dyslipidemia. The acute toxicity assessment was conducted, following a single oral dose of 0.25–2.0 g/kg in healthy rats, and rats were observed up to 14 days. The hot water extract (1.0 g/kg) and the water : acetone extract (0.5, 1.0, and 1.5 g/kg) were administered to Wistar rats for 28 days in the subchronic study. Hypoglycemic and antihyperglycemic activities (dose response studies) of cold water, hot water, and water : acetone extracts of the polyherbal mixture were evaluated at the doses of 0.5, 1.0, and 1.5 g/kg in healthy and streptozotocin-induced diabetic rats (70 mg/kg, ip), respectively. Acute toxicity study showed that the polyherbal drug did not cause any change in animals throughout the experimental period of 14 days. The administration of the hot water extract and the water : acetone extract of the polyherbal drug for 28 days did not produce changes in the selected biochemical and hematological parameters in Wistar rats (p > 0.05). The histological assessment corroborated the biochemical findings with no significant treatment-related changes in the kidney and liver. The treatment of polyherbal drug significantly lowered the serum glucose concentration compared to the diabetic control rats (p < 0.05) while it did not lead to a severe reduction of glucose concentration in healthy rats. The hot water and water : acetone extracts of the polyherbal drug showed a statistically significant improvement on total area under the glucose tolerance curve in diabetic rats (p < 0.05), reflecting dose-dependent antihyperglycemic effects of the drug. Based on the results, we conclude that the aforementioned antidiabetic polyherbal remedy is free of toxic/adverse effects at the equivalent human therapeutic dose in healthy Wistar rats and would be a safe therapeutic agent for long-term treatments.

Joining forces: the need to combine science and ethics to address problems of validity and translation in neuropsychiatry research using animal models

BACKGROUND

Current policies regulating the use of animals for scientific purposes are based on balancing between potential gain of knowledge and suffering of animals used in experimentation. The balancing process is complicated, on the one hand by plurality of views on our duties towards animals, and on the other hand by more recent discussions on uncertainty in the probability of reaching the final aim of the research and problems of translational failure.

METHODS

The study combines ethical analysis based on a literature review with neuropsychiatry-related preclinical research as a case study.

RESULTS

Based on the analysis and the case study we show that neuropsychiatry-related preclinical research is an especially interesting case from an ethical perspective. The 3R principles (Replacement, Reduction and Refinement) are used to minimize the negative consequences for the animals used in research. However, neuropsychiatric research is characterized by specific challenges in assessing the probability of success of reaching the final aim, due to our limited mechanistic knowledge of human neuropsychiatric illness. Consequently, the translational value of the currently used animal models may be difficult to prove, which undermines the validity of these models and complicated the ethical assessment.

CONCLUSIONS

We conclude that a combined approach that deals with both science and the ethical dimensions is necessary to address the problems of validity and translation in neuropsychiatry-related preclinical research. We suggest this approach to comprise first, improved experimental methods, e.g. by using systematic reviews, second, a more patients-based approach that leads to models that reflect interindividual variation better, and third, more interdisciplinary cooperation.

The International Mouse Phenotyping Consortium (IMPC): a functional catalogue of the mammalian genome that informs conservation

The International Mouse Phenotyping Consortium (IMPC) is building a catalogue of mammalian gene function by producing and phenotyping a knockout mouse line for every protein-coding gene. To date, the IMPC has generated and characterised 5186 mutant lines. One-third of the lines have been found to be non-viable and over 300 new mouse models of human disease have been identified thus far. While current bioinformatics efforts are focused on translating results to better understand human disease processes, IMPC data also aids understanding genetic function and processes in other species. Here we show, using gorilla genomic data, how genes essential to development in mice can be used to help assess the potentially deleterious impact of gene variants in other species. This type of analyses could be used to select optimal breeders in endangered species to maintain or increase fitness and avoid variants associated to impaired-health phenotypes or loss-of-function mutations in genes of critical importance. We also show, using selected examples from various mammal species, how IMPC data can aid in the identification of candidate genes for studying a condition of interest, deliver information about the mechanisms involved, or support predictions for the function of genes that may play a role in adaptation. With genotyping costs decreasing and the continued improvements of bioinformatics tools, the analyses we demonstrate can be routinely applied.

Humanized Mice as Unique Tools for Human-Specific Studies

With an increasing human population, medical research is pushed to progress into an era of precision therapy. Humanized mice are at the very heart of this new forefront where it is acutely required to decipher human-specific disease pathogenesis and test an array of novel therapeutics. In this review, “humanized” mice are defined as immunodeficient mouse engrafted with functional human biological systems. Over the past decade, researchers have been conscientiously making improvements on the development of humanized mice as a model to closely recapitulate disease pathogenesis and drug mechanisms in humans. Currently, literature is rife with descriptions of novel and innovative humanized mouse models that hold a significant promise to become a panacea for drug innovations to treat and control conditions such as infectious disease and cancer. This review will focus on the background of humanized mice, diseases, and human-specific therapeutics tested on this platform as well as solutions to improve humanized mice for future clinical use.

Publication bias in animal research presented at the 2008 Society of Critical Care Medicine Conference

Background

To determine a direct measure of publication bias by determining subsequent full-paper publication (P) of studies reported in animal research abstracts presented at an international conference (A).

Methods

We selected 100 random (using a random-number generator) A from the 2008 Society of Critical Care Medicine Conference. Using a data collection form and study manual, we recorded methodology and result variables from A. We searched PubMed and EMBASE to June 2015, and DOAJ and Google Scholar to May 2017 to screen for subsequent P. Methodology and result variables were recorded from P to determine changes in reporting from A. Predictors of P were examined using Fisher’s Exact Test.

Results

62% (95% CI 52–71%) of studies described in A were subsequently P after a median 19 [IQR 9–33.3] months from conference presentation. Reporting of studies in A was of low quality: randomized 27% (the method of randomization and allocation concealment not described), blinded 0%, sample-size calculation stated 0%, specifying the primary outcome 26%, numbers given with denominators 6%, and stating number of animals used 47%. Only being an orally presented (vs. poster presented) A (14/16 vs. 48/84, p = 0.025) predicted P. Reporting of studies in P was of poor quality: randomized 39% (the method of randomization and allocation concealment not described), likely blinded 6%, primary outcome specified 5%, sample size calculation stated 0%, numbers given with denominators 34%, and number of animals used stated 56%. Changes in reporting from A to P occurred: from non-randomized to randomized 19%, from non-blinded to blinded 6%, from negative to positive outcomes 8%, from having to not having a stated primary outcome 16%, and from non-statistically to statistically significant findings 37%. Post-hoc, using publication data, P was predicted by having positive outcomes (published 62/62, unpublished 33/38; p = 0.003), or statistically significant results (published 58/62, unpublished 20/38; p < 0.001).

Conclusions

Only 62% (95% CI 52–71%) of animal research A are subsequently P; this was predicted by oral presentation of the A, finally having positive outcomes, and finally having statistically significant results. Publication bias is prevalent in critical care animal research.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2574-0) contains supplementary material, which is available to authorized users.

Tolerability of a rapid-escalation vinblastine-prednisolone protocol in dogs with mast cell tumours

Optimal chemotherapy protocols for high-risk mast cell tumours (MCTs) are unknown. The purpose of this study was to determine the tolerability and toxicity profile of a rapidly escalating vinblastine and prednisolone protocol (VPP) in which 3.00 mg/m2 was administered once 7 days apart: at day 14 and at day 21. Dogs with chemotherapy-naïve MCTs presenting to the Oncology Service of a single institution were prospectively enrolled to receive escalating vinblastine, and haematology and a standardised quality-of-life questionnaire were assessed prior to each dosage. Thirty-four dogs were included: 30 with microscopic disease treated with adequate local therapy and four with macroscopic disease. Of 220 doses of vinblastine administered, 4% were associated with grade 3 and 4 toxicity. A total of 70% of dogs tolerated 3.00 mg/m2 given 7 days apart at day 14 and 21, although 29% of dogs developed dose-limiting toxicities and 8% discontinued the protocol due to toxicity. In conclusion, VPP was well-tolerated overall, although prior to further dose intensity optimisation, it is important to determine if dose intensity is linked to outcome in canine MCT to avoid unwarranted toxicity.

The European Citizens' Stop Vivisection Initiative and the revision of Directive

Animal experimentation is presented to the public as an ongoing debate between research scientists on one hand, and the animal protection community on the other. An opportunity to break out of this mindset presented itself in the form of a European Citizens' Initiative, Stop Vivisection, which challenged Directive 2010/63/EU of the European Parliament and of the Council on the protection of animals for scientific purposes. The manifesto of the initiative called upon the European Commission to replace the existing Directive with a new proposal that does away with animal experimentation, and instead makes compulsory the use of human data as a predictive modality for the study of human diseases and responses to drugs. Although the Initiative succeeded in gathering the required one million signatures, the European Commission ultimately rejected the proposal. However, some of the lessons learned from the Initiative may well be relevant to the revision of Directive 2010/63/EU, due to take place by 2017.

Expectations for the methodology and translation of animal research: a survey of the general public, medical students and animal researchers in North America

To determine what are considered acceptable standards for animal research (AR) methodology and translation rate to humans, a validated survey was sent to: a) a sample of the general public, via Sampling Survey International (SSI; Canada), Amazon Mechanical Turk (AMT; USA), a Canadian city festival (CF) and a Canadian children's hospital (CH); b) a sample of medical students (two first-year classes); and c) a sample of scientists (corresponding authors and academic paediatricians). There were 1379 responses from the general public sample (SSI, n = 557; AMT, n = 590; CF, n = 195; CH, n = 102), 205/330 (62%) medical student responses, and 23/323 (7%, too few to report) scientist responses. Asked about methodological quality, most of the general public and medical student respondents expect that: AR is of high quality (e.g. anaesthesia and analgesia are monitored, even overnight, and 'humane' euthanasia, optimal statistical design, comprehensive literature review, randomisation and blinding, are performed), and costs and difficulty are not acceptable justifications for lower quality (e.g. costs of expert consultation, or more laboratory staff). Asked about their expectations of translation to humans (of toxicity, carcinogenicity, teratogenicity and treatment findings), most expect translation more than 60% of the time. If translation occurred less than 20% of the time, a minority disagreed that this would "significantly reduce your support for AR". Medical students were more supportive of AR, even if translation occurred less than 20% of the time. Expectations for AR are much higher than empirical data show to have been achieved.

Species differences in tumour responses to cancer chemotherapy

Despite advances in chemotherapy, radiotherapy and targeted drug development, cancer remains a disease of high morbidity and mortality. The treatment of human cancer patients with chemotherapy has become commonplace and accepted over the past 100 years. In recent years, and with a similar incidence of cancer to people, the use of cancer chemotherapy drugs in veterinary patients such as the dog has also become accepted clinical practice. The poor predictability of tumour responses to cancer chemotherapy drugs in rodent models means that the standard drug development pathway is costly, both in terms of money and time, leading to many drugs failing in Phase I and II clinical trials. This has led to the suggestion that naturally occurring cancers in pet dogs may offer an alternative model system to inform rational drug development in human oncology. In this review, we will explore the species variation in tumour responses to conventional chemotherapy and highlight our understanding of the differences in pharmacodynamics, pharmacokinetics and pharmacogenomics between humans and dogs. Finally, we explore the potential hurdles that need to be overcome to gain the greatest value from comparative oncology studies.

The Human Model: Changing Focus on Autism Research

The lack of live human brain cells for research has slowed progress toward understanding the mechanisms underlying autism spectrum disorders. A human model using reprogrammed patient somatic cells offers an attractive alternative, as it captures a patient's genome in relevant cell types. Despite the current limitations, the disease-in-a-dish approach allows for progressive time course analyses of target cells, offering a unique opportunity to investigate the cellular and molecular alterations before symptomatic onset. Understanding the current drawbacks of this model is essential for the correct data interpretation and extrapolation of conclusions applicable to the human brain. Innovative strategies for collecting biological material and clinical information from large patient cohorts are important for increasing the statistical power that will allow for the extraction of information from the noise resulting from the variability introduced by reprogramming and differentiation methods. Working with large patient cohorts is also important for understanding how brain cells derived from diverse human genetic backgrounds respond to specific drugs, creating the possibility of personalized medicine for autism spectrum disorders.

Expectations for methodology and translation of animal research: a survey of health care workers

Background

Health care workers (HCW) often perform, promote, and advocate use of public funds for animal research (AR); therefore, an awareness of the empirical costs and benefits of animal research is an important issue for HCW. We aim to determine what health-care-workers consider should be acceptable standards of AR methodology and translation rate to humans.

Methods

After development and validation, an e-mail survey was sent to all pediatricians and pediatric intensive care unit nurses and respiratory-therapists (RTs) affiliated with a Canadian University. We presented questions about demographics, methodology of AR, and expectations from AR. Responses of pediatricians and nurses/RTs were compared using Chi-square, with P < .05 considered significant.

Results

Response rate was 44/114(39%) (pediatricians), and 69/120 (58%) (nurses/RTs). Asked about methodological quality, most respondents expect that: AR is done to high quality; costs and difficulty are not acceptable justifications for low quality; findings should be reproducible between laboratories and strains of the same species; and guidelines for AR funded with public money should be consistent with these expectations. Asked about benefits of AR, most thought that there are sometimes/often large benefits to humans from AR, and disagreed that “AR rarely produces benefit to humans.” Asked about expectations of translation to humans (of toxicity, carcinogenicity, teratogenicity, and treatment findings), most: expect translation >40% of the time; thought that misleading AR results should occur <21% of the time; and that if translation was to occur <20% of the time, they would be less supportive of AR. There were few differences between pediatricians and nurses/RTs.

Conclusions

HCW have high expectations for the methodological quality of, and the translation rate to humans of findings from AR. These expectations are higher than the empirical data show having been achieved. Unless these areas of AR significantly improve, HCW support of AR may be tenuous.

Integrating human pluripotent stem cells into drug development

Integration of physiologically relevant in vitro assays at the earliest stages of drug discovery may improve the likelihood of successfully translating preclinical discoveries to the clinic. Assays based on in vitro-differentiated, human pluripotent stem cell (IVD hPSC)-derived cells, which may better model human physiology, are starting to impact the drug discovery process, but their implementation has been slower than originally anticipated. In this Perspective, we discuss imperatives for incorporating IVD hPSCs into drug discovery and the associated challenges.

The methodological quality of animal research in critical care: the public face of science

BACKGROUND

Animal research (AR) findings often do not translate to humans; one potential reason is the poor methodological quality of AR. We aimed to determine this quality of AR reported in critical care journals.

METHODS

All AR published from January to June 2012 in three high-impact critical care journals were reviewed. A case report form and instruction manual with clear definitions were created, based on published recommendations, including the ARRIVE guidelines. Data were analyzed with descriptive statistics.

RESULTS

Seventy-seven AR publications were reviewed. Our primary outcome (animal strain, sex, and weight or age described) was reported in 52 (68%; 95% confidence interval, 56% to 77%). Of the 77 publications, 47 (61%) reported randomization; of these, 3 (6%) reported allocation concealment, and 1 (2%) the randomization procedure. Of the 77 publications, 31 (40%) reported some type of blinding; of these, disease induction (2, 7%), intervention (7, 23%), and/or subjective outcomes (17, 55%) were blinded. A sample size calculation was reported in 4/77 (5%). Animal numbers were missing in the Methods section in 16 (21%) publications; when stated, the median was 32 (range 6 to 320; interquartile range, 21 to 70). Extra animals used were mentioned in the Results section in 31 (40%) publications; this number was unclear in 23 (74%), and >100 for 12 (16%). When reporting most outcomes, numbers with denominators were given in 35 (45%), with no unaccounted numbers in 24 (31%), and no animals excluded from analysis in 20 (26%). Most (49, 64%) studies reported >40, and another 19 (25%) reported 21 to 40 statistical comparisons. Internal validity limitations were discussed in 7 (9%), and external validity (to humans) discussed in 71 (92%), most with no (30, 42%) or only a vague (9, 13%) limitation to this external validity mentioned.

CONCLUSIONS

The reported methodological quality of AR was poor. Unless the quality of AR significantly improves, the practice may be in serious jeopardy of losing public support.

A call for urgent monitoring of food and water security based on relevant indicators for the Arctic

This perspective paper argues for an urgent need to monitor a set of 12 concrete, measurable indicators of food and water security in the Arctic over time. Such a quantitative indicator approach may be viewed as representing a reductionist rather than a holistic perspective, but is nevertheless necessary for actually knowing what reality aspects to monitor in order to accurately understand, quantify, and be able to project critical changes to food and water security of both indigenous and non-indigenous people in the Arctic. More relevant indicators may be developed in the future, taking us further toward reconciliation between reductionist and holistic approaches to change assessment and understanding. However, the potential of such further development to improved holistic change assessment is not an argument not to urgently start to monitor and quantify the changes in food and water security indicators that are immediately available and adequate for the Arctic context.

Systematic reviews of animal models: methodology versus epistemology

Systematic reviews are currently favored methods of evaluating research in order to reach conclusions regarding medical practice. The need for such reviews is necessitated by the fact that no research is perfect and experts are prone to bias. By combining many studies that fulfill specific criteria, one hopes that the strengths can be multiplied and thus reliable conclusions attained. Potential flaws in this process include the assumptions that underlie the research under examination. If the assumptions, or axioms, upon which the research studies are based, are untenable either scientifically or logically, then the results must be highly suspect regardless of the otherwise high quality of the studies or the systematic reviews. We outline recent criticisms of animal-based research, namely that animal models are failing to predict human responses. It is this failure that is purportedly being corrected via systematic reviews. We then examine the assumption that animal models can predict human outcomes to perturbations such as disease or drugs, even under the best of circumstances. We examine the use of animal models in light of empirical evidence comparing human outcomes to those from animal models, complexity theory, and evolutionary biology. We conclude that even if legitimate criticisms of animal models were addressed, through standardization of protocols and systematic reviews, the animal model would still fail as a predictive modality for human response to drugs and disease. Therefore, systematic reviews and meta-analyses of animal-based research are poor tools for attempting to reach conclusions regarding human interventions.