Guidelines for planning and conducting high-quality research and testing on animals

Animal models for preventing seroma after surgery: a systematic review and meta-analysis

Novel interventions for seroma prevention are urgently needed in clinical practice. Animal models are pivotal tools for testing these interventions; however, a significant translational gap persists between clinical and animal model outcomes. This systematic review aims to assess the methodological characteristics and quality of animal models utilized for seroma prevention. A meta-analysis was performed to estimate the expected seroma incidence rate for control groups and determine the effect size of typical interventions. We systematically retrieved all studies describing animal models in which seroma formation was induced. Methodological characteristics, risks of bias, and study quality were assessed. Seroma volume and -incidence data were used for the meta-analysis. In total, 55 studies were included, with 42 eligible for meta-analysis. Rats (69%) were the most frequently used species, with mastectomy (50%) being the predominant surgical procedure in these models. Despite significant risks of bias across all studies, an improving trend in reporting quality per decade was observed. The meta-analysis revealed an average seroma incidence of 90% in typical control groups. The average intervention halved the seroma incidence (RR = 0.49; CI 0.35, 0.70) and significantly reduced seroma volume (SMD = -3.31; CI -4.21, -2.41), although notable heterogeneity was present. In conclusion, animal models for seroma prevention exhibit methodological flaws and multiple risks of bias. Implementing sufficiently powered positive and negative control groups could improve the internal validity of these models. More research is needed for further development of animal seroma models.

Contribution of mechanoreceptors to spinal cord injury-induced mechanical allodynia

ABSTRACT

Evidence from previous studies supports the concept that spinal cord injury (SCI)-induced neuropathic pain (NP) has its neural roots in the peripheral nervous system. There is uncertainty about how and to which degree mechanoreceptors contribute. Sensorimotor activation-based interventions (eg, treadmill training) have been shown to reduce NP after experimental SCI, suggesting transmission of pain-alleviating signals through mechanoreceptors. The aim of the present study was to understand the contribution of mechanoreceptors with respect to mechanical allodynia in a moderate mouse contusion SCI model. After genetic ablation of tropomyosin receptor kinase B expressing mechanoreceptors before SCI, mechanical allodynia was reduced. The identical genetic ablation after SCI did not yield any change in pain behavior. Peptidergic nociceptor sprouting into lamina III/IV below injury level as a consequence of SCI was not altered by either mechanoreceptor ablation. However, skin-nerve preparations of contusion SCI mice 7 days after injury yielded hyperexcitability in nociceptors, not in mechanoreceptors, which makes a substantial direct contribution of mechanoreceptors to NP maintenance unlikely. Complementing animal data, quantitative sensory testing in human SCI subjects indicated reduced mechanical pain thresholds, whereas the mechanical detection threshold was not altered. Taken together, early mechanoreceptor ablation modulates pain behavior, most likely through indirect mechanisms. Hyperexcitable nociceptors seem to be the main drivers of SCI-induced NP. Future studies need to focus on injury-derived factors triggering early-onset nociceptor hyperexcitability, which could serve as targets for more effective therapeutic interventions.

Levels of evidence for human system risk evaluation

NASA uses a continuous risk management process to seek out new knowledge of spaceflight-induced risk to human health and performance. The evidence base that informs the risk assessments in this domain is constantly changing as more information is gleaned from a continuous human presence in space and from ongoing research. However, the limitations of this evidence are difficult to characterize because fewer than 700 humans have ever flown in space, and information comes from a variety of sources that span disciplines, including engineering, medicine, food and nutrition, and many other life sciences. The Human System Risk Board (HSRB) at NASA is responsible for assessing risk to astronauts and communicating this risk to agency decision-makers. A critical part of that communication is conveying the uncertainty regarding the understanding of the changes that spaceflight induces in human processes and the complex interactions between humans and the spacecraft. Although the strength of evidence grades is common in the academic literature, these scores are often not useful for the problems of human spaceflight. The HSRB continues to update the processes used to report the levels of evidence. This paper describes recent updates to the methods used to assign the level of evidence scores to the official risk postures and to the causal diagrams used by the HSRB.

Novel Tumor Organoid-Based Mouse Model to Study Image Guided Radiation Therapy of Rectal Cancer After Noninvasive and Precise Endoscopic Implantation

PURPOSE

Preoperative (neoadjuvant) radiation therapy (RT) is an essential part of multimodal rectal cancer therapy. Recently, total neoadjuvant therapy (TNT), which combines simultaneous radiochemotherapy with additional courses of chemotherapy, has emerged as an effective approach. TNT achieves a pathologic complete remission in approximately 30% of resected patients, opening avenues for treatment strategies that avoid radical organ resection. Furthermore, recent studies have demonstrated that anti-programmed cell death protein 1 immunotherapy can induce clinical complete responses in patients with specific genetic alterations. There is significant potential to enhance outcomes through intensifying, personalizing, and de-escalating treatment approaches. However, the heterogeneous response rates to RT or TNT and strategies to sensitize patients without specific genetic changes to immunotherapy remain poorly understood.

METHODS AND MATERIALS

We developed a novel orthotopic mouse model of rectal cancer based on precisely defined endoscopic injections of tumor organoids that reflect tumor heterogeneity. Subsequently, we employed endoscopic- and computed tomography-guided RT and validated rectal tumor growth and response rates to therapy using small-animal magnetic resonance imaging and endoscopic follow-up.

RESULTS

Rectal tumor formation was successfully induced in all mice after 2 organoid injections. Clinically relevant RT regimens with 5 × 5 Gy significantly delayed clinical signs of tumor progression and significantly improved survival. Consistent with human disease, rectal tumor progression correlated with the development of liver and lung metastases. Notably, long-term survivors after RT showed no evidence of tumor recurrence, as demonstrated by in vivo radiologic tumor staging and histopathologic examination.

CONCLUSIONS

Our novel mouse model combines orthotopic tumor growth via noninvasive and precise rectal organoid injection and small-animal RT. This model holds significant promise for investigating the effect of tumor cell-intrinsic aspects, genetic alterations of the host, and exogenous factors (eg, nutrition or microbiota) on RT outcomes. Furthermore, it allows for the exploration of combination therapies involving chemotherapy, immunotherapy, or novel targeted therapies.

Therapeutic effect of dietary ingredients on cellular senescence in animals and humans: A systematic review

BACKGROUND

Cellular senescence has been regarded as a therapeutic target for ageing and age-related diseases. Several senotherapeutic agents have been proposed, including compounds derived from natural products which hold the translational potential to promote healthy ageing. This systematic review examined the association of dietary ingredients with cellular senescence in animals and humans, with an intent to identify dietary ingredients with senotherapeutic potential.

METHODS

This systematic review was registered at PROSPERO International prospective register of systematic reviews (Reg #: CRD42022338885). The databases PubMed and Embase were systematically searched for key terms related to cellular senescence, senescence markers, diets, nutrients and bioactive compounds. Intervention and observational studies on human and animals investigating the effects of dietary ingredients via oral administration on cellular senescence load were included. The SYRCLE's risk of bias tool and Cochrane risk of bias tool v2.0 were used to assess the risk of bias for animal and human studies respectively.

RESULTS

Out of 5707 identified articles, 83 articles consisting of 78 animal studies and 5 human studies aimed to reduce cellular senescence load using dietary ingredients. In animal studies, the most-frequently used senescence model was normative ageing (26 studies), followed by D-galactose-induced models (17 studies). Resveratrol (8 studies), vitamin E (4 studies) and soy protein isolate (3 studies) showed positive effects on reducing the level of senescence markers such as p53, p21, p16 and senescence-associated ß-galactosidase in various tissues of physiological systems. In three out of five human studies, ginsenoside Rg1 had no positive effect on reducing senescence in muscle tissues after exercise. The risk of bias for both animal and human studies was largely unclear.

CONCLUSION

Resveratrol, vitamin E and soy protein isolate are promising senotherapeutics studied in animal models. Studies testing dietary ingredients with senotherapeutic potential in humans are limited and translation is highly warranted.

Beyond compliance: harmonising research and husbandry practices to improve experimental reproducibility using fish models

Reproducibility in animal research is impacted by the environment, by husbandry practices in the laboratory and by the animals' provenance. These factors, however, are often not adequately considered by researchers. A disconnect between researchers and animal care staff can result in inappropriate housing and husbandry decisions for scientific studies with those animals. This is especially the case for the research in neuro-behaviour, epigenetics, and the impact of climate change, as heritable phenotypic, behavioural or physiological changes are known to result from the animals' environmental housing, husbandry, provenance and prior experience. This can lead to greater variation (even major differences) in data outcomes among studies, driving scientific uncertainties. Herein, we illustrate some of the endpoints measured in fish studies known to be intrinsically linked to the environment and husbandry conditions and assess the significance of housing and husbandry practice decisions for research adopting these endpoints for different fish species. We highlight the different priorities and challenges faced by researchers and animal care staff and how harmonising their activities and building greater understanding of how husbandry practices affect the fish will improve reproducibility in research outcomes. We furthermore illustrate how improving engagement between stakeholders, including regulatory bodies, can better underpin fish husbandry decisions and where researchers could help to drive best husbandry practices through their own research with fish models.

Rat Model of Isoproterenol-Induced Myocardial Injury

Isoproterenol (ISO) administration produces significant biochemical and histological changes including oxidative stress, reactive oxygen species (ROS) overproduction, and inflammation that leads to aggravation of myocardial injury. Subcutaneous or intraperitoneal ISO injection into rats can replicate several features of human heart disease, making it a useful tool for comprehending the underlying mechanisms and evaluating potential therapeutic strategies. In the present chapter, we elaborate on how depending on the precise experimental goals and the intended level of severity, different dosages and regimens are employed to induce myocardial injury.

Intermediate gray matter interneurons in the lumbar spinal cord play a critical and necessary role in coordinated locomotion

Locomotion is a complex task involving excitatory and inhibitory circuitry in spinal gray matter. While genetic knockouts examine the function of individual spinal interneuron (SpIN) subtypes, the phenotype of combined SpIN loss remains to be explored. We modified a kainic acid lesion to damage intermediate gray matter (laminae V-VIII) in the lumbar spinal enlargement (spinal L2-L4) in female rats. A thorough, tailored behavioral evaluation revealed deficits in gross hindlimb function, skilled walking, coordination, balance and gait two weeks post-injury. Using a Random Forest algorithm, we combined these behavioral assessments into a highly predictive binary classification system that strongly correlated with structural deficits in the rostro-caudal axis. Machine-learning quantification confirmed interneuronal damage to laminae V-VIII in spinal L2-L4 correlates with hindlimb dysfunction. White matter alterations and lower motoneuron loss were not observed with this KA lesion. Animals did not regain lost sensorimotor function three months after injury, indicating that natural recovery mechanisms of the spinal cord cannot compensate for loss of laminae V-VIII neurons. As gray matter damage accounts for neurological/walking dysfunction in instances of spinal cord injury affecting the cervical or lumbar enlargement, this research lays the groundwork for new neuroregenerative therapies to replace these lost neuronal pools vital to sensorimotor function.

Gastroprotective effect of Artemisia absinthium L.: A medicinal plant used in the treatment of digestive disorders

ETHNOPHARMACOLOGICAL RELEVANCE

Wormwood (Artemisia absinthium L.) is traditionally used for stomach pain and gastric relief. However, its possible gastroprotective effect has not yet been experimentally evaluated.

AIM OF THE STUDY

This study evaluated the gastroprotective effect of aqueous extracts obtained through hot and room temperature maceration of A. absinthium aerial parts in rats.

MATERIALS AND METHODS

The gastroprotective effect of hot aqueous extract (HAE) and room temperature aqueous extract (RTAE) from A. absinthium aerial parts were evaluated in rats using a model of acute gastric ulcer induced by ethanol p.a. The stomachs were collected to measure the gastric lesion area and histological and biochemical analysis. UHPLC-HRMS/MS analysis was used to determine the chemical profile of the extracts.

RESULTS

Eight main peaks in the UHPLC chromatogram were identified in both HAE and RTAE extracts: tuberonic acid glycoside (1), rupicolin (2), 2-hydroxyeupatolide (3), yangabin (4), sesartemin (5), artemetin (6), isoalantodiene (7), and dehydroartemorin (8). For RTAE, a higher diversity of sesquiterpene lactones was observed. The groups treated with RTAE at 3%, 10%, and 30% presented a gastroprotective effect, reducing the lesion area by 64.68%, 53.71%, and 90.04%, respectively, when compared with the vehicle (VEH)-treated group. On the other hand, the groups treated with HAE at 3%, 10%, and 30% presented values of lesion areas higher than those of the VEH group. Changes in the submucosa layer, inflammatory process with edema, cellular infiltration, and mucin depletion were detected in the gastric mucosa exposed to ethanol, which was fully prevented by RTAE treatment. Neither HAE nor RTAE could increase the reduced glutathione levels in the injured gastric tissue, but RTAE (30%) reduced the formation of lipid hydroperoxides. When the rats were pre-treated with NEM (a chelator of non-protein thiols) or L-NAME (non-selective nitric oxide synthase inhibitor), the RTAE lost the ability to protect the gastric mucosa.

CONCLUSIONS

This study corroborates the ethnopharmacological use of this specie to treat gastric disorders revealing the gastroprotective effect of the room-temperature aqueous extract of A. absinthium aerial parts. Its mode of action may involve the ability of the infusion to maintain the gastric mucosal barrier integrity.

Ultra-high field cardiac MRI in large animals and humans for translational cardiovascular research

A key step in translational cardiovascular research is the use of large animal models to better understand normal and abnormal physiology, to test drugs or interventions, or to perform studies which would be considered unethical in human subjects. Ultrahigh field magnetic resonance imaging (UHF-MRI) at 7 T field strength is becoming increasingly available for imaging of the heart and, when compared to clinically established field strengths, promises better image quality and image information content, more precise functional analysis, potentially new image contrasts, and as all in-vivo imaging techniques, a reduction of the number of animals per study because of the possibility to scan every animal repeatedly. We present here a solution to the dual use problem of whole-body UHF-MRI systems, which are typically installed in clinical environments, to both UHF-MRI in large animals and humans. Moreover, we provide evidence that in such a research infrastructure UHF-MRI, and ideally combined with a standard small-bore UHF-MRI system, can contribute to a variety of spatial scales in translational cardiovascular research: from cardiac organoids, Zebra fish and rodent hearts to large animal models such as pigs and humans. We present pilot data from serial CINE, late gadolinium enhancement, and susceptibility weighted UHF-MRI in a myocardial infarction model over eight weeks. In 14 pigs which were delivered from a breeding facility in a national SARS-CoV-2 hotspot, we found no infection in the incoming pigs. Human scanning using CINE and phase contrast flow measurements provided good image quality of the left and right ventricle. Agreement of functional analysis between CINE and phase contrast MRI was excellent. MRI in arrested hearts or excised vascular tissue for MRI-based histologic imaging, structural imaging of myofiber and vascular smooth muscle cell architecture using high-resolution diffusion tensor imaging, and UHF-MRI for monitoring free radicals as a surrogate for MRI of reactive oxygen species in studies of oxidative stress are demonstrated. We conclude that UHF-MRI has the potential to become an important precision imaging modality in translational cardiovascular research.

First study on microscopic and molecular detection of Acanthocheilonema reconditum and Leishmania infantum coinfection in dogs in Southwest Colombia

Background and Aim

Canine vector-borne diseases represent an important issue for the welfare and health of animals, but also have great zoonotic potential. These diseases are caused by bacteria, nematodes such as filariae, and other parasites such as Leishmania spp. Given the difficulty in differentiating common microfilariae in dogs by microscopy and serological methods, molecular techniques such as polymerase chain reaction (PCR) and sequencing should be valuable for reaching a reliable diagnosis. This study aimed to use microscopy and PCR to identify the microfilarial species in dogs from Valle del Cauca, Colombia, and a possible association with Leishmania infantum parasites.

Materials and Methods

This study was conducted on 270 dogs from Pradera and Florida municipalities. Microfilariae were detected in dogs by optical microscopy and amplification with 5.8S-ITS2-28S. Species identification was achieved through the amplification of the gene cytochrome oxidase I (COX1).

Results

Microscopic detection of microfilariae was possible in 4.81% (13/270) of the dogs. In addition, by PCR of COX1 and Sanger sequencing of ITS2, Acanthocheilonema reconditum was identified as the circulating microfilarial species in 12 dogs, coinfecting with the species L. infantum (Leishmania donovani complex).

Conclusion

To the best of our knowledge, this is the first report on A. reconditum and L. infantum mixed infection in dogs in Colombia, particularly in the Valle del Cauca.

Questionable Research Practices, Low Statistical Power, and Other Obstacles to Replicability: Why Preclinical Neuroscience Research Would Benefit from Registered Reports

Replicability, the degree to which a previous scientific finding can be repeated in a distinct set of data, has been considered an integral component of institutionalized scientific practice since its inception several hundred years ago. In the past decade, large-scale replication studies have demonstrated that replicability is far from favorable, across multiple scientific fields. Here, I evaluate this literature and describe contributing factors including the prevalence of questionable research practices (QRPs), misunderstanding of p-values, and low statistical power. I subsequently discuss how these issues manifest specifically in preclinical neuroscience research. I conclude that these problems are multifaceted and difficult to solve, relying on the actions of early and late career researchers, funding sources, academic publishers, and others. I assert that any viable solution to the problem of substandard replicability must include changing academic incentives, with adoption of registered reports being the most immediately impactful and pragmatic strategy. For animal research in particular, comprehensive reporting guidelines that document potential sources of sensitivity for experimental outcomes is an essential addition.

Animal researchers shoulder a psychological burden that animal ethics committees ought to address

Animal ethics committees (AECs) typically focus on the welfare of animals used in experiments, neglecting the potential welfare impact of that animal use on the animal laboratory personnel. Some of this work, particularly the killing of animals, can impose significant psychological burdens that can diminish the well-being of laboratory animal personnel, as well as their capacity to care for animals. We propose that AECs, which regulate animal research in part on the basis of reducing harm, can and ought to require that these harms to researchers are reduced as well. The paper starts by presenting evidence of these burdens and their harm, giving some examples showing how they may be mitigated. We then argue that AECs are well placed to account for these harms to personnel and ought to use their power to reduce their occurrence. We conclude by responding to four potential objections: (1) that this problem should be addressed through health and safety administration, not research ethics administration; (2) that the proposal is unjustifiably paternalistic; (3) that these harms to laboratory animal personnel ought to occur, given their treatment of animals; and (4) that mitigating them may lead to worse treatment of research animals.

Preregistration of animal research protocols: development and 3-year overview of preclinicaltrials.eu

Open, prospective registration of a study protocol can improve research rigour in a number of ways. Through preregistration, key features of the study’s methodology are recorded and maintained as a permanent record, enabling comparison of the completed study with what was planned. By recording the study hypothesis and planned outcomes a priori, preregistration creates transparency and can reduce the risk of several common biases, such as hypothesising after results are known and outcome switching or selective outcome reporting. Second, preregistration raises awareness of measures to reduce bias, such as randomisation and blinding. Third, preregistration provides a comprehensive listing of planned studies, which can prevent unnecessary duplication and reduce publication bias. Although commonly acknowledged and applied in clinical research since 2000, preregistration of animal studies is not yet the norm. In 2018 we launched the first dedicated, open, online register for animal study protocols: wwwpreclinicaltrialseu. Here, we provide insight in the development of preclinicaltrials.eu (PCT) and evaluate its use during the first 3 years after its launch. Furthermore, we elaborate on ongoing developments such as the rise of comparable registries, increasing support for preregistration in the Netherlands—which led to the funding of PCT by the Dutch government—and pilots of mandatory preregistration by several funding bodies. We show the international coverage of currently registered protocols but with the overall low number of (pre)registered protocols.

A Narrative Review of Experimental Models to Study Vascular Grafts Infections

Background

Many experimental models have been developed to decipher the mechanisms of vascular graft and endograft infections (VGEIs), and to elaborate strategies to prevent or treat their occurrence. A systematic literature research was conducted to identify the most accurate models for studying VGEIs, depending on the research question.

Methods

A narrative literature search was conducted using the MEDLINE and Cochrane databases, with no set limit on the date of publication, up to 10 August 2021. Ex vivo, in vitro, and in vivo animal studies on VGEIs, published in English or French, were selected. Cross references retrieved from selected articles on PubMed database were also included. Data on microorganisms and grafts studied, details of experimental models, and of graft implantation and removal in animal studies were collected.

Results

A total of 243 studies were included in the review after reading the full length articles: 55 in vitro studies, 169 animal studies, 17 studies which used both in vitro and animal models, and two ex vivo studies. Many differences in model characteristics were seen. The main in vitro model was the incubation of a graft sample in a bacterial solution, used to study the first steps of infection. In animals, vascular large animal models (dogs and pigs) were the most commonly described but supplanted over time by extravascular and particularly subcutaneous mouse and rat models, which have been reported increasingly over the last few years. In animal models, antibiotic prophylaxis and therapy were rarely administered (27.4% and 19.9%, respectively), and vascular reconstruction after VGEIs even less frequently (9.8%).

Conclusion

Despite protocol discrepancies, it was possible to dinstinguish three main experimental models (i.e., in vitro and in vivo vascular models, and extravascular models), which all remain of interest to study specific phases of VGEIs.

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Experimental models of vascular (endo)graft infections (VGEIs) can be split into in vitro, extravascular, and vascular ones.

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Each of these three groups can help answer specific questions on VGEIs.

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To improve reproducibility, future experimental studies require standardisation.

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Experimental studies should reproduce real life conditions as accurately as possible.

Role of Environment and Experimenter in Reproducibility of Behavioral Studies With Laboratory Mice

Behavioral phenotyping of mice has received a great deal of attention during the past three decades. However, there is still a pressing need to understand the variability caused by environmental and biological factors, human interference, and poorly standardized experimental protocols. The inconsistency of results is often attributed to the inter-individual difference between the experimenters and environmental conditions. The present work aims to dissect the combined influence of the experimenter and the environment on the detection of behavioral traits in two inbred strains most commonly used in behavioral genetics due to their contrasting phenotypes, the C57BL/6J and DBA/2J mice. To this purpose, the elevated O-maze, the open field with object, the accelerating rotarod and the Barnes maze tests were performed by two experimenters in two diverse laboratory environments. Our findings confirm the well-characterized behavioral differences between these strains in exploratory behavior, motor performance, learning and memory. Moreover, the results demonstrate how the experimenter and the environment influence the behavioral tests with a variable-dependent effect, often with mutually exclusive contributions. In this context, our study highlights how both the experimenter and the environment can have an impact on the strain effect size without altering the direction of the conclusions. Importantly, the general agreement on the results is reached by converging evidence from multiple measures addressing the same trait. In conclusion, the present work elucidates the contribution of both the experimenter and the laboratory environment in the intricate field of reproducibility in mouse behavioral phenotyping.

The 'R' principles in laboratory animal experiments

Since the Three Rs of replacement, reduction and refinement was proposed by Russel and Birch in 1959, researchers have a moral duty to minimize harm to animals. Even though animal experiments are performed by the Three Rs concept, animal researches which do not comply with international rules and standards are not accepted as well. As animal welfare has been important global issues, the methods to assess animal welfare compromise and distress have been proposed. Humanity is accepted as the goal of the Three Rs, however, another fourth R, ‘Refusal’ of fruitless protocol or ‘Responsibility’ for the experimental animal and social, scientific status of the animal experiments has been proposed. After establishing goals of animal research in a respective society, reliable knowledge can be obtained while improving laboratory animal welfare.

Innovative Human Three-Dimensional Tissue-Engineered Models as an Alternative to Animal Testing

Animal testing has long been used in science to study complex biological phenomena that cannot be investigated using two-dimensional cell cultures in plastic dishes. With time, it appeared that more differences could exist between animal models and even more when translated to human patients. Innovative models became essential to develop more accurate knowledge. Tissue engineering provides some of those models, but it mostly relies on the use of prefabricated scaffolds on which cells are seeded. The self-assembly protocol has recently produced organ-specific human-derived three-dimensional models without the need for exogenous material. This strategy will help to achieve the 3R principles.