Pathology Principles and Practices for Analysis of Animal Models

Working with Miraculous Mice: Mus musculus as a Model Organism

The laboratory mouse has been described as a "miracle" model organism, providing a window by which we may gain an understanding of ourselves. Since the first recorded mouse experiment in 1664, the mouse has become the most used animal model in biomedical research. Mice are ideally suited as a model organism because of their small size, short gestation period, large litter size, and genetic similarity to humans. This article provides a broad overview of the laboratory mouse as a model organism and is intended for undergraduates and those new to working with mice. We delve into the history of the laboratory mouse and outline important terminology to accurately describe research mice. The types of laboratory mice available to researchers are reviewed, including outbred stocks, inbred strains, immunocompromised mice, and genetically engineered mice. The critical role mice have played in advancing knowledge in the areas of oncology, immunology, and pharmacology is highlighted by examining the significant contribution of mice to Nobel Prize winning research. International mouse mutagenesis programs and accurate phenotyping of mouse models are outlined. We also explain important considerations for working with mice, including animal ethics; the welfare principles of replacement, refinement, and reduction; and the choice of mouse model in experimental design. Finally, we present practical advice for maintaining a mouse colony, which involves adequate training of staff, the logistics of mouse housing, monitoring colony health, and breeding strategies. Useful resources for working with mice are also listed. The aim of this overview is to equip the reader with a broad appreciation of the enormous potential and some of the complexities of working with the laboratory mouse in a quest to improve human health. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC.

Pilot study to evaluate isolation by size of circulating tumour cells in canine oral melanoma

Liquid biopsy for circulating tumour cell (CTC) detection is generally unexplored in veterinary medicine. Dogs with highly aggressive and heterogeneous tumours, such as oral malignant melanoma (OMM), could benefit from studies involving size-based isolation methods for CTCs, as they do not depend on specific antibodies. This pilot study aimed to detect CTCs from canine OMM using Isolation by Size of Epithelial Tumor Cells (ISET), a microfiltration methodology, followed by immunocytochemistry (ICC) with Melan-A, PNL2, and S100 antibodies. Ten canine patients diagnosed by histopathology and confirmed as OMM by immunohistochemistry were enrolled, their prognostic data was assessed, and blood samples were collected for CTC analysis. Results have shown the detection of intact cells in 9/10 patients. ICC has shown 3/9 Melan-A-positive, 3/9 PNL2-positive, and 8/9 S100-positive patients, confirming the importance of opting for a multimarker assay. A significant number of negative-stained CTCs were found, suggesting their high heterogeneity in circulation. Microemboli stained with either PNL2 or S100 were found in a patient with a high isolated cell count and advanced clinical stage. Preliminary statistical analysis shows a significant difference in CTC count between patients with and without lymph node metastasis (p < .05), which may correlate with tumour metastatic potential. However, we recommend further studies with more extensive sampling to confirm this result. This pilot study is the first report of intact CTC detection in canine OMM and the first application of ISET in veterinary medicine, opening new possibilities for liquid biopsy studies in canine OMM and other tumours.

Ferrets as Models for Viral Respiratory Disease

Domestic ferrets (Mustela putorius furo) have been used in biomedical research to study influenza viruses since the early 20th century. Ferrets have continued to gain importance for the study of viral respiratory disease due to their disease susceptibility and anatomic similarities to humans. Here we review features of ferret biology and management that should be considered when planning to work with this species, particularly in models of respiratory disease. We specifically discuss biosafety and husbandry, clinical and pathologic assessments, and anesthetic considerations for ferrets with respiratory disease and systemic illness. These considerations are important for animal welfare, fidelity of the model to human disease, and ensuring accuracy and reproducibility of acquired data. Finally, we briefly review the use of ferrets to study respiratory diseases by discussing their respiratory anatomy and 2 frequently studied viral respiratory diseases, influenza and coronavirus disease 2019 (COVID-19).

Implementing Digital Pathology into Veterinary Academics and Research

The advantages of digital pathology (DP) have been recognized as early as 1963, but only within the last decade or so have the advancements of slide scanners and viewing software made the use and implementation of DP feasible in the classroom and in research. Several factors must be considered prior to undertaking the project of implementing the DP workflow in any setting, but particularly in an academic environment. Sustained and open dialogue with information technology (IT) is critical to the success of this enterprise. In addition to IT, there is a multitude of criteria to consider when determining the best hardware and software to purchase to support the project. The goals and limitations of the laboratory and the requirements of its users (students, instructors, and researchers) will ultimately direct these decisions. The objectives of this article are to provide an overview of the opportunities and challenges associated with the integration of DP in education and research, to highlight some important IT considerations, and to discuss some of the requirements and functionalities of some hardware and software options.

Factors Limiting the Translatability of Rodent Model-Based Intranasal Vaccine Research to Humans

The intranasal route of vaccination presents an attractive alternative to parenteral routes and offers numerous advantages, such as the induction of both mucosal and systemic immunity, needle-free delivery, and increased patient compliance. Despite demonstrating promising results in preclinical studies, however, few intranasal vaccine candidates progress beyond early clinical trials. This discrepancy likely stems in part from the limited predictive value of rodent models, which are used frequently in intranasal vaccine research. In this review, we explored the factors that limit the translatability of rodent-based intranasal vaccine research to humans, focusing on the differences in anatomy, immunology, and disease pathology between rodents and humans. We also discussed approaches that minimize these differences and examined alternative animal models that would produce more clinically relevant research.

Reduced SARS-CoV-2 disease outcomes in Syrian hamsters receiving immune sera: Quantitative image analysis in pathologic assessments

There is a need to standardize pathologic endpoints in animal models of SARS-CoV-2 infection to help benchmark study quality, improve cross-institutional comparison of data, and assess therapeutic efficacy so that potential drugs and vaccines for SARS-CoV-2 can rapidly advance. The Syrian hamster model is a tractable small animal model for COVID-19 that models clinical disease in humans. Using the hamster model, the authors used traditional pathologic assessment with quantitative image analysis to assess disease outcomes in hamsters administered polyclonal immune sera from previously challenged rhesus macaques. The authors then used quantitative image analysis to assess pathologic endpoints across studies performed at different institutions using different tissue processing protocols. The authors detail pathological features of SARS-CoV-2 infection longitudinally and use immunohistochemistry to quantify myeloid cells and T lymphocyte infiltrates during SARS-CoV-2 infection. High-dose immune sera protected hamsters from weight loss and diminished viral replication in tissues and reduced lung lesions. Cumulative pathology scoring correlated with weight loss and was robust in distinguishing IgG efficacy. In formalin-infused lungs, quantitative measurement of percent area affected also correlated with weight loss but was less robust in non-formalin-infused lungs. Longitudinal immunohistochemical assessment of interstitial macrophage infiltrates showed that peak infiltration corresponded to weight loss, yet quantitative assessment of macrophage, neutrophil, and CD3+ T lymphocyte numbers did not distinguish IgG treatment effects. Here, the authors show that quantitative image analysis was a useful adjunct tool for assessing SARS-CoV-2 treatment outcomes in the hamster model.

The Antioxidant Properties of Alfalfa (Medicago sativa L.) and Its Biochemical, Antioxidant, Anti-Inflammatory, and Pathological Effects on Nicotine-Induced Oxidative Stress in the Rat Liver

Medicago sativa Linn or alfalfa is a tonic plant rich in proteins, vitamins, and minerals that is used to treat many diseases due to its pharmacological properties such as anti-inflammatory and antioxidant activities. So, the aim of this study was to evaluate the efficacy of alfalfa methanolic extract (AME) on the prevention of liver damage caused by nicotine. The total phenols, flavonoids levels, and the free radical scavenging activity of its extract (IC50) were measured. In this study, 30 Wistar rats were randomly divided into 5 groups as control (untreated), N (nicotine only), T1, T2, and T3 (nicotine + AME 100, 250, and 500 mg/kg/day, respectively). AME (orally) and nicotine (intraperitoneal injection, 0.5 mg/kg/day) were then administered for 21 days. Weight gain, the liver-to-body weight ratio, liver functional enzymes, and the lipid profile were measured. Moreover, we evaluated oxidative stress, proinflammatory parameters, and histopathological changes in the liver. Total phenols, flavonoids, and IC50 were determined as $51.68\pm 0.62$  mg GAE/g, $18.55\pm 1.01$  mg QE/g, and $350.91\pm 16.46$  μg/ml, respectively. Nicotine changed the measured parameters to abnormal. AME increased weight gain, the liver-to-body weight ratio, and enzymatic antioxidant levels and decreased malondialdehyde, liver functional enzymes, and proinflammatory cytokine levels. The lipid profile and histopathological changes have also been improved by AME in a dose-dependent manner. The results showed that AME in a dose-dependent manner by improving the inflammation and oxidative damage could improve the liver damage caused by nicotine.

The Ideal Time for Iron Administration in Anemia Secondary to Blood Loss-An Experimental Animal Model

BACKGROUND

Anemia and iron deficiency are two of the main public health problems worldwide, associated with negative outcomes in surgical patients. This experimental study aimed to create a model of acute iron deficiency with anemia through blood loss and extensive surgery. Afterwards, intravenous iron was administered to correct the iron deficiency and to improve the hematological parameters in distinct moments regarding the surgical time. To assess the optimum time for therapeutic intervention, experimental subjects were compared, performing clinical, paraclinical, and histological examinations, as well.

METHODS

Male rats (n = 35), aged 11-13 months, were randomly designated into six groups. Anemia and iron deficiency were obtained through a 15% blood volume loss, followed by major surgical intervention (femur fracture and osteosynthesis using Kirschner wire). Therapeutic intervention was obtained with an intravenous ferric carboxymaltose infusion, as follows: group II: intraoperative (n = 7), group III: 48 h after surgery (n = 7), group IV: 48 h before surgery (n = 5), and group V: seven days before surgery (n = 6). Group I (n = 5) was left anemic, while group 0 (n = 5) was nonanemic without therapeutic intervention.

RESULTS AND DISCUSSION

In group I, serum iron lower than in group 0 (27.04 ± 6.92 μg/dL versus 60.5 ± 2.34 μg/dL), as well as hemoglobin (10.4 ± 0.54 g/dL versus 14.32 ± 2.01 g/dL) and ferritin values (22.52 ± 0.53 ng/mL versus 29.86 ± 3.97 ng/mL), validated the experimental model. Regarding wound healing after surgical trauma, we observed that neovascularization was more significant in group III, followed by group V, with fewer neutrophils, a well-represented and rich in lymphomonocytes inflammatory infiltrate associated with the biggest collagen fiber dimensions. The periosteal reaction and callus area presented thicker trabeculae in groups II and III compared to the anemic group.

CONCLUSIONS

This original experimental study assessed the effect of perioperative intravenous iron administration at a specific time by comparing the weight, hematological, and iron status-defining parameters, as well as histological characteristics of the included subjects. The present findings highlight that correcting the iron deficiency in emergency settings through intravenous iron administration intraoperatively or 48 h postoperatively could determine the improved bioumoral parameters, as well as a better evolution of the postoperative wound and bone healing compared to the anemic group or subjects that received therapeutic intervention 48 h before surgery.

Biopharmaceutics 4.0, Advanced Pre-Clinical Development of mRNA-Encoded Monoclonal Antibodies to Immunosuppressed Murine Models

Administration of mRNA against SARS-CoV-2 has demonstrated sufficient efficacy, tolerability and clinical potential to disrupt the vaccination field. A multiple-arm, cohort randomized, mixed blind, placebo-controlled study was designed to investigate the in vivo expression of mRNA antibodies to immunosuppressed murine models to conduct efficacy, safety and bioavailability evaluation. Enabling 4.0 tools we reduced animal sacrifice, while interventions were designed compliant to HARRP and SPIRIT engagement: (a) Randomization, blinding; (b) pharmaceutical grade formulation, monitoring; (c) biochemical and histological analysis; and (d) theoretic, statistical analysis. Risk assessment molded the study orientations, according to the ARRIVE guidelines. The primary target of this protocol is the validation of the research hypothesis that autologous translation of Trastuzumab by in vitro transcribed mRNA-encoded antibodies to immunosuppressed animal models, is non-inferior to classical treatments. The secondary target is the comparative pharmacokinetic assessment of the novel scheme, between immunodeficient and healthy subjects. Herein, the debut clinical protocol, investigating the pharmacokinetic/pharmacodynamic impact of mRNA vaccination to immunodeficient organisms. Our design, contributes novel methodology to guide the preclinical development of RNA antibody modalities by resolving efficacy, tolerability and dose regime adjustment for special populations that are incapable of humoral defense.

Challenges and Opportunities for the Veterinary Pathologist in Biomedical Research

Animal models have critical roles in biomedical research in promoting understanding of human disease and facilitating development of new therapies and diagnostic techniques to improve human and animal health. In the study of myriad human conditions, each model requires in-depth characterization of its assets and limitations in order for it to be used to greatest advantage. Veterinary pathology expertise is critical in understanding the relevance and translational validity of animal models to conditions under study, assessing morbidity and mortality, and validating outcomes as relevant or not to the study interventions. Clear communication with investigators and education of research personnel on the use and interpretation of pathology endpoints in animal models are critical to the success of any research program. The veterinary pathologist is underutilized in biomedical research due to many factors including misconceptions about high fiscal costs, lack of perceived value, limited recognition of their expertise, and the generally low number of veterinary pathologists currently employed in biomedical research. As members of the multidisciplinary research team, veterinary pathologists have an important role to educate scientists, ensure accurate interpretation of pathology data, maximize rigor, and ensure reproducibility to provide the most reliable data for animal models in biomedical research.

Genetically Engineered Mouse Models of Liver Tumorigenesis Reveal a Wide Histological Spectrum of Neoplastic and Non-Neoplastic Liver Lesions

Genetically engineered mouse models (GEMM) are an elegant tool to study liver carcinogenesis in vivo. Newly designed mouse models need detailed (histopathological) phenotyping when described for the first time to avoid misinterpretation and misconclusions. Many chemically induced models for hepatocarcinogenesis comprise a huge variety of histologically benign and malignant neoplastic, as well as non-neoplastic, lesions. Such comprehensive categorization data for GEMM are still missing. In this study, 874 microscopically categorized liver lesions from 369 macroscopically detected liver "tumors" from five different GEMM for liver tumorigenesis were included. The histologic spectrum of diagnosis included a wide range of both benign and malignant neoplastic (approx. 82%) and non-neoplastic (approx. 18%) lesions including hyperplasia, reactive bile duct changes or oval cell proliferations with huge variations among the various models and genetic backgrounds. Our study therefore critically demonstrates that models of liver tumorigenesis can harbor a huge variety of histopathologically distinct diagnosis and, depending on the genotype, notable variations are expectable. These findings are extremely important to warrant the correct application of GEMM in liver cancer research and clearly emphasize the role of basic histopathology as still being a crucial tool in modern biomedical research.