Use of Humanized Mice to Study the Pathogenesis of Autoimmune and Inflammatory Diseases

Animal models of lupus nephritis: the past, present and a future outlook

Lupus nephritis (LN) is the most severe end-organ pathology in Systemic Lupus Erythematosus (SLE). Research has enhanced our understanding of immune effectors and inflammatory pathways in LN. However, even with the best available therapy, the rate of complete remission for proliferative LN remains below 50%. A deeper understanding of the resistance or susceptibility of renal cells to injury during the progression of SLE is critical for identifying new targets and developing effective long-term therapies. The complex and heterogeneous nature of LN, combined with the limitations of clinical research, make it challenging to investigate the aetiology of this disease directly in patients. Hence, multiple murine models resembling SLE-driven nephritis are utilised to dissect LN's cellular and genetic mechanisms, identify therapeutic targets, and screen novel compounds. This review discusses commonly used spontaneous and inducible mouse models that have provided insights into pathogenic mechanisms and long-term maintenance therapies in LN.

In vivo development of immune tissue in human intestinal organoids transplanted into humanized mice

Human intestinal organoids (HIOs) derived from pluripotent stem cells provide a valuable model for investigating human intestinal organogenesis and physiology, but they lack the immune components required to fully recapitulate the complexity of human intestinal biology and diseases. To address this issue and to begin to decipher human intestinal-immune crosstalk during development, we generated HIOs containing immune cells by transplanting HIOs under the kidney capsule of mice with a humanized immune system. We found that human immune cells temporally migrate to the mucosa and form cellular aggregates that resemble human intestinal lymphoid follicles. Moreover, after microbial exposure, epithelial microfold cells are increased in number, leading to immune cell activation determined by the secretion of IgA antibodies in the HIO lumen. This in vivo HIO system with human immune cells provides a framework for future studies on infection- or allergen-driven intestinal diseases.

Humanized mouse models for immuno-oncology research

Immunotherapy has emerged as a promising treatment paradigm for many malignancies and is transforming the drug development landscape. Although immunotherapeutic agents have demonstrated clinical efficacy, they are associated with variable clinical responses, and substantial gaps remain in our understanding of their mechanisms of action and specific biomarkers of response. Currently, the number of preclinical models that faithfully recapitulate interactions between the human immune system and tumours and enable evaluation of human-specific immunotherapies in vivo is limited. Humanized mice, a term that refers to immunodeficient mice co-engrafted with human tumours and immune components, provide several advantages for immuno-oncology research. In this Review, we discuss the benefits and challenges of the currently available humanized mice, including specific interactions between engrafted human tumours and immune components, the development and survival of human innate immune populations in these mice, and approaches to study mice engrafted with matched patient tumours and immune cells. We highlight the latest advances in the generation of humanized mouse models, with the aim of providing a guide for their application to immuno-oncology studies with potential for clinical translation.

Targeted suppression of Dpt-specific B cells in humanized Rag2- γc- mouse model of HDM allergy

Der p 1 is one of the major allergenic molecules of Dermatophagoides pteronyssinus, causing house dust mite (HDM) allergy. The pathological B cells produce allergen-specific IgE antibodies that mediate the hypersensitivity reaction, therefore the selective elimination of these B cells is a legitimate therapeutic goal in allergy. Chimeric molecule Dp51-72 able to cross-link B cell inhibitory complement receptor type 1 and BCR on Der p 1-specific B cells was constructed. The signalling capabilities of this molecule have been tested on human B cells. A humanized mouse model of HDM allergy has been used to test the in vivo effects of the chimeric molecule administration. Administering the chimeric molecule to immunodeficient Rag2- γc- mice transferred with PBMCs from allergic patients resulted in reduction of allergen-specific IgE antibodies in the sera, and reduced infiltration of immune cells in lung histology preparations. Reduced numbers of human CD45⁺ and CD4⁺ cells in the lungs as well as inhibition of mast cell degranulation were also observed. The treatment with Dp51-72 chimera significantly decreased the local levels of anti-Dpt IgE antibodies in the bronchoalveolar lavage fluid (BALF). The binding of the chimeric molecule to tonsillar B cells triggers the tyrosine phosphorylation of 30-32 kDa protein, which is most likely involved in the inhibitory process. Administration of constructed chimeric molecules to humanized mice with developed inflammation resulted in specific suppression of disease-associated IgE antibody-producing cells and preserved lung histology. This effective approach could be further developed into a therapeutic agent for treatment of patients with HDM allergy.

An improved cell line-derived xenograft humanized mouse model for evaluation of PD-1/PD-L1 blocker BMS202-induced immune responses in colorectal cancer

The establishment of an in vivo mouse model mimicking human tumor-immune environments provides a promising platform for immunotherapy assessment, drug discovery and clinical decision guidance. To this end, we construct humanized NCG mice by transplanting human hCD34 ⁺ hematopoietic progenitors into non-obese diabetic (NOD) Cg- Prkdc ^scidIL2rg ^tm1Wjl /Sz (null; NCG) mice and monitoring the development of human hematopoietic and immune systems (Hu-NCG). The cell line-derived xenograft (CDX) Hu-NCG mouse models are set up to assess the outcome of immunotherapy mediated by the small molecule BMS202. As a PD-1/PD-L1 blocker, BMS202 shows satisfactory antitumour efficacy in the HCT116 and SW480 xenograft Hu-NCG mouse models. Mechanistically, BMS202 exerts antitumour efficacy by improving the tumor microenvironment and enhancing the infiltration of hCD8 ⁺ T cells and the release of hIFNγ in tumor tissue. Thus, tumor-bearing Hu-NCG mice are a suitable and important in vivo model for preclinical study, particularly in cancer immunotherapy.

Mice with humanized immune system as novel models to study HIV-associated pulmonary hypertension

People living with HIV and who receive antiretroviral therapy have a significantly improved lifespan, compared to the early days without therapy. Unfortunately, persisting viral replication in the lungs sustains chronic inflammation, which may cause pulmonary vascular dysfunction and ultimate life-threatening Pulmonary Hypertension (PH). The mechanisms involved in the progression of HIV and PH remain unclear. The study of HIV-PH is limited due to the lack of tractable animal models that recapitulate infection and pathobiological aspects of PH. On one hand, mice with humanized immune systems (hu-mice) are highly relevant to HIV research but their suitability for HIV-PH research deserves investigation. On another hand, the Hypoxia-Sugen is a well-established model for experimental PH that combines hypoxia with the VEGF antagonist SU5416. To test the suitability of hu-mice, we combined HIV with either SU5416 or hypoxia. Using right heart catheterization, we found that combining HIV+SU5416 exacerbated PH. HIV infection increases human pro-inflammatory cytokines in the lungs, compared to uninfected mice. Histopathological examinations showed pulmonary vascular inflammation with arterial muscularization in HIV-PH. We also found an increase in endothelial-monocyte activating polypeptide II (EMAP II) when combining HIV+SU5416. Therefore, combinations of HIV with SU5416 or hypoxia recapitulate PH in hu-mice, creating well-suited models for infectious mechanistic pulmonary vascular research in small animals.

Leveraging whole blood based functional flow cytometry assays to open new perspectives for rheumatoid arthritis translational research

Despite introduction of biological disease modifying anti-rheumatic drugs (DMARDs) for Rheumatoid arthritis (RA) treatment, therapeutic strategies do not always lead to disease control and remission. Hence, a more efficient patient stratification and monitoring biomarkers and tools are needed to enable a more personalized medicine. We used a whole blood based functional flow cytometry assay to characterize immune cells from RA patients (treated or not), healthy donors and psoriatic arthritis (PsA) patients according to their responses to LPS and/or anti-TNFα (infliximab, IFX). Activation marker expression was measured using a 10-color flow cytometry panel following a no-wash protocol. Naïve-to-treatment RA patients had a stronger inflammatory profile in comparison to healthy donors at basal level. Higher expression of activation markers (CD69 and/or CD11b) on NK, B cells and granulocytes and lower expression of the adhesion molecule CD62L were measured on monocytes, granulocytes and B cells. After LPS, naïve RA patients' cells were less capable of regulating CD69, CD11b, CD16 or CD62L showing impaired activation capabilities. Upon LPS and IFX co-incubation, hierarchical clustering analysis showed different profiles between cohorts. We believe that this whole blood-based approach should further be assessed for RA patient characterization as it provides new perspectives for stratification and/or monitoring.

Animal Models for Autoimmune Hepatitis: Are Current Models Good Enough?

Autoimmune liver diseases like autoimmune hepatitis, primary biliary cholangitis, primary sclerosing cholangitis, and IgG4-related cholangitis are chronic inflammatory diseases of the liver with an autoimmune background. The therapy of autoimmune hepatitis targets the autoreactive immune system and is largely dependent on the use of glucocorticoids and cytostatic drugs. In contrast, the treatment of cholestatic autoimmune liver diseases is restricted to the use of secondary or semi-synthetic bile acids, like ursodeoxycholic acid or obeticholic acid. Although the management of the disease using such drugs works well for the majority of patients, many individuals do not respond to standard therapy. In addition, chronic treatment with glucocorticoids results in well-known side effects. Further, the use of bile acids is a symptomatic therapy that has no direct immunomodulatory effect. Thus, there is still a lot of room for improvement. The use of animal models has facilitated to elucidate the pathogenesis of autoimmune liver diseases and many potential target structures for immunomodulatory therapies have been identified. In this review, we will focus on autoimmune hepatitis for which the first animal models have been established five decades ago, but still a precise treatment for autoimmune hepatitis, as obtainable for other autoimmune diseases such as rheumatoid arthritis or multiple sclerosis has yet to be introduced. Thus, the question arises if our animal models are too far from the patient reality and thus findings from the models cannot be reliably translated to the patient. Several factors might be involved in this discrepancy. There is first and foremost the genetic background and the inbred status of the animals that is different from human patients. Here the use of humanized animals, such as transgenic mice, might reduce some of the differences. However, there are other factors, such as housing conditions, nutrition, and the microbiome that might also play an important role. This review will predominantly focus on the current status of animal models for autoimmune hepatitis and the possible ways to overcome discrepancies between model and patient.

Preclinical Models to Evaluate the Human Response to Autoantigen and Antigen-Specific Immunotherapy in Human Type 1 Diabetes

Type 1 Diabetes (T1D) is an autoimmune disease that results from the destruction of pancreatic islet β-cells by auto-reactive T cells. The clinical management of T1D faces the lack of fully predictive biomarkers in its preclinical stage and of antigen-specific therapies to induce or re-induce immune tolerance to β-cell autoantigens and prevent its development. From a therapeutic standpoint, preclinical models of T1D have fallen short of directly translating into humans. To circumvent this limitation, preclinical models are being optimized to allow defining autoantigen epitopes that are presented to T cells and directly apply to the human. In this review, we propose to make a point on the latest available models such as humanized immunodeficient NOD mice models and HLA and autoantigen transgenic mice and their application in the context of T1D.

Murine models for studying immunopathogenesis in gastrointestinal lesions: How to go about it

Gastro-intestinal (GI) lesions are common outcome to diverse etiological agents affecting the GI tract. It requires significant expertise to accurately diagnose the fundamental cause and treat accordingly. A better understanding of the immunological underpinning of these lesions is of great importance to ensure their successful management. Availability of specific animal models allows us to understand the subtle differences among diverse disease conditions and help decide upon the treatment trajectories. Since murine models are best suited for studying the immunopathogenesis of any disease, we will restrict our discussions here to the available murine models and their applications to study gastrointestinal lesions. In this review, we have systematically examined and compared the variety of mice models that are routinely used to study Inflammatory Bowel disease (IBD) and also how they can be leveraged to address specific questions relating to IBD.

Comparison of Genetically Engineered Immunodeficient Animal Models for Nonclinical Testing of Stem Cell Therapies

For the recovery or replacement of dysfunctional cells and tissue—the goal of stem cell research—successful engraftment of transplanted cells and tissues are essential events. The event is largely dependent on the immune rejection of the recipient; therefore, the immunogenic evaluation of candidate cells or tissues in immunodeficient animals is important. Understanding the immunodeficient system can provide insights into the generation and use of immunodeficient animal models, presenting a unique system to explore the capabilities of the innate immune system. In this review, we summarize various immunodeficient animal model systems with different target genes as valuable tools for biomedical research. There have been numerous immunodeficient models developed by different gene defects, resulting in many different features in phenotype. More important, mice, rats, and other large animals exhibit very different immunological and physiological features in tissue and organs, including genetic background and a representation of human disease conditions. Therefore, the findings from this review may guide researchers to select the most appropriate immunodeficient strain, target gene, and animal species based on the research type, mutant gene effects, and similarity to human immunological features for stem cell research.

Targeted knockdown of Kv1.3 channels in T lymphocytes corrects the disease manifestations associated with systemic lupus erythematosus

Lupus nephritis (LN) is an autoimmune disease with substantial morbidity/mortality and limited efficacy of available therapies. Memory T (Tm) lymphocytes infiltrate LN kidneys, contributing to organ damage. Analysis of LN, diabetic nephropathy, and healthy donor kidney biopsies revealed high infiltration of active CD8⁺ Tm cells expressing high voltage-dependent Kv1.3 potassium channels-key T cell function regulators-in LN. Nanoparticles that selectively down-regulate Kv1.3 in Tm cells (Kv1.3-NPs) reduced CD40L and interferon-γ (IFNγ) in Tm cells from LN patients in vitro. Kv1.3-NPs were tested in humanized LN mice obtained by engrafting peripheral blood mononuclear cells (PBMCs) from LN patients into immune-deficient mice. LN mice exhibited features of the disease: increased IFNγ and CD3⁺CD8⁺ T cell renal infiltration, and reduced survival versus healthy donor PBMC engrafted mice. Kv1.3-NP treatment of patient PBMCs before engraftment decreased CD40L/IFNγ and prolonged survival of LN mice. These data show the potential benefits of targeting Kv1.3 in LN.

Human CD34+ Hematopoietic Stem Cell-Engrafted NSG Mice: Morphological and Immunophenotypic Features

Immunodeficient mice engrafted with human immune cells represent an innovative tool to improve translatability of animal models for the study of human diseases. Immunophenotyping in these mice focuses on engraftment rates and cellular differentiation in blood and secondary lymphoid organs, and is predominantly carried out by FACS (fluorescent activated cell sorting) analysis; information on the morphological aspects of engraftment and the prevalence of histologic lesions is limited. We histologically examined 3- to 6-month-old NSG mice, naïve or engrafted with CD34⁺ human hemopoietic stem cells (HSC), and employed a quantitative immunohistochemical approach to identify human and murine cell compartments, comparing the results with the FACS data. NSG mice mainly exhibited incidental findings in lungs, kidneys, testes, and adrenal glands. A 6-month-old NSG mouse had a mediastinal lymphoblastic lymphoma. The lymphoid organs of NSG mice lacked typical lymphoid tissue architecture but frequently exhibited small periarteriolar leukocyte clusters in the spleen. Mice engrafted with human HSC frequently showed nephropathy, ovarian atrophy, cataract, and abnormal retinal development, lesions considered secondary to irradiation. In addition, 20% exhibited multisystemic granulomatous inflammatory infiltrates, dominated by human macrophages and T cells, leading to the observed 7% mortality and morbidity. Immunophenotypic data revealed variable repopulation of lymphoid organs with hCD45⁺ human cells, which did not always parallel the engraftment levels measured via FACS. The study describes the most common pathological features in young NSG mice after human HSC engraftment. As some of these lesions contribute to morbidity, morphological assessment of the engraftment at tissue level might help improve immunophenotypic evaluations of this animal model.

Rejection of xenogeneic porcine islets in humanized mice is characterized by graft-infiltrating Th17 cells and activated B cells

Xenogeneic porcine islet transplantation is a promising potential therapy for type 1 diabetes (T1D). Understanding human immune responses against porcine islets is crucial for the design of optimal immunomodulatory regimens for effective control of xenogeneic rejection of porcine islets in humans. Humanized mice are a valuable tool for studying human immune responses and therefore present an attractive alternative to human subject research. Here, by using a pig-to-humanized mouse model of xenogeneic islet transplantation, we described the human immune response to transplanted porcine islets, a process characterized by dense islet xenograft infiltration of human CD45⁺ cells comprising activated human B cells, CD4⁺ CD44⁺ IL-17⁺ Th17 cells, and CD68⁺ macrophages. In addition, we tested an experimental immunomodulatory regimen in promoting long-term islet xenograft survival, a triple therapy consisting of donor splenocytes treated with ethylcarbodiimide (ECDI-SP), and peri-transplant rituximab and rapamycin. We observed that the triple therapy effectively inhibited graft infiltration of T and B cells as well as macrophages, promoted transitional B cells both in the periphery and in the islet xenografts, and provided a superior islet xenograft protection. Our study therefore indicates an advantage of donor ECDI-SP treatment in controlling human immune cells in promoting long-term islet xenograft survival.

Recent updates on the basic mechanisms and pathogenesis of inflammatory bowel diseases in experimental animal models

The specific pathogenesis underlining inflammatory bowel disease (IBD) is very complicated, and it is further more difficult to clearly explain the pathophysiology of 2 major forms of IBD, Crohn’s disease (CD) and ulcerative colitis (UC), and both disorders affect individuals throughout life. Despite every extensive effort, the interplay among genetic factors, immunological factors, environmental factors and intestinal microbes is still completely unrevealed. Animal models are indispensable to find out mechanistic details that will facilitate better preclinical setting to target specific components involved in the pathogenesis of IBD. Based on many recent reports, dysbiosis of the commensal microbiota is implicated in the pathogenesis of several diseases, not only IBD but also colon cancer, obesity, psoriasis as well as allergic disorders, in both human and animal models. Advanced technologies including cell-specific and inducible knockout systems, which are recently employed to mouse IBD models, have further enhanced the ability of developing new therapeutic strategies for IBD. Furthermore, data from these mouse models highlight the critical involvement of dysregulated immune responses and impaired colonic epithelial defense system in the pathogenesis of IBD. In this review, we will explain from the history of animal models of IBD to the recent reports of the latest compounds, therapeutic strategies, and approaches tested on IBD animal models.

A humanized mouse model to study mast cells mediated cutaneous adverse drug reactions

Recently a G‐protein‐coupled receptor, MAS Related GPR Family Member X2 (MRGPRX2), was identified as a specific receptor on human mast cells responsible for IgE independent adverse drug reactions (ADR). Although a murine homologue, Mrgprb2, has been identified for this receptor, its affinity for many ADR‐causing drugs is poor making it difficult to undertake in vivo studies to examine mechanisms of ADR and to develop therapeutic strategies. Here, we have created humanized mice capable of generating MRGPRX2‐expressing human MCs allowing for the study of MRGPRX2 MCs‐mediated ADR in vitro as well as in vivo. Humanized mice were generated by hydrodynamic‐injection of plasmids expressing human GM‐CSF and IL‐3 into NOD‐scid IL2R‐γ^−/− strain of mice that had been transplanted with human hematopoietic stem cells. These GM/IL‐3 humice expressed high numbers of tissue human MCs but the MRGPRX2 receptor expressed in MCs were limited to few body sites including the skin. Importantly, large numbers of MRGPRX2‐expressing human MCs could be cultured from the bone marrow of GM/IL‐3 humice revealing these mice to be an important source of human MCs for in vitro studies of MRGPRX2‐related MCs activities. When GM/IL‐3 humice were exposed to known ADR causing contrast agents (meglumine and gadobutrol), the humice were found to experience anaphylaxis analogous to the clinical situation. Thus, GM/IL‐3 humice represent a valuable model for investigating in vivo interactions of ADR‐causing drugs and human MCs and their sequelae, and these mice are also a source of human MRGPRX2‐expressing MCs for in vitro studies.

Recent Advancements and Applications of Human Immune System Mice in Preclinical Immuno-Oncology

Significant advances in immunotherapies have resulted in the increasing need of predictive preclinical models to improve immunotherapeutic drug development, treatment combination, and to prevent or minimize toxicity in clinical trials. Immunodeficient mice reconstituted with human immune system (HIS), termed humanized mice or HIS mice, permit detailed analysis of human immune biology, development, and function. Although this model constitutes a great translational model, some aspects need to be improved as the incomplete engraftment of immune cells, graft versus host disease and the lack of human cytokines and growth factors. In this review, we discuss current HIS platforms, their pathology, and recent advances in their development to improve the quality of human immune cell reconstitution. We also highlight new technologies that can be used to better understand these models and how improved characterization is needed for their application in immuno-oncology safety, efficacy, and new modalities therapy development.

Suppression of autoreactive T and B lymphocytes by anti-annexin A1 antibody in a humanized NSG murine model of systemic lupus erythematosus

Systemic lupus erythematosus is a chronic inflammatory disease which involves multiple organs. Self-specific B and T cells play a main role in the pathogenesis of lupus and have been defined as a logical target for selective therapy. The protein annexin A1 (ANX A1) is a modulator of the immune system involving many cell types. An abnormal expression of ANX A1 was found on activated B and T cells during autoimmunity, suggesting its importance as a potential therapeutic target. We hypothesize that it may be possible to down-regulate the activity of autoreactive T and B cells from lupus patients in a humanized immunodeficient mouse model by treating them with an antibody against ANX A1. When cultured in the presence of anti-ANX A1, peripheral blood mononuclear cells (PBMC) from lupus patients showed a decreased number of immunoglobulin (Ig)G anti-dsDNA antibody-secreting plasma cells, decreased T cell proliferation and expression of activation markers and increased B and T cell apoptosis. We employed a humanized model of SLE by transferring PBMCs from lupus patients to immunodeficient non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice. The humanized animals presented autoantibodies, proteinuria and immunoglobulin deposition in the renal glomeruli. Treatment of these NOD-SCID mice with an anti-ANX A1 antibody prevented appearance of anti-DNA antibodies and proteinuria, while the phosphate-buffered saline (PBS)-injected animals had high levels after the transfer. The treatment reduced the levels of autoantibodies to several autoantigens, lupus-associated cytokines and disease symptoms.

Characterization of CXCR5+ CD8+ T-cells in humanized NSG mice

Humanized NOD/SCID/IL-2 receptor γ-chain^null (huNSG) mice recapitulate some features of human T-cell populations that can be exploited in basic and pre-clinical research. CXCR5⁺ T CD8⁺ T-cells play an important role in the control of viral infections and tumors. Indeed, they have been associated with low-level HIV replication, making them a possible novel correlate of protection, and potentially useful in the eradication of HIV reservoirs. Here, by flow cytometry, we evaluated the reconstitution of CXCR5⁺ CD8⁺ T-cells in huNSG mice engrafted with CD34⁺ hematopoietic stem cells. This population was readily generated in huNSG mice, and where particularly confined to spleen and lymph nodes. These cells exhibited a follicular-like phenotype, with expression of Programmed Death (PD)-1, Inducible T-cell costimulatory (ICOS), and absence of CCR7. Moreover, CXCR5⁺ CD8⁺ T-cells had a higher expression of interleukin (IL)-21 and a higher cytotoxic potential compared with CXCR5^- cells. HIV infection did not affect the frequencies of CXCR5⁺ CD8⁺ T-cells in secondary lymphoid organs. Finally, taking advantage of the high proportion of naïve T-cells in huNSG mice, we evaluated the in vitro response of splenic T-cells to the follicular profile-polarizing cytokines Transforming Growth Factor (TGF)-β1 and IL-23. After in vitro treatment, there was an increase in CXCR5⁺ CD8⁺ T-cells, which exhibited high levels of PD-1, CD40 L and low expression of CCR7. Thus, there is a reconstitution of CXCR5⁺ CD8⁺ T-cells in huNSG mice, supporting the use of this model for exploring the biology and role of this cell population in healthy and diseased conditions.

Humanized Mouse Models of Rheumatoid Arthritis for Studies on Immunopathogenesis and Preclinical Testing of Cell-Based Therapies

Rodent models of rheumatoid arthritis (RA) have been used over decades to study the immunopathogenesis of the disease and to explore intervention strategies. Nevertheless, mouse models of RA reach their limit when it comes to testing of new therapeutic approaches such as cell-based therapies. Differences between the human and the murine immune system make it difficult to draw reliable conclusions about the success of immunotherapies. To overcome this issue, humanized mouse models have been established that mimic components of the human immune system in mice. Two main strategies have been pursued for humanization: the introduction of human transgenes such as human leukocyte antigen molecules or specific T cell receptors, and the generation of mouse/human chimera by transferring human cells or tissues into immunodeficient mice. Recently, both approaches have been combined to achieve more sophisticated humanized models of autoimmune diseases. This review discusses limitations of conventional mouse models of RA-like disease and provides a closer look into studies in humanized mice exploring their usefulness and necessity as preclinical models for testing of cell-based therapies in autoimmune diseases such as RA.

Concise Review: Exploring Immunomodulatory Features of Mesenchymal Stromal Cells in Humanized Mouse Models

With their immunosuppressive features, human mesenchymal stromal cells (MSCs), sometimes also termed as mesenchymal stem cells, hold great potential as a cell-based therapy for various immune-mediated diseases. Indeed, MSCs have already been approved as a treatment for graft versus host disease. However, contradictory data from clinical trials and lack of conclusive proof of efficacy hinder the progress toward wider clinical use of MSCs and highlight the need for more relevant disease models. Humanized mice are increasingly used as models to study immune-mediated disease, as they simulate human immunobiology more closely than conventional murine models. With further advances in their resemblance to human immunobiology, it is very likely that humanized mice will be used more commonly as models to investigate MSCs with regard to their therapeutic safety and their immunomodulatory effect and its underlying mechanisms. Recent studies that explore the immunosuppressive features of MSCs in humanized mouse models will be discussed in this review. Stem Cells 2019;37:298-305.

Recent advances in mouse models for systemic sclerosis

SSc is a complex rheumatoid disease characterized by autoimmunity, fibrosis and vasculopathy. Mouse models provide powerful research tools for exploring the pathogenesis of the human diseases. Each mouse model can represent a specific way leading to the development of disease. Moreover, mouse models can be used to investigate the role of candidate molecule in the pathogenesis of disease. So far, more than twenty mouse models for SSc have been established and provide new insights in the understanding of the pathogenesis of SSc. In this review, we provide an overview on recent advances in the field of experimental SSc. We introduce novel mouse models generated in the recent years and discuss their relevance to the SSc pathogenesis. Moreover, we summarize and discuss recent findings in the pathogenesis of classical SSc mouse models.

The effects of fermentation products of prebiotic fibres on gut barrier and immune functions in vitro

The beneficial effects of prebiotic fibres on human health have been related to their capacities to alter the gut microbiota and modify the growth of beneficial microorganisms. It is long appreciated that bacterial metabolites affect the host’s physiology. The inner lining of the intestinal tract is the first level of interaction between the host and bacteria and their metabolites. Therefore, we set out to test the effects of five common dietary fibres (oat β-glucan 28%; oat β-glucan 94%; dried chicory root containing inulin 75%; xylo-oligosaccharide; inulin 90%) and maltodextrin, after fermentation by human gut microbiota in vitro, on measures of gut barrier integrity using a Caco-2/HT29-MTX co-culture as well as mucus production and immune parameters using HT29-MTX and HT29 cell models, respectively. Our data show that all fibres, fermentation products increased the tightness of the gut barrier with oat β-glucan 28% having the largest effect. Fermentation supernatants were tested also in models of the compromised gut barrier (leaky gut). After the addition of ethanol as basolateral stressor, only fermentation supernatant of oat β-glucan 28%, oat β-glucan 94% and maltodextrin improved the gut barrier integrity, while oat β-glucan 28% and dried chicory root containing inulin 75% significantly improved the gut barrier integrity after addition of rhamnolipids as apical stressor. Using the Luminex Technology, we demonstrated an important role of oat β-glucan fermentation products in modulating cytokine and chemokine productions. Furthermore, treating the goblet cells with effluent from xylo-oligosaccharide fermentation significantly increased mucus production. In summary, our data emphasize the potential positive effects of fermentation supernatant of dietary fibres on gut-related physiological outcomes and show that prebiotic fibres may have promising potential to induce specific gut health benefits.

An Immune System-Modified Rat Model for Human Stem Cell Transplantation Research

Due to its lack of both innate and acquired immune responses to human cells, the NODSCIDIl2rγ^−/− (NSG) mouse model has become an important tool for human stem cell research. When compared with the mouse, the rat is physiologically more similar to humans and offers advantages in preclinical efficacy studies on human stem cells, particularly in evaluating neural, hepatic, and cardiac functions. Therefore, we generated a human SIRPα⁺Prdkc^−/−Il2rγ^−/− rat model, denoted NSG-like (NSGL) rat, which expresses human SIRPα and is abolished in the development of B, T, and natural killer cells. When compared with Prdkc^−/−Il2rγ^−/− (SG) rats, NSGL rats allow more efficient engraftment of human cancer cells and human pluripotent stem cells. In addition, only NSGL rats, but not SG rats, can be engrafted with human hematopoietic stem cells to reconstitute the human immune system. Therefore, NSGL rats represent an improved xenotransplantation model for efficacy studies of human stem cells.

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Generation of human SIRPα⁺Prkdc^−/−Il2rγ^−/− NSG-like (NSGL) rat model

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NSGL rats lack B, T, and NK cells but express human SIRPα

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NSGL rats can be efficiently engrafted with human stem cells

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NSGL rats can be reconstituted by human HSCs to generate a human immune system

Humanizing the mouse immune system to study splanchnic organ inflammation

It is well known that alterations in splanchnic organ perfusion and/or immune regulation may produce inflammatory tissue injury similar to that observed in several human disorders such as ischaemia and reperfusion injury, food allergies, diabetes, inflammatory bowel disease and graft-versus-host disease. Mouse models have been tremendously important in defining the roles of the circulation, leukocyte trafficking, inflammatory mediator generation, immune regulation and the intestinal microbiota in the pathogenesis of acute and chronic inflammation. However, few of the promising interventions or therapeutics reported in mouse models of inflammatory diseases have been translated to clinically effective treatments in patients. There is growing concern that because of the significant differences that exist between the murine and human immune systems, mouse models may not adequately recapitulate the immuno-pathogenesis of inflammatory diseases. This inconvenient reality has prompted a number of investigators to undertake a series of studies to humanize the murine immune system via adoptive transfer of human lymphoid or progenitor cells into a new generation of immuno-deficient recipients. In this review, we summarize the recent advances that have been made in the development of humanized mice and describe how these mouse models are being used to study the pathophysiology of splanchnic organ inflammation. In addition, we discuss the limitations of the different approaches and present potential solutions for the continued improvement of these important animal models.

Crimean-Congo haemorrhagic fever virus: Past, present and future insights for animal modelling and medical countermeasures

Crimean–Congo haemorrhagic fever (CCHF) is a widespread tick‐borne viral zoonosis with a case‐fatality rate ranging from 9% to 50% in humans. Although a licensed vaccine to prevent infection by the CCHF virus (CCHFV) exists, its ability to induce neutralizing antibodies is limited and its efficacy against CCHFV remains undetermined. In addition, controlling CCHF infections by eradication of the tick reservoir has been ineffective, both economically and logistically, and the treatment options for CCHF remain limited. In this review, we first critically discuss the existing animal models to evaluate therapeutics for CCHF. We then review the therapeutic options for CCHF that have been investigated in human cases, followed by investigational drugs that have been evaluated in pre‐clinical studies. We highlight the importance of understanding human prognostic factors in developing an animal model for CCHF that recapitulates hallmarks of human disease and its implication for selecting therapeutic candidates.

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.

A Novel Human Systemic Lupus Erythematosus Model in Humanised Mice

Mouse models have contributed to the bulk of knowledge on Systemic Lupus Erythematosus (SLE). Nevertheless, substantial differences exist between human and mouse immune system. We aimed to establish and characterise a SLE model mediated by human immune system. Injection of pristane into immunodeficient mice reconstituted with human immune system (humanised mice) recapitulated key SLE features, including: production of human anti-nuclear autoantibodies, lupus nephritis, and pulmonary serositis. There was a reduction in the number of human lymphocytes in peripheral blood, resembling lymphopenia in SLE patients. Concurrently, B cells and T cells were systemically hyperactivated, with a relative expansion of CD27⁺ and CD27⁻IgD⁻ memory B cells, increased number of plasmablasts/plasma cells, and accumulation of effector memory T cells. There was also an increased production of human pro-inflammatory cytokines, including: IFN-γ, IL-8, IL-18, MCP-1, and IL-6, suggesting their role in SLE pathogenesis. Increased expression of type I IFN signature genes was also found in human hepatocytes. Altogether, we showed an SLE model that was mediated by human immune system, and which recapitulated key clinical and immunological SLE features. The advancements of humanised mice SLE model would provide an in vivo platform to facilitate translational studies and pre-clinical evaluations of human-specific mechanisms and immunotherapies.

Data against a Common Assumption: Xenogeneic Mouse Models Can Be Used to Assay Suppression of Immunity by Human MSCs

Much of what we know about immunology suggests that little is to be gained from experiments in which human cells are administered to immunocompetent mice. Multiple reports have demonstrated that this common assumption does not hold for experiments with human mesenchymal stem/stromal cells (hMSCs). The data demonstrate that hMSCs can suppress immune responses to a variety of stimuli in immunocompetent mice by a range of different mechanisms that are similar to those employed by mouse MSCs. Therefore, further experiments with hMSCs in mice will make it possible to generate preclinical data that will improve both the efficacy and safety of the clinical trials with the cells that are now in progress.

Humanized mice: A brief overview on their diverse applications in biomedical research

Model animals naturally differ from humans in various respects and results from the former are not directly translatable to the latter. One approach to address this issue is humanized mice that are defined as mice engrafted with functional human cells or tissues. In humanized mice, we can investigate the development and function of human cells or tissues (including their products encoded by human genes) in the in vivo context of a small animal. As such, humanized mouse models have played important roles that cannot be substituted by other animal models in various areas of biomedical research. Although there are obvious limitations in humanized mice and we may need some caution in interpreting the results obtained from them, it is reasonably expected that they will be utilized in increasingly diverse areas of biomedical research, as the technology for preparing humanized mice are rapidly improved. In this review, I will describe the methodology for generating humanized mice and overview their recent applications in various disciplines including immunology, infectious diseases, drug metabolism, and neuroscience.

Tumor Necrosis Factor and Lymphotoxin in Regulation of Intestinal Inflammation

Ulcerative colitis and Crohn's disease are the major forms of inflammatory bowel disease. Cytokines of the tumor necrosis factor (TNF) family play an important role in the regulation of intestinal inflammation. In this review, we discuss the function of key cytokines of this family - TNF and lymphotoxin (LT) - in mucosal healing, IgA production, and in control of innate lymphoid cells (ILCs), novel regulators of mucosal homeostasis in the gut. TNF plays a central role in the pathogenesis of inflammatory bowel diseases (IBD). LT regulates group 3 of ILCs and IL-22 production and protects the epithelium against damage by chemicals and mucosal bacterial pathogens. In addition, we discuss major mouse models employed to study the mechanism of intestinal inflammation, their advantages and limitations, as well as application of TNF blockers in the therapy for IBD.

Eosinophilic esophagitis: published evidences for disease subtypes, indications for patient subpopulations, and how to translate patient observations to murine experimental models

Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder of the esophagus and commonly classified as a Th2-type allergy. Major advances in our understanding of the EoE pathophysiology have recently been made, but clinicians struggle with highly unpredictable therapy responses indicative of phenotypic diversity within the patient population. Here, we summarize evidences for the existence of EoE subpopulations based on diverse inflammatory characteristics of the esophageal tissue in EoE. Additionally, clinical characteristics of EoE patients support the concept of disease subtypes. We conclude that clinical and experimental evidences indicate that EoE is an umbrella term for conditions that are unified by esophageal eosinophilia but that several disease subgroups with various inflammatory esophageal patterns and/or different clinical features exist. We further discuss strategies to study the pathophysiologic differences as observed in EoE patients in murine experimental EoE. Going forward, models of EoE that faithfully mimic EoE subentities as defined in humans will be essential because mechanistic studies on triggers which regulate the onset of diverse EoE subpopulations are not feasible in patients. Understanding how and why different EoE phenotypes develop will be a first and fundamental step to establish strategies that integrate individual variations of the EoE pathology into personalized therapy.

CNS autoimmune disease after Streptococcus pyogenes infections: animal models, cellular mechanisms and genetic factors

Streptococcus pyogenes infections have been associated with two autoimmune diseases of the CNS: Sydenham's chorea (SC) and Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcus infections (PANDAS). Despite the high frequency of pharyngeal streptococcus infections among children, only a small fraction develops SC or PANDAS. This suggests that several factors in combination are necessary to trigger autoimmune complications: specific S. pyogenes strains that induce a strong immune response toward the host nervous system; genetic susceptibility that predispose children toward an autoimmune response involving movement or tic symptoms; and multiple infections of the throat or tonsils that lead to a robust T_h17 cellular and humoral immune response when untreated. In this review, we summarize the evidence for each factor and propose that all must be met for the requisite neurovascular pathology and behavioral deficits found in SC/PANDAS.

Atherosclerotic Plaque Destabilization in Mice: A Comparative Study

Atherosclerosis-associated diseases are the main cause of mortality and morbidity in western societies. The progression of atherosclerosis is a dynamic process evolving from early to advanced lesions that may become rupture-prone vulnerable plaques. Acute coronary syndromes are the clinical manifestation of life-threatening thrombotic events associated with high-risk vulnerable plaques. Hyperlipidemic mouse models have been extensively used in studying the mechanisms controlling initiation and progression of atherosclerosis. However, the understanding of mechanisms leading to atherosclerotic plaque destabilization has been hampered by the lack of proper animal models mimicking this process. Although various mouse models generate atherosclerotic plaques with histological features of human advanced lesions, a consensus model to study atherosclerotic plaque destabilization is still lacking. Hence, we studied the degree and features of plaque vulnerability in different mouse models of atherosclerotic plaque destabilization and find that the model based on the placement of a shear stress modifier in combination with hypercholesterolemia represent with high incidence the most human like lesions compared to the other models.