Species differences in the structure and function of the immune system

Haemolymphatic tissues of captive boa constrictor (Boa constrictor): Morphological features in healthy individuals and with boid inclusion body disease

Knowledge on the structure and composition of the haematopoietic tissue (HT) is essential to understand the basic immune functions of the immune system in any species. For reptiles, it is extremely limited, hence we undertook an in-depth in situ investigation of the HT (bone marrow, thymus, spleen, lymphatic tissue of the alimentary tract) in the common boa (Boa constrictor). We also assessed age- and disease-related changes, with a special focus on Boid Inclusion Body Disease, a highly relevant reptarenavirus-associated disease in boid snakes. The HT was subjected to gross, histological and ultrastructural examination, including special stains to highlight collagen and reticulin fibers and iron, immunohistochemistry, in situ hybridization and morphometric analyses. In general, the HT was dominated by T cells and lacked a clear structural organization, such as follicle formation. BIBD was associated with significantly higher cellularity and a granulomatous response in the spleen, and the presence of virus-infected haematopoietic cells in the bone marrow, suggesting the latter as a persistent source of viremia.

Establishment and Validation of Fecal Secretory Immunoglobulin A Measurement for Intestinal Mucosal Health Assessment in Wild Lemurs

The measurement of biomarkers in blood and excreta can enable immune status assessment and provide prognostic information on individual health outcomes. In this respect, the fecal measurement of secretory immunoglobulin A (sIgA), the primary mammalian antibody for mucosal defense, has recently received increased interest in a few anthropoid primates, but a fecal sIgA assay for use in strepsirrhine primates has not yet been reported. Here, we develop and analytically validate a cost-effective in-house sandwich enzyme immunoassay for the extraction and measurement of sIgA in feces of redfronted lemurs (Eulemur rufifrons). We also tested a simple method for sIgA extraction that can be used under remote field conditions and undertook experiments to assess the robustness of sIgA concentrations to variation in processing and storage conditions of fecal extracts. Our analytical validation revealed that the assay recognizes immunoreactive sIgA in redfronted lemur feces, that sIgA can be measured accurately with no potential interference from the fecal matrix, and that assay reagents and performance are highly stable over time. The field-friendly extraction procedure produced sIgA results strongly correlated with those generated by a standard laboratory extraction method. Short-term storage at room temperature resulted in a slight decline in sIgA concentrations, whereas freezing extracts at -20°C kept sIgA levels stable for at least 3 months. Longer-term storage of >5 months, however, led to a significant decline of sIgA concentrations. Multiple freeze-thaw cycles did not affect sIgA levels. This study, therefore, provides the basis for measuring fecal sIgA in lemurs and possibly other strepsirrhines. When samples are processed properly and stored frozen, and when sIgA analysis can be performed within 3 months upon sample collection, fecal sIgA measurements can become a valuable tool for monitoring aspects of immunity and health in both zoo-housed and wild-living lemurs.

Active CNS delivery of oxycodone in healthy and endotoxemic pigs

BACKGROUND

The primary objective of this study was to advance our understanding of active drug uptake at brain barriers in higher species than rodents, by examining oxycodone brain concentrations in pigs.

METHODS

This was investigated by a microdialysis study in healthy and endotoxemic conditions to increase the understanding of inter-species translation of putative proton-coupled organic cation (H+/OC) antiporter-mediated central nervous system (CNS) drug delivery in health and pathology, and facilitate the extrapolation to humans for improved CNS drug treatment in patients. Additionally, we sought to evaluate the efficacy of lumbar cerebrospinal fluid (CSF) exposure readout as a proxy for brain unbound interstitial fluid (ISF) concentrations. By simultaneously monitoring unbound concentrations in blood, the frontal cortical area, the lateral ventricle (LV), and the lumbar intrathecal space in healthy and lipopolysaccharide (LPS)-induced inflammation states within the same animal, we achieved exceptional spatiotemporal resolution in mapping oxycodone transport across CNS barriers.

RESULTS

Our findings provide novel evidence of higher unbound oxycodone concentrations in brain ISF compared to blood, yielding an unbound brain-to-plasma concentration ratio (Kp,uu,brain) of 2.5. This supports the hypothesis of the presence of the H+/OC antiporter system at the blood-brain barrier (BBB) in pigs. Despite significant physiological changes, reflected in pig Sequential Organ Failure Assessment, pSOFA scores, oxycodone blood concentrations and its active net uptake across the BBB remained nearly unchanged during three hours of i.v. infusion of 4 µg/kg/h LPS from Escherichia coli (O111:B4). Mean Kp,uu,LV values indicated active uptake also at the blood-CSF barrier in healthy and endotoxemic pigs. Lumbar CSF concentrations showed minimal inter-individual variability during the experiment, with a mean Kp,uu,lumbarCSF of 1.5. LPS challenge caused a slight decrease in Kp,uu,LV, while Kp,uu,lumbarCSF remained unaffected.

CONCLUSIONS

This study enhances our understanding of oxycodone pharmacokinetics and CNS drug delivery in both healthy and inflamed conditions, providing crucial insights for translating these findings to clinical settings.

Exploring the effects of environmentally relevant concentrations of tris(2-chloroethyl) phosphate on tadpole health: A comprehensive analysis of intestinal microbiota and hepatic transcriptome

Tris(2-chloroethyl) phosphate (TCEP), a chlorinated organophosphate ester, is commonly found in aquatic environments. Due to its various toxic effects, it may pose a risk to the health of aquatic organisms. However, the potential impacts of TCEP exposure on the intestinal microbiota and hepatic function in amphibians have not been reported. This study investigated the impact of long-term exposure to environmentally relevant concentrations of TCEP (0, 3, and 90 μg/L) on the intestinal microbiota and hepatic transcriptome of Polypedates megacephalus tadpoles. The results showed that the body size of the tadpoles decreased significantly with an increase in TCEP concentration. Additionally, TCEP exposure affected the diversity and composition of the intestinal microbiota in tadpoles, leading to significant changes in the relative abundance of certain bacterial groups (the genera Aeromonas decreased and Citrobacter increased) and potentially promoting a more even distribution of microbial species, as indicated by a significant increase in the Simpson index. Moreover, the impact of TCEP on hepatic gene expression profiles in tadpoles was significant, with the majority of differentially expressed genes (DEGs) (709 out of 906 total DEGs in 3 μg/L of TCEP versus control, and 344 out of 387 DEGs in 90 μg/L of TCEP versus control) being significantly down-regulated, which were primarily related to immune response and immune system process. Notably, exposure to TCEP significantly reduced the relative abundance of the genera Aeromonas and Cetobacterium in the tadpole intestine. This reduction was positively correlated with the down-regulated expression of immune-related genes in the liver of corresponding tadpoles. In summary, these findings provide empirical evidence of the potential health risks to tadpoles exposed to TCEP at environmentally relevant concentrations.

The thymus road to a T cell: migration, selection, and atrophy

The thymus plays a pivotal role in generating a highly-diverse repertoire of T lymphocytes while preventing autoimmunity. Thymus seeding progenitors (TSPs) are a heterogeneous group of multipotent progenitors that migrate to the thymus via CCR7 and CCR9 receptors. While NOTCH guides thymus progenitors toward T cell fate, the absence or disruption of NOTCH signaling renders the thymus microenvironment permissive to other cell fates. Following T cell commitment, developing T cells undergo multiple selection checkpoints by engaging with the extracellular matrix, and interacting with thymic epithelial cells (TECs) and other immune subsets across the different compartments of the thymus. The different selection checkpoints assess the T cell receptor (TCR) performance, with failure resulting in either repurposing (agonist selection), or cell death. Additionally, environmental cues such as inflammation and endocrine signaling induce acute thymus atrophy, contributing to the demise of most developing T cells during thymic selection. We discuss the occurrence of acute thymus atrophy in response to systemic inflammation. The thymus demonstrates high plasticity, shaping inflammation by abrogating T cell development and undergoing profound structural changes, and facilitating regeneration and restoration of T cell development once inflammation is resolved. Despite the challenges, thymic selection ensures a highly diverse T cell repertoire capable of discerning between self and non-self antigens, ultimately egressing to secondary lymphoid organs where they complete their maturation and exert their functions.

The Development of a Highly Potent and Selective Human Toll-like Receptor 2 Agonist: Synthesis and Biological Evaluation of CaLGL-1 and Its Derivatives

Toll-like receptor 2 (TLR2) plays a crucial role in detecting microbial pathogen-associated molecular patterns, offering potential applications as an adjuvant for vaccines and antitumor therapies. Here, we present the gram-scale synthesis of CaLGL-1 and its derivatives, natural products known for activating mouse TLR2 (EC50 = 3.2 μM). This synthesis involves a streamlined six-step reaction sequence utilizing oxidant-promoted acetalization, effectively preserving the acid-sensitive glycosidic bond for maintaining the compounds' functional integrity. Our structure-activity relationship studies identified R-7d as a potent human TLR2 activator. It demonstrated subnanomolar activity (EC50 = 116 pM) in human THP-1 cells, comparable to that of diprovocim (EC50 = 110 pM). Experiments revealed that R-7d enhances NF-kB promoter activation through TLR2/TLR1 heterodimers rather than TLR2/TLR6. The discovery of R-7d as a robust human TLR2 agonist opens up new possibilities for combination therapies.

Bringing the Genomic Revolution to Comparative Oncology: Human and Dog Cancers

Dogs are humanity's oldest friend, the first species we domesticated 20,000-40,000 years ago. In this unequaled collaboration, dogs have inadvertently but serendipitously been molded into a potent human cancer model. Unlike many common model species, dogs are raised in the same environment as humans and present with spontaneous tumors with human-like comorbidities, immunocompetency, and heterogeneity. In breast, bladder, blood, and several pediatric cancers, in-depth profiling of dog and human tumors has established the benefits of the dog model. In addition to this clinical and molecular similarity, veterinary studies indicate that domestic dogs have relatively high tumor incidence rates. As a result, there are a plethora of data for analysis, the statistical power of which is bolstered by substantial breed-specific variability. As such, dog tumors provide a unique opportunity to interrogate the molecular factors underpinning cancer and facilitate the modeling of new therapeutic targets. This review discusses the emerging field of comparative oncology, how it complements human and rodent cancer studies, and where challenges remain, given the rapid proliferation of genomic resources. Increasingly, it appears that human's best friend is becoming an irreplaceable component of oncology research.

Frequency of Besnoitia besnoiti and Neospora caninum antibodies in cattle and small ruminants from greater Cairo and Beni Suef governorates, Egypt

Livestock industry is a pivotal sector for providing food, work places and monetary support for Egyptian people. Besnoitia besnoiti and Neospora caninum are protozoan parasites that are responsible for significant economic losses in ruminants, particularly in cattle. Besnoitia besnoiti can cause fertility problems and a general loss in productivity, while N. caninum is a major cause of abortion and neonatal abnormalities in infected animals. There is little information on the existence of these protozoa in Egypt, thus we conducted this study to reveal the current situation in cattle (n = 264), sheep (n = 151), and goats (n = 25). Serum samples were collected from governorates of Cairo, Giza, and Beni Suef, representing the most densely populated regions in Egypt. Using commercial ELISAs, an overall estimation among all tested animals (n = 440) revealed 7.7%, 13.2%, and 0.9% as seropositive rates for B. besnoiti, N. caninum, and mixed infection, respectively. Animal species (cattle vs sheep vs goat) and age of cattle (less than vs >1 year old) were analyzed as risk factors for infection. Regarding B. besnoiti, the seroprevalence was significantly higher in cattle than in sheep and goats and in adult cattle than calves. For N. caninum infection, no significant differences were recorded, although the seropositive rates were higher in cattle, and in adult cattle. This study provides the first seroprevalence data for B. besnoiti in all surveyed animals in the regions included, and in sheep and goats from Egypt, and supports the current knowledge for the occurrence of N. caninum in Egypt.

The aged microenvironment impairs BCL6 and CD40L induction in CD4+ T follicular helper cell differentiation

Weakened germinal center responses by the aged immune system result in diminished immunity against pathogens and reduced efficacy of vaccines. Prolonged contacts between activated B cells and CD4+ T cells are crucial to germinal center formation and T follicular helper cell (Tfh) differentiation, but it is unclear how aging impacts the quality of this interaction. Peptide immunization confirmed that aged mice have decreased expansion of antigen-specific germinal center B cells and reduced antibody titers. Furthermore, aging was associated with accumulated Tfh cells, even in naïve mice. Despite increased numbers, aged Tfh had reduced expression of master transcription factor BCL6 and increased expression of the ectonucleotidase CD39. In vitro activation revealed that proliferative capacity was maintained in aged CD4+ T cells, but not the costimulatory molecule CD40L. When activated in vitro by aged antigen-presenting cells, young CD4+ naïve T cells generated reduced numbers of activated cells with upregulated CD40L. To determine the contribution of cell-extrinsic influences on antigen-specific Tfh induction, young, antigen-specific B and CD4+ T cells were adoptively transferred into aged hosts prior to peptide immunization. Transferred cells had reduced expansion and differentiation into germinal center B cell and Tfh and reduced antigen-specific antibody titers when compared to young hosts. Young CD4+ T cells transferred aged hosts differentiated into Tfh cells with reduced PD-1 and BCL6 expression, and increased CD39 expression, though they maintained their mitochondrial capacity. These results highlight the role of the lymphoid microenvironment in modulating CD4+ T cell differentiation, which contributes to impaired establishment and maintenance of germinal centers.

Developing a pragmatic consensus procedure supporting the ICH S1B(R1) weight of evidence carcinogenicity assessment

The ICH S1B carcinogenicity global testing guideline has been recently revised with a novel addendum that describes a comprehensive integrated Weight of Evidence (WoE) approach to determine the need for a 2-year rat carcinogenicity study. In the present work, experts from different organizations have joined efforts to standardize as much as possible a procedural framework for the integration of evidence associated with the different ICH S1B(R1) WoE criteria. The framework uses a pragmatic consensus procedure for carcinogenicity hazard assessment to facilitate transparent, consistent, and documented decision-making and it discusses best-practices both for the organization of studies and presentation of data in a format suitable for regulatory review. First, it is acknowledged that the six WoE factors described in the addendum form an integrated network of evidence within a holistic assessment framework that is used synergistically to analyze and explain safety signals. Second, the proposed standardized procedure builds upon different considerations related to the primary sources of evidence, mechanistic analysis, alternative methodologies and novel investigative approaches, metabolites, and reliability of the data and other acquired information. Each of the six WoE factors is described highlighting how they can contribute evidence for the overall WoE assessment. A suggested reporting format to summarize the cross-integration of evidence from the different WoE factors is also presented. This work also notes that even if a 2-year rat study is ultimately required, creating a WoE assessment is valuable in understanding the specific factors and levels of human carcinogenic risk better than have been identified previously with the 2-year rat bioassay alone.

Distribution and spatiotemporal development of organised lymphoid tissues in the chicken intestinal tract

Chickens exhibit a distinct immune architecture characterised by the absence of draining lymph nodes and the presence of a well-developed mucosa-associated lymphoid tissue. The structure and spatiotemporal development of chicken lymphoid tissues in the intestine are poorly documented. The macroscopically indistinct structure of chicken Peyer's patches has impeded studies into their development. The generation of CSF1R-eGFP reporter transgenic chickens enables visualisation of the development, organisation and extent of chicken lymphoid tissues by unique macroscopic views. CSF1R-eGFP reporter transgenic chickens were used to investigate the distribution and spatiotemporal development of PP and caecal tonsils in embryonic day 18 to 8-week-old chickens. Peyer's patch anlagen are present at ED18 with a similar frequency and distribution pattern observed in 2- and 8-week-old chickens. These findings can support in ovo and post-hatch mucosal vaccination strategies and the development of vaccine delivery systems targeted to the specialized epithelium overlying the Peyer's patches.

Human Precision-Cut Liver Slices: A Potential Platform to Study Alcohol-Related Liver Disease

Alcohol-related liver disease (ALD) encompasses a range of pathological conditions that are complex to study at the clinical and preclinical levels. Despite the global burden of ALD, there is a lack of effective treatments, and mortality is high. One of the reasons for the unsuccessful development of novel therapies is that experimental studies are hindered by the challenge of recapitulating this multifactorial disorder in vitro, including the contributions of hepatotoxicity, impaired lipid metabolism, fibrosis and inflammatory cytokine storm, which are critical drivers in the pathogenesis of ALD in patients and primary targets for drug development. Here, we present the unique characteristics of the culture of human precision-cut liver slices (PCLS) to replicate key disease processes in ALD. PCLS were prepared from human liver specimens and treated with ethanol alone or in combination with fatty acids and lipopolysaccharide (FA + LPS) for up to 5 days to induce hepatotoxic, inflammatory and fibrotic events associated with ALD. Alcohol insult induced hepatocyte death which was more pronounced with the addition of FA + LPS. This mixture showed a significant increase in the cytokines conventionally associated with the prototypical inflammatory response observed in severe ALD, and interestingly, alcohol alone exhibited a different effect. Profibrogenic activation was also observed in the slices and investigated in the context of slice preparation. These results support the versatility of this organotypic model to study different pathways involved in alcohol-induced liver damage and ALD progression and highlight the applicability of the PCLS for drug discovery, confirming their relevance as a bridge between preclinical and clinical studies.

Immunity-on-a-Chip: Integration of Immune Components into the Scheme of Organ-on-a-Chip Systems

Studying the immune system in vitro aims to understand how, when, and where the immune cells migrate/differentiate and respond to the various triggering events and the decision points along the immune response journey. It becomes evident that organ-on-a-chip (OOC) technology has a superior capability to recapitulate the cell-cell and tissue-tissue interaction in the body, with a great potential to provide tools for tracking the paracrine signaling with high spatial-temporal precision and implementing in situ real-time, non-destructive detection assays, therefore, enabling extraction of mechanistic information rather than phenotypic information. However, despite the rapid development in this technology, integration of the immune system into OOC devices stays among the least navigated tasks, with immune cells still the major missing components in the developed models. This is mainly due to the complexity of the immune system and the reductionist methodology of the OOC modules. Dedicated research in this field is demanded to establish the understanding of mechanism-based disease endotypes rather than phenotypes. Herein, we systemically present a synthesis of the state-of-the-art of immune-cantered OOC technology. We comprehensively outlined what is achieved and identified the technology gaps emphasizing the missing components required to establish immune-competent OOCs and bridge these gaps.

A critical assessment of the cellular defences of the avian respiratory system: are birds in general and poultry in particular relatively more susceptible to pulmonary infections/afflictions?

In commercial poultry farming, respiratory diseases cause high morbidities and mortalities, begetting colossal economic losses. Without empirical evidence, early observations led to the supposition that birds in general, and poultry in particular, have weak innate and adaptive pulmonary defences and are therefore highly susceptible to injury by pathogens. Recent findings have, however, shown that birds possess notably efficient pulmonary defences that include: (i) a structurally complex three-tiered airway arrangement with aerodynamically intricate air-flow dynamics that provide efficient filtration of inhaled air; (ii) a specialised airway mucosal lining that comprises air-filtering (ciliated) cells and various resident phagocytic cells such as surface and tissue macrophages, dendritic cells and lymphocytes; (iii) an exceptionally efficient mucociliary escalator system that efficiently removes trapped foreign agents; (iv) phagocytotic atrial and infundibular epithelial cells; (v) phagocytically competent surface macrophages that destroy pathogens and injurious particulates; (vi) pulmonary intravascular macrophages that protect the lung from the vascular side; and (vii) proficiently phagocytic pulmonary extravasated erythrocytes. Additionally, the avian respiratory system rapidly translocates phagocytic cells onto the respiratory surface, ostensibly from the subepithelial space and the circulatory system: the mobilised cells complement the surface macrophages in destroying foreign agents. Further studies are needed to determine whether the posited weak defence of the avian respiratory system is a global avian feature or is exclusive to poultry. This review argues that any inadequacies of pulmonary defences in poultry may have derived from exacting genetic manipulation(s) for traits such as rapid weight gain from efficient conversion of food into meat and eggs and the harsh environmental conditions and severe husbandry operations in modern poultry farming. To reduce pulmonary diseases and their severity, greater effort must be directed at establishment of optimal poultry housing conditions and use of more humane husbandry practices.

Chronic exposure to UVB induces nephritis and gut microbiota dysbiosis in mice based on the integration of renal transcriptome profiles and 16S rRNA sequencing data

Ultraviolet (UV) is a common and abundant environmental factor that affects daily life. Although the effects of UV radiation on the skin have been extensively reported, studies on the influence of UV radiation on internal organs are still limited. This study aimed to evaluate the influence of UVB exposure on the kidney of mice and to investigate the possible mechanism. In the present study, histopathology changes, oxidative stress, and inflammatory response were used to evaluate the kidney and colon injury induced by UVB exposure. The results showed that the 14-week chronic skin exposure to UVB triggers a kidney injury response characterized by macrophage infiltration, elevated oxidative stress as well as inflammatory and injury markers. The RNA sequencing demonstrated that chronic UVB exposure could alter the kidney transcriptomic profile distinguished by the regulation of genes involved in the Notch signaling pathway, JAK-STAT signaling pathway, and ECM-receptor interaction. Besides, chronic UVB exposure also resulted in gut dysbiosis, manifested as colon macrophage infiltration, stimulated inflammatory responses, impaired barrier integrity, and microbiota structural and functional disorders. The Spearman analysis results further revealed a strong correlation between gut microbiota and kidney injury. In conclusion, skin chronic exposure to UVB causes nephritis and gut microbiota dysbiosis in mice, and these findings provide new insight into the underlying risks of chronic UVB exposure to human wellness.

Comparative physiological anthropogeny: exploring molecular underpinnings of distinctly human phenotypes

Anthropogeny is a classic term encompassing transdisciplinary investigations of the origins of the human species. Comparative anthropogeny is a systematic comparison of humans and other living nonhuman hominids (so-called "great apes"), aiming to identify distinctly human features in health and disease, with the overall goal of explaining human origins. We begin with a historical perspective, briefly describing how the field progressed from the earliest evolutionary insights to the current emphasis on in-depth molecular and genomic investigations of "human-specific" biology and an increased appreciation for cultural impacts on human biology. While many such genetic differences between humans and other hominids have been revealed over the last two decades, this information remains insufficient to explain the most distinctive phenotypic traits distinguishing humans from other living hominids. Here we undertake a complementary approach of "comparative physiological anthropogeny," along the lines of the preclinical medical curriculum, i.e., beginning with anatomy and considering each physiological system and in each case considering genetic and molecular components that are relevant. What is ultimately needed is a systematic comparative approach at all levels from molecular to physiological to sociocultural, building networks of related information, drawing inferences, and generating testable hypotheses. The concluding section will touch on distinctive considerations in the study of human evolution, including the importance of gene-culture interactions.

Toxicologic Pathology Forum: Considerations Regarding Determination of Adversity for Immunopathology Findings in Nonclinical Toxicology Studies with Immune-Modulating Therapeutics

The evaluation of changes in the immune system serves to determine the efficacy and potential immunotoxicologic effects of new products under development. Toxicologic pathologists play critical roles in identifying immune system changes that drive the immunosafety determination. Standard pathology evaluations of therapies and chemicals remain similar; however, biopharmaceutical therapies have moved from simply affecting the immune system to being specifically developed to modify the immune system, which can impact interpretation. Recent explosive growth in immunomodulatory therapies presents a challenge to the toxicologic pathologist, toxicologist, and regulatory reviewer in terms of evaluating the clinical relevance and potential adversity of immune system changes. Beyond the recognition of such changes, there is an increasing expectation to evaluate, describe, and interpret how therapies affect complex immune system pathways for both immunomodulatory therapies and non-immunomodulatory drugs with off-target immunotoxic effects. In this opinion piece, considerations regarding immune system evaluation, the current landscape of immunomodulatory therapies, a brief description of immunotoxicologic (and immunopathologic) endpoints, the importance of integrating such immunosafety data, and relevance to adversity determination are discussed. Importantly, we describe how the current paradigm of determining adversity for immune system changes may be challenging or insufficient and propose a harmonized and flexible approach for assessing adversity.

Comparative Aspects of Ricin Toxicity by Inhalation

The pathogenesis of ricin toxicity following inhalation has been investigated in many animal models, including the non-human primate (predominantly the rhesus macaque), pig, rabbit and rodent. The toxicity and associated pathology described in animal models are broadly similar, but variation appears to exist. This paper reviews the published literature and some of our own unpublished data and describes some of the possible reasons for this variation. Methodological variation is evident, including method of exposure, breathing parameters during exposure, aerosol characteristics, sampling protocols, ricin cultivar, purity and challenge dose and study duration. The model species and strain used represent other significant sources of variation, including differences in macro- and microscopic anatomy, cell biology and function, and immunology. Chronic pathology of ricin toxicity by inhalation, associated with sublethal challenge or lethal challenge and treatment with medical countermeasures, has received less attention in the literature. Fibrosis may follow acute lung injury in survivors. There are advantages and disadvantages to the different models of pulmonary fibrosis. To understand their potential clinical significance, these factors need to be considered when choosing a model for chronic ricin toxicity by inhalation, including species and strain susceptibility to fibrosis, time it takes for fibrosis to develop, the nature of the fibrosis (e.g., self-limiting, progressive, persistent or resolving) and ensuring that the analysis truly represents fibrosis. Understanding the variables and comparative aspects of acute and chronic ricin toxicity by inhalation is important to enable meaningful comparison of results from different studies, and for the investigation of medical countermeasures.

3D anatomy of autonomic innervations in immune organs of a non-human primate and the human

Direct neural inputs to immune organs have been observed for decades, with their functions in neuroimmune regulation being increasingly appreciated. However, the current knowledge of such neural structures, particularly those in primate immune organs, remains incomplete. In this study, we comprehensively assessed the 3D anatomy of autonomic (i.e., sympathetic and parasympathetic) innervations in the immune organs of the rhesus macaque monkey and the human for the first time. Aided with the advanced technique of whole-tissue immunolabeling and lightsheet fluorescence imaging, we revealed the densely organized sympathetic architecture in the parenchyma of the adult monkey and human spleens. On the other hand, only sparse, if any, sympathetic inputs were observed inside the lymph nodes, Peyer's patches, or thymus. In contrast, there were minimal parasympathetic innervations in the parenchyma of these examined immune organs. Together, this work has documented the unique patterns of autonomic innervations in different immune organs of a non-human primate and the human, serving as an essential reference for future research on neuroimmune regulation in the field.

Issues for patchy tissues: defining roles for gut-associated lymphoid tissue in neurodevelopment and disease

Individuals diagnosed with neurodevelopmental conditions such as autism spectrum disorder (ASD; autism) often experience tissue inflammation as well as gastrointestinal dysfunction, yet their underlying causes remain poorly characterised. Notably, the largest components of the body's immune system, including gut-associated lymphoid tissue (GALT), lie within the gastrointestinal tract. A major constituent of GALT in humans comprises secretory lymphoid aggregates known as Peyer's patches that sense and combat constant exposure to pathogens and infectious agents. Essential to the functions of Peyer's patches is its communication with the enteric nervous system (ENS), an intrinsic neural network that regulates gastrointestinal function. Crosstalk between these tissues contribute to the microbiota-gut-brain axis that altogether influences mood and behaviour. Increasing evidence further points to a critical role for this signalling axis in neurodevelopmental homeostasis and disease. Notably, while the neuroimmunomodulatory functions for Peyer's patches are increasingly better understood, functions for tissues of analogous function, such as caecal patches, remain less well characterised. Here, we compare the structure, function and development of Peyer's patches, as well as caecal and appendix patches in humans and model organisms including mice to highlight the roles for these essential tissues in health and disease. We propose that perturbations to GALT function may underlie inflammatory disorders and gastrointestinal dysfunction in neurodevelopmental conditions such as autism.

Tamoxifen Prevents Peritendinous Adhesions: A Preliminary Report

Background

Scarless healing comprises the ultimate goal after an injury. Since tendon healing results in a fibrotic scar, an injured tendon can never regain the mechanical potential and strength of its uninjured form. A wide variety of studies focus on the tendon healing with an absent or minimal peritendinous adhesions. However, no simple method has managed it at all. Possible complex actions and peritendinous environmental events take place during the tendon healing process. Tamoxifen (TAM), besides its breast cancer-related usage, is a potent antifibrotic drug. Here, we aimed to reduce the peritendinous adhesion with TAM administration.

Methods

Achilles tendons of 44 Wistar albino rats were randomly distributed in 4 groups. In group 1, bilateral lower extremities were used as control and sham. Groups 2 and 3 were comprised of low-dose (1 mg/kg) and high-dose (40 mg/kg) systemic administration of TAM, respectively. Group 4 included local administration (1 mg/kg) of TAM. Biomechanical, macroscopical, and histopathological analyses were done and compared statistically. Biomechanically, the maximum force that led to tendon rupture was determined, and tensile force data were recorded via tensile testing device. Macroscopical and histopathological analysis were composed of the quantity, quality, and grade of peritendinous adhesions.

Results

Macroscopic and histopathologic findings revealed that groups 2 and 3 had a variety of values ranging between slight to severe adhesions. In group 2, almost half of the animals had moderate adhesions, whereas in group 3, the majority of the animals had moderate adhesions. There were no animals with moderate or severe adhesions in group 4. Statistically significant values were calculated between sham and control groups. Biomechanically, group 2 showed the most significant result. The tendons in group 2 had the highest stiffness when maximal force was applied to rupture the tendons. Henceforth, all these consequences were proven statistically.

Conclusion

We achieved less peritendinous adhesion with the local administration of TAM when compared to systemic administration of TAM. A better understanding of the peritendinous environmental process will reveal to develop new therapies in the prevention of peritendinous adhesions.

Immune and non-immune functions of adipose tissue leukocytes

Adipose tissue is a complex dynamic organ with whole-body immunometabolic influence. Much of the work into understanding the role of immune cells in adipose tissue has been in the context of obesity. These investigations have also uncovered a range of typical (immune) and non-typical functions exerted by adipose tissue leukocytes. Here we provide an overview of the adipose tissue immune system, including its role as an immune reservoir in the whole-body response to infection and as a site of parasitic and viral infections. We also describe the functional roles of specialized immunological structures found within adipose tissue. However, our main focus is on the recently discovered 'non-immune' functions of adipose tissue immune cells, which include the regulation of adipocyte homeostasis, as well as responses to changing nutrient status and body temperature. In doing so, we outline the therapeutic potential of the adipose tissue immune system in health and disease.

Role of thymus in health and disease

The thymus is a primary lymphoid organ, essential for the development of T-cells that will protect from invading pathogens, immune disorders, and cancer. The thymus decreases in size and cellularity with age referred to as thymus involution or atrophy. This involution causes decreased T-cell development and decreased naive T-cell emigration to the periphery, increased proportion of memory T cells, and a restricted, altered T-cell receptor (TCR) repertoire. The changes in composition and function of the circulating T cell pool as a result of thymic involution led to increased susceptibility to infectious diseases including the recent COVID and a higher risk for autoimmune disorders and cancers. Thymic involution consisting of both structural and functional loss of the thymus has a deleterious effect on T cell development, T cell selection, and tolerance. The mechanisms which act on the structural (cortex and medulla) matrix of the thymus, the gradual accumulation of genetic mutations, and altered gene expressions may lead to immunosenescence as a result of thymus involution. Understanding the molecular mechanisms behind thymic involution is critical for identifying diagnostic biomarkers and targets for treatment help to develop strategies to mitigate thymic involution-associated complications. This review is focused on the consequences of thymic involution in infections, immune disorders, and diseases, identifying potential checkpoints and potential approaches to sustain or restore the function of the thymus particularly in elderly and immune-compromised individuals.

From bats to pangolins: new insights into species differences in the structure and function of the immune system

Species differences in the structure and function of the immune system of laboratory animals are known to exist and have been reviewed extensively. However, the number and diversity of wild and exotic species, along with their associated viruses, that come into contact with humans has increased worldwide sometimes with lethal consequences. Far less is known about the immunobiology of these exotic and wild species. Data suggest that species differences of the mechanisms of inflammation, innate immunity and adaptive immunity are all involved in the establishment and maintenance of viral infections across reservoir hosts. The current review attempts to collect relevant data concerning the basics of innate and adaptive immune functions of exotic and wild species followed by identification of those differences that may play a role in the maintenance of viral infections in reservoir hosts.

Novel, Emerging Chip Models of the Blood-Brain Barrier and Future Directions

The use of microfluidic chips is now allowing for more advanced modelling of the blood-brain barrier (BBB) in vitro, recapitulating heterotypic interactions, 3D architecture, and physiological flow. This chapter will give an introduction to these new technologies and how they are being applied to model the BBB and neurovascular unit (NVU). A foundational understanding of the fluid dynamics germane to the effective use of these chips will be set and an overview of how physical phenomena at the microscale can be exploited to enable new possibilities to control the cell culture environment. The four main approaches to construct microfluidic blood vessel mimetics will be discussed with examples of how these techniques are being applied to model the BBB and more recently to study specific neurovascular disease processes. Finally, practical guidance will be given for researchers wishing to adopt these new techniques along with a summary of the challenges, limitations faced, and new opportunities opened up by these advanced cell culture systems.

Sex differences in recovery of motor function in a rhesus monkey model of cortical injury

BACKGROUND

Stroke disproportionately affects men and women, with women over 65 years experiencing increased severity of impairment and higher mortality rates than men. Human studies have explored risk factors that contribute to these differences, but additional research is needed to investigate how sex differences affect functional recovery and hence the severity of impairment. In the present study, we used our rhesus monkey model of cortical injury and fine motor impairment to compare sex differences in the rate and degree of motor recovery following this injury.

METHODS

Aged male and female rhesus monkeys were trained on a task of fine motor function of the hand before undergoing surgery to produce a cortical lesion limited to the hand area representation of the primary motor cortex. Post-operative testing began two weeks after the surgery and continued for 12 weeks. All trials were video recorded and latency to retrieve a reward was quantitatively measured to assess the trajectory of post-operative response latency and grasp pattern compared to pre-operative levels.

RESULTS

Postmortem analysis showed no differences in lesion volume between male and female monkeys. However, female monkeys returned to their pre-operative latency and grasp patterns significantly faster than males.

CONCLUSIONS

These findings demonstrate the need for additional studies to further investigate the role of estrogens and other sex hormones that may differentially affect recovery outcomes in the primate brain.

Genetically engineered mouse models of esophageal cancer

BACKGROUND

Esophageal cancer is the most common cause of cancer-related death worldwide with a diverse geographical distribution, poor prognosis, and diagnosis in advanced stages of the disease. Identification of the mechanisms involved in esophageal cancer development is evaluative to improve outcomes for patients. Genetically engineered mouse models (GEMMs) of cancer provide the physiologic, molecular, and histologic features of the human tumors to determine the pathogenesis and treatments for cancer, hence exhibiting a source of tremendous potential for oncology research. The advancement of cancer modeling in mice has improved to the extent that researchers can observe and manipulate the disease process in a specific manner. Despite the significant differences between mice and humans, mice can be great models for human oncology researches due to similarities between them at the molecular and physiological levels. Due to most of the existing esophageal cancer GEMMs do not propose an ideal system for pathogenesis of the disease, genetic risks, and microenvironment exposure, so identification of challenges in GEM modeling and well-developed technologies are required to obtain the most value for patients. In this review, we describe the biology of human and mouse, followed by the exciting esophageal cancer mouse models with a discussion of applicability and challenges of these models for generating new GEMMs in future studies.

Preclinical models for studying immune responses to traumatic injury

Traumatic injury initiates a large and complex immune response in the minutes after the initial insult, comprising of simultaneous pro- and anti-inflammatory responses. In patients that survive the initial injury, these immune responses are believed to contribute towards complications such as the development of sepsis and multiple organ dysfunction syndrome. These post-traumatic complications affect a significant proportion of patients and are a major contributing factor for poor outcomes and an increased burden on healthcare systems. Therefore, understanding the immune responses to trauma is crucial for improving patient outcomes through the development of novel therapeutics and refining resuscitation strategies. In order to do this, preclinical animal models must mimic human immune responses as much as possible, and as such, we need to understand the constraints of each species in the context of trauma. A number of species have been used in this field; however, these models are limited by their genetic background and their capacity for recapitulating human immune function. This review provides a brief overview of the immune response in critically injured human patients and discusses the most commonly used species for modelling trauma, focusing on how their immune response to serious injury and haemorrhage compares to that of humans.

Preclinical Stroke Research and Translational Failure: A Bird's Eye View on Preventable Variables

Despite achieving remarkable success in understanding the cellular, molecular and pathophysiological aspects of stroke, translation from preclinical research has always remained an area of debate. Although thousands of experimental compounds have been reported to be neuro-protective, their failures in clinical setting have left the researchers and stakeholders in doldrums. Though the failures described have been excruciating, they also give us a chance to refocus on the shortcomings. For better translational value, evidences from preclinical studies should be robust and reliable. Preclinical study design has a plethora of variables affecting the study outcome. Hence, this review focusses on the factors to be considered for a well-planned preclinical study while adhering to guidelines with emphasis on the study design, commonly used animal models, their limitations with special attention on various preventable attritions including comorbidities, aged animals, time of dosing, outcome measures and physiological variables along with the concept of multicentric preclinical randomized controlled trials. Here, we provide an overview of a panorama of practical aspects, which could be implemented, so that a well-defined preclinical study would result in a neuro-protectant with better translational value.

Applications of Mouse Models to the Study of Food Allergy

Mouse models of allergic disease offer numerous advantages when compared to the models of other animals. However, selection of appropriate mouse models is critical to advance the field of food allergy by revealing mechanisms of allergy and for testing novel therapeutic approaches. All current mouse models for food allergy have weaknesses that may limit their applicability to human disease. Aspects such as the genetic predisposition to allergy or tolerance from the strain of mouse used, allergen dose, route of exposure (oral, intranasal, intraperitoneal, or epicutaneous), damage of the epithelial barrier, use of adjuvants, food matrix effects, or composition of the microbiota should be considered prior to the selection of a specific murine model and contemplated according to the intended purpose of the study. This chapter reviews our current knowledge on the application of mouse models to food allergy research and the variables that may influence the successful development of each type of model.

Protein sequence comparison of human and non-human primate tooth proteomes

In the context of human evolution, the study of proteins may overcome the limitation of the high degradation of ancient DNA over time to provide biomolecular information useful for the phylogenetic reconstruction of hominid taxa. In this study, we used a shotgun proteomics approach to compare the tooth proteomes of extant human and non-human primates (gorilla, chimpanzee, orangutan and baboon) in order to search for a panel of peptides able to discriminate between taxa and further help reconstructing the evolutionary relationships of fossil primates. Among the 25 proteins shared by the five genera datasets, we found a combination of peptides with sequence variations allowing to differentiate the hominid taxa in the proteins AHSG, AMBN, APOA1, BGN, C9, COL11A2, COL22A1, COL3A1, DSPP, F2, LUM, OMD, PCOLCE and SERPINA1. The phylogenetic tree confirms the placement of the samples in the appropriate genus branches. Altogether, the results provide experimental evidence that a shotgun proteomics approach on dental tissue has the potential to detect taxonomic variation, which is promising for future investigations of uncharacterized and/or fossil hominid/hominin specimens. SIGNIFICANCE: A shotgun proteomics approach on human and non-human primate teeth allowed to identify peptides with taxonomic interest, highlighting the potential for future studies on hominid fossils.

The Effects of Deoxynivalenol on the Ultrastructure of the Sacculus Rotundus and Vermiform Appendix, as Well as the Intestinal Microbiota of Weaned Rabbits

Deoxynivalenol (DON) is a mycotoxin found in grains that poses a potential threat to human and animal health, and the gastrointestinal tract is the primary target organ. There are few studies focused on the toxicology of DON to rabbits, especially on the relation among DON, microbiota, and the gut-associated lymphoid tissue. A total of 30 weaned rabbits (35 d) were evenly divided into the control group and DON group (1.5 mg/kg bodyweight (BW)) based on their body weight. After a 24-day trial, the ultrastructures of the sacculus rotundus and vermiform appendix were observed using a scanning electron microscope and transmission electron microscopy. The morphology and microflora in the ileum, caecum, and colon were also examined. The results proved that the ultrastructure of the sacculus rotundus and vermiform appendix, as well as the integrity of the intestinal barrier (especially for the ileum), were impaired after DON was administrated to the rabbits. Compared to the control group, the relative abundance and diversity of the microflora decreased in all three intestinal segments in the DON group, particularly in the ileum and caecum. In conclusion, the toxic effect of DON on weaned rabbits may be performed by destroying the structure of the sacculus rotundus and vermiform appendix, as well as affecting the structure and diversity of the intestinal flora.

Genomic, microbial and environmental standardization in animal experimentation limiting immunological discovery

Background

The use of inbred mice housed under standardized environmental conditions has been critical in identifying immuno-pathological mechanisms in different infectious and inflammatory diseases as well as revealing new therapeutic targets for clinical trials. Unfortunately, only a small percentage of preclinical intervention studies using well-defined mouse models of disease have progressed to clinically-effective treatments in patients. The reasons for this lack of bench-to-bedside transition are not completely understood; however, emerging data suggest that genetic diversity and housing environment may greatly influence muring immunity and inflammation.

Results

Accumulating evidence suggests that certain immune responses and/or disease phenotypes observed in inbred mice may be quite different than those observed in their outbred counterparts. These differences have been thought to contribute to differing immune responses to foreign and/or auto-antigens in mice vs. humans. There is also a growing literature demonstrating that mice housed under specific pathogen free conditions possess an immature immune system that remarkably affects their ability to respond to pathogens and/or inflammation when compared with mice exposed to a more diverse spectrum of microorganisms. Furthermore, recent studies demonstrate that mice develop chronic cold stress when housed at standard animal care facility temperatures (i.e. 22–24 °C). These temperatures have been shown alter immune responses to foreign and auto-antigens when compared with mice housed at their thermo-neutral body temperature of 30–32 °C.

Conclusions

Exposure of genetically diverse mice to a spectrum of environmentally-relevant microorganisms at housing temperatures that approximate their thermo-neutral zone may improve the chances of identifying new and more potent therapeutics to treat infectious and inflammatory diseases.

Resolving Peto's paradox: Modeling the potential effects of size-related metabolic changes, and of the evolution of immune policing and cancer suppression

The intrinsic risk of cancer increases with body size and longevity; however, big long-lived species do not exhibit this increase, a contradiction named Peto's paradox. Five hypotheses potentially resolving this paradox were modeled using the multistage model of carcinogenesis. The five hypotheses were based on (1) intrinsic changes in metabolic rate with body size; adaptive increase in immune policing of (2) cancer cells or (3) cells with driver mutations; or adaptive increase in cancer suppression via (4) decreased somatic mutation rate, or (5) increased genetic control. Parameter changes needed to stabilize cancer risk in three types of cancer were estimated for tissues scaled from mouse size and longevity to human and blue whale levels. The metabolic rate hypothesis alone was rejected due to a conflict between the required interspecific effect with the observed intraspecific effect of size on cancer risk, but some metabolic change was optionally incorporated in the other models. Necessary parameter changes in immune policing and somatic mutation rate far exceeded values observed; however, natural selection increasing the genetic suppression of cancer was generally consistent with data. Such adaptive increases in genetic control of cancers in large and/or long-lived animals raise the possibility that nonmodel animals will reveal novel anticancer mechanisms.

Sex-Specific Regulation of Gene Expression Networks by Surfactant Protein A (SP-A) Variants in Alveolar Macrophages in Response to Klebsiella pneumoniae

Surfactant protein A (SP-A) in addition to its surfactant-related functions interacts with alveolar macrophages (AM), the guardian cells of innate immunity in the lungs, and regulates many of its functions under basal condition and in response to various pressures, such as infection and oxidative stress. The human SP-A locus consists of two functional genes, SFTPA1 and SFTPA2, and one pseudogene. The functional genes encode human SP-A1 and SP-A2 proteins, respectively, and each has been identified with several genetic variants. SP-A variants differ in their ability to regulate lung function mechanics and survival in response to bacterial infection. Here, we investigated the effect of hSP-A variants on the AM gene expression profile in response to Klebsiella pneumoniae infection. We used four humanized transgenic (hTG) mice that each carried SP-A1 (6A², 6A⁴) or SP-A2 (1A⁰, 1A³), and KO. AM gene expression profiling was performed after 6 h post-infection. We found: (a) significant sex differences in the expression of AM genes; (b) in response to infection, 858 (KO), 196 (6A²), 494 (6A⁴), 276 (1A⁰), and 397 (1A³) genes were identified (P < 0.05) and some of these were differentially expressed with ≥2 fold, specific to either males or females; (c) significant SP-A1 and SP-A2 variant-specific differences in AM gene expression; (d) via Ingenuity Pathway Analysis (IPA), key pathways and molecules were identified that had direct interaction with TP53, TNF, and cell cycle signaling nodes; (e) of the three pathways (TNF, TP-53, and cell cycle signaling nodes) studied here, all variants except SP-A2 (1A³) female, showed significance for at least 2 of these pathways, and KO male showed significance for all three pathways; (f) validation of key molecules exhibited variant-specific significant differences in the expression between sexes and a similarity in gene expression profile was observed between KO and SP-A1. These results reveal for the first time a large number of biologically relevant functional pathways influenced in a sex-specific manner by SP-A variants in response to infection. These data may assist in studying molecular mechanisms of SP-A-mediated AM gene regulation and potentially identify novel therapeutic targets for K. pneumoniae infection.

Nonproliferative and Proliferative Lesions of the Rat and Mouse Hematolymphoid System

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative changes in rats and mice. The purpose of this publication is to provide a standardized nomenclature for classifying changes observed in the hematolymphoid organs, including the bone marrow, thymus, spleen, lymph nodes, mucosa-associated lymphoid tissues, and other lymphoid tissues (serosa-associated lymphoid clusters and tertiary lymphoid structures) with color photomicrographs illustrating examples of the lesions. Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. The nomenclature for these organs is divided into 3 terminologies: descriptive, conventional, and enhanced. Three terms are listed for each diagnosis. The rationale for this approach and guidance for its application to toxicologic pathology are described in detail below.

Development of Dog Immune System: From in Uterus to Elderly

Immune system recognize and fight back foreign microorganisms and inner modifications that lead to deficient cell and tissue functions. During a dog's life, the immune system needs to adapt to different physiological conditions, assuring surveillance and protection in a careful and controlled way. Pregnancy alters normal homeostasis, requiring a balance between immunity and tolerance. The embryos and fetus should be protected from infections, while the female dog must tolerate the growing of semi-allografts in her uterus. After birth, newborn puppies are at great risk of developing infectious diseases, because their immune system is in development and immune memory is absent. Passive transfer of immunity through colostrum is fundamental for puppy survival in the first weeks of life, but hampers the development of an active immune response to vaccination. At the end of life, dogs experience a decline in the structure and functional competence of the immune system, compromising the immune responses to novel antigenic challenges, such as infections and vaccines. Therefore, the current article reviews the general processes related to the development of the dog´s immune system, providing an overview of immune activity throughout the dog's life and its implications in canine health, and highlighting priority research goals.

Strain differences in histopathological features of lymphoid tissues of SD and F344 rats in a T cell-dependent antibody response assay of cyclophosphamide

When conducting histopathological evaluation of lymphoid tissues, it is necessary to know the variability and strain differences in histological features of different sites of lymphoid tissues. To investigate in detail the variability of lymphoid tissues and strain differences of control rats as well as those of immune reactivity and sensitivity to immunosuppression, we performed a histopathological analysis of various lymphoid tissues in conjunction with the evaluation of immune function in a T cell-dependent antibody response (TDAR) assay with cyclophosphamide (CP) in Sprague Dawley (SD) and F344 rats. Six-week-old male SD and F344 rats were orally treated with CP at 0 (control) or 4 mg/kg/day for 28 days; keyhole limpet hemocyanin (KLH) was introduced intravenously on Days 14 and 23, and the serum concentrations of anti-KLH antibodies were measured. HE staining and immunohistochemistry for T-cell (CD3) and B-cell (CD45RA) markers were performed using tissues from the spleen, thymus, and various lymph nodes. In CP-treated rats of both strains, decreased concentrations of anti-KLH antibodies were observed. Histopathological analysis revealed decreased lymphocytes mainly in the B-cell area, and these changes induced by CP treatment were more prominent in the F344 rats than in the SD rats. The present study also demonstrated that some of the lymphoid tissues of the control F344 rats were less developed than those of the control SD rats, suggesting that F344 rats might be easily affected by CP-induced immunosuppression. This information concerning rat strain differences in lymphoid tissues will be useful in histopathological evaluation for drug-induced immunotoxicity.

Distinct release strategies are required to modulate macrophage phenotype in young versus aged animals

The role of innate immunity and macrophages in the host response to biomaterials has received renewed attention. A context-dependent spectrum of macrophage phenotypes are shown to affect tissue integration and performance of implanted biomaterials and medical devices. Recent studies by our group demonstrated that the host response in aged animals was characterized by delayed macrophage recruitment, differences in marker expression and a shifted pro-inflammatory (M1) response, associated with an unresolved host response in the long-term. The present work sought to study the effects of single and sequential cytokine delivery regimens in aged mice to restore delayed recruitment of macrophages and shift the inflammatory host response towards an M2-like phenotype, using MCP-1 (macrophage chemotactic protein-1) and IL-4 (interleukin-4), respectively. Implantation of cytokine-eluting implants showed a preserved response to MCP-1 in both young and aged animals, restoring delayed macrophage recruitment in aged mice. However, the response elicited by IL-4, sequential delivery of MCP-1/IL-4 and coating components was distinct in young versus aged mice. While single delivery of IL-4 did not counteract the high inflammatory response observed in aged mice, the sequential delivery of MCP-1/IL-4 was capable of restoring both recruitment and shifting the macrophage response towards an M2-like phenotype, associated with decreased implant scarring in the long-term. In young mice, sequential delivery was not as effective as IL-4 alone at promoting an M2-like response, but did result in a reduction of M1 macrophages and capsule deposition downstream. These results demonstrate that a proper understanding of patient/context-dependent biological responses are needed to design biomaterial-based therapies with improved outcomes in the setting of aging.

Biocompatibility of common implantable sensor materials in a tumor xenograft model

Real-time monitoring of tumor microenvironment parameters using an implanted biosensor could provide valuable information on the dynamic nature of a tumor's biology and its response to treatment. However, following implantation biosensors may lose functionality due to biofouling caused by the foreign body response (FBR). This study developed a novel tumor xenograft model to evaluate the potential of six biomaterials (silicon dioxide, silicon nitride, Parylene-C, Nafion, biocompatible EPOTEK epoxy resin, and platinum) to trigger a FBR when implanted into a solid tumor. Biomaterials were chosen based on their use in the construction of a novel biosensor, designed to measure spatial and temporal changes in intra-tumoral O2 , and pH. None of the biomaterials had any detrimental effect on tumor growth or body weight of the murine host. Immunohistochemistry showed no significant changes in tumor necrosis, hypoxic cell number, proliferation, apoptosis, immune cell infiltration, or collagen deposition. The absence of biofouling supports the use of these materials in biosensors; future investigations in preclinical cancer models are required, with a view to eventual applications in humans. To our knowledge this is the first documented investigation of the effects of modern biomaterials, used in the production of implantable sensors, on tumor tissue after implantation. © 2018 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1620-1633, 2019.

The spleen morphophysiology of fruit bats

Spleen is one of the important lymphoid organs with wide variations of morphological and physiological functions according to species. Morphology and function of the spleen in bats, which are hosts to several viral strains without exhibiting clinical symptoms, remain to be fully elucidated. This study aims to examine the spleen morphology of fruit bats associated with their physiological functions. Spleen histological observations were performed in three fruit bats species: Cynopterus titthaecheilus (n = 9), Rousettus leschenaultii (n = 3) and Pteropus vampyrus (n = 3). The spleens of these fruit bats were surrounded by a thin capsule. Red pulp consisted of splenic cord and wide vascular space filled with blood. Ellipsoids in all three studied species were found numerously and adjacent to one another forming macrophages aggregates. White pulp consisted of periarteriolar lymphoid sheaths (PALS), lymphoid follicles and marginal zone. The lymphoid follicle contained a germinal centre and a tingible body macrophage that might reflect an active immune system. The marginal zone was prominent and well developed. This study reports some differences in spleen structure of fruit bats compared to other bat species previously reported and discusses possible physiological implications of the spleen based on its morphology.

The cellular basis of fibrotic tendon healing: challenges and opportunities

Tendon injuries are common and can dramatically impair patient mobility and productivity, resulting in a significant socioeconomic burden and reduced quality of life. Because the tendon healing process results in the formation of a fibrotic scar, injured tendons never regain the mechanical strength of the uninjured tendon, leading to frequent reinjury. Many tendons are also prone to the development of peritendinous adhesions and excess scar formation, which further reduce tendon function and lead to chronic complications. Despite this, there are currently no treatments that adequately improve the tendon healing process due in part to a lack of information regarding the contributions of various cell types to tendon healing and how their activity may be modulated for therapeutic value. In this review, we summarize recent efforts to identify and characterize the distinct cell populations involved at each stage of tendon healing. In addition, we examine the mechanisms through which different cell populations contribute to the fibrotic response to tendon injury, and how these responses can be affected by systemic factors and comorbidities. We then discuss gaps in our current understanding of tendon fibrosis and highlight how new technologies and research areas are shedding light on this clinically important and intractable challenge. A better understanding of the complex cellular environment during tendon healing is crucial to the development of new therapies to prevent fibrosis and promote tissue regeneration.

Obesogenic diet in aging mice disrupts gut microbe composition and alters neutrophil:lymphocyte ratio, leading to inflamed milieu in acute heart failure

Calorie-dense obesogenic diet (OBD) is a prime risk factor for cardiovascular disease in aging. However, increasing age coupled with changes in the diet can affect the interaction of intestinal microbiota influencing the immune system, which can lead to chronic inflammation. How age and calorie-enriched OBD interact with microbial flora and impact leukocyte profiling is currently under investigated. Here, we tested the interorgan hypothesis to determine whether OBD in young and aging mice alters the gut microbe composition and the splenic leukocyte profile in acute heart failure (HF). Young (2-mo-old) and aging (18-mo-old) mice were supplemented with standard diet (STD, ∼4% safflower oil diet) and OBD (10% safflower oil) for 2 mo and then subjected to coronary artery ligation to induce myocardial infarction. Fecal samples were collected pre- and post-diet intervention, and the microbial flora were analyzed using 16S variable region 4 rRNA gene DNA sequencing and Quantitative Insights Into Microbial Ecology informatics. The STD and OBD in aging mice resulted in an expansion of the genus Allobaculum in the fecal microbiota. However, we found a pathologic change in the neutrophil:lymphocyte ratio in aging mice in comparison with their young counterparts. Thus, calorie-enriched OBD dysregulated splenic leukocytes by decreasing immune-responsive F4/80+ and CD169+ macrophages in aging mice. OBD programmed neutrophil swarming with an increase in isoprostanoid levels, with dysregulation of lipoxygenases, cytokines, and metabolite-sensing receptor expression. In summary, calorie-dense OBD in aging mice disrupted the composition of the gut microbiome, which correlates with the development of integrative and system-wide nonresolving inflammation in acute HF.-Kain, V., Van Der Pol, W., Mariappan, N., Ahmad, A., Eipers, P., Gibson, D. L., Gladine, C., Vigor, C., Durand, T., Morrow, C., Halade, G. V. Obesogenic diet in aging mice disrupts gut microbe composition and alters neutrophil:lymphocyte ratio, leading to inflamed milieu in acute heart failure.

Immunological aspects of allogeneic pancreatic islet transplantation: a comparison between mouse and human

Pancreatic islet allotransplantation is a treatment for patients with severe forms of type 1 diabetes. As long-term graft function and survival are not yet optimal, additional studies are warranted in order to continue improving transplant outcomes. The mechanisms of islet graft loss and tolerance induction are often studied in murine diabetes models. Despite numerous islet transplantation studies successfully performed over recent years, translation from experimental mouse models to human clinical application remains elusive. This review aims at critically discussing the strengths and limitations of current mouse models of diabetes and experimental islet transplantation. In particular, we will analyze the causes leading to diabetes and compare the immunological mechanisms responsible for rejection between mouse and human. A better understanding of the experimental mouse models should facilitate translation to human clinical application.

An in vitro model mimics the contact of biomaterials to blood components and the reaction of surrounding soft tissue

The therapeutic efficacy of a medical product after implantation depends strongly on the host-initiated fibrotic response (foreign body reaction). For novel biomaterials, it is of high relevance to understand this fibrotic process. As an alternative to in vivo studies, in vitro models mimic parts of the whole foreign body reaction. Aim of this study was to develop a wound model with key cells and matrix proteins in coculture. This approach combined blood components such as primary macrophages in a plasma-derived fibrin hydrogel, directly exposed to reference biomaterials (PTFE, glass, titanium). The soft tissue reaction is resembled by integrating fibroblasts in a collagen or a fibrin matrix. Those two experimental setups were conducted to show whether a long-term in vitro culture of 13 days is feasible. The response to reference biomaterials was assessed by multi-parametric analyses, comprising molecular profiling (cytokines, collagen I and ß-actin) and tissue remodeling (cell adherence, histological structure, tissue deposition). Polytetrafluorethylene (PTFE) and titanium were tested as references to correlate the in vitro evaluation to previous in vivo studies. Most striking, both model setups evaluated references' fibrotic characteristics as previously reported by in vivo studies. STATEMENT OF SIGNIFICANCE: We present a test platform applied for assessments on the foreign body reaction to biomaterials. This test system consists of blood components - macrophages and plasma-derived fibrin - as well as fibroblasts and collagen, generating a three-dimensional wound microenvironment. By this modular approach, we achieved a suitable test for long-term studies and overcame the limited short-term stability of whole blood tests. In contrast to previous models, macrophages' viability is maintained during the extended culture period and excels the quality of the model. The potential to evaluate a foreign body reaction in vitro was demonstrated with defined reference materials. This model system might be of high potential as a screening platform to identify novel biomaterial candidates.

Evolution of the Supermodel: Progress in Modelling Radiotherapy Response in Mice

Mouse models are essential tools in cancer research that have been used to understand the genetic basis of tumorigenesis, cancer progression and to test the efficacies of anticancer treatments including radiotherapy. They have played a critical role in our understanding of radiotherapy response in tumours and normal tissues and continue to evolve to better recapitulate the underlying biology of humans. In addition, recent developments in small animal irradiators have significantly improved in vivo irradiation techniques, allowing previously unimaginable experimental approaches to be explored in the laboratory. The combination of contemporary mouse models with small animal irradiators represents a major step forward for the radiobiology field in being able to much more accurately replicate clinical exposure scenarios. As radiobiology studies become ever more sophisticated in reflecting developments in the clinic, it is increasingly important to understand the basis and potential limitations of extrapolating data from mice to humans. This review provides an overview of mouse models and small animal radiotherapy platforms currently being used as advanced radiobiological research tools towards improving the translational power of preclinical studies.