Histopathology of the thymus

Network meta-analysis of the molecular mechanisms and signaling pathways underlying alcohol-induced thymic atrophy

BACKGROUND

Thymic atrophy is characterized by loss of thymocytes, destruction of thymic architecture, and a subsequent decrease in naïve T cells with compromised immunity. Thymic atrophy occurs during aging. Environmental factors including alcohol misuse also induce thymic atrophy. Despite the link between alcohol misuse and thymic atrophy, the underlying mechanism is understudied. We aimed to identify molecules and signaling pathways that underly alcohol-induced thymic atrophy during aging.

METHODS

F344 rats were given 3-day binge-ethanol (4.8 g/kg/day; 52% w/v; i.g.) and the thymus was collected and weighed. Molecular mechanisms underlying ethanol-induced thymic atrophy were investigated by network meta-analysis using the QIAGEN Ingenuity Pathway Analysis (IPA). The molecules associated with ethanol were identified from the QIAGEN Knowledge Base (QKB) and those associated with thymic atrophy were identified from QKB and Mouse Genome Informatics (MGI). Aging-mediated Differential Expression Genes (DEGs) from mouse thymocytes were obtained from the Gene Expression Omnibus (GEO) database (GSE132136). The relationship between the molecules and associated signaling pathways were studied using IPA.

RESULTS

Binge-ethanol decreased thymic weight in F344 rats. Our meta-analysis using IPA identified molecules commonly shared by ethanol and thymic atrophy through which simulation with ethanol increased thymic atrophy. We then obtained aging-mediated DEGs from the atrophied thymocytes. We found that ethanol contributed to thymic atrophy through modulation of the aging-mediated DEGs. Our network meta-analysis suggests that ethanol may augment thymic atrophy through increased expression of cytokines (e.g., IL-6, IL-17A and IL-33) along with their regulators (e.g., STAT1 and STAT3).

CONCLUSIONS

Exposure to alcohol may augment thymic atrophy by altering the activity of key inflammatory mediators, such as STAT family members and inflammatory cytokines. These findings provide insights into the signaling pathways and upstream regulators that underly alcohol-induced thymic atrophy during aging, suggesting that alcohol consumption could prepone thymic atrophy.

A multi-organ map of the human immune system across age, sex and ethnicity

Understanding tissue biology's heterogeneity is crucial for advancing precision medicine. Despite the centrality of the immune system in tissue homeostasis, a detailed and comprehensive map of immune cell distribution and interactions across human tissues and demographics remains elusive. To fill this gap, we harmonised data from 12,981 single-cell RNA sequencing samples and curated 29 million cells from 45 anatomical sites to create a comprehensive compositional and transcriptional healthy map of the healthy immune system. We used this resource and a novel multilevel modelling approach to track immune ageing and test differences across sex and ethnicity. We uncovered conserved and tissue-specific immune-ageing programs, resolved sex-dependent differential ageing and identified ethnic diversity in clinically critical immune checkpoints. This study provides a quantitative baseline of the immune system, facilitating advances in precision medicine. By sharing our immune map, we hope to catalyse further breakthroughs in cancer, infectious disease, immunology and precision medicine.

Evolution of T cells in the cancer-resistant naked mole-rat

Naked mole-rats (NMRs) are best known for their extreme longevity and cancer resistance, suggesting that their immune system might have evolved to facilitate these phenotypes. Natural killer (NK) and T cells have evolved to detect and destroy cells infected with pathogens and to provide an early response to malignancies. While it is known that NMRs lack NK cells, likely lost during evolution, little is known about their T-cell subsets in terms of the evolution of the genes that regulate their function, their clonotypic diversity, and the thymus where they mature. Here we find, using single-cell transcriptomics, that NMRs have a large circulating population of γδT cells, which in mice and humans mostly reside in peripheral tissues and induce anti-cancer cytotoxicity. Using single-cell-T-cell-receptor sequencing, we find that a cytotoxic γδT-cell subset of NMRs harbors a dominant clonotype, and that their conventional CD8 αβT cells exhibit modest clonotypic diversity. Consistently, perinatal NMR thymuses are considerably smaller than those of mice yet follow similar involution progression. Our findings suggest that NMRs have evolved under a relaxed intracellular pathogenic selective pressure that may have allowed cancer resistance and longevity to become stronger targets of selection to which the immune system has responded by utilizing γδT cells.

Morphometric Analysis of the Thymic Epithelial Cell (TEC) Network Using Integrated and Orthogonal Digital Pathology Approaches

The thymus, a central primary lymphoid organ of the immune system, plays a key role in T cell development. Surprisingly, the thymus is quite neglected with regards to standardized pathology approaches and practices for assessing structure and function. Most studies use multispectral flow cytometry to define the dynamic composition of the thymus at the cell population level, but they are limited by lack of contextual insight. This knowledge gap hinders our understanding of various thymic conditions and pathologies, particularly how they affect thymic architecture, and subsequently, immune competence. Here, we introduce a digital pathology pipeline to address these challenges. Our approach can be coupled to analytical algorithms and utilizes rationalized morphometric assessments of thymic tissue, ranging from tissue-wide down to microanatomical and ultrastructural levels. This pipeline enables the quantitative assessment of putative changes and adaptations of thymic structure to stimuli, offering valuable insights into the pathophysiology of thymic disorders. This versatile pipeline can be applied to a wide range of conditions that may directly or indirectly affect thymic structure, ranging from various cytotoxic stimuli inducing acute thymic involution to autoimmune diseases, such as myasthenia gravis. Here, we demonstrate applicability of the method in a mouse model of age-dependent thymic involution, both by confirming established knowledge, and by providing novel insights on intrathymic remodeling in the aged thymus. Our orthogonal pipeline, with its high versatility and depth of analysis, promises to be a valuable and practical toolset for both basic and translational immunology laboratories investigating thymic function and disease.

Primary and secondary defects of the thymus

The thymus is the primary site of T-cell development, enabling generation, and selection of a diverse repertoire of T cells that recognize non-self, whilst remaining tolerant to self- antigens. Severe congenital disorders of thymic development (athymia) can be fatal if left untreated due to infections, and thymic tissue implantation is the only cure. While newborn screening for severe combined immune deficiency has allowed improved detection at birth of congenital athymia, thymic disorders acquired later in life are still underrecognized and assessing the quality of thymic function in such conditions remains a challenge. The thymus is sensitive to injury elicited from a variety of endogenous and exogenous factors, and its self-renewal capacity decreases with age. Secondary and age-related forms of thymic dysfunction may lead to an increased risk of infections, malignancy, and autoimmunity. Promising results have been obtained in preclinical models and clinical trials upon administration of soluble factors promoting thymic regeneration, but to date no therapy is approved for clinical use. In this review we provide a background on thymus development, function, and age-related involution. We discuss disease mechanisms, diagnostic, and therapeutic approaches for primary and secondary thymic defects.

Small fetal thymus and adverse perinatal outcome in maternal vasculitis: A prospective case-control study

BACKGROUND

Ultrasonographic evaluation of fetal thymus size may be used to predict the adverse perinatal outcome in pregnant women with vasculitis.

AIM

To compare fetal thymus size in pregnant women with vasculitis and healthy pregnant women and to evaluate whether fetal thymus size predicts the adverse perinatal outcome.

METHODS

Twenty-two pregnant women with previously diagnosed vasculitis, 18 of them with Behçet's disease, three with Takayasu arteritis, and one with Wegener's granulomatosis, were included in the case group. The control group comprised 66 healthy pregnant women whose gestational ages matched the case group. Thymic thoracic ratio (TTR) was measured to assess fetal thymus size in the view of three vessels and trachea.

RESULTS

In the case group, fetal TTR was significantly lower (0.32 ± 0.03 vs. 0.36 ± 0.02, p = < 0.001). Fetal TTR was significantly lower in those using prednisone than those not (p = .001) in the case group. There was no significant difference in fetal TTR between colchicine used and not used (p = .078) in the case group. Also, for the TTR, a sensitivity of 100% and a specificity of 92% were achieved with a cut-off value of 0.33 for predicting adverse perinatal outcomes.

CONCLUSION

The fetuses of pregnant women with maternal vasculitis had a smaller TTR. The small fetal thymus may alert clinicians to possible adverse perinatal outcomes and, with other supporting risk factors, may help predict adverse perinatal outcomes in pregnant women with vasculitis.

Fetal Thymus Size at 19-22 Weeks of Gestation: A Possible Marker for the Prediction of Low Birth Weight?

INTRODUCTION

The purpose was to compare thymus size measured during second trimester screening of fetuses who were subsequently small for gestational age at birth (weight below 10th percentile, SGA group) with fetuses with normal birth weight (control group). We hypothesized that measuring the fetal thymic-thoracic ratio (TT-ratio) might help predict low birth weight.

METHODS

Using three-vessel view echocardiograms from our archives, we measured the anteroposterior thymus size and the intrathoracic mediastinal diameter to derive TT-ratios in the SGA (n = 105) and control groups (n = 533) between 19+0 and 21+6 weeks of gestation. We analyzed the association between TT-ratio and SGA adjusted to the week of gestation using logistic regression. Finally, we determined the possible TT-ratio cut-off point for discrimination between SGA and control groups by means of receiver operating characteristics (ROC) curve analysis.

RESULTS

The TT-ratio was significantly higher in the SGA group than in the control group (p < 0.001). An increase of the TT-ratio by 0.1 was associated with a 3.1-fold increase in the odds of diagnosing SGA. We determined that a possible discrimination cut-off point between SGA and healthy controls was achieved using a TT-ratio of 0.390 (area under the ROC curve 0.695).

CONCLUSION

An increased TT-ratio may represent an additional prenatal screening parameter that improves the prediction of birth weight below the 10th percentile. Prospective studies are now needed to evaluate the use of fetal thymus size as predictive parameter for adverse fetal outcome.

Fetal thymic-thoracic ratio in pregnancies with familial Mediterranean fever

OBJECTIVE

To investigate the thymic-thoracic ratio (TTR) in fetuses of pregnant women with familial Mediterranean fever (FMF).

STUDY DESIGN

This prospective case-control study was conducted with 43 pregnant women diagnosed with FMF and 43 gestational age-matched healthy controls. Pregnant women between 28 and 40 weeks who applied for antenatal care were included in the study. Healthy pregnant women whose age and gestational week matched were defined as the control group.

RESULTS

TTR was significantly lower in the FMF group compared to the control group. The mean TTR value was 0.34 ± 0.03 in the FMF group and 0.36 ± 0.02 in the control group (p < 0.001). TTR was significantly lower in those with FMF duration of ten years or more than those with FMF of less than ten years (p < 0.001). In addition, pregnant women who had an attack during pregnancy had lower TTR (p < 0.001). TTR was significantly associated with white blood cell count, neutrophil count, monocyte count, platelet count, mean platelet volume, C-reactive protein, red cell distribution width, and platelet‑to‑lymphocyte ratio.

CONCLUSION

Besides the inflammation during the FMF attacks, the ongoing subclinical inflammation between the attacks might affect the fetal thymus size. Since TTR is an easily applicable method, it can be used to evaluate fetal inflammation.

Assessment of Chronic Toxicity of an Ayurvedic Herbo-Metallic Formulation Rasaraj Rasa in Wistar Rats

Objectives

This study aimed to assess the adverse effects of Rasaraj Rasa tablets after repeated oral administration for 180 days in Wistar rats.

Methods

Wistar rats were divided into five groups, of which three were treated with 54, 162, and 270 mg/kg body weight of Rasaraj Rasa, respectively, which correspond to one, three, and five times the proposed human therapeutic dose, for 180 days consecutively. The fifth group (satellite) also received 270 mg/kg body weight of Rasaraj Rasa for 180 days. Body weight and food intake were measured weekly. At the end of the study, all rats were sacrificed, and their blood, serum, and organs were collected and examined using hematology, serum biochemistry, gross pathology, and histopathology tests. In contrast, the satellite group was kept for 4 weeks after treatment.

Results

No significant treatment-related toxicological findings were observed in the clinical features, body weight, laboratory findings, and pathological findings of the high-dose treated groups, when compared to those of the control group.

Conclusion

The no-observed-adverse-effect-level for Rasaraj Rasa in Wistar rats is set at 270 mg/kg body weight.

A Knock-In Mouse Model of Thymoma With the GTF2I L424H Mutation

INTRODUCTION

The pathogenesis of thymic epithelial tumors remains largely unknown. We previously identified GTF2I L424H as the most frequently recurrent mutation in thymic epithelial tumors. Nevertheless, the precise role of this mutation in tumorigenesis of thymic epithelial cells is unclear.

METHODS

To investigate the role of GTF2I L424H mutation in thymic epithelial cells in vivo, we generated and characterized a mouse model in which the Gtf2i L424H mutation was conditionally knocked-in in the Foxn1+ thymic epithelial cells. Digital spatial profiling was performed on thymomas and normal thymic tissues with GeoMx-mouse whole transcriptome atlas. Immunohistochemistry staining was performed using both mouse tissues and human thymic epithelial tumors.

RESULTS

We observed that the Gtf2i mutation impairs development of the thymic medulla and maturation of medullary thymic epithelial cells in young mice and causes tumor formation in the thymus of aged mice. Cell cycle-related pathways, such as E2F targets and MYC targets, are enriched in the tumor epithelial cells. Results of gene set variation assay analysis revealed that gene signatures of cortical thymic epithelial cells and thymic epithelial progenitor cells are also enriched in the thymomas of the knock-in mice, which mirrors the human counterparts in The Cancer Genome Atlas database. Immunohistochemistry results revealed similar expression pattern of epithelial cell markers between mouse and human thymomas.

CONCLUSIONS

We have developed and characterized a novel thymoma mouse model. This study improves knowledge of the molecular drivers in thymic epithelial cells and provides a tool for further study of the biology of thymic epithelial tumors and for development of novel therapies.

Immunohistochemical Characterization of Proliferative Lesions in the Thymus of Aging CD-1 Mice From Two Studies on the RITA Database, With Special Reference to the Perivascular Space

Thymic lymphoid hyperplasia is a common age-related finding, which occurs particularly in female CD-1 mice. The main differential diagnoses are malignant lymphoma and thymoma. A systematic investigation of control groups from two carcinogenicity studies was performed including measurements of thymic size, and the immunohistochemistry (IHC) markers pan-Cytokeratin (pan-CK) for thymic epithelial cells; CD3 and CD45R/B220 for T and B lymphocytes, respectively; CD31 for endothelial cells; and F4/80 for macrophages. Thymoma can be differentiated by increased numbers of proliferating epithelial cells demonstrated by pan-CK IHC staining. Differentiation between lymphoid hyperplasia and lymphoma is more challenging as a mixture of B and T lymphocytes can be present in both findings. The present investigation showed that the thymic perivascular space is the compartment where the increased numbers of lymphocytes in hyperplasia are localized and not the medulla, as previously thought. The lymphoepithelial compartment is atrophic to the same extent in thymi diagnosed with age-related involution or lymphoid hyperplasia. Both diagnoses are thus related to variations in lymphoid cellularity of the nonepithelial perivascular space, which is continuous with the perithymic tissue. Likewise, lymphomas have a predilection to colonize the perivascular space and to spare the lymphoepithelial compartment.

Physicochemical Characterizations and Pharmacokinetic Evaluation of Pentazocine Solid Lipid Nanoparticles against Inflammatory Pain Model

Pentazocine (PTZ), a narcotic-antagonist analgesic, has been extensively used in the treatment of initial carcinogenic or postoperative pain. Hepatic first-pass metabolism results in low oral bioavailability and high dose wastage. Herein, 10 mg (-)-Pentazocine (HPLC-grade) was incorporated to solid lipid nanoparticles (SLNs) using a double water-oil-water (w/o/w) emulsion by solvent emulsification–evaporation technique, followed by high shear homogenization to augment its oral bioavailability, considering the lymphatic uptake. The resulting SLNs were characterized for zeta potential (ZP), particle size (PS), and polydispersity index (PDI) using a zetasizer. The entrapment efficiency (EE) and loading capacity (LC) were calculated. Chemical interactions, through the identification of active functional groups, were assessed by Fourier-transformed infrared (FTIR) spectroscopy. The nature (crystallinity) of the SLNs was determined by X-ray diffractometry (XRD). The surface morphology was depicted by transmission electron microscopy (TEM). In vitro (in Caco-2 cells) and in vivo (in male Wistar rats) investigations were carried out to evaluate the PTZ release behavior and stability, as well as the cellular permeation, cytotoxicity, systemic pharmacokinetics, antinociceptive, anti-inflammatory, and antioxidative activities of PTZ-loaded SLNs, mainly compared to free PTZ (marketed conventional dosage form). The optimized PTZ-loaded SLN2 showed significantly higher in vitro cellular permeation and negligible cytotoxicity. The in vivo bioavailability and pharmacokinetics parameters (t1/2, Cmax) of the PTZ-loaded SLNs were also significantly improved, and the nociception and inflammation, following carrageenan-induced inflammatory pain, were markedly reduced. Concordantly, PTZ-loaded SLNs showed drastic reduction in the oxidative stress (e.g., malonaldehyde (MDA)) and proinflammatory cytokines (e.g., Interleukin (IL)-1β, -6, and TNF-α). The histological features of the paw tissue following, carrageenan-induced inflammation, were significantly improved. Taken together, the results demonstrated that PTZ-loaded SLNs can improve the bioavailability of PTZ by bypassing the hepatic metabolism via the lymphatic uptake, for controlled and sustained drug delivery.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

FEMA GRAS assessment of natural flavor complexes: Origanum oil, thyme oil and related phenol derivative-containing flavoring ingredients

In 2015, the Expert Panel of the Flavor and Extract Manufacturers Association (FEMA) initiated a re-evaluation of the safety of over 250 natural flavor complexes (NFCs) used as flavor ingredients, mostly consisting of a variety of essential oils and botanical extracts. This publication, seventh in the series, re-evaluates NFCs with constituent profiles dominated by phenolic derivatives including carvacrol, thymol and related compounds using a constituent-based procedure first published in 2005 and updated in 2018. The procedure is based on the chemical characterization of each NFC as intended for commerce and the estimated intake of the constituent congeneric groups. The procedure applies the threshold of toxicological concern (TTC) concept and evaluates relevant data on absorption, metabolism, genotoxic potential and toxicology of the constituent congeneric groups and the NFC under evaluation. Herein, the FEMA Expert Panel affirmed the generally recognized as safe (GRAS) status of seven phenolic derivative-based NFCs, Origanum Oil (Extractive) (FEMA 2828), Savory Summer Oil (FEMA 3013), Savory Summer Oleoresin (FEMA 3014), Savory Winter Oil (FEMA 3016), Savory Winter Oleoresin (FEMA 3017), Thyme Oil (FEMA 3064) and Thyme White Oil (FEMA 3065) under their conditions of intended use as flavor ingredients.

Development of thymic tumor in [LSL:KrasG12D; Pdx1-CRE] mice, an adverse effect associated with accelerated pancreatic carcinogenesis

Pancreatic Ductal AdenoCarcinoma (PDAC) represents about 90% of pancreatic cancers. It is one of the most aggressive cancer, with a 5-year survival rate below 10% due to late diagnosis and poor therapeutic efficiency. This bad prognosis thus encourages intense research in order to better understand PDAC pathogenesis and molecular basis leading to the development of innovative therapeutic strategies. This research frequently involves the KC (LSL:KrasG12D;Pdx1-CRE) genetically engineered mouse model, which leads to pancreatic cancer predisposition. However, as frequently encountered in animal models, the KC mouse model also exhibits biases. Herein, we report a new adverse effect of KrasG12D mutation in KC mouse model. In our hands, 10% of KC mice developed clinical signs reaching pre-defined end-points between 100- and 150-days post-parturition, and associated with large thymic mass development. Histological and genetic analyses of this massive thymus enabled us (1) to characterize it as a highly proliferative thymic lymphoma and (2) to detect the unexpected recombination of the Lox-STOP-Lox cassette upstream KrasG12D allele and subsequent KRASG12D protein expression in all cells composing thymic masses. Finally, we highlighted that development of such thymic tumor was associated with accelerated pancreatic carcinogenesis, immune compartment disorganization, and in some cases, lung malignancies.

Histology of some major immune system organs in Lake Van fish Alburnus tarichi (Güldenstädt, 1814) (Cyprinidae)

The teleostean immune system is variable between and within taxa in terms of morphology. Accordingly, in the current study, the histology of some immune organs (thymus, kidney and spleen) of Lake Van fish (Alburnus tarichi) was investigated. For this purpose, the tissues from eight mature fish were fixed and embedded in paraffin wax, and then the sections were stained with haematoxylin and eosin, Mallory's triple, periodic acid-Schiff and Alcian blue (pH of 2.5) for histologic examinations. In the thymus, no clear discrimination of the cortex and medulla was observed. Lymphoid cells within a reticulo-epithelial network were the predominant cell type in the thymus. The other components in the thymus were macrophages and myoid, mast-like, plasma-like, cystic cells, Hassall's corpuscles, and single or multiple epithelial cystic structures. In the kidney, the head kidney, a major haematopoietic site, consisted of lymphoid and non-lymphoid zones within a reticular network. Cells exhibiting mitotic figures were also detected in the haematopoietic tissue of the head kidney. Haematopoietic tissue was also found in the trunk kidney dispersed amongst the excretory components. The spleen was composed of red and white pulp. The red pulp comprised abundant erythrocytes, whilst the white pulp contained leucocytes with a reticular network. Ellipsoids were also determined in the white pulp. Melanomacrophage centres were found in all of the examined lymphoid tissues of the fish. These findings, which were reported, herein, for the first time will provide reference knowledge for future studies of this anadromous fish.

A spontaneous thymic carcinosarcoma in a young Sprague Dawley rat

We encountered a case of spontaneous thymic carcinosarcoma in a young Crl:CD (Sprague Dawley) rat. Grossly, a white multinodular mass replaced the thymus in the thoracic cavity. Histologically, multiple nodules were separated by fibrous stroma, and each nodule included isolated regions that were composed of epithelial or non-epithelial tumor cells. The epithelial tumor cells were relatively large and round to polygonal cells with large nuclei and weakly eosinophilic cytoplasm. These cells were cytokeratin-positive and vimentin-negative. These cells infiltrated the lungs. The non-epithelial tumor cells were poorly differentiated, small, round to spindle-shaped cells with small nuclei and basophilic cytoplasm. These cells were vimentin-positive and mostly cytokeratin-negative. Many islands of cartilage were observed near non-epithelial cells. Based on these findings, the tumor was diagnosed as a primary thymic carcinosarcoma consisting of a malignant thymoma composed of epithelial tumor cells and a mesenchymal chondrosarcoma composed of non-epithelial tumor cells.

Toxicity of humidifier disinfectant polyhexamethylene guanidine hydrochloride by two-week whole body-inhalation exposure in rats

The use of polyhexamethylene guanidine hydrochloride (PHMG·HCl) as a humidifier disinfectant caused an outbreak of pulmonary disease, leading to the deaths of pregnant women and children in South Korea. However, limited information is available on the inhalation toxicity of PHMG·HCl. Therefore, this study aimed to characterize the subacute inhalation toxicity of PHMG·HCl by whole-body exposure in rats. F344 rats were exposed to 0 mg/m³, 1 mg/m³, 5 mg/m³, or 25 mg/m³ of PHMG·HCl for 6 h/day, 5 days/week for two weeks via whole-body inhalation. Emaciation and rale were observed in rats in the 25 mg/m³ PHMG·HCl group. Significant changes in body weight, hematology, serum chemistry and organ weight were observed in all PHMG·HCl-exposed groups. Gross lesions showed ballooning or red focus in the lungs of rats in the PHMG·HCl-exposed groups. In histopathological examination, most of histological lesions (including degeneration, atrophy, ulcer, inflammatory cell infiltration, inflammation, and fibrosis in nasal cavity, larynx, trachea, and lungs) indicated tissue damage by PHMG·HCl in all PHMG·HCl-exposed groups. Additionally, atrophy of the spleen, thymus, and reproductive organs; immaturity of the testes; and cell debris in the epididymides were affected by the reduction in body weight in PHMG·HCl-exposed groups. In conclusion, two-week repeated whole-body inhalation exposure of rats to PHMG·HCl reveled toxic effects on the respiratory system and secondary effects on other organs. The results of this study indicate that the no observable adverse effect level (NOAEL) for PHMG·HCl is below 1 mg/m³.

Celastrol Efficacy by Oral Administration in the Adjuvant-Induced Arthritis Model

Background: We previously demonstrated that celastrol has significant anti-inflammatory and bone protective effects when administered via the intraperitoneal route. For further preclinical evaluation, an effective oral administration of celastrol is crucial. Here we aimed to study the therapeutic dose range for its oral administration.

Methods: Celastrol (1–25 μg/g/day, N = 5/group) was administrated orally to female adjuvant-induced arthritis (AIA) rats after 8 days of disease induction for a period of 14 days. A group of healthy (N = 8) and arthritic (N = 15) gender- and age-matched Wistar rats was used as controls. During the treatment period, the inflammatory score, ankle perimeter, and body weight were measured. At the end of the treatment, the animals were sacrificed, blood was collected for clinical pathology, necropsy was performed with collection of internal organs for histopathological analysis, and paw samples were used for disease scoring.

Results: Doses higher than 2.5 μg/g/day of celastrol reduced the inflammatory score and ankle swelling, preserved joint structure, halted bone destruction, and diminished the number of synovial CD68+ macrophages. Bone resorption and turnover were also reduced at 5 and 7.5 μg/g/day doses. However, the dose of 7.5 μg/g/day was associated with thymic and liver lesions, and higher doses showed severe toxicity.

Conclusion: Oral administration of celastrol above 2.5 μg/g/day ameliorates arthritis. This data supports and gives relevant information for the development of a preclinical test of celastrol in the setting of a chronic model of arthritis since rheumatoid arthritis is a long-term disease.

The effects of feed naturally contaminated with Fusarium mycotoxins on the thymus in suckling piglets

In this study, feed naturally containing Fusarium mycotoxins was fed to gilts during the perinatal period, and the effects on the thymus were investigated in one-week-old piglets. Twenty gilts were divided into equal control (0.26 mg deoxynivalenol, DON) and experimental (5.08 mg DON, 0.09 mg zearalenone and 21.61 mg fusaric acid per kg of feed) groups. One suckling piglet from each litter (n = 20) was sacrificed at one week of age to obtain thymus samples for further analysis. The cortex to medulla ratio of the thymus was morphometrically analysed using NIS Elements BR (Nikon) software. Paraffin-embedded thymus sections were stained to quantify apoptosis (with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling - TUNEL method), cellular proliferation (Ki-67) and macrophages (MAC 387). The results showed that the thymus cortex (P = 0.023) to medulla (P = 0.023) ratio was significantly lower in the experimental group. The number of apoptotic cells (cortex, P = 0.010, medulla, P = 0.001) and the number of proliferating cells in the thymus cortex (P = 0.001) and medulla (P < 0.001) were significantly higher in the experimental group. Our results indicate that feeding Fusarium mycotoxins to a parent animal during the perinatal period induces significant alterations in the thymus of one-week-old piglets, which indicates an immunosuppressive effect in piglets.

Cystic thymic degeneration with pseudoepitheliomatous hyperplasia in a Beagle puppy: an idiopathic lesion?

A 6-mo-old female Beagle dog was inappetent and depressed. The radiographic, ultrasonographic, and computed tomographic examination of the chest revealed a 10 × 7 cm multicystic mediastinal structure interpreted as altered thymus, in association with moderate pleural effusion that laboratory tests confirmed as hemothorax. No history of trauma or anticoagulant drug intoxication was reported, and no coagulation disorders were detected. Afterward, medial cranial sternotomy was performed to remove the altered tissue. Histologically, this tissue was compatible with a thymic remnant, characterized by numerous cystic lesions, mostly blood filled and lined by flattened-to-cuboidal epithelial cells, occasionally projecting into the surrounding stroma, and forming cytokeratin-positive ribbons, trabeculae, and papillae. Lymphocytes were scant, and numerous areas of congestion and hemorrhage were present throughout the samples. This case of idiopathic thymic hemorrhage with cystic degeneration of the thymus and pseudoepitheliomatous hyperplasia was an incidental finding; the dog recovered from surgery uneventfully.

Activation of the extrinsic apoptotic pathway in the thymus of piglets infected with PRRSV-1 strains of different virulence

In the last decade, the outbreaks caused by virulent porcine reproductive and respiratory syndrome virus (PRRSV) strains from both PRRSV-1 and PRRSV-2 have considerably increased. PRRSV is able to modulate the host's immune response through the induction of apoptosis of cells in lymphoid organs like thymus, increasing the susceptibility to secondary infectious agents. The present study aimed to compare the impact of two PRRSV-1 strains, a field low virulent strain (3249 strain) and a virulent strain (Lena strain), in the thymus of infected pigs, focusing on clinical signs, histological analysis, viraemia, thymus viral load and the study of the different routes of apoptosis phenomena by immunohistochemistry. Sera and thymus samples were collected from infected animals with 3249 strain, Lena strain and mock-infected animals at 1, 3, 6, 8 and 13 days post-infection (dpi). Lena-infected animals showed severe clinical disease, high sera and thymus viral loads with evident thymic atrophy since 6 dpi, matching with PRRSV-N protein, TUNEL and cCasp3 expression in the thymic cortex. In both infected groups, there was an increase in the number of cells expressing molecules related to the extrinsic pathway of apoptosis (cCasp8 and Fas) in cortex and medulla, showing an important role in the apoptosis induction produced in thymus of PRRSV-infected piglets. The extensive apoptosis in the thymus through this pathway would lead to a decrease in the number of mature T lymphocytes and the sustained release of viral particles, which may explain the greater severity of the clinical signs observed in Lena-infected pigs.

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.

Impaired histomorphology might provoke cell cycle regulators alteration in thymus of children with various congenital heart defects

Thymus, as a primary site of appropriate adaptive immunity formation, is an essential organ in face of a self-tolerance as well as a potential menace from impairment of body integrity. Due to vital selection processes during differentiation and maturation of T lymphocytes, control over cell survival and programmed cell death must be orchestrated in detail. Indeed, thymus is highly sensitive to wide spectrum of stressors that initiate acute structural changes. Hypoxia, one of the most common complications in congenital heart defects (CHDs) patients, provokes stress-induced thymus involution. Disrupted embryolonic development of thymus in association with congenital heart defects, may negatively affect physiological immune mechanisms. We propose that detailed analysis of thymic morphology could critically contribute to unveil the pathophysiology of diseases associated with disrupted adaptive immunity in children with heterogeneous congenital heart diseases.

Assessment of respiratory and systemic toxicity of Benzalkonium chloride following a 14-day inhalation study in rats

Background

Although biocides at low concentrations have been used to control pests, they can be more harmful than industrial chemicals as humans are directly and frequently exposed to such biocides. Benzalkonium chloride (BAC or BKC) is a non-toxic substance used to control pests. Recently, BAC has been increasingly used as a component in humidifier disinfectants in Korea, raising a serious health concern. Moreover, it poses significant health hazards to workers handling the chemical because of direct exposure. In the present study, we aimed to evaluate the respiratory toxicity of BAC due to its inhalation at exposure concentrations of 0.8 (T1 group), 4 (T2 group) and 20 (T3 group) mg/m³.

Results

In our previous study on the acute inhalational toxicity of BAC, bleeding from the nasal cavity was observed in all the rats after exposure to 50 mg/m³ BAC. Therefore, in this study, 20 mg/m³ was set as the highest exposure concentration, followed by 4 and 0.8 mg/m³ as the medium and low concentrations for 6 h/day and 14 days, respectively. After exposure, recovery periods of 2 and 4 weeks were provided. Additionally, alveolar lavage fluid was analyzed in males of the BAC-exposed groups at the end of exposure and 2 weeks after exposure to evaluate oxidative damage.

In the T3 group exposed to BAC, deep breathing, hoarseness, and nasal discharge were observed along with a decline in feed intake and body weight, and nasal discharge was also observed in the T1 and T2 groups. ROS/RNS, IL-1β, IL-6, and MIP-2 levels decreased in a concentration-dependent manner in the bronchoalveolar lavage fluid. Histopathological examination showed cellular changes in the nasal cavity and the lungs of the TI, T2, and T3 groups.

Conclusions

As a result, it was confirmed that the target organs in the respiratory system were the nasal cavity and the lungs. The adverse effects were evaluated as reversible responses to oxidative damage. Furthermore, the no observed adverse effect level was found to be less than 0.8 mg/m³ and the lowest benchmark dose was 0.0031 mg/m³. Accordingly, the derived no-effect level of BAC was calculated as 0.000062 mg/m³.

Influence of maternal HIV infection on fetal thymus size

Objective To reveal the effect of a maternal human immunodeficiency virus (HIV) infection on the fetal thymus size. Methods The sonographic fetal thymus size was measured retrospectively in 105 pregnancies with maternal HIV infection and in 615 uncomplicated singleton pregnancies. The anteroposterior thymic and the intrathoracic mediastinal diameter were determined in the three-vessel view and their quotient, the thymic-thoracic ratio (TT ratio), was calculated. The study group was subdivided into three groups by the maternal viral load on the date of ultrasound (<50 cop./mL, 50-1000 cop./mL, >1000 cop./mL). Furthermore, an association between prognostic factors of the HIV infection such as the lymphocyte count, CD4/CD8 ratio, HIV medication and the thymus size, was investigated using correlation analyses. Results Fetal thymus size in pregnancies of HIV-positive mothers showed to be noticeably larger than in uncomplicated pregnancies. The mean TT ratio in the HIV-positive group was 0.389 and in the control group 0.345 (P < 0.001). There was no association between any maternal HIV parameter or medication and the size of the thymus gland. Conclusion Maternal HIV infection was associated with an increased fetal thymus size. Further consequences of intrauterine HIV exposure for fetal outcome and the development of the immune system of HIV-exposed uninfected (HEU) infants must be discussed.

Preclinical toxicity evaluation of JD5037, a peripherally restricted CB1 receptor inverse agonist, in rats and dogs for treatment of nonalcoholic steatohepatitis

JD5037 is a novel peripherally restricted CB1 receptor (CB1R) inverse agonist being developed for the treatment of visceral obesity and its metabolic complications, including nonalcoholic fatty liver disease and dyslipidemia. JD5037 was administered by oral gavage at 10, 40, and 150 mg/kg/day dose levels for up to 34 days to Sprague Dawley rats, and at 5, 20, and 75 mg/kg/day dose levels for 28 consecutive days to Beagle dogs. In rats, higher incidences of stereotypic behaviors were observed in 10 mg/kg females and 40 mg/kg males, and slower responses for reflex and sensory tests were observed only in males at 10 and 40 mg/kg during neurobehavioral testing. Sporadic minimal incidences of decreased activity (males) and seizures (both sexes) were observed in rats during daily clinical observations, without any clear dose-relationship. Male dogs at 75 mg/kg during treatment period, but not recovery period, had an increased incidence of gut associated lymphoid tissue hyperplasia and inflammation in the intestine. In both species, highest dose resulted in lower AUCs indicative of non-linear kinetics. Free access to food increased the plasma AUC∞ by ~4.5-fold at 20 mg/kg in dogs, suggesting presence of food may help in systemic absorption of JD5037 in dogs. Based on the study results, 150 mg/kg/day in rats, and 20 and 75 mg/kg/day doses in male and female dogs, respectively, were determined to be the no-observed-adverse-effect-levels (NOAELs).

Comparative Incidences and Biological Outcomes for Thymoma in Various Rat Strains in National Toxicology Program Studies

Thymomas from 277 Fischer 344/N (F344/N), 10 Sprague Dawley (HSD:Sprague Dawley SD) (SD), 129 Wistar Han [Crl:WI(Han)] (WH), and 4 Wistar Outbred (WO) rats were reviewed from long-term studies in the National Toxicology Program (NTP) database. The incidence of thymomas in F344/N rats was slightly higher in males than in females, while the incidences in SD and WH rats were higher in females than in males. Only male WO rats were used in NTP studies. Of the 277 thymomas in F344/N rats, 235 (84.8%) were benign and 42 (15.2%) malignant, 14 of which exhibited metastasis. Of the 10 thymomas in SD rats, 5 (50%) were benign and 5 (50%) were malignant, one of which exhibited metastasis. Of the 129 thymomas in WH rats, 126 (98%) were benign and 3 (2%) were malignant, 1 with metastasis. Of the 4 thymomas in WO rats, 3 (75%) were benign and 1 (25%) was malignant, with no metastases. Malignant thymomas in F344/N and WH rats showed a propensity to be the cause of death and to result in early mortality, whereas the benign thymomas were associated less often with decreased survival. No occurrences of this neoplasm were reported to be related to exposure to any test articles.

Burden of disease at the same limit of exposure to airborne polycyclic aromatic hydrocarbons varies significantly across countries depending on the gap in longevity

Atmospheric polycyclic aromatic hydrocarbons (PAHs) disproportionately affect human health across the globe, and differential exposure is believed to drive the unequal health burden. Therefore, this study assessed and compared the burden of disease, in disability-adjusted life years (DALYs), at the same level (or limit) of exposure to atmospheric PAHs in nine countries. We calculated the DALYs per person-year per ng/m³ of benzo[a]pyrene from ten cancers and thirty-four non-cancer adverse outcomes using published toxicity information and country-specific disease severity. Exposure duration was averaged over 30 years and we adjusted for early-life vulnerability to cancer. The DALYs per person-year per ng/m³ of fifteen other individual PAHs was calculated using relative potency factors, and toxicity factors derived from quantitative structure-activity relationships. We found that even at the same level of exposure to PAHs, the incremental burdens of disease varied substantially across countries. For instance, they varied by about 2-3 folds between Nigeria and the USA. Countries having the lowest longevity had the highest DALYs per person-year per ng/m³ of each PAH. Kruskal-Wallis test (α = 0.05) showed that the variation across countries was significant. The post hoc tests detected a significant difference between two countries when the gap in longevity was >10 years. This suggests that countries having very low average life expectancy require more stringent PAH limit. Linear or exponential function of average longevity gave valid approximation of the DALYs per person-year per ng/m³ of benzo[a]pyrene or phenanthrene, respectively. Furthermore, we used global gridded surface benzo[a]pyrene concentrations and global population dataset for 2007, with spatial resolution of 0.1° × 0.1°, to calculate the contribution of differential exposures to the estimated DALYs per person-year. We found that in six out of nine countries, differential exposures to PAH contribute less to the estimated health loss than differential severities of the diseases. This indicates that the risk to health from PAHs may be underreported if the severities of the diseases in the countries are not considered.

Impact of PRRSV strains of different in vivo virulence on the macrophage population of the thymus

The emergence of "highly pathogenic" isolates of porcine reproductive and respiratory syndrome virus (HP-PRRSV) has raised new concerns about PRRS control. Cells from the porcine monocyte-macrophage lineage represent the target for this virus, which replicates mainly in the lung, and especially in HP-PRRSV strains, also in lymphoid organs, such as the thymus. This study aimed at evaluating the impact of two PRRSV strains of different virulence on thymic macrophages as well as after heterologous vaccination. After experimental infection with PR11 and PR40 PRRSV1 subtype 1 strains (low and high virulent, respectively) samples from thymus were analysed by histopathology and immunohistochemistry for PRRSV N protein, TUNEL, CD172a, CD163, CD107a and BA4D5 expression. Mortality was similar in both infected groups, but lung lesions and thymus atrophy were more intense in PR40 group. Animals died at 10-14 dpi after PR11 or PR40 infection showed the most severe histopathological lesions, with a strong inflammatory response of the stroma and extensive cell death phenomena in the cortex. These animals presented an increase in the number of N protein, CD172a, CD163 and BA4D5 positive cells in the stroma and the cortex together with a decrease in the number of CD107a positive cells. Our results highlight the recruitment of macrophages in the thymus, the increase in the expression of CD163 and the regulation of the host cytotoxic activity by macrophages. However, no marked differences were observed between PR11- and PR40-infected animals. Heterologous vaccination restrained virus spread and lesions extent in the thymus of PR40-infected animals.

Thymomas and Associated Hyperplastic Lesions in Wistar Hannover Rats

Thymomas occur prevalently in aged Wistar Hannover (WH) rats, along with hyperplastic lesions that cannot be categorized as thymomas. We compared the histological features of hyperplastic lesions and thymomas in WH rats, the incidences of these lesions, and the relationship of these lesions to the degree of thymic involution and also compared these lesions with those of Sprague Dawley (SD) rats in 4-, 13-, 26-, and 104-week studies. There were no morphological differences between hyperplastic cells and benign tumor cells in thymomas. The histological difference between hyperplastic lesions and thymomas was the size of the proliferative areas and the number of medullary differentiation areas. The hyperplastic lesions of the thymus in WH rats might have a potential for progression to thymomas due to the observed multiple hyperplastic lesions or mixed lesions with thymomas. The incidence of these proliferative lesions in the thymus was higher in females than in males. Further, the incidence of these proliferative lesions was higher in WH rats than in SD rats. Thymic involution was more severe in males than in females and more severe in SD rats than in WH rats. The differences in involution progression may have been reflected in the incidence of thymic proliferative lesions in SD and WH rats.

Duration dependent effect of chronic stress on primary and secondary lymphoid organs and their reversibility in rats

The present study was undertaken to investigate whether or not chronic stress effect and its reversibility on lymphoid organs is duration dependent. Male rats were exposed to restraint (1 h) followed by a gap of 4 h to forced swimming exercise (15 min) daily for 2, 4 and 8 weeks. After each exposure period, rats were allowed to recover for 6 weeks. Stress exposure resulted in duration dependent decreases in weight of thymus and axillary lymph nodes, lymphocyte counts of spleen, thymus and axillary lymph nodes and number of islets of white pulp of spleen and increases in apoptotic index of splenocytes, thymocytes and lymphocytes of axillary lymph nodes. All the parameters of lymphoid organs studied showed significant alterations in 2 weeks of stress exposure indicated their sensitivity to stress effects in short term exposure and thymus was the most sensitive organ among all. The alterations in all the parameters of spleen and majority of parameters of thymus and axillary lymph nodes returned to control level in recovery group rats of 2 and 4 weeks exposure but not in that of 8 weeks exposure. The present study for the first time reveal that severity of stress effects on lymphoid organs increases with increasing duration of exposure and shorter the exposure period faster the recovery. In addition, an in vitro study showed that corticosterone caused apoptosis of thymocytes, splenocytes and lymphocytes of axillary lymph nodes in dose dependent manner. Thus corticosterone induced death of cells of lymphoid organs under stress is the major cause of involution of lymphoid organs.

The burden of disease attributable to ambient PM2.5-bound PAHs exposure in Nagpur, India

Exposure to PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs) can elicit several types of cancer and non-cancer effects. Previous studies reported substantial burdens of PAH-induced lung cancer, but the burdens of other cancer types and non-cancer effects remain unknown. Thus, we estimate the cancer and non-cancer burden of disease, in disability-adjusted life years (DALYs), attributable to ambient PM_2.5-bound PAHs exposure in Nagpur district, India, using risk-based approach. We measured thirteen PAHs in airborne PM_2.5 sampled from nine sites covering urban, peri-urban and rural areas, from February 2013 to June 2014. We converted PAHs concentrations to benzo[a]pyrene equivalence (B[a]P_eq) for cancer and non-cancer effects using relative potency factors, and relative toxicity factors derived from quantitative structure-activity relationships, respectively. We calculated time-weighted exposure to B[a]P_eq, averaged over 30 years, and adjusted for early-life susceptibility to cancer. We estimated the DALYs/year using B[a]P_eq exposure levels, published toxicity data, and severity of the diseases from Global Burden of Disease 2016 database. The annual average concentration of total PM_2.5-bound PAHs was 458 ± 246 ng/m³ and resulted in 49,500 DALYs/year (0.011 DALYs/person/year). The PAH-related DALYs followed this order: developmental (mostly cardiovascular) impairments (55.1%) > cancer (26.5%) or lung cancer (23.1%) > immunological impairments (18.0%) > reproductive abnormalities (0.4%).

Divergent hypersensitivity responses following topical application of the quaternary ammonium compound, didecyldimethylammonium bromide

Didecyldimethylammonium bromide (DDAB) is a fourth generation dialkyl-quaternary ammonium compound (QAC) that is used in numerous products for its antimicrobial properties. While many QACs have been associated with allergic disease, the toxicity and sensitization of DDAB have not been thoroughly investigated. The purpose of these studies was to evaluate the irritancy and sensitization potential of DDAB following dermal application in a murine model. DDAB induced significant irritancy (0.0625-2%), evaluated by ear swelling in female BALB/c mice. Initial evaluation of the sensitization potential was conducted using the local lymph node assay (LLNA) at concentrations ranging from 0.0625% to 2%. A concentration-dependent increase in lymphocyte proliferation was observed with a calculated EC3 value of 0.057%. Immune cell phenotyping along with local and systemic IgE levels were evaluated following 4 and 14 days of dermal application. Phenotypic analyses revealed significant and dose-responsive increases in the absolute number of B-cells, CD4⁺ T-cells, CD8⁺ T-cells, and dendritic cells in the draining lymph nodes (DLNs) following 4 and 14 days of dermal exposure with significant increases in the number of activated B-cells and dendritic cells. However, increased activation of CD4⁺ T-cell and CD8⁺ T-cells was only observed following four days of DDAB exposure. Exposure to DDAB also induced increased production of IgE as evaluated by phenotypic analysis of DLN B-cells (IgE⁺ B-cells) and measurement of total serum IgE levels following 14 days but not four days of dermal application. Significant increases in gene expression were observed in the DLN (Il-4, Il-10, and ox40l) and ear (tslp) following 4 and 14 days of DDAB exposure. These results demonstrate the potential for development of irritation and hypersensitivity responses to DDAB following dermal exposure and raise concerns about the effects of exposure duration on hypersensitivity responses.

Elucidation of the pathology and tissue distribution of Lagovirus europaeus GI.2/RHDV2 (rabbit haemorrhagic disease virus 2) in young and adult rabbits (Oryctolagus cuniculus)

Lagovirus europaeus GI.2, also known as RHDV2 or RHDVb, is an emerging virus that causes rabbit haemorrhagic disease (RHD) in European rabbits (Oryctolagus cuniculus). In contrast to L. europaeus GI.1 (or RHDV/RHDVa) viruses that are only pathogenic for adults, GI.2 causes clinical disease in both adults and kittens. However, detailed descriptions of the pathology of this virus that may provide insight into its pathogenicity and emergence are lacking. Using an Australian GI.2 field strain isolated in 2015, we provide the first detailed description of pathology, viral antigen distribution and tissue load of GI.2 in adult and 5-week old New Zealand white rabbits using histology, immunohistochemistry and RT-qPCR. Liver was the target organ, but in contrast to GI.1 viruses, lesions and inflammatory responses did not differ between adults and kittens. Lymphocytic inflammation, proposed to be protective in kittens infected with GI.1, was notably absent. We also present the first descriptions of bone marrow changes in RHD, including decreased myeloid-to-erythroid ratio. Consistent with other pathogenic lagoviruses, intracellular viral antigen was demonstrated in hepatocytes and cells of the mononuclear phagocytic system. In terminal stages of disease, viral loads were highest in liver, serum and spleen. Despite the small sample size, our data suggest that unlike early European GI.2 strains, the pathogenicity of the Australian GI.2 virus is similar to GI.1 viruses. Additionally, GI.2 was fatal for all (n = 5) inoculated kittens in this study. This may significantly alter RHD epidemiology in the field, and may impact biocontrol programs for invasive rabbits in Australia where GI.1 viruses are intentionally released.

Spontaneous malignant myoid thymoma in an aged female Fischer 344 rat

A whitish mass approximately 30 mm in diameter was noted in the anterior mediastinum of a 67-week-old female Fischer 344 rat. Histopathologically, two types of tumor cells were identified on the basis of morphologic features: epithelial tumor cells with a tubular or cord-like growth pattern and rhabdomyosarcomatous tumor cells characterized by the presence of cross-striations. Immunohistochemically, the epithelial tumor cells reacted positively for cytokeratin AE1/AE3, and some reacted positively for p63, which is expressed in normal thymic epithelial cells. The rhabdomyosarcomatous tumor cells stained positively for desmin, sarcomeric actin, and S-100 protein, which coincides with the stainability of normal thymic myoid cells. Since the tumor was also found to have malignant features such as high proliferative activity, cytologic atypia, and necrotic behavior, it was diagnosed as a malignant myoid thymoma. We believe that this is the first case report of such a tumor in a rodent.

Background data on NOD/Shi-scid IL-2Rγnull mice (NOG mice)

To obtain background data of NOD/Shi-scid IL-2Rγ^null (NOG) mice, severely immunedeficient mice, a total of 120 animals were examined at 7, 26 and 52 weeks-old (20 mice/sex/group). The survival rate at 52 weeks-old was 95% (19/20) in both sexes. Clinically, circling behavior in one direction along the cage wall was observed in males after 8 weeks and females after 47 weeks-old, and hunchback position was found in males after 32 weeks-old. Hematologically, lymphocyte count markedly decreased at all ages, while white blood cell count increased in several mice at 52 weeks-old. Blood chemistry results revealed high values of aspartate aminotransferase, lactate dehydrogenase and creatine phosphokinase in some females at 26 weeks-old, without any related histological change. Histologically, lymphoid hypoplasia characterized by severe lymphocyte depletion with poorly developed tissue architectures was observed. In addition, spongiotic change in the nerve tissue was observed in both sexes at 7 and 26 weeks-old, and intracytoplasmic materials known as tubular aggregates in the skeletal muscles were found in males terminated at 26 and 52 weeks-old and in females at 52 weeks-old. Malignant lymphoma was found in one female euthanized at 20 weeks-old. Further, small intestinal adenoma, hepatocellular adenoma, leukemia, cerebral lipomatous hamartoma, Harderian gland adenoma and uterine polyp were also observed, and their incidences were low except for that of uterine polyp. This study provided detailed background data on NOG mice up to 52 weeks-old and provided information on appropriate use of NOG mice in the various research fields.

Time course of polyhexamethyleneguanidine phosphate-induced lung inflammation and fibrosis in mice

Pulmonary fibrosis is a chronic progressive disease with unknown etiology and has poor prognosis. Polyhexamethyleneguanidine phosphate (PHMG-P) causes acute interstitial pneumonia and pulmonary fibrosis in humans when it exposed to the lung. In a previous study, when rats were exposed to PHMG-P through inhalation for 3 weeks, lung inflammation and fibrosis was observed even after 3 weeks of recovery. In this study, we aimed to determine the time course of PHMG-P-induced lung inflammation and fibrosis. We compared pathological action of PHMG-P with that of bleomycin (BLM) and investigated the mechanism underlying PHMG-P-induced lung inflammation and fibrosis. PHMG-P (0.9 mg/kg) or BLM (1.5 mg/kg) was intratracheally administered to mice. At weeks 1, 2, 4 and 10 after instillation, the levels of inflammatory and fibrotic markers and the expression of inflammasome proteins were measured. The inflammatory and fibrotic responses were upregulated until 10 and 4 weeks in the PHMG-P and BLM groups, respectively. Immune cell infiltration and considerable collagen deposition in the peribronchiolar and interstitial areas of the lungs, fibroblast proliferation, and hyperplasia of type II epithelial cells were observed. NALP3 inflammasome activation was detected in the PHMG-P group until 4 weeks, which is suspected to be the main reason for the persistent inflammatory response and exacerbation of fibrotic changes. Most importantly, the pathological changes in the PHMG-P group were similar to those observed in humidifier disinfectant-associated patients. A single exposure of PHMG-P led to persistent pulmonary inflammation and fibrosis for at least 10 weeks.

Epigenetic response of imprinted domains during carcinogenesis

Background

Imprinted domains have been identified as targets for aberrant DNA methylation during carcinogenesis, but it remains unclear when these epigenetic alterations occur and how they contribute to tumor progression. Epigenetic instability at key cis-regulatory elements within imprinted domains can concomitantly activate proto-oncogenes and turn off tumor suppressor genes. Thus, to further characterize the epigenetic response of imprinted domains during carcinogenesis, we compared the stability of DNA methylation at a variety of cis-regulatory elements within imprinted domains in two fundamentally different mouse tumors, benign and malignant, induced by the KrasG12D mutation.

Results

We report that imprinted domains remain stable in benign processes but are highly susceptible to epigenetic alterations in infiltrative lesions. The preservation of DNA methylation within imprinted domains in benign tumors throughout their duration suggests that imprinted genes are not involved with the initiation of carcinogenesis or the growth of tumors. However, the frequent detection of DNA methylation changes at imprinting control regions in infiltrative lesions suggest that imprinted genes are associated with tumor cells gaining the ability to defy tissue boundaries.

Conclusion

Overall, this study demonstrates that imprinted domains are targeted for DNA hypermethylation when benign tumor cells transition to malignant. Thus, monitoring DNA methylation within imprinted domains may be useful in evaluating the progression of neoplasms.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0393-8) contains supplementary material, which is available to authorized users.

Fetal thymus size in pregnant women with diabetic diseases

AIM

The aim of our study was to assess fetal thymus size in diabetic pregnancies compared with normal pregnancies.

METHODS

Sonographic fetal thymus size was retrospectively assessed in 161 pregnancies with maternal diabetes and in 161 uncomplicated pregnancies matched by gestational age. The anteroposterior thymic and the intrathoracic mediastinal diameter were measured and the quotient was calculated [thymic-thoracic ratio (TT-ratio)]. In addition, we defined the quotient of the anteroposterior thymic diameter and the head circumference as thymus-head ratio (TH-ratio). The maternal diabetes cases were subdivided into three groups: (1) diet-controlled gestational diabetes, (2) insulin-dependent gestational diabetes and (3) preexisting maternal diabetes.

RESULTS

TT-ratio and TH-ratio were smaller in pregnancies with maternal diabetes (P<0.001 and P<0.001, respectively). In all three maternal diabetes subgroups, the TT-ratio and the TH-ratio were lower compared with the control group (P<0.001 for each group).

CONCLUSIONS

Reduced fetal thymus size seems to be associated with diabetic pregnancy. We introduce fetal thymus size as a new potential prognostic parameter for maternal diabetes.

The lymphoid system: a review of species differences

While an understanding of the structure and function of a generically described immune system is essential in contemporary biomedicine, it is clear that a one-size-fits-all approach applied across multiple species is fraught with contradictions and inconsistencies. Nevertheless, the breakthroughs achieved in immunology following the application of observations in murine systems to that of man have been pivotal in the advancement of biology and human medicine. However, as additional species have been used to further address biologic and safety assessment questions relative to the structure and function of the immune system, it has become clear that there are differences across species, gender, age and strain that must be considered. The meaningfulness of these differences must be determined on a case-by-case basis. This review article attempts to collect, consolidate and discuss some of these species differences thereby aiding in the accurate placement of new observations in a proper immunobiological and immunopathological perspective.

Retinoic-acid-orphan-receptor-C inhibition suppresses Th17 cells and induces thymic aberrations

Retinoic-acid-orphan-receptor-C (RORC) is a master regulator of Th17 cells, which are pathogenic in several autoimmune diseases. Genetic Rorc deficiency in mice, while preventing autoimmunity, causes early lethality due to metastatic thymic T cell lymphomas. We sought to determine whether pharmacological RORC inhibition could be an effective and safe therapy for autoimmune diseases by evaluating its effects on Th17 cell functions and intrathymic T cell development. RORC inhibitors effectively inhibited Th17 differentiation and IL-17A production, and delayed-type hypersensitivity reactions. In vitro, RORC inhibitors induced apoptosis, as well as Bcl2l1 and BCL2L1 mRNA downregulation, in mouse and nonhuman primate thymocytes, respectively. Chronic, 13-week RORC inhibitor treatment in rats caused progressive thymic alterations in all analyzed rats similar to those in Rorc-deficient mice prior to T cell lymphoma development. One rat developed thymic cortical hyperplasia with preneoplastic features, including increased mitosis and reduced IKAROS expression, albeit without skewed T cell clonality. In summary, pharmacological inhibition of RORC not only blocks Th17 cell development and related cytokine production, but also recapitulates thymic aberrations seen in Rorc-deficient mice. While RORC inhibition may offer an effective therapeutic principle for Th17-mediated diseases, T cell lymphoma with chronic therapy remains an apparent risk.

The Natural History of Pneumonic Tularemia in Female Fischer 344 Rats after Inhalational Exposure to Aerosolized Francisella tularensis Subspecies tularensis Strain SCHU S4

The inbred Fischer 344 rat is being evaluated for testing novel vaccines and therapeutics against pneumonic tularemia. Although primary pneumonic tularemia in humans typically occurs by inhalation of aerosolized bacteria, the rat model has relied on intratracheal inoculation of organisms because of safety and equipment issues. We now report the natural history of pneumonic tularemia in female Fischer 344 rats after nose-only inhalational exposure to lethal doses of aerosolized Francisella tularensis subspecies tularensis, strain SCHU S4. Our results are consistent with initial uptake of aerosolized SCHU S4 from the nasal cavity, lungs, and possibly the gastrointestinal tract. Bacteremia with hematogenous dissemination was first detected 2 days after exposure. Shortly thereafter, the infected rats exhibited fever, tachypnea, and hypertension that persisted for 24 to 36 hours and then rapidly decreased as animals succumbed to infection between days 5 and 8 after exposure. Tachycardia was observed briefly, but only after the core body temperature and blood pressure began to decrease as the animals were near death. Initial neutrophilic and histiocytic inflammation in affected tissues became progressively more fibrinous and necrotizing over time. At death, as many as 10¹⁰ colony-forming units were found in the lungs, spleen, and liver. Death was attributed to sepsis and disseminated intravascular coagulation. Overall, the pathogenesis of pneumonic tularemia in the female F344 rat model appears to replicate the disease in humans.

Epigenetic instability at imprinting control regions in a Kras(G12D)-induced T-cell neoplasm

Although aberrant DNA methylation within imprinted domains has been reported in a variety of neoplastic diseases, it remains largely uncharacterized in the context of carcinogenesis. In this study, we induced T-cell lymphoma in mice by employing a breeding scheme involving mouse strains, LSL-Kras(G12D) and MMTV-Cre. We then systematically surveyed imprinted domains for DNA methylation changes during tumor progression using combined bisulfite restriction analysis and NGS-based bisulfite sequencing. We detected hyper- or hypo-methylation at the imprinting control regions (ICRs) of the Dlk1, Peg10, Peg3, Grb10, and Gnas domains. These DNA methylation changes at ICRs were more prevalent and consistent than those observed at the promoter regions of well-known tumor suppressors, such as Mgmt, Fhit, and Mlh1. Thus, the changes observed at these imprinted domains are the outcome of isolated incidents affecting DNA methylation settings. Within imprinted domains, DNA methylation changes tend to be restricted to ICRs as nearby somatic differentially methylated regions and promoter regions experience no change. Furthermore, detailed analyses revealed that small cis-regulatory elements within ICRs tend to be resistant to DNA methylation changes, suggesting potential protection by unknown trans-factors. Overall, this study demonstrates that DNA methylation changes at ICRs are dynamic during carcinogenesis and advocates that detection of aberrant DNA methylation at ICRs may serve as a biomarker to enhance diagnostic procedures.

Arsenic-induced dose-dependent modulation of the NF-κB/IL-6 axis in thymocytes triggers differential immune responses

Arsenic contamination of drinking water is a matter of global concern. Arsenic intake impairs immune responses and leads to a variety of pathological conditions including cancer. In order to understand the intricate tuning of immune responses elicited by chronic exposure to arsenic, a mouse model was established by subjecting mice to different environmentally relevant concentrations of arsenic in drinking water for 30days. Detailed study of the thymus, a primary immune organ, revealed arsenic-mediated tissue damage in both histological specimens and scanning electron micrographs. Analysis of molecular markers of apoptosis by Western blot revealed a dose-dependent activation of the apoptotic cascade. Enzymatic assays supported oxidative stress as an instigator of cell death. Interestingly, assessment of inflammatory responses revealed disparity in the NF-κB/IL-6/STAT3 axis, where it was found that in animals consuming higher amounts of arsenic NF-κB activation did not lead to the classical IL-6 upregulation response. This deviation from the canonical pathway was accompanied with a significant rise in numbers of CD4+ CD25+ FoxP3 expressing cells in the thymus. The cytokine profile of the animals exposed to higher doses of arsenic also indicated an immune-suppressed milieu, thus validating that arsenic shapes the immune environment in context to its dose of exposure and that at higher doses it leads to immune-suppression. Our study establishes a novel role of arsenic in regulating immune homeostasis in context to its dose, where, at higher doses, arsenic related upregulation of NF-κB cascade takes on an alternative role that is correlated with increased immune-suppression.

Maturity-related Variability of the Thymus in Cynomolgus Monkeys (Macaca fascicularis)

Terminal body weights (TBWs), thymus weight parameters, and thymus morphology were retrospectively evaluated in 453 cynomolgus monkeys assigned to control groups on nonclinical toxicity studies. Morphology of bone, ovary, and testis/epididymis were used to determine maturity status of individual animals. There was no correlation between TBW and thymus weight (absolute and/or relative to TBW or brain weight). Thymus weight parameters and grades of decreased lymphocytes in the thymus were highly variable in immature animals compared to mature animals. There was also high (up to 11-fold) variability of thymus weight parameters within a given control group on the same study (generally 3 or 4 animals per sex). Several parameters evaluated had more pronounced age-related changes in males when compared to females. Our results demonstrate the inherent variability of thymus weight parameters and morphologic observations for cynomolgus monkeys on toxicology studies. Changes in thymus parameters in cynomolgus monkeys are unreliable indicators of immunomodulation or immunotoxicity in the absence of other relevant findings. Therefore, the thymus parameters commonly evaluated in preclinical safety assessments should not be the primary data set used to determine the presence of a direct test article-related effect on the immune system.