Journal of Toxicologic Pathology最新文献

Tobacco smoking is a major risk factor for human cancers including urinary bladder carcinoma. In a previous study, nicotine was shown to enhance rat urinary bladder carcinogenesis in a two-stage carcinogenesis model. In this study, we examined the progressive effects of nicotine on bladder carcinogenesis in F344 rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). Nicotine, administered in drinking water for 52 weeks following 4 weeks of BBN treatment, significantly increased the incidence and multiplicity of invasive urothelial carcinoma in a dose-dependent manner. The Ki67 labeling index of bladder papillomas was significantly increased by nicotine in a dose-dependent manner. However, nicotine treatment did not affect the incidence or total number of tumors, and nicotine administration alone for 52 weeks did not result in any neoplastic lesions. These data suggest that while nicotine does not initiate carcinogenesis, it has the potential to promote invasive urinary cancers.

Intraepidermal nerve fiber (IENF) density is commonly evaluated to diagnose peripheral neuropathy. However, conventional two-dimensional (2D) analysis using rodent models shows high interstudy variability. Three-dimensional (3D) IENF analysis has been proposed for human skin biopsies because the spatial location of each nerve can be easily determined. However, no studies have compared 2D and 3D analyses of mouse cutaneous nerve fibers under the same conditions. We aimed to establish a more accurate analysis method for mouse cutaneous nerve fibers. We used the glabrous plantar metatarsal skin of male C57BL/6J mice. The middle area of the plantar skin was used for 2D and 3D analyses, and the marginal area was also investigated in the 3D analysis. Tissue transparency, nerve fiber-specific antibodies, confocal microscopy, and IMARIS software were used for the 3D analysis. The 3D analysis clearly defined branching points and continuity, allowing accurate IENF density measurement. Conversely, the 2D analysis could not accurately determine IENF density because it could not detect the continuity of the nerve from the dermis to epidermis. Thus, the actual IENF density from the 3D analysis was significantly less than that from the 2D analysis. In addition, the density and length of IENFs in the middle area were significantly higher than those in the marginal area. This 3D approach enables the precise capture of IENF trajectories with various parameters, establishing a standard method for evaluating peripheral neuropathy models. Furthermore, our findings indicate that comparative studies aiming to analyze mouse IENF need to consider the site of skin sampling.

Histopathological, immunohistochemical, and ultrastructural characteristics of lymphocytic thyroiditis in an untreated four-year-old male beagle were described. Histopathologically, the thyroid glands were composed of two distinct cell types: round to oval cells with eosinophilic granular cytoplasm (Type A), which is consistent with the features of oncocytic oxyphils, and larger round cells with amphophilic or pale cytoplasm (Type B). These cell types extensively and diffusely infiltrated with a mixture of lymphocytes and plasma cells, destroying the follicular structure. Immunohistochemistry revealed that Type A cells were positive for thyroglobulin and cytochrome C, and that Type B cells were positive for calcitonin, synaptophysin, and cytochrome C. These results indicate that Type A and B cells stem from follicular and C cells, respectively. Ultrastructural investigation showed that microfollicles and microvilli were evident in the cytoplasm and along the luminal surface of Type A cells. Thus, the lymphocytic thyroiditis observed in the beagle exhibited a morphology similar to that of Hashimoto thyroiditis in humans, particularly in view of an oncocytic alteration of follicular cells.

Pulmonary emphysema is primarily attributable to prolonged exposure to cigarette smoke. Novel tobacco substitutes, such as heated tobacco products, have emerged as healthier alternatives to cigarettes. The effects of short-term inhalation of a heated tobacco product, Ploom TECH+ (PT+), on the lungs of mice were compared with those of 3R4F reference cigarettes. Male 10-week-old C57BL mice were exposed to clean air (control), 3R4F, or PT+ for 1 h/d, 5 d/week for two or four weeks. After four weeks of exposure, the number of inflammatory cells and proportion of neutrophils and lymphocytes in the bronchoalveolar lavage fluid and the number of macrophages in the lung tissue increased significantly in mice exposed to 3R4F but not in those exposed to PT+. Changes in the expression of genes related to inflammation-related factors were observed in the lung tissues of mice exposed to 3R4F for two and four weeks. Chemokine (C-C motif) ligand 17, resistin-like alpha, and lipocalin 2 were among the upregulated genes. In our previous short-term tobacco inhalation study, these genes were identified as useful markers of emphysema effects induced by exposure to cigarette smoke from Peace cigarettes, detectable before pulmonary histological changes appeared. These effects were not observed in the PT+-exposed mice. These data suggest that PT+ caused less damage to the lungs of mice than 3R4F, particularly regarding the induction of emphysema.

Rodents are widely used to study the toxicity of chemicals; however, differences between species indicate that the results from rodents are not always directly transferable to humans. The health of workers exposed to various chemicals and particulates at high doses or for long periods is at risk. Respiratory bronchioles and lobular structures, which are demarcated by interlobular septa, are key sites for occupational lung diseases such as pneumoconiosis; however, these structures vary among animal species. Understanding these differences is crucial for studying the pathology of human occupational lung diseases. However, there is a lack of reviews focusing on these structures in different species. This review explores the lung anatomy of various mammals and its functional importance in disease to connect animal studies with human occupational lung diseases. Our results indicate that artiodactyls, especially small pig breeds and goats, are ideal for research because their respiratory bronchioles and lobular structures are similar to those of humans. This review aims to enhance the use of experimental animal data and improve our understanding of human occupational lung diseases, thereby facilitating early disease detection, treatment, and prevention.

Chimeric mice with humanized liver are considered a useful tool to predict drug pharmacokinetics and in vivo toxicity in humans. The PXB-mouse is one of such chimeric (humanized) mouse models with more than 70% of human hepatocytes in their liver, which can produce human albumin with human-type bile secretion and express human xenobiotic metabolizing enzymes. However, data are limited regarding the properties of such humanized mice in hepatotoxicity studies. This study aimed to explore the distinctive characteristics of chimeric PXB-mice with humanized liver that can influence susceptibility to hepatotoxicity. Morphologically, the PXB-mice have a diffuse hepatic macrovesicular and microvesicular steatosis in the transplanted human hepatocytes, which can be suppressed after human growth hormone treatment. The humanized liver of the PXB-mice has a metabolic zonation of glutamine synthetase, cytochrome P450 2E1, and argininosuccinate synthase 1, similar to normal liver in rodents and humans. The transplanted human hepatocytes in the PXB liver have a markedly decreased N-cadherin expression compared with normal human liver. Scanning electron microscopy revealed formation of septum-like structures encircling the transplanted human hepatocytes in the PXB liver, which consists of an accumulation of fibers in the space of Disse under transmission electron microscopy and is immunolabeled for laminin. Overall, the present report demonstrated the morphological and immunohistochemical characteristics of the PXB-mice with humanized liver along with some abnormalities in the cell adhesion of the transplanted human hepatocytes. These findings would be useful for hepatotoxicity studies using humanized animal models.

Veterinary forensic medicine has received increasing attention in recent years from the perspectives of animal abuse, veterinary malpractice, wildlife protection, and zoonosis. Veterinary forensic medicine, equivalent to human forensic medicine, is a relatively new field. Compared with Europe and the United States of America, Japan currently lags behind in both the education and practice of veterinary forensic medicine. However, the situation regarding animals in Japan has changed dramatically in recent years, and the need for veterinary forensic medicine is increasing. This manuscript provides an overview of veterinary forensic medicine and a brief description of its current status and prospects in Japan.

Bladder cancer is treated by surgical removal of the tumor followed by injection of anticancer drugs or the Bacillus Calmette-Guerin vaccine. However, there are insufficient effective drug options depending on the risk category of bladder cancer. One of the reasons for this is the limited number of suitable experimental models that reproduce the pathology of bladder cancer for each risk category. There has been increasing interest in the patient-derived xenograft model as an experimental model to reproduce the original nature of the tumor in a patient. However, there are unresolved problems regarding its practical use, such as the low success rate of engraftment, variation in the growth rate between experiments, and the lack of a reliable method to prepare a patient-derived xenograft model from cryopreserved tumor tissue. In this study, the effect of scaffold material on the preparation of a bladder cancer patient-derived xenograft model was investigated and it was found that gelatin/polyethylene glycol-based hydrogel offers advantages for engraftment of cryopreserved bladder cancer tissue. It was shown that the proliferation of cryopreserved bladder cancer cells was promoted with less necrosis and thrombi around the tissue when transplanted into immunodeficient animals with glycol-based hydrogel compared to transplantation with Matrigel or without any scaffold. This study proposes a new method to generate patient-derived xenograft models from cryopreserved bladder cancer tissue, which is expected to have improved proliferation activity after transplantation.

In liver fibrosis, the possible causes of irreversibility include the accumulation of collagen I during extracellular matrix remodeling, together with the deposition of elastic fibers in later stages. Drug development targeting liver fibrosis should preferably employ models that closely mimic human diseases. To better understand the progress of fibrosis in a cynomolgus monkey liver fibrosis model, we evaluated the time-course of changes in the fibrosis score, collagens, and elastic fibers. The animals were subcutaneously administered thioacetamide twice a week (experiment 1) or once every 2 weeks (experiment 2). Liver tissues were collected at 8 and 16 (experiment 1) or 10 and 20 (experiment 2) weeks of administration, and 12 weeks after withdrawal (experiments 1 and 2). The fibrosis score was evaluated by Masson's trichrome staining. Immunohistochemistry for collagen Ia1, III, and IV, and Elastica van Gieson staining were also performed. Fibrosis was observed from week 8 (experiment 1) or 10 (experiment 2), and in most animals, it progressed during the administration period. After withdrawal, the fibrosis scores tended to decrease. Collagen IV was predominant in the early stage but was replaced by collagen I after 20 weeks in both experiments. Collagen III distributed mostly along with collagen I throughout the study period. The elastic fibers deposition was markedly limited throughout the experiment. Fibrous component examination showed that the main collagen type contributing to fibrosis shifted from collagen IV to I after 20 weeks or later and revealed that the fibrosis status is not fully reflected in the fibrosis score.

We report the features of spontaneous bilateral thyroid follicular cell carcinoma in a 10-year-old male beagle. Necropsy revealed bilateral masses on the trachea, corresponding to the left and right sides of the thyroid gland. The masses were elastic, encapsulated, and distinct, with no connecting tumor tissues between them. Histologically, the tumor cells exhibited a predominant sheet-like growth pattern in both masses, and small follicular structures containing colloids were observed. Immunohistochemically, >50% of the tumor cells were positive for thyroglobulin. In the sheet-like growth area, all tumor cells were positive for cytokeratin and approximately 50% of them were positive for vimentin. The tumor cells were negative for calcitonin and parathormone. Electron microscopy of the tumor cells revealed colloid droplets and lysosomes in the cytoplasm, which are characteristics of follicular cells of the thyroid gland, although they were abnormally shaped and smaller in size compared to the normal cells. Many calcitonin-positive C cells were observed in the nodule area without a capsule in the left mass and were scattered within the tumor in the right mass. C cells were found individually and were negative for Ki-67 expression. Therefore, each of these cells was deemed to be derived from an individual C-cell complex. Based on these morphological features, the tumor was diagnosed as spontaneous bilateral thyroid follicular cell carcinoma of the compact cellular carcinoma subtype. This is the first report of electron microscopic findings and co-expression of cytokeratin and vimentin in thyroid follicular cell carcinoma in beagles.