Journal of Toxicologic Pathology最新文献

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.

In Japan, forensic medicine was established in the early 1900s to investigate potential criminal activities. However, only a few veterinary courses in forensic science are available, and the training of forensic specialists has lagged. This study aimed to review the current status of veterinary forensic medicine in Japan. Veterinary forensics has recently been established, along with the publication of textbooks on animal abuse and wildlife forensics. Veterinary forensics can be broadly divided into the following categories: 1) criminal science, which includes the identification of animal abuse and neglect, and the responses to lawsuits; 2) monitoring of food safety and zoonosis; and 3) determination of the cause of death to support wildlife conservation efforts (wildlife forensics). The target animal species include mammals, reptiles, amphibians, and honeybees. To elucidate animal abuse, postmortem computed tomography and histopathological examinations are employed to determine the factors that lead to death.

This technical report presents a collection of illustrative images and concise descriptions of non-neoplastic microscopic findings noted in transgenic CByB6F1-Tg(HRAS)2Jic (Tg.rasH2) mice from 26-week-carcinogenicity studies. A unique finding in the Tg.rasH2 strain was the skeletal muscle myopathy observed in nearly all animals, particularly affecting the femoralis and pectoralis muscles, diaphragm, and subcutaneous muscles. Pigment was noted in various organs, particularly in the spleen due to the C57BL/6J background. Mononuclear and/or mixed cell inflammatory infiltrates occurred in various tissues, with or without secondary changes, similar to other rodent and non-rodent laboratory species. Vascular anomalies were sporadically noted, mainly in the uterus. Other notable findings included extramedullary hematopoiesis in the spleen; alveolar macrophage infiltrate (often with eosinophilic crystals) in the lung; and proliferative findings in several tissues, such as the lung (bronchiolo-alveolar hyperplasia), adrenal cortex (subcapsular hyperplasia), and uterus (cystic-endometrial hyperplasia). This paper also includes illustrations of other less frequently incidental findings. The information presented in this manuscript aims to serve as a valuable reference for pathologists and researchers and expected to offer contextual insights for carcinogenicity and other toxicological studies utilizing this animal model.

Amyloidosis is characterized by the extracellular deposition of insoluble protein fibrils that cause cellular damage and dysfunction in organs and tissues. Multiple types of amyloidosis and their causative precursor proteins have been identified in humans and animals. In toxicological studies, a high incidence of spontaneous amyloidosis has been reported in CD-1 mice; however, the precursor protein responsible remains unclear. In contrast, B6C3F1 mice have a low incidence of amyloidosis. This study aimed to identify the types of amyloidosis and causative precursor proteins in CD-1 mice and investigate the role of copy number variations (CNVs) in genes encoding precursor proteins in different mouse species. Histopathological examination revealed amyloids in multiple organs, which were confirmed by direct fast scarlet staining. Immunohistochemistry and liquid chromatography-tandem mass spectrometry analyses revealed that the deposition was derived from serum amyloid A (SAA1 and 2), suggesting that the CD-1 mice had AA amyloidosis. Copy number variation assays demonstrated higher copy numbers of SAA1 and SAA2 in CD-1 mice with amyloidosis than in C3H/He mice (the parent strain of B6C3F1 mice). These findings suggest that the high copy numbers of SAA1 and SAA2 may contribute to the high incidence of AA amyloidosis in CD-1 mice. This study examined spontaneous amyloidosis in CD-1 mice and revealed the correlation between SAA1 and SAA2 CNVs in the pathogenesis of the disease and the genetic factors influencing amyloidosis in mice.

Occupational exposure to aromatic amines is a major risk factor for urinary bladder cancer. Our previous studies showed that acetoaceto-o-toluidine, which is produced using o-toluidine as a raw material, promotes urinary bladder carcinogenesis in rats. We also found high concentrations of o-toluidine, a human bladder carcinogen, in the urine of acetoaceto-o-toluidine-treated rats, indicating that urinary o-toluidine derived from acetoaceto-o-toluidine may play an important role in bladder carcinogenesis. However, this has not been investigated in humans. In the present study, we used non-humanized (F1-TKm30 mice) and humanized-liver mice established by human hepatocyte transplantation to compare differences in urinary acetoaceto-o-toluidine metabolites produced by human and mouse liver cells. We also examined the changes in acetoaceto-o-toluidine-induced mRNA expression in the liver and the proliferative effects on the bladder epithelium. Urinary o-toluidine was detected in both non-humanized and humanized mice. Acetoaceto-o-toluidine metabolites in the urine, cell proliferation activities, and DNA damage in the bladder urothelium were similar in non-humanized and humanized-liver mice. RNA expression analysis revealed that CYP1A2 expression increased in the livers of humanized-liver mice, and Cyp2c29 expression (equivalent to human CYP2C9/19) increased in the livers of non-humanized mice. These data suggest that acetoaceto-o-toluidine may be a human carcinogen, as evidenced by the detection of urinary o-toluidine in acetoaceto-o-toluidine-treated humanized-liver mice. This animal model is important for extrapolating toxicity data from animals to humans.

The liver, a major organ involved in substance metabolism, is highly susceptible to toxicity induced by chemicals and their metabolites. Although damage-associated molecular patterns (DAMPs) have been implicated in the development of sterile inflammation following cell injury, their involvement in chemically induced hepatocellular injury remains underexplored. This study aimed to determine the role of high-mobility group box 1 (HMGB1), a DAMP, in a rat model of liver injury treated with thioacetamide, a hepatotoxicant. The rats were administered thioacetamide and treated with HMGB1 neutralizing antibody. Histopathological analysis revealed the absence of significant differences between control rats and HMGB1 neutralizing antibody-treated rats. However, HMGB1 neutralizing antibody-treated rats showed a reduction in the hepatic devitalization enzymes, a decrease in the number of anti-inflammatory cluster of differentiation 163⁺ M2 macrophages and neutrophils in the injured area, and a decrease in cytokine expression. These results suggest that HMGB1 leads to the progression of inflammation after chemically induced hepatocyte injury and may represent a therapeutic target for mitigating such injury.