Journal of Toxicologic Pathology最新文献

Inflammation of the cardiac coronary artery in ICR mice is occasionally observed in toxicity studies; however, this has not been well explored histologically. Herein, we investigated the detailed histology of the associated lesions in 6-8-week-old ICR mice. Coronary artery inflammation in the right ventricular wall was observed in 10 of 142 mice (7.0%). Histopathological examination revealed hypertrophy of the vascular smooth muscle cells and perivascular infiltration of macrophages in mild cases. In moderate to marked cases, single-cell necrosis of vascular smooth muscle cells, hemorrhage of the tunica media, and fibrinoid necrosis of the vessel wall were observed, in addition to the changes seen in mild cases. Electron microscopic examination of moderate cases revealed a discontinuous internal elastic lamina suggestive of rupture, and vascular smooth muscle cells beneath the elastic lamina showed degeneration and necrosis. These findings suggest that the lesions developed as a rupture of the internal elastic lamina and necrosis of vascular smooth muscle cells, while leaked plasma components caused vascular and perivascular inflammation. In ICR mice, dystrophic calcinosis (DCC) is known to occur rarely in the right ventricle. DCC is defined as focal calcification in necrotic myocardial fibers, the pathogenesis of which is considered to involve ectopic calcification. Since calcification was not observed in any part of the heart, including the inflammation region, the pathophysiology of cardiac arterial inflammation seen in our ICR mice was considered to differ from that of DCC.

In subcutaneous tumor models, changes in the tumor microenvironment can lead to differences in therapeutic treatment responses between the subcutaneous and parent tumors. Accordingly, we generated a lung carcinogenesis model that combines genetically modified mice (Tg-rasH2 mice) with two-stage chemical carcinogenesis as an alternative to the subcutaneous tumor model. In this model, Tg-rasH2 mice were treated with 1-ethyl-1-nitrosourea, followed by butylhydroxytoluene. Mice developed lung adenomas five weeks after treatment initiation. Subsequently, anti-mouse PD-1 antibody (α-mPD-1) or isotype control was administered intraperitoneally twice a week for 4 weeks. Tumor growth was examined by measuring the relative tumor area in serially sliced lung histopathological specimens. No statistically significant differences were observed in the relative lung tumor areas between treated and control groups. A second experiment then examined the antitumor efficacy of α-mPD-1 combined with gemcitabine in a mouse model. Mice were treated identically as in Experiment 1, except that the treated group received once-weekly intraperitoneal injections of 10 mg/kg gemcitabine. In contrast to Experiment 1, the combined treatment significantly reduced the relative tumor areas in the lungs. This result also resembles that of a phase III clinical trial (ORIENT-12), showing that patients with non-small-cell lung carcinoma benefited from combination treatment with gemcitabine and the anti-human PD-1 antibody sintilimab. Thus, this mouse model could be a feasible means to preclinically evaluate the antitumor efficacy of different immunotherapy and chemotherapy drug combinations.

In safety evaluations of chemicals, there is an urgent need to develop short-term methods to replace long-term carcinogenicity tests. We have reported that immunohistochemistry for γ-H2AX, a well-established biomarker of DNA damage, can detect bladder carcinogens at an early stage using histopathological specimens from 28-day repeated-dose oral toxicity studies in rats. Given the markedly low level of γ-H2AX formation in the bladder urothelium of untreated rats, an increase in γ-H2AX-positive cells following chemical exposure can be relatively easy to identify. Among the 100 compounds examined to date, bladder carcinogens can be detected with high sensitivity (33/39; 84.6%) and specificity (58/61; 95.1%). As expected, γ-H2AX formation levels tended to be high following exposure to genotoxic bladder carcinogens, whereas nongenotoxic bladder carcinogens also increased the number of γ-H2AX-positive cells, probably through secondary DNA damage associated with sustained proliferative stimulation. γ-H2AX formation in the bladder urothelium reflects species differences in susceptibility to bladder carcinogenesis between rats and mice and shows a clear dose-dependency associated with the intensity of tumor development as well as high reproducibility. Some of the bladder carcinogens that showed false-negative results in the evaluation of γ-H2AX alone could be detected by combined evaluation with immunostaining for bladder stem cell markers, including aldehyde dehydrogenase 1A1. This method may be useful for the early detection of bladder carcinogens, as it can be performed by simple addition of conventional immunostaining using formalin-fixed paraffin-embedded tissues from 28-day repeated-dose toxicity studies in rodents, which are commonly used in safety evaluations of chemical substances.

The carcinogenicity of 2,2'-[1,2-ethanediylbis(oxymethylene)]bis-oxirane (ethylene glycol diglycidyl ether; EGDE), 3-hydroxy-2-naphthoic acid (HNA), and acetoacetanilide (AAA) was investigated using a medium-term rat liver bioassay for an occupational safety assessment. F344 male rats were administered a single intraperitoneal injection of diethylnitrosamine (200 mg/kg body weight (bw)/day) and then starting 2 weeks later, they received EGDE at 6, 20, and 60 mg/kg bw/day, HNA at 20, 60, and 200 mg/kg bw/day, or AAA at 60, 200, and 600 mg/kg bw/day by oral gavage for 6 weeks. The animals in the positive control group received phenobarbital sodium solution (PB, 25 mg/kg bw/day) by oral gavage and those in the negative control group received a vehicle (water/corn oil) during the administration period of test substances in this model. All animals were subjected to two-thirds partial hepatectomy at week 3 and euthanized at week 8. Neither the number nor the area of hepatocellular foci positive for glutathione S-transferase placental form (GST-P) increased in any of the EGDE, HNA, or AAA treated groups. However, the number and area of GST-P-positive foci significantly increased in the positive control group treated with PB. The results indicate that EGDE, HNA, and AAA lack hepatocarcinogenicity in rats.

The development of in vitro toxicity assessment methods using cultured cells has gained popularity for promoting animal welfare in animal experiments. Herein, we briefly discuss the current status of hepatoxicity assessment using human- and rat-derived hepatocytes; we focus on the liver organoid method, which has been extensively studied in recent years, and discuss how toxicologic pathologists can use their knowledge and experience to contribute to the development of in vitro chemical hepatotoxicity assessment methods for drugs, pesticides, and chemicals. We also propose how toxicological pathologists should assess toxicity regarding the putative distribution of undifferentiated and differentiated cells in the organoid when liver organoids are observed in hematoxylin and eosin-stained specimens. This was done while considering the usefulness and limitations of in vitro studies for toxicologic pathology assessment.

A 104-week-old male CD (SD) rat exhibited enlargement of the left testis. Microscopically, this mass was demarcated from the testis by fibrous connective tissue and characterized by cystic dilatation with single-layered columnar cells and papillary proliferation connected to the solid growth area without clear boundaries. In the solid growth area, cells were dissected into irregular alveolar nests by scant fibrous tissue with small blood vessels. The nuclei of proliferating cells were variable in size and round- to oval-shaped, and their cytoplasm was pale or eosinophilic and sometimes contained vacuoles or eosinophilic granules. Immunohistochemically, the tumor cells were positive for vimentin and cytokeratin (CK) 7. Since CK7 was exclusively positive in the rete testis epithelium of the naïve rat, it was valuable to diagnose this tumor as rete testis-originated. Based on these results and the lack of apparent pleomorphism, mitotic figures, and metastasis, the present case was diagnosed as rete testis adenoma.

In order to elucidate the effects of swim bladder inflation failure on swim bladder carcinogenesis, we investigated the sequential histopathological changes of swim bladders at 13, 24, 35, and 53 days post-hatch (dph) in medakas with an uninflated swim bladder, which was experimentally induced by denying access to the air-water interface between 0 and 6 dph. The reactive oxygen species (ROS) levels were measured at 24 dph. An uninflated swim bladder was induced in 47.3% of the fish denied access to the air-water interface (the denied group). The total incidence of swim bladder adenoma was 54.1% in the denied group; however, these tumors were observed in all fish with an uninflated swim bladder. In fact, these tumors were observed from 13 dph and onwards. The TBARS levels of the juveniles showed a 2.6-fold increase in fish with an uninflated swim bladder in the denied group compared to that in the control group. It is speculated that swim bladder inflation failure has some effects on the gas gland to produce ROS, leading to DNA damage in the gas glandular epithelium, which develops into swim bladder adenomas. Consequently, it is concluded that denying access to the air-water interface between 0 and 6 dph in medaka is an easy method of inducing swim bladder tumors in a short-term period, and is a useful method for producing tumor-bearing fish.

A 32-year-old woman attempted suicide by ingesting Gloriosa bulbs and died approximately 2 days later. Toxicological examination revealed a potentially fatal blood concentration of colchicine (0.096 mg/L). In addition to the increased mitotic figures in the gastrointestinal mucosa, a unique finding for acute colchicine intoxication, pathological examination showed microvesicular lipid droplets in the liver, kidney, heart, and conduction system. Furthermore, central chromatolysis of neurons was observed in the pontine nucleus, medial accessory olivary nucleus, nucleus of the solitary tract, and nucleus ambiguus. Grumose degeneration of the cerebellar dentate nucleus was also evident. These pathological findings may help identify colchicine intoxication, even in the absence of evidence suggesting ingestion during autopsy. Moreover, pathological changes in the heart and central nervous system may be associated with the development of serious complications of acute colchicine intoxication.

Vestibular organs consist of the maculae staticae, which are located in both the utricle and saccule, as well as the semicircular ducts and their ampullas. There have been no reports on specimen preparation methods for vestibular organs, including maculae staticae or semicircular ducts. In this study, we investigated highly reproducible methods of preparing vestibular organ specimens for histopathological examinations. We established a method that allows researchers to observe the utricle and saccule, including otoliths, the ampulla of a semicircular duct, and parts of semicircular ducts. This highly reproducible method is useful for histopathological analysis of mice with symptoms of abnormal equilibrium caused by medical toxicity and genetic modification.