Historical Control Data of Spontaneous Pathological Findings in C57BL/6J Mice Used in 18-Month Dietary Carcinogenicity Assays.

A retrospective analysis in C57BL6/J mice used in dietary carcinogenicity studies was performed to determine the survival rate, causes of death and incidences of spontaneous non-tumoral and tumoral findings. Data were collected from 1600 mice from control dose groups of sixteen 18-month carcinogenicity assays performed between 2003 and 2021 at the same test facility with similar environmental conditions and experimental procedures. The survival rate was high in both sexes (81%-85%) and the causes of humane euthanasia or death were mainly non-tumoral (chronic ulcerative dermatitis, atrial thrombosis). Benign tumors were more frequent than malignant tumors and females were more affected than males. Pituitary gland adenoma in females, lymphoma, bronchioloalveolar adenoma, and harderian gland adenoma in both sexes were the most common tumors. Systemic amyloidosis, the most frequent non-tumoral lesion, was observed variably across studies without sex predilection. The analysis by cohort (3 time periods of 6 years) showed a tendency toward higher incidences of lymphoma and pituitary gland adenoma and lower incidences of amyloidosis over time. The results presented here provide for the first time a robust set of control historical data in untreated C57BL/6J mice kept for 18 months contributing to build in depth knowledge of this animal model.

The Application, Challenges, and Advancement Toward Regulatory Acceptance of Digital Toxicologic Pathology: Results of the 7th ESTP International Expert Workshop (September 20-21, 2019).

With advancements in whole slide imaging technology and improved understanding of the features of pathologist workstations required for digital slide evaluation, many institutions are investigating broad digital pathology adoption. The benefits of digital pathology evaluation include remote access to study or diagnostic case materials and integration of analysis and reporting tools. Diagnosis based on whole slide images is established in human medical pathology, and the use of digital pathology in toxicologic pathology is increasing. However, there has not been broad adoption in toxicologic pathology, particularly in the context of regulatory studies, due to lack of precedence. To address this topic, as well as practical aspects, the European Society of Toxicologic Pathology coordinated an expert international workshop to assess current applications and challenges and outline a set of minimal requirements needed to gain future regulatory acceptance for the use of digital toxicologic pathology workflows in research and development, so that toxicologic pathologists can benefit from digital slide technology.

An atypical case of histiocytic sarcoma in a Wistar rat (Rattus norvegicus).

Histiocytic sarcoma is the most frequent hematopoietic tumor in rats. We report here a histiocytic sarcoma infiltrating the liver, the spleen and the pancreas from a Wistar rat. In the liver, the tumor was associated with oval cell and bile duct hyperplasia. The cells looked like neoplastic histocytic cells described in this species but with some particularities (e.g. lack of multinucleated giant cells). At immunohistochemistry, neoplastic cells in the liver were vimentine positive but lysozyme and CD68 negative. In the kidney, lysozyme-positive cytoplasmic droplets were observed. We describe here an atypical case of histiocytic sarcoma in the rat and we compare the nature of these neoplastic cells to other species.

A mammary gland adenomyoepithelioma in a C57BL/6 mouse.

Mammary gland adenomyoepitheliomas are benign complex mammary gland tumors composed of neoplastic cells of epithelial and myoepithelial origins, described in many species (humans, dogs, cats, rats) and rarely in mice. We report here an adenomyoepithelioma in a C57BL/6 female mouse. Histologically, tubes and cords formed by neoplastic epithelial cells were separated by bundles of neoplastic myoepithelial cells in a clear and partially mucinous matrix. The tumor displayed characteristics of a benign neoplastic proliferation with a compressive growth pattern, and moderate cellular pleomorphism and mitotic index. At immunohistochemistry, the epithelial cells were strongly cytokeratin positive; the myoepithelial cells were weakly cytokeratin positive and strongly smooth muscle actin positive. This is to our knowledge, the first report of a mammary gland adenomyoepithelioma in a C57BL/6 mouse.

Evaluation of the antiandrogenic effects of flutamide, DDE, and linuron in the weanling rat assay using organ weight, histopathological, and proteomic approaches.

The Organization for Economic Cooperation and Development (OECD) is currently funding the validation of the Hershberger assay as a rapid in vivo means of identifying (anti-) androgens. However, as the assay measures weight changes in the androgen-sensitive tissues of castrated rats, the evaluation of the androgen-stimulated intact weanling as a more ethical model to use in the assay has been requested. As part of the OECD validation exercise two weak antiandrogens, 1,1-dichloro-2,2-bis(4 chlorophenyl)ethane (DDE) and linuron (LIN), were investigated in our laboratory at several dose levels in the testosterone propionate (TP)-stimulated weanling using flutamide (FM) as a positive control. In addition to weight measurements (sex accessory tissues [SATs], epididymides, and testes), histopathological assessment of the seminal vesicles, prostate, and testes was conducted for vehicle control, TP-stimulated, and TP-stimulated animals treated with FM or the top dose level of DDE or LIN. The modulation of a novel prostate protein associated with apoptosis, L-amino acid oxidase (LAO), was evaluated in these same treatment groups. Our gravimetric data (supported by the histopathology data) indicated that the weanling assay can detect SAT and epididymal weight changes induced by the antiandrogens evaluated. Inconsistent and variable data were recorded for the testicular weight and histopathological effects, suggesting that the testis is of little value in the identification of antiandrogens using this model. Three isoforms of LAO were identified, and all were regulated by TP. Modulation of LAO by the antiandrogens indicated that this protein could be a biomarker for endocrine disruption in male rodents.

Historical control data of neoplastic lesions in the Wistar Hannover Rat among eight 2-year carcinogenicity studies.

Incidences of neoplastic lesions were evaluated in untreated Hannover Wistar Rats RjHan: WI (470 males and 470 females) used as control animals in eight carcinogenicity studies. All these studies were performed in a similar environment either for the in vivo and the postmortem evaluation. The major neoplastic lesions were found in the endocrine, integumentary and reproductive systems. Pituitary adenoma was the most frequent neoplasm and occurred in 33.9% of the males and 54.6% of the female rats. The other most frequent tumors in males were thyroid C-cell adenoma (8.6%), pancreatic islet cell adenoma (8.1%), subcutaneous fibrosarcoma (6.6%), subcutaneous fibroma (4.7%), benign pheochromocytoma (3.4%), and cutaneous keratoacanthoma (3.4%). In females, the other highest incidences were mammary fibroadenoma (29%), uterine endometrial stromal polyp (18.1%), mammary adenocarcinoma (14.2%), mammary fibroadenoma with atypia (13.7%), thyroid C-cell adenoma (7.5%), benign thymoma (3.7%), and subcutaneous fibrosarcoma (3.6%). All these data were compared to previously published historical control data. This retrospective analysis was undergone in order to illustrate the result of a stable organization which guarantees a robust historical data base for neoplastic and non neoplastic findings.

Protein profiling of rat ventral prostate following chronic finasteride administration: identification and localization of a novel putative androgen-regulated protein.

To better understand the effects of antiandrogens on the prostate, we investigated the changes in the proteome of rat ventral prostate (VP) following treatment with a well characterized 5alpha-reductase inhibitor, finasteride. Sprague-Dawley rats were treated daily by gavage with finasteride at 0, 1, 5, 25, and 125 mg/kg/day. Changes in plasma hormone levels as well as the weight and histology of sex accessory tissues were determined after 28 days of treatment and showed a dose-related decrease of VP weights together with a marked atrophy of the tissue visible at the macroscopic and microscopic levels. In addition, significant reductions in seminal vesicle and epididymis weights were noted. VP proteins were analyzed by two-dimensional gel electrophoresis: 37 proteins, mainly involved in protein synthesis, processing, and cellular trafficking and in metabolism, detoxification, and oxidative stress, were identified as modulated by finasteride. The prominent feature of this study is the demonstration of finasteride dose-dependent up-regulation of a protein similar to l-amino-acid oxidase 1 (Lao1). An up-regulation of this protein was also observed with the antiandrogen flutamide. Lao1 expression occurred as early as 48 h after antiandrogen administration and persisted throughout the treatment duration. Immunohistochemistry showed that this protein was only detectable in epithelial cells and secretory vesicles. Altogether these data point to a potential use of Lao1 to reveal antiandrogen-induced prostate injury.

Delayed neutralization of interferon-gamma prevents lethality in primate Gram-negative bacteremic shock.

OBJECTIVE: Whether anticytokine therapies have a place in the treatment of severe sepsis and septic shock remains a question. Although a number of preclinical studies have shown efficacy in primate models of bacteremic shock when administered prophylactically, these same therapies have a significantly diminished effectiveness when administered therapeutically. This study investigated whether delayed administration of a novel anti-human interferon-gamma monoclonal antibody could improve outcome and reduce organ injury in a lethal model of Escherichia coli bacteremia, when administered after the onset of shock. DESIGN: Randomized, prospective, double-blinded intervention study. SUBJECTS: Cynomolgus monkeys. INTERVENTIONS: Treatment with a humanized monoclonal antibody directed against human interferon-gamma (INNO 202), administered after the onset of shock, induced by the infusion of live E. coli. MEASUREMENTS AND MAIN RESULTS: Five of the six vehicle-treated monkeys died or were killed within 24-72 hrs after E. coli administration, and all died within 5 days. In contrast, six of the eight animals treated with the anti-interferon-gamma survived for 7 days, and three of the eight animals survived 14 days (p = .013 vs. vehicle). Delayed treatment with the anti-interferon-gamma monoclonal antibody did not restore hemodynamics or reduce the amount of crystalloid-containing fluid required to resuscitate the animals but did attenuate renal failure (p < .05) and the magnitude of the inflammatory cytokine response (p < .05). CONCLUSIONS: In a primate model of E. coli bacteremic shock, delayed neutralization of interferon-gamma after the onset of shock improved survival and attenuated the pathologic changes associated with the development of organ dysfunction. These findings suggest that interferon-gamma blockade represents a potentially effective mode of late intervention in lethal septic shock.