This article provides a brief overview of the second scientific session of the 37th Annual Symposium of the Society of Toxicologic Pathology in Indianapolis, Indiana, on June 18, 2018. The session ...was entitled “Acute Kidney Injury (AKI): The Toxicologic Pathologist’s Constant Companion” and was co-chaired by Drs. Zaher Radi and Torrie Crabbs. The fundamentals of tubule and interstitial anatomy were covered by Dr. Kevin McDorman, followed by a review of International Harmonization of Nomenclature and Diagnostic Criteria, Standard for Exchange of Nonclinical Data, and Drug-Induced Kidney Injury terminology, which was presented by Dr. Torrie Crabbs. Dr. Bruce Molitoris gave a talk on renal hemodynamics, microcirculation, and ischemia. Advances and challenges on new therapies and clinical targets of AKI were presented by Dr. Brad Rovin, and the session ended with a review from Dr. Zaher Radi on immunopathology of AKI.
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Vaccines targeting highly conserved proteins can protect broadly against diverse viral strains. When a vaccine is administered to the respiratory tract, protection against disease is especially ...powerful. However, it is important to establish that this approach is safe. When vaccinated animals later encounter viruses, does reactivation of powerful local immunity, including T cell responses, damage the lungs? This study investigates the safety of mucosal vaccination of the respiratory tract. Non-replicating adenoviral vaccine vectors expressing conserved influenza virus proteins were given intranasally. This vaccine-induced protection persists for at least 15 months. Vaccination did not exacerbate inflammatory responses or tissue damage upon influenza virus infection. Instead, vaccination with nucleoprotein reduced cytokine responses and histopathology, while neutrophil and T cell responses resolved earlier. The results are promising for safe vaccination at the site of infection and thus have implications for the control of influenza and other respiratory viruses.
Rodent progressive cardiomyopathy (PCM) encompasses a constellation of microscopic findings commonly seen as a spontaneous background change in rat and mouse hearts. Primary histologic features of ...PCM include varying degrees of cardiomyocyte degeneration/necrosis, mononuclear cell infiltration, and fibrosis. Mineralization can also occur. Cardiotoxicity may increase the incidence and severity of PCM, and toxicity-related morphologic changes can overlap with those of PCM. Consequently, sensitive and consistent detection and quantification of PCM features are needed to help differentiate spontaneous from test article-related findings. To address this, we developed a computer-assisted image analysis algorithm, facilitated by a fully convolutional network deep learning technique, to detect and quantify the microscopic features of PCM (degeneration/necrosis, fibrosis, mononuclear cell infiltration, mineralization) in rat heart histologic sections. The trained algorithm achieved high values for accuracy, intersection over union, and dice coefficient for each feature. Further, there was a strong positive correlation between the percentage area of the heart predicted to have PCM lesions by the algorithm and the median severity grade assigned by a panel of veterinary toxicologic pathologists following light microscopic evaluation. By providing objective and sensitive quantification of the microscopic features of PCM, deep learning algorithms could assist pathologists in discerning cardiotoxicity-associated changes.
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This article provides a synopsis of the first two presentations from the second scientific session of the 37th Annual Symposium of the Society of Toxicologic Pathology in Indianapolis, Indiana, on ...June 18, 2018; the session focused on acute kidney injury. The first presentation, given by Dr. Kevin McDorman, focused on “Fundamentals of Renal Tubule and Interstitial Anatomy and Physiology.” Several common background findings from toxicity studies were additionally discussed. Lastly, factors that impact the relevance and usefulness of historical control data, such as quality and consistency of histopathology, were discussed. The second presentation, given by Dr. Torrie Crabbs, provided a review of International Harmonization of Nomenclature and Diagnostic Criteria (INHAND), Standard for Exchange of Nonclinical Data (SEND), and drug-induced kidney injury (DIKI) nomenclature. INHAND is a global collaborative project that provides internationally accepted standardized nomenclature and diagnostic criteria for proliferative and nonproliferative changes in laboratory animals in toxicity and carcinogenicity studies. SEND is currently a required standard for data submission to the Food and Drug Administration (FDA). Since the FDA has indicated its preference for INHAND nomenclature, SEND will predominately use INHAND terminology; thus, familiarity with INHAND terminology is critical for toxicologic pathologists. The diagnostic features of three common DIKI findings, in addition to several complicated INHAND terminologies, were reviewed.
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We previously developed a computer-assisted image analysis algorithm to detect and quantify the microscopic features of rodent progressive cardiomyopathy (PCM) in rat heart histologic sections and ...validated the results with a panel of five veterinary toxicologic pathologists using a multinomial logistic model. In this study, we assessed both the inter-rater and intra-rater agreement of the pathologists and compared pathologists’ ratings to the artificial intelligence (AI)-predicted scores. Pathologists and the AI algorithm were presented with 500 slides of rodent heart. They quantified the amount of cardiomyopathy in each slide. A total of 200 of these slides were novel to this study, whereas 100 slides were intentionally selected for repetition from the previous study. After a washout period of more than six months, the repeated slides were examined to assess intra-rater agreement among pathologists. We found the intra-rater agreement to be substantial, with weighted Cohen’s kappa values ranging from k = 0.64 to 0.80. Intra-rater variability is not a concern for the deterministic AI. The inter-rater agreement across pathologists was moderate (Cohen’s kappa k = 0.56). These results demonstrate the utility of AI algorithms as a tool for pathologists to increase sensitivity and specificity for the histopathologic assessment of the heart in toxicology studies.
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The 2019 annual National Toxicology Program Satellite Symposium, entitled “Pathology Potpourri,” was held in Raleigh, North Carolina, at the Society of Toxicologic Pathology’s 38th annual meeting. ...The goal of this symposium was to present and discuss challenging diagnostic pathology and/or nomenclature issues. This article presents summaries of the speakers’ talks along with select images that were used by the audience for voting and discussion. Various lesions and topics covered during the symposium included aging mouse lesions from various strains, as well as the following lesions from various rat strains: rete testis sperm granuloma/fibrosis, ovarian cystadenocarcinoma, retro-orbital schwannoma, periductal cholangiofibrosis of the liver and pancreas, pars distalis hypertrophy, chronic progressive nephropathy, and renal tubule regeneration. Other cases included polyovular follicles in young beagle dogs and a fungal blood smear contaminant. One series of cases challenged the audience to consider how immunohistochemistry may improve the diagnosis of some tumors. Interesting retinal lesions from a rhesus macaque emphasized the difficulty in determining the etiology of any particular retinal lesion due to the retina’s similar response to vascular injury. Finally, a series of lesions from the International Harmonization of Nomenclature and Diagnostic Criteria Non-Rodent Fish Working Group were presented.
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Samples of biologic specimens and their derivatives (eg, wet tissues, paraffin-embedded tissue blocks, histology slides, frozen tissues, whole blood, serum/plasma, and urine) are routinely collected ...during the course of nonclinical toxicity studies. Good Laboratory Practice regulations and/or guidance specify minimum requirements for specimen retention duration, with the caveat that retention of biologic specimens need not extend beyond the duration of sample stability. However, limited availability of published data regarding stability for various purposes following storage of each specimen type has resulted in confusion, uncertainty, and inconsistency as to the appropriate duration for storage of these specimens. To address these issues, a working group of the Society of Toxicologic Pathology Scientific and Regulatory Policy Committee was formed to review published information, regulations, and guidance pertinent to this topic and to summarize the current practices and rationales for retention duration through a survey-based approach. Information regarding experiences reaccessing biologic specimens and performing sample stability investigations was also collected. Based on this combined information, the working group developed several points to consider that may be referenced when developing or revising sample retention practices.
This Points to Consider article is a product of a Society of Toxicologic Pathology (STP) Working Group commissioned by the Scientific and Regulatory Policy Committee (SRPC) of the STP. It has been reviewed and approved by the SRPC and Executive Committee of the STP, the British Society of Toxicologic Pathologists (BSTP) and European Society of Toxicologic Pathology (ESTP) but it does not represent a formal Best Practice recommendation; rather, it is intended to provide key “points to consider” in designing nonclinical studies or interpreting data from toxicity and safety studies in support of regulatory submissions. The points expressed in this document are those of the authors and do not reflect views or policies of the employing institutions. Readers of Toxicologic Pathology are encouraged to send their thoughts on these articles or ideas for new topics to the Editor.
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A number of issues may arise during the conduct of a study which can complicate interpretation of in vitro and in vivo datasets. Speakers discussed the implications of differing interpretations and ...how to avoid complicating factors during study planning and execution. Consideration needs to be given to study design factors including defining objectives, consideration of expected pharmacological effects, dose selection and drug kinetics, species used, and vehicle selection. In addition, the effects of vivarium temperature effects on various endpoints, how to control variables affecting clinical pathology, and how early death animals, common background findings, and artifacts can affect histopathology interpretation all play into the final interpretation of study data.
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Several chemicals and pharmaceuticals increase the incidence of hemangiosarcomas (HSAs) in mice, but the relevance to humans is uncertain. Recently, canine HSAs were identified as a powerful tool for ...investigating the pathogenesis of human HSAs. To characterize the cellular phenotype of canine HSAs, we evaluated immunoreactivity and/or messenger RNA (mRNA) expression of markers for hematopoietic stem cells (HSCs), endothelial cells (ECs), a tumor suppressor protein, and a myeloid marker in canine HSAs. Neoplastic canine cells expressed EC markers and a myeloid marker, but expressed HSC markers less consistently. The canine tumor expression results were then compared to previously published immunoreactivity results for these markers in human and mouse HSAs. There are 2 noteworthy differences across species: (1) most human HSAs had HSC marker expression, indicating that they were comprised of tumor cells that were less differentiated than those in canine and mouse tumors; and (2) human and canine HSAs expressed a late-stage EC maturation marker, whereas mouse HSAs were negative, suggesting that human and canine tumors may retain greater differentiation potential than mouse tumors. These results indicate that HSA development is variable across species and that caution is necessary when discussing translation of carcinogenic risk from animal models to humans.
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It is unclear whether the process of spontaneous and chemically induced hemangiosarcoma and hemangioma formation in mice involves the transformation of differentiated endothelial cells (ECs) or ...recruitment of multipotential bone marrow–derived hematopoietic stem cells or endothelial progenitor cells (EPCs), which show some degree of endothelial differentiation. In the present study, immunohistochemical staining for hematopoietic stem cell markers (CD45 and CD34), EC markers (vascular endothelial growth factor receptor 2 VEGFR2, CD31, and factor VIII–related antigen), and a myeloid lineage marker (CD14) was employed to better define the origin of hemangiosarcomas and hemangiomas in mice. Staining was negative for CD45, factor VIII–related antigen, and CD14 and positive for CD34, VEGFR2, and CD31, indicating that mouse hemangiosarcomas and hemangiomas are composed of cells derived from EPCs expressing CD34, VEGFR2, and CD31 but not factor VIII–related antigen. The lack of CD45 expression suggests that mouse vascular tumors may arise from EPCs that are at a stage later than hematopoietic stem cells. Since factor VIII–related antigen expression is known to occur later than CD31 expression in EPCs, our observations may indicate that these tumor cells are arrested at a stage prior to complete differentiation. In addition, myeloid lineage cells do not appear to contribute to hemangiosarcoma and hemangioma formation in mice.
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