Morphologic Features and Deep Learning-Based Analysis of Canine Spermatogenic Stages.

In nonclinical toxicity studies, stage-aware evaluation is often expected to assess drug-induced testicular toxicity. Although stage-aware evaluation does not require identification of specific stages, it is important to understand microscopic features of spermatogenic staging. Staging of the spermatogenic cycle in dogs is a challenging and time-consuming process. In this study, we first defined morphologic features for the eight spermatogenic stages in standard histology sections (H&E slides) of dog testes. For image analysis, we defined the key morphologic features of five stages/pooled stage groups (I-II, III-IV, V, VI-VII, and VIII). These criteria were used to develop a deep learning (DL) algorithm for staging of the spermatogenic cycle of control dog testes using whole slide images. In addition, a DL-based nucleus segmentation model was trained to detect and quantify the number of different germ cells, including spermatogonia, spermatocytes, and spermatids. Identification of spermatogenic stages and quantification of germ cell populations were successfully automated by the DL models. Combining these two algorithms provided color-coding visual spermatogenic staging and quantitative information on germ cell populations at specific stages that would facilitate the stage-aware evaluation and detection of changes in germ cell populations in nonclinical toxicity studies.

Interstitial Adipocytes in the Beagle Dog and New Zealand White Rabbit Choroid Plexus.

The choroid plexus (CP) produces cerebrospinal fluid and has epithelial, interstitial, and vascular compartments. The CP is a potential site of toxicity, and recognizing the normal microanatomy in different animal models is important for the pathologist. In preclinical studies with beagle dog and New Zealand white rabbits, we observed variable numbers of adipocytes in the CP interstitium of control and xenobiotic-treated animals. The adipocytes were unilocular and consistent morphologically with white adipose tissue. There was a striking variability in the number of adipocytes; however, the presence of adipocytes was not associated with other microscopic findings that would suggest a pathologic process. The morphology of adipocytes was reminiscent of what is observed normally in the interstitium of other tissues like skeletal muscle, bone marrow, and the subcutis. Therefore, we propose that the interstitial adipocytes not be recorded as a finding in preclinical studies unless the adipocytes are altered spontaneously (ie, lipoma) or after xenobiotic treatment.

Brief Overview: Assessment of Compound-induced Acute Kidney Injury Using Animal Models, Biomarkers, and In Vitro Platforms.

The inability to unequivocally predict translatable drug-induced kidney injury in nonclinical studies during pharmacological development is evidenced by drug attrition in human clinical trials. Eight urinary proteins have been qualified as renal safety biomarkers for limited context of use in nonclinical drug development studies in rats. Formal qualification of human renal safety biomarkers is pending the submission of data from prospective clinical trials and analyses of biomarker performance to the Food and Drug Administration and European Medicines Agency by the Foundation for the National Institutes of Health and Predictive Safety Testing Consortium's Nephrotoxicity Working Group. In vitro kidney platforms may be leveraged to investigate the potential risk of compound-induced acute kidney injury and/or dysfunction. The early assessment of drug-related kidney safety profiles using biomarker-level changes in animal models and in vitro platforms could significantly reduce renal safety-related drug attrition; yet, there are no well-validated in vitro systems to enable comprehensive investigations of compound-induced nephrotoxicity. Thus, histopathology remains the gold standard for diagnosing nephron-specific damage. Traditional and emerging biomarker panels should be combined with histopathology and/or cytopathology to enable early identification of compound-induced kidney injury.

The companion dog as a unique translational model for aging.

The dog is a unique species due to its wide variation among breeds in terms of size, morphology, behaviour and lifespan, coupled with a genetic structure that facilitates the dissection of the genetic architecture that controls these traits. Dogs and humans co-evolved and share recent evolutionary selection processes, such as adaptation to digest starch-rich diets. Many diseases of the dog have a human counterpart, and notably Alzheimer's disease, which is otherwise difficult to model in other organisms. Unlike laboratory animals, companion dogs share the human environment and lifestyle, are exposed to the same pollutants, and are faced with pathogens and infections. Dogs represented a very useful model to understand the relationship between size, insulin-like growth factor-1 genetic variation and lifespan, and have been used to test the effects of dietary restriction and immunotherapy for Alzheimer's disease. Very recently, rapamycin was tested in companion dogs outside the laboratory, and this approach where citizens are involved in research aimed at the benefit of dog welfare might become a game changer in geroscience.

Artifactual Stratum Corneum Calcification of the Beagle Dog Tongue.

Examination of H&E-stained tongue samples from a 26-week intravenous infusion study of Beagle dogs, utilizing a compound with no recognized effect on mineral metabolism, exhibited superficial stratum corneum calcification in both treated and control animals. This resulted in the search for possible causes of the finding to help clarify confounding issues. Retrospective examination of 11 studies performed before the signal case indicated that the problem existed in the testing facility but was not recognized. Prior to 2008, this finding was not observed, perhaps indicating the requirement for a change in procedures or suppliers. Based on the hypothesis that the calcium salts were deposited from bone during processing, a series of tests was performed by fixing tongue and femur along with different tissues, processed routinely to slide, and stained with H&E and von Kossa stains. We conclude that the presence of superficial stratum corneum calcification of the tongue in dogs demonstrated in toxicology studies is an artifactual change related to the processing of tissues, specifically the fixation of tongue in the same container as bone and stomach. This change should not be confused with compound-related effects, even when the incidence varies between controls and treated animals.