Pathology
Introduction
Our experienced team performs a systematic histopathological characterization of genetically modified mouse lines to improve the understanding of mammalian gene function and its role in the development of human diseases, contributing to ways of preventing and treating them.
Integrated in the multi-systemic phenotyping pipeline at the German Mouse Clinic, the pathological screen plays a vital role in connecting the various in vivo phenotyping findings and recognizing further phenotypes not detected in the high-throughput primary phenotyping pipeline. (IMPReSS).
With our extensive archive of tissues samples, stored as formalin-fixed paraffin-embedded blocks and glass slides, the Pathology Screen promotes basic and translational research with various institutions worldwide. Researchers interested in our archived materials are invited to contact the German Mouse Clinic Management Team (E-mail).
Standard Screening
During the necropsy mutant and age-, sex- and strain-background-matched control mice (adult or aged) are examined and fully macroscopically described. The exact body and organ weight/length measurements and description of gross changes in the tissues are recorded and photographed by our expert necropsy technical personnel. The macroscopic terminology used is in agreement with the Mammalian Phenotype (MP) Ontology for high-throughput phenotyping (Phenotyping Protocols for Pipeline: German Mouse Clinic).
The tissues are collected, fixed overnight in 4 % neutral buffered formalin and embedded in paraffin. For histological examination, Hematoxylin-Eosin (H&E) staining is routinely used in the following 30 tissues:
| Cerebrum | Salivary glands | Liver | Stomach | Epididymis |
| Cerebellum | Trachea | Gallbladder | Small intestine | Male accessory glands* |
| Lymph nodes | Thyroid | Kidney | Large intestine | Mammary gland |
| Spleen | Parathyroid | Adrenal gland | Pancreas | Ovary |
| Thymus | Heart | Urinary bladder | Skeletal muscle | Uterus |
| Skin | Lung | Esophagus | Testis | Vagina |
* (seminal vesicles, coagulating glands, prostate gland, bulbourethral glands, preputial glands)
Other tissues such as interscapular brown adipose tissue and perigonadal and inguinal white adipose tissues, pituitary gland, nasopharynx, sciatic nerve and bone can also be histologically examined on special request.
The high-throughput routine microscopic analysis is performed by experienced veterinary or medical pathologists to identify the incidence and severity of morphological manifestations of disease, considering sex, age and strain background derived-lesions and sectioning/staining artefacts (Figure 1). The terms used in the annotation of the histopathological findings derive from the Mouse Pathology Ontology (MPATH) providing a description of pathological processes.
All stained tissues on glass slides are scanned and the use of digital documentation of histopathological findings as well as standardized terminology allow images of tissues to be copied and their histopathological diagnosis to be shared into a wider phenotyping community.
Specific targeted analysis
Assuming findings in the standard histopathological routine work, additional specific targeted evaluations such as special histochemical (Periodic acid–Schiff, Masson’s trichrome, Alcian Blue, Sirius Red, Von Kossa, Fontana-Masson, Luxol Fast Blue, Congo Red, Weigert’s elastic stain, Turnbull’s blue, Perls’ Prussian blue, Tartrate resistant acid phosphatase (TRAP), immunohistochemistry and immunofluorescence stainings can be performed. These provide further insights into the histopathological findings such as localization and quantification (histomorphometry) of specific cells, tissue components and cell processes on histological sections.
The immunohistochemistry and immunofluorescence techniques, using more than 120 primary antibodies for mouse, rat or human tissues, have been adapted and established for mouse tissues and are performed in an automated slide staining system to address subcellular location and expression patterns of proteins for the following cellular processes/research areas: hematology and hemato-oncology, cell and tissue markers, stem cell markers, cell cycle and cellular degradation processes, signal transduction, growth factors, endocrine markers and phospho-specific antibodies
In addition, digital histological images can be used along deep learning computational models to identify and quantify cellular or subcellular structures enabling more insights into a traditionally qualitative histopathological evaluation. The assessments can include for example cells (adipocytes in adipose tissue, neuron cell body in cortical cerebrum), subcellular components (biomarker Ki-67-positive nuclei), specific structures (glomeruli in renal tissue, Figure 2) and area-based measurements (renal pelvic region). These analyses are performed in collaboration with the Applied Biology Computational group (ACB: Science).
