For many years our team performs a systematic histopathological characterisation of genetically modified mouse lines in order 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 standard screening phenotyping pipeline of the German Mouse Clinic, the pathological screen plays a vital role in correlating the in vivo phenotyping findings and recognising further phenotypes not detected in high-throughput mouse phenotyping pipelines (https://www.mousephenotype.org/impress/).
During the necropsy, mutant and control mice are health monitored and fully morphologically characterised. The exact body and organ weight/length measurements and description of lesions in the organs are recorded and photographed by our experienced necropsy technical personnel. The macroscopically terminology used is in agreement with the mouse phenotyping annotation of data for high-throughput phenotyping (https://www.mousephenotype.org/impress/procedures/14).
The organs are collected, fixed in 4 % neutral buffered formalin and embedded in paraffin. For histological examination, haematoxylin-eosin stain (HE) is routinely used in the 28 organs listed below. Other organs such as brown and white fat, pituitary gland, nasopharynx, skeletal muscle, sciatic nerve and bone can also be histologically examined on as a special request.
|Cervical lymph node||Adrenals||Funiculus spermaticus|
|Trachea||Urinary bladder||Male accessory gland|
The microscopic analysis is performed by experienced veterinary or medical pathologists in identifying the incidence and severity of morphological manifestations of disease, taking into account sex, age and strain background derived-lesions and sectioning/staining artefacts. The use of digital documentation of histopathological findings (Hamamatsu scanner) and standardised terminology allow images of tissues to be copied and its pathological diagnosis to be shared into a wider phenotyping community.
Specific targeted analysis
Assuming findings in the standard screening pipeline, additional specific targeted evaluations such special histochemical stains (Masson’s trichrome, Weigert’s elastic stain, Turnbull’s blue, Perls’ Prussian blue, Luxol Fast Blue, Tartrate resistant acid phosphatase (TRAP) and Periodic acid–Schiff), immunohistochemistry and double immunohistochemistry can be performed to provide further insight into the histopathological findings such as localisation and quantification (histomorphometry) of specific cells, tissue components and cell processes on histological sections.
The immunohistochemistry technique, using more than 200 primary antibodies for mouse, rat or human tissues, has been adapted and established for mouse tissue and is performed in an automated slide staining system (Discovery Ventana Medical System, Roche) to address expression patterns of proteins for the following issues: hematology and hemato-oncology, cell and tissue markers, stem cell marker, cell cycle and processes, signal transduction, growth factors, endocrine markers and phospho-specific antibodies.
The photomicrographs below illustrate some of our histopathological findings.
A: Macroscopic appearance of the liver from a Jak1S645P+/− mouse reveals a congestive liver with irregular margins and prominent vessels. H&E stainings of the liver show a dilation of the hepatic sinusoidal plexus. Anti-CD31 IHC for endothelial cells illustrates an increased vascularization in the mutant liver. Scale bars: 200 μm; 500 μm. B: Reticulin silver staining (Gomori’s trichrome staining) visualizes an increase in hyperplastic hepatocytes neighbored by atrophic hepatocytes in a Jak1S645P+/− mouse. Masson’s trichrome staining excludes the presence of fibrosis in Jak1S645P+/− mice. Anti–p-Stat3 IHC depicts phosphorylation and nuclear localization of Stat3 in the hepatocytes of Jak1S645P+/− mice compared with Jak1wt mice demonstrating activation of the JAK/STAT pathway. Scale bar = 200 μm.
Sabrautzki et al., 2013, An ENU Mutagenesis-Derived Mouse Model with a Dominant Jak1 Mutation Resembling Phenotypes of Systemic Autoimmune Disease, The American Journal of Pathology, Vol. 183, No. 2, August 2013. doi:10.1016/j.ajpath.2013.04.027