Incidence of spontaneous lymphomas in non-experimental NOD/Shi-scid, IL-2Rγnull (NOG) mice

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

Data on long-term survival of the NOD/Shi-scid IL-2Rγnull (NOG) mouse in two facilities

The objective of this study was to investigate an appropriate observation period for an evaluation of tumorigenicity in NOD/Shi-scid IL-2 Rγ^null (NOG) mice. At SNBL, 19 male and 19 female NOG mice were observed the general condition from 7 weeks old up to 68 weeks old and at FBRI, 7 male and 16 female NOG mice were observed the general condition throughout the lifespan from 7 weeks old. The survival rate started to decline rapidly around 54 to 56 weeks of age in both facilities without a facility difference. Based on these survival data, it seems reasonable to terminate a tumorigenicity study at 52 weeks of age.

Spontaneous granulocytic leukemia in a NOD/Shi-scid IL-2Rγnull mouse

Here, we report a case of spontaneous granulocytic leukemia in a 51-week-old male NOD/Shi-scid IL-2Rγ ^null (NOG) mouse. The mouse showed progressive anemia and rough respiratory movement. Macroscopically, the spleen was discolored and enlarged. Histologically, the bone marrow of the sternum and femur was highly cellular and almost exclusively filled with neoplastic cells. The nuclei of neoplastic cells were large, oval to slightly irregular in shape, and a small number of cells had kidney- or ring-shaped nuclei. Neoplastic cells extensively infiltrated the organs, and the spleen and liver were prominently involved. Immunohistochemically, a large population of neoplastic cells in the red pulp of the spleen and sinusoid of the liver was positive for myeloperoxidase. Based on the histological features, this case was diagnosed with granulocytic leukemia. This novel information on spontaneous tumors may be helpful for the appropriate use of this mouse strain in further research.

Establishment of a Patient-Derived Xenograft Model of Colorectal Cancer in CIEA NOG Mice and Exploring Smartfish Liquid Diet as a Source of Omega-3 Fatty Acids

Cancer patient-derived xenografts (PDXs) better preserve tumor characteristics and microenvironment than traditional cancer cell line derived xenografts and are becoming a valuable model in translational cancer research and personalized medicine. We have established a PDX model for colorectal cancer (CRC) in CIEA NOG mice with a 50% engraftment rate. Tumor fragments from patients with CRC (n = 5) were engrafted in four mice per tumor (n = 20). Mice with established PDXs received a liquid diet enriched with fish oil or placebo, and fatty acid profiling was performed to measure fatty acid content in whole blood. Moreover, a biobank consisting of tissue and blood samples from patients was established. Histology, immunohistochemistry and in situ hybridization procedures were used for staining of tumor and xenograft tissue slides. Results demonstrate that key histological characteristics of the patients’ tumors were retained in the established PDXs, and the liquid diets were consumed as intended by the mice. Some of the older mice developed lymphomas that originated from human Ki67⁺, CD45⁺, and EBV⁺ lymphoid cells. We present a detailed description of the process and methodology, as well as possible issues that may arise, to refine the method and improve PDX engraftment rate for future studies. The established PDX model for CRC can be used for exploring different cancer treatment regimes, and liquid diets enriched with fish oil may be successfully delivered to the mice through the drinking flasks.

Efficient production of immunodeficient non-obese diabetic/Shi-scid IL2rγnull mice via the superovulation technique using inhibin antiserum and gonadotropin

Severe immunodeficient mice are an essential tool for the examination of the efficacy and safety of new therapeutic technologies as a humanized model. Previously, non-obese diabetic (NOD)/Shi-scid IL2rγ^null (NOG) mice were established as immunodeficient mice by combining interleukin-2 receptor-γ chain-knockout mice and NOD/Shi-scid mice. The NOG mice are used frequently in the research of therapeutic monoclonal antibodies and regenerative medicine for human diseases. Establishment of an efficient production system of NOG mice, using optimized reproductive techniques, is required to accelerate research. In this study, we investigated the efficacy of the superovulation technique using equine chorionic gonadotropin (eCG) and inhibin antiserum (IAS) in NOG mice of various ages (4, 8, 12, 24, or 54 weeks). Additionally, we examined the fertilizing and developmental ability of the oocytes through in-vitro fertilization using frozen-thawed sperm, embryo culture and embryo transfer. The results showed that NOG mice produced the highest number of oocytes at 12 weeks old following the co-administration of eCG and IAS (collectively IASe) (70 oocytes/female). IASe was more effective in increasing the number of oocytes v. eCG at all ages. The IASe-derived oocytes demonstrated the ability to fertilize and develop into blastocysts and pups. Finally, we demonstrated that three strains of genetically modified NOG mice were efficiently produced through the optimized reproductive techniques. In summary, we developed an efficient system for the production of immunodeficient mice using 12-week-old, IASe-treated female NOG mice.

Comparison of biological features between severely immuno-deficient NOD/Shi-scid Il2rgnull and NOD/LtSz-scid Il2rgnull mice

Biological background data up to 11 weeks of age and tumorigenic susceptibility to xenotransplantation with HeLa cells were compared between severely immuno-deficient NOG and NSG mice. The body weight was lower in NOG mice than in NSG mice. Severe depletion of peripheral blood lymphocytes and lymphoid hypoplasia that are well-known characteristics of these mice were equally observed. No lymphoproliferative lesions developed in any mouse of either strain. The occurrence of ectopic exocrine gland and cyst was a common finding in the thymus of both strains. In addition, minimal spongiotic change was observed in the medulla oblongata and spinal cord in both strains, and its incidence in female NOG mice was a little higher than that in NSG mice. In the adrenal, subcapsular cell hyperplasia that is known as an age-related change in non-genetically modified mice developed earlier and its incidence was higher in NSG mice than in NOG mice. The development of female genital organs of NOG mice was slightly retarded in comparison with that of NSG mice. To evaluate tumorigenic susceptibility to xenotransplantation, female mice were implanted in the dorsal subcutis with 1×10³ to 1×10⁶ cells/head of HeLa cells, and were checked up to 16 weeks after implantation. As a result, there was no significant strain difference on tumor formation rate and tumor volume. In conclusion, the present study clearly demonstrated that NOG and NSG mice showed no distinct strain differences in either biological features or biological disadvantages.