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Systemic and eosinophilic lesions in rats with spontaneous eosinophilia (mes rats)
S Muto1, M Hayashi, N Matsushita
1Toxicology Laboratories, R&D, Kissei Pharmaceutical Co., Ltd., shinichi_muto@pharm.kissei.co.jp
Abstract:
The mes rat is from an inbred mutant colony of rats with spontaneous eosinophilia. In order to investigate the pathogenesis of the mes rat, the histopathology and hematology for 76 mes rats were examined at several weeks of age. Tissue eosinophilia developed at 8 weeks of age when the blood eosinophil was 500 cells per microliter or more. Subsequently, eosinophilia progressed with age, and splenic eosinophilopoiesis and erythropoiesis appeared simultaneously. Many inflammatory lesions were induced after 10 weeks of age when the blood eosinophils became 1,000 cells per microliter or more. Gastroenteritis and mesenteric lymphadenitis were seen in 44 of 47 (94%) and 31 of 47 (66%) rats, respectively, after 10 weeks of age. Aortitis that deteriorated with age was found in 19 of 39 (49%) rats after 12 weeks of age. Hepatic fibrosis was found in four rats that exhibited severe eosinophilia and anemia. These results are comparable to the features of a hypereosinophilic syndrome in humans and other animals.
Insights
The mes rat, a model for hypereosinophilic syndrome, develops tissue eosinophilia and inflammatory lesions including gastroenteritis and aortitis with age. These findings offer insights into eosinophilic disease pathogenesis.
Area of Science:
- Veterinary Pathology
- Hematology
- Immunology
Background:
- The mes rat is an inbred mutant colony exhibiting spontaneous eosinophilia.
- Understanding the pathogenesis of this model is crucial for studying eosinophilic disorders.
Purpose of the Study:
- To investigate the histopathology and hematology of mes rats to elucidate the pathogenesis of spontaneous eosinophilia.
- To correlate the development of tissue eosinophilia and inflammatory lesions with blood eosinophil counts and age.
Main Methods:
- Histopathological examination of tissues from 76 mes rats at various ages.
- Hematological analysis, focusing on blood eosinophil counts.
- Age-based correlation of observed pathological changes.
Main Results:
- Tissue eosinophilia emerged by 8 weeks (≥500 eosinophils/µL), progressing with age.
- Splenic eosinophilopoiesis and erythropoiesis occurred concurrently.
- Significant inflammatory lesions, including gastroenteritis (94%) and mesenteric lymphadenitis (66%), appeared after 10 weeks (≥1000 eosinophils/µL).
- Aortitis (49%) worsened with age, and hepatic fibrosis was noted in severe cases.
Conclusions:
- Mes rats exhibit age-dependent eosinophilia and inflammatory pathology.
- The observed features resemble human and animal hypereosinophilic syndromes.
- This model is valuable for studying the mechanisms and consequences of sustained eosinophilia.