Modeling of chronic systemic inflammation with minimal clinical manifestation in an experimental rat study

Introduction. Chronic systemic inflammation (CSI) is a pathologic process that significantly worsens the life prognosis of patients. The need for a detailed study of the pathogenesis of this condition and testing new approaches to its treatment requires the creation of reproducible experimental models. The aim of the study was to develop a representative experimental model of CSI in rats using repeated subcutaneous administration of complete Freund’s adjuvant (CFA). Materials and Methods. Twenty male Wistar stock rats divided into CFA (n = 10) and control (n = 10) groups and were used in the experiment. Animals of the experimental group were injected with CFA subcutaneously in the interscapular region twice with an interval of 2 weeks (0.1 ml/kg). The control group was injected with saline solution according to the same protocol. Body weight was assessed weekly. Clinical blood analysis was performed before modeling and on days 7 and 21. At the end of the study, spleen mass index (SMI) was detected and tissue histologic picture was evaluated. Results. A decrease in the rate of body weight gain was observed in animals from the CFA group. In the same group, a statistically significant increase in the total number of leukocytes, lymphocytes and IMC (p < 0.05), a decrease in the level of erythrocytes and hemoglobin, as well as histological signs of inflammatory infiltration in the lungs and hyperplasia of the lymphoid tissue of the spleen were revealed. Conclusions. Repeated subcutaneous administration of CFA induces mild but stable systemic immune activation without pronounced local damage. The obtained model of CSF is reproducible and can be used in preclinical studies of chronic inflammation.

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