IL-1β in Irrigation Fluid and MRNA Expression in Synovial Tissue of the Knee Joint as Therapeutic Markers of Inflammation in Collagen Antibody-Induced Arthritis

Objective: We studied the relationship between the severity of inflammation and IL-1β production and relative expression level of IL-1β mRNA in irrigation fluid and synovial tissue obtained from the knee joint during the acute stage of a murine model of type II collagen antibody-induced arthritis (CAIA). This model is used to identify potential therapeutic markers for treating rheumatoid arthritis. Methods: Irrigation fluid and synovium tissue were harvested from the knee joint of BALB/c mice in acute stage of CAIA induction. The IL-1β protein level was measured by enzyme-linked immunosorbent assay, and the relative expression level of IL-1β mRNA was analyzed by reverse transcription-polymerase chain reaction. Two investigators analyzed expression levels and histopathological changes. Results: IL-1β concentration was higher in irrigation fluid from the knee joint than in the serum in the acute stage of CAIA. The relative expression level of IL-1β mRNA was elevated in synovial tissue. Histopathological changes in the knee joint and foot indicated similar severity. Conclusions: IL-1β concentration in irrigation fluid and relative expression level of IL-1β mRNA in the synovium have potential as therapeutic markers in studying and treating CAIA.