Significance of Pericardial Cytokines in Giant Cell Myocarditis in Rats

- Pathological Comparison to Viral Myocarditis in Mice -

Abstract

To investigate the precise disease progression in myocarditis, Lewis rats were injected with porcine cardiac myosin, and C₃H/He mice were inoculated with coxsackievirus B3. Both were killed serially, and the hearts were stained with hematoxylin-eosin to compare their pathological characteristics. In viral myocarditis, viral replication in the myocardium resulted in myocardial necrosis with inflammation, and the lesions were distributed transmurally, as previously reported. On the other hand, in giant cell myocarditis, inflammatory lesions appeared at first around the capillaries in the epicardium, and thereafter spread transmurally. Pericardial effusion was noticed in all the rats with myocarditis in the fulminant stage. Levels of interleukin (IL)-1β and IL-6 in the pericardial effusion were elevated compared with the serum cytokines at the peak of inflammation. However, interferon-γ in both the pericardial effusion and serum was not elevated. The cause of the myocardial lesions that developed in rats with giant cell myocarditis may be some active inflammatory process via the pericardial effusion.