Turning Point in Myocarditis

Myocarditis is an acute inflammatory disease of the heartand a precursor of dilated cardiomyopathy.1–8 Myocar-ditis is often characterized by a cellular infiltrate, and if inflammation of the myocardium does not resolve during the acute stage, the heart may be compromised because of necrosis and direct loss of myocytes,9 injury from granulo-matous inflammation,10,11 or fibrosis attributable to prolifer-ation of fibroblasts and collagen deposition.12,13 Once the myocardium becomes fibrotic, there may be loss of function. In this issue of Circulation Research, Kania et al describe a novel system to study fibrosis in myocarditis and the origins of the fibrosis in a mouse model.14 Mice expressing enhanced green fluorescent protein (EGFP) were used as donors of prominin 1 cells, which may directly lead to fibrosis during the development of the chronic disease state in myocarditis and cardiomyopathy. Prominin 1 cells are precursors of