Transient receptor potential (TRP) channels and cardiac fibrosis

Cardiac fibrosis is associated with most cardiac diseases. Fibrosis is an accumulation of excessive extracellular matrix proteins (ECM) synthesized by cardiac fibroblasts and myofibroblasts. Fibroblasts are the most prevalent cell type in the heart, comprising 75% of cardiac cells. Myofibroblasts are hardly present in healthy normal heart tissue, but appear abundantly in diseased hearts. Cardiac fibroblasts are activated by a variety of pathological stimuli, such as myocardial injury, oxidative stress, mechanical stretch, and elevated autocrine-paracrine mediators, thereby undergoing proliferation, differentiation to myofibroblasts, and production of various cytokines and ECM proteins. A number of signaling pathways and bioactive molecules are involved and work in concert to activate fibroblasts and myofibroblasts in the fibrogenesis cascade. Fibroblasts and myofibroblasts are not only principal ECM producers, but also play a central role in fibrogenesis and myocardial remodeling in fibrotic heart disease. Thus, understanding the biological processes of cardiac fibroblasts will provide novel insights into the underlying mechanisms of fibrosis and provide potential targets for developing antifibrotic drugs. Recent studies demonstrate that Ca2+ signal is essential for fibroblast proliferation, differentiation, and ECM-protein production. This review focuses on the recent advances in understanding molecular mechanisms of Ca2+ signaling in cardiac fibrogenesis, and potential role of Ca(2+)-permeable channels, in particular, the transient potential (TRP) channels in fibrotic heart disease. TRP channels are highly expressed in cardiac fibroblasts. TRPM7 has been shown to be essential in TGFβ1 mediated fibrogenesis, and TRPC3 has been demonstrated to play an essential role in regulating fibroblast function. Thus, the Ca2+-permeable TRP channels may serve as potential novel targets for developing anti-fibrotic drugs.