Cross-communication between fibroblasts and cardiomyocytes.

The myocardium is composed of various cell types including cardiomyocytes, fibroblasts, endothelial cells, and leukocytes. Although cardiomyocytes count for up to 85% of a heart’s volume, the actual cell number of cardiomyocytes account for just 30–40% of all cardiac cells. Non-cardiomyocytes constitute 60–70% of a cardiac cell and approximately 90% of these non-cardiomyocytes represent fibroblasts (1,2). Previously, the function and viability of cardiomyocytes have been treated as a primary research interest area, while fibrosis was considered as a secondary effect from the changes in cardiomyocytes. However, recent studies have suggested an influence of fibroblasts over cardiomyocytes (3,4).