Cardiac fibroblast physiology and pathology.

Cardiac function is mediated by interactions between the cellular constituents of the heart, as well as the extracellular matrix. The major cell types of the heart include cardiac fibroblasts, myocytes, endothelial cells, and vascular smooth muscle cells. In addition, there are also resident stem cells and transient cell types, such as immune cells. Interactions in the heart include chemical, mechanical, and electrical signals, which vary depending on the developmental stage, disease state, and specific cell type. Understanding how these different signals interact at the molecular, cellular, and organ levels is important for better understanding cardiac function under a variety of physiological and pathological conditions. Cardiac fibroblasts play key roles in maintaining normal cardiac form and function, as well as in the cardiac remodeling process during pathological conditions, such as myocardial infarction and hypertension. Regardless of normal or pathological status of the heart, fibroblasts have multiple functions, such as synthesis and deposition of extracellular matrix and cell-cell communication with other cardiac cells, including myocytes and endothelial cells. Interactions with other cell types can affect multiple cell signaling pathways (e.g., ERK, JNK, and p38), the expression and secretion of numerous growth factors and cytokines, microRNA exchange, gene and protein expression, and angiogenesis. In this review, we provide insight into the cardiac fibroblast under normal and pathological conditions to illustrate their importance in maintaining proper cardiac function.