Periostin is produced by myofibroblasts after activation of resident fibroblasts [57,58,59,60] in response to stress and during different cardiac pathological conditions, such as myocardial infarction or dilated cardiomyopathy, and is secreted into the extracellular milieu and localizes to areas of fibrosis and collagen accumulation. The gene discussed is POSTN; the disease is dilated cardiomyopathy.