Stem cells and cardiac hypertrophy

The concept that the adult heart is a terminally differentiated organ has been generally accepted for many years. As a post-mitotic organ, the heart has been considered to be characterized by a predetermined number of parenchymal cells. This number is held to be defined at birth, and is preserved until death of the organ and/or the organism. According to this concept, the increase of myocardial mass, or in other words, myocardial hypertrophy, is interpreted on the basis of growth of single terminally differentiated myocytes, able to produce contractile elements and organelles, but not capable of division. Ventricular remodelling has been envisaged, therefore, as a balance between the phenomenon leading to either increase in cardiac mass, in other words hypertrophy, or loss of myocytes, as occurring in apoptosis or necrosis.