Connective tissue cells in healing rat myocardium. A study of cell reactions in rhythmically contracting environment.

To better understand the tendency of myocardium to heal by scarring rather than regeneration, the authors examined the responses of connective tissue cells (CTCs) after three types of necrotizing injuries. Derived from myocardial interstitial cells, CTCs proliferated in both the connective tissue space and the compartment of necrotic myocytes. They assumed various cell forms: fibrocytelike CTCs throughout the sites of injury deposited extracellular scar tissue elements, established CTC-myocyte contacts, and helped anchor myocytes to scar tissue with myotendonlike specializations; CTCs with more complex forms established CTC-myocyte relationships, suggesting important roles in communication and tissue remodeling. CTCs within scar tissue differentiated into myofibrocytes, chondrocytes, and possibly smooth muscle cells. Most scar tissue elements were disposed in the long axis of myocytes. These alterations in form indicate that CTCs have various roles in myocardial repair and suggest that a number of the roles are modulated by contractile forces.