Elastic Fibers in Myocardial Scars in Rats: Development Teraction with Other Components

This work was designed to determine the course of development of elastic fibers in myocardial scars in rats and their relationship to other components of such structures. Light and electron microscopic observations were made on tissues from 24 rats, killed at sequent stages from 4 to 24 days postinjury. By both techniques, elastic fibers, shown to be forming by 4 days, had increased in size and number with maturation of the scar. At later stages they became interdigitated with the stumps of viable myocytes. We also saw that these fibers often had formed close contacts with the cell surfaces of myofibroblasts and nonvascular smooth muscle cells; a process found in some other situations but not previously in myocardial scars. This information is relevant, in particular, to the dynamics of myocardial scars and thus to the maintenance of function in the injured heart, but also to elastic fiber behavior in general. The integral role of elastic fibers in cell-matrix interactions as well as their biomechanical function is emphasized.