Mast cell and myofibroblast in wound healing.

Growing evidence in the literature indicates that mast cells are integrally involved in the process of dermal wound repair. They are resident cells of the normal dermis and have several cytokines stored in their granules that are stimulatory to fibroblasts. They also contain serine proteases that may be involved in remodeling of the extracellular matrix during healing. Mast cells are found in increased numbers in acute wounds and in certain chronic fibrotic diseases. Their influence on fibroblast growth and collagen production may be an important element in fibrosis. The effects of mast cell mediators on dermal fibroblasts are currently being explored by our laboratory and others. Myofibroblasts are implicated in the phenomenon of wound contraction. These phenotypically altered fibroblasts express some features of smooth muscle cells, notably actin filaments, and are abundant in granulation tissue. It has been proposed that they are responsible for wound contraction and possibly certain types of contracture. However, this hypothesis has been challenged by studies demonstrating the presence of myofibroblasts in wounds that do not contract, or the process of contraction in vitro in the absence of myofibroblasts. At this time the issue remains open to debate and further research.