SEM of epithelial mediated wound in mice.

Wound edges are drawn together by a process known as wound contraction. Myofibroblasts are thought to mediate this contractile force. However, up to 25% of the surface area of a wound may close in the first few days, long before significant numbers of myofibroblasts appear in the wound bed. This suggests that another contractile force exists in the margins of the wound tissue. This force appears to be mediated by a band comprised of fusiform shaped epidermal cells. These cells are circumferentially distributed with respect to the wound margin. Microfilaments, similar in size to actin filaments and/or tonofilaments, can be observed in these cells. The filaments are aligned with the long axis of the epithelial cells that comprise the contractile band. Thus, wound contraction may in all likelihood be a biphasic phenomenon initially involving epidermal cells followed by the myofibroblasts.