The role of apoptosis in wound healing.

Wound healing involves a series of rapid increases in specific cell populations that prepare the wound for repair, deposit new matrices and finally, mature the wound. Upon completing their tasks, these specific cell types must be eliminated from the wound prior to the progression to the next phase of healing. The most logical method of cellular down-regulation is through apoptosis. Apoptosis allows for the eliminations of entire populations without tissue damage or an inflammatory response. This review discusses which cells dominate the various phases of tissue repair and how the cellular pattern may vary after differing types of injury. The potential mechanisms involved in the down-regulation of inflammation and fibrosis are also covered. The studies that support the hypothesis that apoptosis is involved in the regulation of wound healing are discussed. The evidence supporting potential cell signals involved in the induction of apoptosis in tissue repair are examined. Finally, the review ends with a presentation of how dysregulation of apoptosis can lead to pathologic forms of healing such as excessive scarring and fibrosis. By understanding the mechanisms controlling apoptosis and tissue repair, one may eventually develop therapeutic modalities to minimize scarring, a final pathway for many disease processes.