Cellular and nutritional interactions in healing wounds.

Whatever the signals which trigger the repair process, it is clear that the rate of healing is dependent on the local delivery of oxygen and other nutrients. New tissue growth is centered around a blood vessel, which is sprouting new capillaries to supply the advancing cells. The endothelial buds grow towards areas of low oxygen tension, but they will not do so unless they have been preceded by macrophage invasion. Macrophages probably act as director cells to provide a chemotactic signal for endothelium to follow and to release stimulatory substances for fibroblast formation and activation. The synthesis of collagen by fibroblasts seems to be crucially dependent on the availability of molecular oxygen. The main function of polymorphonuclear leukocytes in the wound is to resist infection. An important mechanism by which white cells selectively kill bacteria uses oxygen. Thus, any treatment that augments the local oxygen supply or helps to avoid hypoperfusion of the wound will tend to increase the rate of healing and decrease the susceptibility to infection.