Platelet-activating factor: improvement in wound healing by a chemotactic factor.

Platelet-activating factor (PAF) is chemotactic for inflammatory cells and activates macrophages but, unlike growth factors, which have been demonstrated to accelerate healing, it has no effects on cell proliferation. The possible role of PAF in wound healing has not been explored previously. We examined the effect of different topical concentrations of PAF on the paired rat surgical incision model. Samples harvested on different days after wounding were evaluated for tensiometry and histology. Samples treated with 1 microgram, but not with 0.1 or 10 micrograms, showed an increase in maximal breaking strength (33.2%, 25.6%, and 4.9% by days 5, 7, and 12, respectively), reaching significance on days 5 and 7. Samples treated with 1 microgram PAF demonstrated a greater cellular infiltration (fibroblasts and monocytes) on day 7. Further histochemical studies revealed an increase of macrophages by day 7. Treatment with PAF receptor antagonist blocked the response to PAF but had no effect on normal wound healing, suggesting that, although PAF can accelerate healing, its endogenous production does not play a key role in normal wound repair. Our results demonstrate promotion of wound healing by PAF, a phospholipid chemotactic factor not previously shown to have wound-healing properties. This study gives new insights into how cytokines act to promote healing and suggests a strategy for improving wound repair with a monocyte chemotactic factor.