The role of mast cells in wound healing.

Mast cells are known to participate in three phases of wound healing: the inflammatory reaction, angiogenesis and extracellular-matrix reabsorption. The inflammatory reaction is mediated by released histamine and arachidonic acid metabolites. Compound 48/80 and disodium-cromoglycate are both able to increase skin breaking strength shortly after wounding. Under light and electron microscopy we found that small, granule-poor, irregular mast cells (MLMC) accumulate in the wound. This suggests that the small MLMC (mucosal-like mast cells) migrate into the skin during wound healing, and that both CTMC (connective-tissue mast cells) and MLMC are involved in tissue repair. Moreover, there is some evidence that mast cells participate in angiogenesis, since heparin is able to stimulate endothelial-cell migration and proliferation in vitro, and protamine to inhibit these processes and also angiogenesis in vivo. When the effect of protamine on wound breaking strength was examined, we encountered a decrease which was not prevented by heparin administration. Further studies are needed to demonstrate that protamine is specifically involved in inhibiting heparin-mediated angiogenesis in wounded tissue. Finally, mast cells may play a role in the extracellular matrix remodelling, on the basis of in-vitro experiments (but there are still no in-vivo data).