Fine Regulation during Wound Healing by Mast Cells, a Physiological Role Not Yet Clarified.

Mast cells (MCs) are bone marrow-derived cells capable of secreting many active molecules, ranging from the mediators stored in specific granules, some of which have been known about for several decades (histamine, heparin), to small molecules produced immediately upon stimulation (membrane lipid derivatives, nitric oxide), to a host of constitutively secreted, multifunctional cytokines. With the aid of a wide array of mediators, the activated MCs control the key events of inflammation and therefore participate in the regulation of local immune response. On the basis of the structure, origin, principal subtypes, localization and function of these cells, their involvement in injury repair is therefore to be considered in acute and chronic conditions, respectively. The importance of MCs in regulating the healing processes is underscored by the proposed roles of a surplus or a deficit of their mediators in the formation of exuberant granulation tissue (such as keloids and hypertrophic scars), the delayed closure or dehiscence of wounds and the transition of acute to chronic inflammation.