Skin mast cell promotion of matrix remodeling in burn wound healing in mice : relevance of chymase

Inflammation, granulation, and collagen accumulation, which are observed in the wound healing process, occasionally lead to hypertrophic scarring. Several in vitro reports have suggested that skin mast cells (MCs) and their major protease, chymase, participate in the healing process as well as in fibrotic skin diseases. The present study examined the potential involvement of MCs and MC chymase in the healing of burns in mouse dorsal skin. The size of the burn wounds, density of the capillaries, collagen accumulation, MC number, and chymase activity were measured before and 1, 3, 7, and 14 days after burning. The healing process corresponded strongly with MC density and chymase activity in both acute and subacute phases. The maximum decrease in MC number and chymase activity occurred on day 3 when tissue loss due to necrosis was maximal. From day 7 to 14, the burn wounds retracted rapidly accompanied by increases in capillaries and collagen fibers, in correspondence with fast increments in MC numbers and chymase activity at the wound edges. The present results combined with previous in vitro results strongly support the contention that skin MC chymase plays a role in the normal wound healing process, and presumably in dermal fibrotic disorders.