Mast cell reactivity at the margin of human skin wounds: an early cell marker of wound survival?

Detecting the vitality of mechanical skin wounds (antemortem versus postmortem injury) in human cadavers remains a specifically forensic problem. To determine whether skin mast cells (MCs) are activated during the very early phase of human wound healing we performed a histomorphometric evaluation of the extent of MC enzyme loss as an indication of MC degranulation at the wound margins of skin wounds in 64 human cadavers. We compared the number of tryptase-reactive MCs, which are said not to loose all of their enzyme activity during degranulation process, with the number of naphthol AS-D chloroacetate esterase (NAS-DClAE)-positive MCs, which loose their complete enzyme activity in the form of enzyme-positive granula after activation. The enzyme activity was evaluated on sequential histological sections after autopsy as an indirect quantification of the number of degranulated MCs. Most of the victims had died within 10-60 min after injury (n=50), 12 survived between 60 min and 24h, and only 2 victims survived more than 24h (12 days each). The number of enzyme-positive MCs were counted in six successive visual fields (0.785 mm(2)) on the one hand located parallel to and--on the other hand--at increasing distances outward from the wound margins. In victims surviving the injury less than 60 min the average number of NAS-DClAE-reactive MCs next to the wound margin was significantly lower than the number of tryptase-reactive MCs. The extent of the reduction in NAS-DClAE-reactive MC counts correlated inversely with the distance from the wound edges. Our findings show that MCs undergo very early loss of NAS-DClAE activity at wound margins, and thus appear to be an early cell marker of wound survival. However, definitive evidence that the enzyme loss (degranulation) represents a vital process can only be obtained by comparing MC enzyme loss induced by injury during intact circulation with the MC reaction to injury inflicted very shortly after cardiac arrest, a question that can only be answered by animal experiments.