Complex challenges of estimating the age and vitality of muscle wounds: a study with matrix metalloproteinases and their inhibitors on animal and human tissue samples

Abstract

The estimation of wound age and wound vitality is a recurring task in forensic routine work and has been subject of forensic research for a long time. By now, an unrestrictedly reliable marker or set of markers has not been found. In a study on myocardial infarctions, matrix metalloproteinases (MMP) 2 and 9 as well as tissue inhibitor of matrix metalloproteinases 1 (TIMP-1) were detected immunohistochemically in mechanically wounded myocardium (ECG electrodes, vessel ligations). Against this background, the potency of MMP-9, MMP-2, and TIMP-1 as markers for the estimation of wound age and wound vitality was tested in a broad approach with human tissue samples drawn during autopsies and with an animal model, the isolated perfused Langendorff heart. The study comprised samples of injured human skeletal muscle, injured human myocardium, rats' hearts with vital wounds, and rats' hearts with postmortem-inflicted wounds that were all stained immunohistochemically. The results showed great scattering, leading to the conclusion that MMP-2, MMP-9, and TIMP-1 are not suitable for wound age estimation. Merely the results for TIMP-1 suggested that this marker might be able to differentiate between vital and postmortem-inflicted wounds. With a view to the promising results of the preceding study, the results underline the necessity to test possible markers of wound age/wound vitality on a large and diverse sample set.

Keywords: Immunohistochemistry; Myocardium; Skeletal muscle; Wound age; Wound vitality.

Fig. 1

Study protocols for rats’ hearts with vital wounds (H1-H16) and with postmortem-inflicted wounds (CH1-CH8). Hearts with vital wounds were mounted onto the Langendorff system, injured by stabbing the left chamber after a stabilisation period of 20 min and fixed in formalin after different “survival times”. Hearts with postmortem-inflicted injuries were injured by stabbing the left chamber. Time intervals before and after stabbing varied

Fig. 2

Examples of very inhomogeneous staining results of human skeletal muscle injuries (100-fold magnification). a Wound age group D (8–12 h), MMP-9, staining intensity III. b Wound age group D (8–12 h), TIMP-1, staining intensity 0. c Wound age group B (few min–4 h), MMP-9, staining intensity III. d Wound age group B (few min–4 h), TIMP-1, staining intensity III

Fig. 3

Comparison between staining results (MMP-9, 100-fold magnification) of human myocardium injuries due to a infarction with staining intensity III and b sharp violence with staining intensity III. In both cases, a survival time according to group A has to be assumed

Fig. 4

Example of staining results of rats’ hearts with postmortem-inflicted injuries (100-fold magnification). a MMP-2. b MMP-9. c TIMP-1. The depicted heart (CH2) was injured 3 h after excision and fixed in formalin after another 3 h. MMP-2 and MMP-9 each present intense staining, whereas TIMP-1 shows no positive staining at all