Expression of matrix metalloproteinase-9 (MMP-9) in human skin within 1 hour after injury through immunohistochemical staining: a pilot study

Matrix metalloproteinase-9 (MMP-9) is involved in tissue remodeling and in skin wound healing. The present study focuses on the MMP-9 expression in epidermal wound healing within 1 h after injury, to test whether MMP-9 can be used to estimate the time of injury in forensic practice.A sample consisting of 5 individuals undergoing surgery was analyzed. With the consent of the patients, sections of skin were removed from the surgical wound at predefined time intervals. For each subject, 8 sections were taken, one for each time interval defined at 0 '- 1' - 3 '- 5' - 10 '- 15' - 30 '- 60' minutes. The specimens were immunostained with MMP-9, and the number of positively stained cells was examined.The number of positively stained cells showed an increasing trend as a function of time. Less than 30 positively stained cells were found in all cases within 3 min. At the post-infliction time of 5 min, the number of positively stained cells exceeded 30 in 3 out of 5 cases. The number of MMP-positive cells exceeded 40 in all cases in over 10 min.In the light of these results, the count of MMP-9 positive cells might be a useful marker in the wound-age estimation within 1 h in forensic setting. More research is required to collect more samples and to compare samples from the hyperacute phase with those from several days after injury.

Senescence of human skeletal muscle impairs the local inflammatory cytokine response to acute eccentric exercise

The impact of aging on the cytokine response of human skeletal muscle to exercise-induced injury remains poorly understood. We enrolled physically active, young (23-35 years old, n=15) and old (66-78 years old, n=15) men to perform 45 min of downhill running (16% descent) at 75% VO2max. Biopsies of vastus lateralis were obtained 24 h before and 72 h after acute eccentric exercise. Transcripts for inflammatory (TNF-alpha, IL-1beta) and anti-inflammatory cytokines (IL-6, TGF-beta1) were quantified by real-time PCR. Before exercise, cytokine transcripts did not differ with age. At old age, exercise induced a blunted accumulation of transcripts encoding the pan-leukocyte surface marker CD18 (young: 10.1-fold increase, P<0.005; old: 4.7-fold increase, P=0.02; young vs. old: P<0.05). In both age groups, CD18 transcript accumulation strongly correlated with TNF-alpha (young, r=0.87, P<0.001; old, r=0.72, P=0.002) and TGF-beta1 transcript accumulation (young, r=0.80, P<0.001; old, r=0.64, P=0.008). At old age, there was no correlation between IL-1beta and CD18 transcript accumulation. Furthermore, exercise induced IL-6 transcript accumulation in young (3.6-fold, P=0.057) but not in old men. Our results suggest that aging impairs the adaptive response of human skeletal muscle to eccentric exercise by differential modulation of a discrete set of inflammatory and anti-inflammatory cytokine genes.