Post-mortem analysis of apoptotic changes associated with human skin bruises

The estimation of the age of skin bruises is of importance in forensic medi cine, especially in child abuse cases. Time-dependent changes in bruise col our and/or associated histological features have been used with a limited d egree of,success. An increased rate of apoptosis in the injured tissue has been considered as a novel time-dependent marker of cell death, by injury i nflicted in a rat model. The object of the present study was to apply the T UNEL method of DNA end labelling to identify and enumerate apoptotic cells in bruised and normal skin in order to study the relationship of apoptotic cell density with the age of the bruise. A commercially available DNA end l abelling kit, TUNEL method, was standardised, validated and used for this p urpose. Twenty unselected post-mortem cases with bruises due to a variety o f causes were studied. The apoptotic cells stained with TUNEL reaction were counted in 10 high power fields in the epidermis, as well as in the dermis of formaldehyde-fixed paraffin-embedded skin specimens. The mean positive cell densities (+/-1 S.E.) were compared with respect to the age of the bru ise. In the epidermis, the mean apoptotic cell count was statistically sign ificantly greater in the bruised skin compared to normal skin in 2- to 6-da y-old bruises; whilst in the dermis the same was true in 3- to 8-day-old br uises. The overall findings suggest that there is a quiescent period prior to the increase in the apoptotic cell activity that is seen following skin bruising. This is so provided the post-mortem skin samples were collected w ithin a lapse of 6 days or less between the time of death and formalin fixa tion and paraffin embedding to avoid the bias made by the difference of len gth of post-mortem interval. (C) 2000 Elsevier Science Ireland Ltd. All rig hts reserved.