Expression of RIPK-1 and S-100B in traumatic brain injury- exploring a forensic cases series.

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Traumatic Brain Injury (TBI) represents one of the leading causes of disability and death globally, with a significant impact on public health. We present 12 cases (age 5-80 years old) of death due to TBI with different post-traumatic interval (PTI). The expression of S-100B and RIPK-1 in pericontusional zones of TBI were studied in forensic cases to understand the vitality and timing of injuries. The anti-RIPK-1 antibodies mainly stained the cytoplasm of the nerve cells. In 3 cases (48 to 56 years old with no other comorbidities; PTI: 2 days to 4 days) antibodies positive for RIPK-1 were found. In 5 cases (48 to 71 years old; PTI: 2 days to 12 days) astrocyte, oligodendrocyte and neurons positive for anti-S-100B were found. In 3 of these 5 cases both antibodies tested were positive. In 7 cases (5-80 years old; one with history of drug abuse, other with no comorbidities, PTI 0h; ) the glial cells were swollen and the submeningeal glial limitans became immunopositive for S100B. Stain accumulations were also observed adjacent to the walls of cerebral vessels, sometimes within the intravascular compartment. The results of the study show that in subjects who suffered a TBI, the expression of RIPK-1 and S-100B at the level of neurons in the pericontusional area was significantly increased compared to the control group. Neurons were not stained for RIPK-1 in cases of sudden cardiac deaths and sudden deaths due to TBI but observed neurons became immunopositive for RIPK-1 some days after TBI. S100-immunopositive neurons were not seen in immediate deaths but were found in cases with survival up to 12 days. Results regarding S100B are in line with existing knowledge. The study of necroptosis with anti-RIPK-1 antibodies could be useful in understanding the extent of secondary injuries and survival time in forensic contexts. However, this is a pilot study and should be extended to a larger number of cases to achieve more reliable results.