Knowledge on trauma survival time prior to death following a lethal traumatic brain injury (TBI) may be essential for legal purposes. Immunohistochemistry studies might allow to narrow down this survival interval. The biomarkers interleukin-6 (IL-6) and glial fibrillary acidic protein (GFAP) are well known in the clinical setting for their usability in TBI prediction. Here, both proteins were chosen in forensics to determine whether neuronal or glial expression in various brain regions may be associated with the cause of death and the survival time prior to death following TBI. IL-6 positive neurons, glial cells and GFAP positive astrocytes all concordantly increase with longer trauma survival time, with statistically significant changes being evident from three days post-TBI (p < 0.05) in the pericontusional zone, irrespective of its definite cortical localization. IL-6 staining in neurons increases significantly in the cerebellum after trauma, whereas increasing GFAP positivity is also detected in the cortex contralateral to the focal lesion. These systematic chronological changes in biomarkers of pericontusional neurons and glial cells allow for an estimation of trauma survival time. Higher numbers of IL-6 and GFAP-stained cells above threshold values in the pericontusional zone substantiate the existence of fatal traumatic changes in the brain with reasonable certainty. Published: xx xx xxxx open Scientific RepoRtS | (2019) 9:11771 | https://doi.org/10.1038/s41598-019-48145-wwww.nature.com/scientificreports www.nature.com/scientificreports/ and compared them to cardiovascular causes of death immunohistochemically and via immunofluorescence for interleukin-6 (IL-6) and glial fibrillary acidic protein (GFAP).IL-6 as a well-known cytokine is a small glycoprotein with a molecular weight less than 30 kDa 27 . It is predominantly expressed by neurons and glial cells in the CNS and mediates complex reactions such as the pro-inflammatory response 28 , but also has neuroprotective potential with trophic, anti-apoptotic and anti-inflammatory characteristics 29,30 . These contrary effects seem to depend on the local IL-6 concentration 31-33 , which increases under certain circumstances such as TBI, subarachnoid hemorrhage or CNS infection 27 . Given its initiator function of acute phase response, it is considered as an early TBI marker 34 . GFAP is one of the most-widely studied proteins in neuropathology. This protein is a type III intermediate filament involved in maintaining the blood brain barrier. GFAP also provides stability in the astrocytes throughout the CNS and is essential for reactive processes such as astrogliosis and glial scar formation 35 .Both IL-6 and GFAP are well-established biomarkers used in living patients with TBI to confirm and predict the existence and severity of the brain injuries and to determine the potential neurological outcome in trauma patients [36][37][38][39][40] . Furthermore, both markers are established for post-mortem biochemistry, with promising results for cerebrospinal fluid in...
Glial fibrillary acidic protein (GFAP) is a well-established astrocytic biomarker for the diagnosis, monitoring and outcome prediction of traumatic brain injury (TBI). Few studies stated an accumulation of neuronal GFAP that was observed in various brain pathologies, including traumatic brain injuries. As the neuronal immunopositivity for GFAP in Alzheimer patients was shown to cross-react with non-GFAP epitopes, the neuronal immunopositivity for GFAP in TBI patients should be challenged. In this study, cerebral and cerebellar tissues of 52 TBI fatalities and 17 controls were screened for immunopositivity for GFAP in neurons by means of immunohistochemistry and immunofluorescence. The results revealed that neuronal immunopositivity for GFAP is most likely a staining artefact as negative controls also revealed neuronal GFAP staining. However, the phenomenon was twice as frequent for TBI fatalities compared to non-TBI control cases (12 vs. 6%). Neuronal GFAP staining was observed in the pericontusional zone and the ipsilateral hippocampus, but was absent in the contralateral cortex of TBI cases. Immunopositivity for GFAP was significantly correlated with the survival time (r = 0.306, P = 0.015), but no correlations were found with age at death, sex nor the post-mortem interval in TBI fatalities. This study provides evidence that the TBI-associated neuronal immunopositivity for GFAP is indeed a staining artefact. However, an absence post-traumatic neuronal GFAP cannot readily be assumed. Regardless of the particular mechanism, this study revealed that the artefact/potential neuronal immunopositivity for GFAP is a global, rather than a regional brain phenomenon and might be useful for minimum TBI survival time determinations, if certain exclusion criteria are strictly respected.
Immunohistochemistry (IHC) has become an integral part in forensic histopathology over the last decades. However, the underlying methods for IHC vary greatly depending on the institution, creating a lack of comparability. The aim of this study was to assess the optimal approach for different technical aspects of IHC, in order to improve and standardize this procedure. Therefore, qualitative results from manual and automatic IHC staining of brain samples were compared, as well as potential differences in suitability of common IHC glass slides. Further, possibilities of image digitalization and connected issues were investigated. In our study, automatic staining showed more consistent staining results, compared to manual staining procedures. Digitalization and digital post-processing facilitated direct analysis and analysis for reproducibility considerably. No differences were found for different commercially available microscopic glass slides regarding suitability of IHC brain researches, but a certain rate of tissue loss should be expected during the staining process.
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