Evaluation of a Set of miRNAs in 26 Cases of Fatal Traumatic Brain Injuries.

In forensic medicine, identifying novel biomarkers for use as diagnostic tools to ascertain causes of death is challenging because of sample degradation. To that aim, a cohort (n = 26) of fatal traumatic brain injuries (TBIs) were tested for three candidate miRNAs (namely, miR-124-3p, miR-138-5p, and miR144-3p). For each case, three FFPE specimens (coup area (CA), contrecoup area (CCA), and the corpus callosum (CC)) were investigated, whereas the FFPE brain tissues of 45 subjects (deceased due to acute cardiovascular events) were used as controls. Relative quantification via the ∆∆Ct method returned significantly higher expression levels of the three candidate miRNAs (p < 0.01) in the TBI cases. No difference was detected in the expression levels of any miRNA investigated in the study among the CA, CCA, and CC. Furthermore, the analyzed miRNAs were unrelated to the TBI samples' post-mortem intervals (PMIs). On the contrary, has-miR-124-3p ahashsa-miR-144-3p were significantly correlated (p < 0.01) with the agonal time in TBI deaths. Since the RNA was highly degraded in autoptic FFPE tissues, it was impossible to analyze the mRNA targets of the miRNAs investigated in the present study, highlighting the necessity of standardizing pre-analytical processes even for autopsy tissues.

Impact of standardization in tissue processing: the performance of different fixatives.

Most tissues in clinical practice are formalin-fixed and paraffin-embedded for histological as well as molecular analyses. The reproducibility and uniformity of molecular analyses is strictly dependent on the quality of the biomolecules, which is highly influenced by pre-analytical processes. In this study, the effect of different fixatives was compared, including formalin, Bouin's solution, RCL2® and TAG-1™ fixatives, by stringent application of ISO standards in mouse liver tissue processing, including formalin-free transport of tissues and tissue grossing in a refrigerated environment. The effect of fixatives was studied in terms of nucleic acid quality at the time of tissue processing and after one year of tissue storage at room temperature in the dark. Furthermore, a microcomputed tomography (CT) scan analysis was applied to investigate the paraffin embedding. The results show that the application of ISO standards in tissue processing allows analysis of 400 bases amplicons from RNA and 1000 bases from DNA, even in extracts from formalin-fixed and paraffin-embedded tissues. However, after one year storage at room temperature in the dark, a degradation of the nucleic acids was observed. Nevertheless, extracts can still be analyzed, but for metachronous tests it is highly recommended to repeat the quantitation of housekeeping genes in order to standardize the extent of nucleic acid degradation.