mRNA expression patterns in human myocardial tissue, pericardial fluid and blood, and its contribution to the diagnosis of cause of death

Gene expression has become an interesting research area in forensic pathology to investigate the process of death at the molecular level. The aims of this study were to analyze changes in gene expression patterns in relation to the cause of death, and to propose new molecular markers of myocardial ischemia of potential use for the postmortem diagnosis of early ischemic heart damage in cases of sudden cardiac death (SCD). We determined mRNA levels of five proteins related with ischemic myocardial damage and repair - TNNI3, MYL3, TGFB1, MMP9 and VEGFA - in specific sites of the myocardium, blood and pericardial fluid in samples from 30 cadavers with different causes of death (SCD, multiple trauma, mechanical asphyxia, and other natural deaths). TNNI3 expression in blood, and MMP9 expression in pericardial fluid, were significantly higher when the cause of death was mechanical asphyxia, probably because of the more sensitive response of these proteins to acute systemic hypoxia/ischemia. Specifically, among SCD cases, increased MYL3, VEGFA and MMP9 values in the anterior wall of the right ventricle were found when the confirmed cause of death was acute myocardial infarction (AMI). Higher TGFB1 expression was found in the interventricular septum when AMI was not the cause of death, most likely as a reflection of the short duration of ischemia. Molecular biology techniques can provide complementary tools for the forensic diagnosis of early ischemic myocardial damage and AMI, and may make it possible to determine the duration and severity of myocardial ischemia.

Studies on RNA integrity and gene expression in human myocardial tissue, pericardial fluid and blood, and its postmortem stability

Analyses of gene expression of ischemic myocardial injury and repair related proteins has been carried out for the first time in samples from five specific sites of the myocardium, pericardial fluid and blood from thirty cadavers in relation to post-mortem interval (PMI). RNA integrity was evaluated by RNA integrity number (RIN), with values ranging from 6.57 to 8.11; sufficiently high levels of integrity to permit further gene amplification. No significant correlations between RIN and PMI in any samples were detected. Prior to target gene expression analysis, a normalization strategy was carried out to assess candidate reference gene stability, involving the analysis and comparison of four common housekeeping genes (Glyceraldehide-3-phosphate dehydrogenase, beta-actin, TATA box binding protein and Cyclophilin A). Gene expression of cardiac troponin I (TNNI3), myosin light chain 3 (MYL3), matrix metalloprotease 9 (MMP9), transforming growth factor beta 1 (TGFB1), and vascular endothelial growth factor A (VEGFA) in myocardial zones and body fluids were subsequently studied by real-time quantitative PCR. Expression levels of all the proteins studied in cardiac zone samples were similar. No statistical differences for expression were detected among proteins taken from any myocardial area. No significant differences were detected for TNNI3 and TGFB1 gene expressions when compared with samples at or under 12h-PMI or over 12h-PMI. However, differences in MYL3, MMP9, and VEGFA gene expression in body fluids were found at PMI periods of over 12h. These interesting results may contribute to the refinement of current knowledge regarding cardiac metabolism and improve understanding of the underlying mechanisms involved in myocardium ischemia and its repair.

Antioxidant-related enzymes in myocardial zones and human pericardial fluid in relation to the cause of death

The aim of this work was to shed light on hypoxic and ischemic processes in the heart that may lead to irreversible or lethal myocardial injury. We determined malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities in human cardiac tissues from 45 medico-legal autopsies of persons who died from different causes. Samples were taken from three different areas of myocardium: the anterior and posterior walls of the left ventricle, and the interventricular septum. We used light microscopy to examine the heart sections (hematoxylin-eosin and Masson's trichromic stains), and studied the K+(Na+ ratio and pericardial fluid. A decrease in GSH-Px activity was found in cases with severe atherosclerosis of the coronary artery in comparison with the group with slight or moderate atherosclerosis. Postmortem activities of GSH-Px and SOD were significantly different in the three myocardial zones studied. An increase in GSH-Px activity in the interventricular septum was noted in cases of cardiac deaths. Antioxidant-related enzymes such as GSH-Px and SOD can therefore be regarded as new biochemical markers indicative of myocardial hypoxia. The possible applications to the postmortem diagnosis of the cause of death are discussed.

Lipoproteins and apolipoproteins in pericardial fluid: new postmortem markers for coronary atherosclerosis

Determinations of lipoproteins (HDL-cholesterol and LDL-cholesterol) and various apolipoproteins (Apo A-I, Lp(a) and Apo B-100) were performed in postmortem pericardial fluid. Studies were carried out on 77 cadavers: 41 adult subjects with a morphological and biochemical diagnosis of intermediate or fresh myocardial infarction and 36 adults with no previous history of myocardial infarction. HDL and LDL were determined by enzymatic methods. Both apolipoproteins (A-I and B-100) were quantified by radio-immunoassay methods and Lp(a) was measured by enzyme immunoassay. Cases with severe atherosclerosis of coronary arteries showed higher levels of Apo B in pericardial fluid compared to cases without atherosclerosis. A significant increase of Apo B was found in cases with a positive diagnosis of myocardial infarction. Due to the high level of Apo B in pericardial fluid, a decrease in the LDL/Apo B ratio, along with a pronounced increase in the Apo B/Apo A ratio, was detected. The determination of Apo B in pericardial fluid can be a useful parameter to be included in biochemical analysis for the postmortem diagnosis of myocardial infarction related to coronary atherosclerosis.

Usefulness of different myocardial sampling zones for the postmortem diagnosis of myocardial infarction

The diagnosis of myocardial infarction requires the use of a group of tests that are very efficient, quick and inexpensive. Another important consideration is the choice of myocardial sampling zones, especially in cases of differential diagnosis between a cardiac injury secondary to a trauma or violent asphyxia and others, secondary to myocardial infarction. The aim of this work was to choose, through discriminant analysis, the most useful zones of cardiac tissue for the quantification of free fatty acids and free carnitine and for the performance of the K/Na quotient, as biochemical parameters for the postmortem diagnosis of myocardial infarction. According to the discriminant analysis performed, seven zones of cardiac tissue are necessary to achieve a differential diagnosis among "myocardial infarction," "other natural deaths," and "violent deaths" with a 71.9% efficacy. Greater diagnostic efficacy was found (78.1%) for differentiating between "natural deaths" and "violent deaths."