Bao-Li Zhu

Stability of endogenous reference genes in postmortem human brains for normalization of quantitative real-time PCR data: comprehensive evaluation using geNorm, NormFinder, and BestKeeper

In forensic molecular pathology, quantitative real-time polymerase chain reaction (RT-qPCR) provides a rapid and sensitive method to investigate functional changes in the death process. Accurate and reliable relative RT-qPCR requires ideal amplification efficiencies of target and reference genes. However, the amplification efficiency, changing during PCR, may be overestimated by the traditional standard curve method. No single gene meets the criteria of an ideal endogenous reference. Therefore, it is necessary to select suitable reference genes for specific requirements. The present study evaluated 32 potential reference genes in the human brain of 15 forensic autopsy cases using three different statistical algorithms, geNorm, NormFinder, and BestKeeper. On RT-qPCR data analyses using a completely objective and noise-resistant algorithm (Real-time PCR Miner), 24 genes met standard efficiency criteria. Validation of their stability and suitability as reference genes using geNorm suggested IPO8 and POLR2A as the most stable ones, and NormFinder indicated that IPO8 and POP4 had the highest expression stabilities, while BestKeeper highlighted ABL1 and ELF1 as reference genes with the least overall variation. Combining these three algorithms suggested the genes IPO8, POLR2A, and PES1 as stable endogenous references in RT-qPCR analysis of human brain samples, with YWHAZ, PPIA, HPRT1, and TBP being the least stable ones. These findings are inconsistent with those of previous studies. Moreover, the relative stability of target and reference genes remains unknown. These observations suggest that suitable reference genes should be selected on the basis of specific requirements, experiment conditions, and the characteristics of target genes in practical applications.

Forensic molecular pathology of violent deaths

In forensic pathology, while classical morphology remains a core procedure to investigate deaths, a spectrum of ancillary procedures has been developed and incorporated to detail the pathology. Among them, postmortem biochemistry is important to investigate the systemic pathophysiological changes involved in the dying process that cannot be detected by morphology. In addition, recent advances in molecular biology have provided a procedure to investigate genetic bases of diseases that might present with sudden death, which is called molecular autopsy. Meanwhile, the practical application of RNA analyses to postmortem investigation has not been accepted due to rapid decay after death; however, recent experimental and practical studies using real-time reverse transcription-PCR have suggested that the relative quantification of mRNA transcripts can be applied in molecular pathology for postmortem investigation of deaths, which may be called advanced molecular autopsy. In a broad sense, forensic molecular pathology implies applied medical sciences to investigate the genetic basis of diseases, and the pathophysiology of diseases and traumas leading to death at a biological molecular level in the context of forensic pathology. The possible applications include analyses of local pathology, including tissue injury, ischemia/hypoxia and inflammation at the site of insult or specific tissue damage from intoxication, systemic responses to violence or environmental hazards, disorders due to intoxication, and systemic pathophysiology of fatal process involving major life-support organs. A review of previous studies suggests that systematic postmortem quantitative analysis of mRNA transcripts can be established from multi-faceted aspects of molecular biology and incorporated into death investigations in forensic pathology, to support and reinforce morphological evidence.

Significance of postmortem biochemistry in determining the cause of death

There have been an abundance of challenging publications on biochemical procedures for investigating death. However, such procedures do not appear to have been effectively incorporated in routine casework. Biochemical profiles at autopsy may show considerable case variations due to various factors involving preexisting disorders, the cause of death, complications, the survival period, and postmortem changes, distributions and localizations of analytes. Postmortem interference may also be caused by various factors, including the status at the time of death, possible supravital reactions, leakage from cell deterioration, diffusion/redistribution, and analytical procedures. Thus, analyses of topographic distribution are also important. When these factors are taken into consideration, biochemical procedures provide useful findings for investigating the cause and process of death, contributory conditions, and predisposing disorders. Meanwhile, recent studies showed that postmortem molecular biological analyses of mRNA of biological reactants in the tissues using RT-PCR are potentially useful for investigating the pathophysiology of death. As above, the use of postmortem biochemistry and molecular biology has advantages for investigating systemic pathophysiological functional changes involved in the dying process. For this purpose, the usefulness of comprehensive analyses of pathological and biochemical findings is suggested as part of laboratory investigations, comprising morphology, toxicology, microbiology, biochemistry and molecular biology, along with diagnostic imaging procedures. These procedures can be effectively incorporated into a full autopsy in the context of risk management. The application of these procedures may depend on the concept of medicolegal autopsy, and it is essential to establish postmortem databases through routine casework.

Combined analyses of creatine kinase MB, cardiac troponin I and myoglobin in pericardial and cerebrospinal fluids to investigate myocardial and skeletal muscle injury in medicolegal autopsy cases.

Creatine kinase-MB (CK-MB), cardiac troponin I (cTnI) and myoglobin (Mb) are biochemical markers of myocardial injury; however, Mb is more abundant in skeletal muscles. The present study involved analysis of these markers in pericardial and cerebrospinal fluids (PCF and CSF) from serial medicolegal autopsy cases (n=295, within 48h) to examine their efficacy in determining the cause of death. Although these markers showed a slight postmortem time-dependent elevation, except for CK-MB in CSF, the distribution depended on the cause of death. Mb levels in PCF and CSF were higher in fatal hyperthermia (heat stroke) and methamphetamine abuse, and CK-MB in both fluids was also higher in the latter. In psychotropic drug intoxication, CK-MB, cTnI and Mb were higher in PCF, but only cTnI was elevated in CSF. In electrocution and cerebrovascular disease, each marker was higher in PCF and also relatively high in CSF. PCF cTnI level was higher in acute pulmonary embolism without significant elevation of any other markers, whereas CSF CK-MB was higher in acute blunt brain injury death and methamphetamine abuse. In most cases of delayed brain injury death, hypothermia (cold exposure) and pneumonia, these markers were low or intermediate in both PCF and CSF; however, sudden cardiac death, asphyxiation and fire fatality cases showed few characteristic findings. These observations suggest that combined analyses of these markers in postmortem PCF and CSF, in addition to blood samples, are helpful for evaluating the severity of myocardial and/or skeletal muscle damage in death processes, in particular for investigating deaths due to hyperthermia, hypothermia, electrocution and intoxication.

Postmortem serum nitrogen compounds and C-reactive protein levels with special regard to investigation of fatal hyperthermia

The present study analyzed serum levels of urea nitrogen (UN), creatinine (Cr), and C-reactive protein (CRP), which are very stable during the early postmortem period, for investigation of the cause of death with special regard to hyperthermia (heat stroke) in serial medico-legal autopsy cases (nxa0=xa0429), excluding fatal injury, intoxication, and fire fatality. In this series, mechanical asphyxiation, drowning, and sudden cardiac death cases (nxa0=xa056, nxa0=xa043, and nxa0=xa0212, respectively) usually showed low levels within postmortem reference ranges for these serum markers, although UN and CRP levels were mildly elevated in cases of sudden cardiac death and cerebrovascular stroke. There were concomitant significant elevations in serum levels of UN (>50xa0mg/dL), Cr (>2xa0mg/dL), and CRP (>2xa0mg/dL) for chronic renal failure, gastrointestinal bleeding, pneumonia, and hypothermia (cold exposure). UN and CRP were especially high for chronic renal failure and pneumonia, respectively. However, hyperthermia cases showed an isolated elevation in the serum Cr level, suggesting an influence of systemic skeletal muscle damage. These serum markers may be practically useful for postmortem investigation of death due to hyperthermia (heat stroke), for which specific pathological and toxicological evidence may not be available.

Tissue-specific differences in mRNA quantification of glucose transporter 1 and vascular endothelial growth factor with special regard to death investigations of fatal injuries

Glucose transporter 1 (GLUT1) and vascular endothelial growth factor (VEGF) have been established as being responsible for cellular adaptation to oxygen deficiency in tissue ischemia and hypoxia mediated by hypoxia-inducible factor 1. We hypothesized that mRNA quantification of these factors in autopsy tissue specimens could have diagnostic significance for investigating the pathology of death, especially after injury. Various cases (total, n=119; less than 48h postmortem) were examined, including fatal blunt injury (n=71) and sharp instrument injury (n=18), as well as asphyxia (strangulation/hanging, n=12) and acute myocardial infarction/ischemia (n=18) as controls. Quantification of mRNA by TaqMan real-time RT-PCR and immunostaining were performed for GLUT1 and VEGF in lung, kidney, and skeletal muscle specimens. The postmortem interval showed no significant influence on the relative quantification of mRNA during the early postmortem period. Characteristic results were found in blunt injury cases: both GLUT1 and VEGF mRNAs decreased in the lung but increased in the skeletal muscle depending on survival time. In the kidney, subacute deaths showed higher GLUT1 mRNA levels compared with acute deaths from blunt injury, but no significant change was found for VEGF mRNA. Immunohistochemistry showed visually predominant GLUT1 immunoreactivity in the renal cortex for cases with a longer survival time, coincident with the results at the mRNA level. Tissue-specific differences in mRNA quantification of GLUT1 and VEGF shed light on tissue ischemia/hypoxia and subsequent tissue-dependent pathophysiological changes leading to death after injury.

Comparative evaluation of postmortem serum concentrations of neopterin and C-reactive protein

The cellular immune response is accompanied by the release of neopterin. The level of neopterin in serum is increased in patients suffering from viral infections, autoimmune diseases, systemic inflammation, allograft rejection and malignant diseases, while that of C-reactive protein (CRP) is known to rise during inflammatory diseases and traumas. To investigate postmortem neopterin and CRP concentrations with regard to the cause of death, we examined cardiac and peripheral blood samples in 474 autopsy cases without advanced decomposition (0-96 years of age, 343 males and 131 females), 2.8 h to 3 days (median, 18.0 h) after death. Survival time was 0.1 h to 5 months (median, 3.0 h) for traumatic death, and 0.1-1, 440 h (median, 2.5 h) for natural death. In autopsied subjects, neopterin concentrations were higher than the clinical reference, independent of the time after death, and depended on the survival time. In cases of acute and subacute death due to trauma, the neopterin level in right heart blood was mildly to moderately elevated (about 50-200 nmol/l) except for sharp instrument injury, whereas the CRP concentration usually remained low (<1 mg/dl). However, a moderate rise in the CRP level (around 1-10 mg/dl) was observed in fatal cases of hypothermia (cold exposure). Markedly elevated serum CRP and neopterin levels (>10 mg/dl and >500 nmol/l, respectively) were detected in cases of delayed death due to trauma involving systemic inflammatory response syndrome (SIRS) and of fatal bacterial infections. For sepsis, the serum CRP level was markedly elevated but the neopterin level was low in some cases. Fatal viral infections usually resulted in a marked elevation in the serum neopterin level (>500 nmol/l) with a mild to moderate rise in the CRP level. Combined analyses of neopterin and CRP may be useful to investigate viral infections and delayed traumatic death involving SIRS to support pathological findings.

Postmortem catecholamine levels in pericardial and cerebrospinal fluids with regard to the cause of death in medicolegal autopsy

Previous studies have suggested that postmortem serum catecholamine levels reflect the magnitude of physical stress responses or toxic/hyperthermic neuronal dysfunction during the death process. The present study investigated postmortem adrenaline (Adr), noradrenaline (Nad), and dopamine (DA) levels in pericardial fluid (PCF) and cerebrospinal fluid (CSF) with regard to the cause of death, compared with right heart blood levels, in serial medicolegal autopsy cases with a postmortem time within 48 h (n=494). Correlations between PCF and CSF Adr levels, and those among right heart blood, PCF, and CSF DA levels were marked (r=0.66-0.83, p<0.0001), but were otherwise lower (r=0.22-0.44). With regard to the cause of death, Adr and Nad levels in PCF, CSF, and right heart blood mostly presented similar findings: these levels were generally high in injury, intoxication, and hyperthermia (heatstroke), but were low in hypothermia (cold exposure). DA levels at each site were higher in injury and intoxication. In addition, higher levels were detected for Nad levels in sharp instrument injury, as well as Adr, Nad, and DA in carbon monoxide intoxication at each site, and for CSF Nad in psychotropic drug intoxication. These findings suggest that characteristic elevations in Adr, Nad, and DA levels in PCF and CSF are involved in systemic responses to fatal stress and toxic neuronal dysfunction, reflecting the magnitude of such responses in individual cases.

Evaluation of postmortem S100B levels in the cerebrospinal fluid with regard to the cause of death in medicolegal autopsy

Previous studies have suggested the usefulness of the postmortem serum S100B level as a marker of the severity of brain damage. In this study, we investigated the S100B level in the cerebrospinal fluid (CSF) in serial autopsy cases (n=216, within 3 days postmortem), including those of blunt injury (n=34: fatal head injury, n=20; others, n=14), sharp instrument injury (n=9), mechanical asphyxiation (n=19), drowning (n=11), fire fatality (n=26), intoxication (n=20), hypothermia (cold exposure, n=16), hyperthermia (heat stroke, n=9), acute cardiac death (n=52) and pneumonia (n=20). The CSF S100B level showed a moderate postmortem time-dependent increase for acute cardiac death (r=0.58, p<0.0001) and asphyxia (r=0.741, p<0.001). In cases of survival time within 48 h, drowning and hypothermia usually showed a lower CSF S100B level (around 500 ng/ml), and the level was higher for delayed head injury death, asphyxia, intoxication, and hyperthermia (around 1500 ng/ml) (p<0.05). In fatal head injury cases, however, CSF S100B did not correlate with the survival time or postmortem interval. A CSF S100B level of >2000 ng/ml in the early postmortem period might be considered a biochemical sign of fatally severe brain damage.

Evaluation of human brain damage in fatalities due to extreme environmental temperature by quantification of basic fibroblast growth factor (bFGF), glial fibrillary acidic protein (GFAP), S100β and single-stranded DNA (ssDNA) immunoreactivities

Fatalities due to extreme environmental temperatures involving hypothermia (cold exposure) and hyperthermia (heat stroke) might present with poor or nonspecific morphological pathologies, which are insufficient to establish the cause of death in forensic practice. The present study immunohistochemically investigated basic fibroblast growth factor (bFGF), glial fibrillary acidic protein (GFAP), S100β and single-stranded DNA (ssDNA) in the parietal lobe and hippocampus of the brain in fatalities from hypothermia (n=15) and hyperthermia (n=18), and compared them to those of controls (n=39), including acute death due to ischemic heart disease, mechanical asphyxiation and drowning. In addition, S100β concentration in cerebrospinal fluid (CSF) was measured. Characteristic findings in hypothermia cases were higher glial bFGF immunopositivity in the cerebral cortex and white matter, and higher S100β immunopositivity in the cerebral cortex with a lower CSF S100β concentration. Hyperthermia showed lower glial GFAP and S100β immunopositivities in the white matter, and higher neuronal ssDNA immunopositivity in the cerebral cortex and hippocampus, accompanied by high glial bFGF and S100β immunopositivities in the cerebral cortex. These findings suggest neuroprotective glial responses without marked neuronal or glial damage in fatal hypothermia, and diffuse neuronal apoptosis despite initiation of neuroprotective cortical astrocyte responses, accompanied by glial damage in the white matter, in fatal hyperthermia. These markers may be useful for evaluating brain damage and responses in fatalities due to extreme environmental temperatures.