Serial analyses of postmortem changes in human skeletal muscle: A case study of alterations in proteome profile, histology, electrolyte contents, water composition, and enzyme activity

Human skeletal muscle mitochondrial pathways are impacted by a neuropathologic diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is associated with reduced lean mass and impaired skeletal muscle mitochondrial and motor function. Although primary mitochondrial defects in AD may underlie these findings, molecular alterations in AD have not been thoroughly examined in human skeletal muscle. Here, we used two human skeletal muscle types, quadriceps (n = 81) and temporalis (n = 66), to compare the proteome of individuals with a neuropathologic AD diagnosis based on AD Neuropathologic Change (ADNPC+: n = 54 temporalis, 44 quadriceps) to controls (ADNPC-: n = 27 temporalis, 22 quadriceps). We determined the effects of ADNPC status within each muscle and within apolipoprotein E4 (APOE4) carriers and APOE4 non-carriers. Pathways that support mitochondrial metabolism, including oxidative phosphorylation, were downregulated in skeletal muscle of ADNPC+ versus ADNPC- individuals. Similar mitochondrial effects were observed across muscle types and APOE4 carrier groups, but nearly four times as many proteins were altered in temporalis versus quadriceps tissue and mitochondrial effects were most pronounced in APOE4 carriers compared to APOE4 non-carriers. Of all detected oxidative phosphorylation proteins, the expression of ~29-61 % (dependent on muscle/APOE4 carrier group) significantly correlated with AD progression, ranked by Clinical Dementia Rating and ADNPC scores. Of these, 23 proteins decreased in expression with greater AD progression in all skeletal muscle type and APOE4 carrier groups. This is the first study to assess differences in the human skeletal muscle proteome in the context of AD. Our work shows that systemic mitochondrial alterations in AD extend to skeletal muscle and these effects are amplified by APOE4 and correlate with AD progression.

Protein degradation patterns as biomarkers for post-mortem interval estimation: A comprehensive review of proteomic approaches in forensic science

The determination of post-mortem interval (PMI) is a critical process for forensic medical-legal investigations. Proteomic techniques are gaining prominence in analysing forensic biological samples. After death, studying the proteins present in human bodies could be critical in discovering important new biomarkers that can serve as reliable indicators of various factors. A literature review is conducted on estimating PMI through protein degradation analysis using PubMed, NCBI, SCOPUS, Research Gate, Science Direct, and Google Scholar. A total of 32 studies were identified and studied. It is found that the most commonly studied tissue type is the skeleton muscle (15 studies), followed by others. The kinetics of several proteins and proteases were particularly correlated with PMI. Different proteins degrade differently after death: alpha-actinin, GAPDH, and alpha-tubulin breakdown slowly, but meta-vinculin breaks down early. Tropomyosin does not change for a long time after death, up to 10 days. Certain markers had a positive correlation with PMI, meaning that their amount increased as PMI hours increased, while other markers showed a negative correlation, suggesting that their number decreased with time. The level of several biological markers, such as SERBP1, COX7B, and SOD2, changed gradually and consistently as the PMI increased. The information gathered from this analysis provides new opportunities for precise PMI measurements in legal contexts by expanding the research area's use in human skeletal tissue.

Proteomic Characterization of Changes in Mouse Brain Cortex Protein Expression at Different Post-Mortem Intervals: A Preliminary Study for Forensic Biomarker Identification

Accuracy in the evaluation of death-induced tissue degradation for thanato-chronological purposes is strictly dependent on the condition of the biological source as well as on the precision of post-mortem interval (PMI) estimation. Thus, the optimization of tissue handling and identification of sensitive post-mortem biomarkers could help establish a timeline for post-mortem events. To this aim, we investigated the proteome changes in cortex samples of 6-week-old female SAMR1 mice over a post-mortem time course. After death, brain tissue was removed immediately (T0), and after 4, 8, 12, 24, and 32 h, four mice were used for each time period, and animals were maintained at 4 °C until brain removal. Dissected tissues were frozen at -80 °C until processed. Proteomic analysis, performed on samples related to early and late PMIs (<24 h and >24 h post-mortem, respectively) showed protein level changes as compared to T0 samples, with a remarkable increase in Calpain11 in the early PMI, as well as in Caspases 7 and 8 together with Gasdermin 3 in late PMI. These findings were confirmed by LIFT mass spectrometry technology and western blot analysis and, although requiring further investigation in other biological samples, suggest that these proteins could be considered as putative biomarkers of different PMIs.

The Role of Protein Degradation in Estimation Postmortem Interval and Confirmation of Cause of Death in Forensic Pathology: A Literature Review

It is well known that proteins are important bio-macromolecules in human organisms, and numerous proteins are widely used in the clinical practice, whereas their application in forensic science is currently limited. This limitation is mainly attributed to the postmortem degradation of targeted proteins, which can significantly impact final conclusions. In the last decade, numerous methods have been established to detect the protein from a forensic perspective, and some of the postmortem proteins have been applied in forensic practice. To better understand the emerging issues and challenges in postmortem proteins, we have reviewed the current application of protein technologies at postmortem in forensic practice. Meanwhile, we discuss the application of proteins in identifying the cause of death, and postmortem interval (PMI). Finally, we highlight the interpretability and limitations of postmortem protein challenges. We believe that utilizing the multi-omics method can enhance the comprehensiveness of applying proteins in forensic practice.

Evaluation of Muscle Proteins for Estimating the Post-Mortem Interval in Veterinary Forensic Pathology

Postmortem cadaveric changes are commonly used to estimate the postmortem interval (PMI) in humans and animals. However, these modifications have been poorly investigated in animals of interest to veterinary forensic pathology. The aim of this study was to investigate the potential use of muscle proteins (desmin and dystrophin) as biomarkers for estimating the PMI in dogs. For this study, 10 dead adult dogs were evaluated for 4 days in a temperature-controlled room at 19 ± 1 °C. For each animal, at 3, 24, 48, 72, and 96 h after death, a 1 × 1 × 1 cm cube of muscle tissue was removed from the vastus lateralis and triceps brachii. Protein expression levels were analyzed by immunohistochemical examination and immunoblot analysis. The obtained results showed rapid dystrophin degradation, with complete disappearance at 72 h after death. In contrast, desmin-positive fibers and desmin protein bands detected by immunoblot were observed on all 4 days of observation. Our findings suggest the potential use of muscle proteins as biomarkers for estimating the PMI in dogs.

A standard protocol for the analysis of postmortem muscle protein degradation: process optimization and considerations for the application in forensic PMI estimation

The analysis of postmortem protein degradation has become of large interest for the estimation of the postmortem interval (PMI). Although several techniques have been published in recent years, protein degradation-based techniques still largely did not exceed basic research stages. Reasons include impractical and complex sampling procedures, as well as highly variable protocols in the literature, making it difficult to compare results. Following a three-step procedure, this study aimed to establish an easily replicable standardized procedure for sampling and processing, and further investigated the reliability and limitations for routine application. Initially, sampling and processing were optimized using a rat animal model. In a second step, the possible influences of sample handling and storage on postmortem protein degradation dynamics were assessed on a specifically developed human extracorporeal degradation model. Finally, the practical application was simulated by the collection of tissue in three European forensic institutes and an international transfer to our forensic laboratory, where the samples were processed and analyzed according to the established protocol.

Systematic Review on Post-Mortem Protein Alterations: Analysis of Experimental Models and Evaluation of Potential Biomarkers of Time of Death

Estimating the post-mortem interval (PMI) is a very complex issue due to numerous variables that may affect the calculation. Several authors have investigated the quantitative and qualitative variations of protein expression on post-mortem biological samples in certain time intervals, both in animals and in humans. However, the literature data are very numerous and often inhomogeneous, with different models, tissues and proteins evaluated, such that the practical application of these methods is limited to date. The aim of this paper was to offer an organic view of the state of the art about post-mortem protein alterations for the calculation of PMI through the analysis of the various experimental models proposed. The purpose was to investigate the validity of some proteins as “molecular clocks” candidates, focusing on the evidence obtained in the early, intermediate and late post-mortem interval. This study demonstrates how the study of post-mortem protein alterations may be useful for estimating the PMI, although there are still technical limits, especially in the experimental models performed on humans. We suggest a protocol to homogenize the study of future experimental models, with a view to the next concrete application of these methods also at the crime scene.

Postmortem Electrical Conductivity Changes of Dicentrarchus labrax Skeletal Muscle: Root Mean Square (RMS) Parameter in Estimating Time since Death

Simple Summary

The estimation of postmortem interval (PMI) still poses a major challenge for pathologists worldwide, making the search for new and more accurate technologies to assist in PMI estimation worthy of growing scientific interest. This study aimed to explore for the first time the use of an oscilloscope coupled with a signal generator, as innovative technology, to evaluate changes in the electrical conductivity of skeletal muscle of sea bass specimens during the early postmortem interval, to find an accurate, quantitative parameter useful in PMI estimation. The use of the oscilloscope, especially for the RMS measured parameter, has been shown here as a promising technology for studying dielectric muscle properties during the early postmortem interval, with the advantage of being a rapid, non-destructive, and inexpensive method.

Abstract

Electric impedance spectroscopy techniques have been widely employed to study basic biological processes, and recently explored to estimate postmortem interval (PMI). However, the most-relevant parameter to approximate PMI has not been recognized so far. This study investigated electrical conductivity changes in muscle of 18 sea bass specimens, maintained at different room temperatures (15.0 °C; 20.0 °C; 25.0 °C), during a 24 h postmortem period using an oscilloscope coupled with a signal generator, as innovative technology. The root mean square (RMS) was selected among all measured parameters, and recorded every 15 min for 24 h after death. The RMS(t) time series for each animal were collected and statistically analyzed using MATLAB^®. A similar trend in RMS values was observed in all animals over the 24 h study period. After a short period, during which the RMS signal decreased, an increasing trend of the signal was recorded for all fish until it reached a peak. Subsequently, the RMS value gradually decreased over time. A strong linear correlation was observed among the time series, confirming that the above time-behaviour holds for all animals. The time at which maximum value is reached strongly depended on the room temperature during the experiments, ranging from 6 h in fish kept at 25.0 °C to 14 h in animals kept at 15.0 °C. The use of the oscilloscope has proven to be a promising technology in the study of electrical muscle properties during the early postmortem interval, with the advantage of being a fast, non-destructive, and inexpensive method, although more studies will be needed to validate this technology before moving to real-time field investigations.

Influencing Factors on Postmortem Protein Degradation for PMI Estimation: A Systematic Review

The present review provides an overview of the current research status on the effects of influencing factors on postmortem protein degradation used to estimate the PMI (postmortem interval). Focus was set on characteristics of internal and external influencing factors and the respective susceptibility and/or robustness of protein degradation. A systematic literature search up to December 2020 was conducted on the effect of influencing factors investigated in the context of postmortem protein degradation in the tissues of animals and humans using the scientific databases PubMed and Google Scholar, as well as the reference lists of eligible articles. We identified ten studies investigating a total of seven different influencing factors in degrading tissues/organs (n = 7) of humans and animals using six different methodological approaches. Although comparison of study outcomes was impeded by the high variety of investigated factors, and by high risk of bias appraisals, it was evident that the majority of the influencing factors concerned affected protein degradation, thus being able to modulate the precision of protein degradation-based PMI estimation. The results clearly highlight the need for a thorough screening for corresponding factors to enable the introduction of appropriate correction factors and exclusion criteria. This seems especially relevant for the protein degradation-based study of human PMI to increase the reliability and precision of the method and to facilitate a broader applicability in routine forensic casework.

Proteomics in Deaths by Drowning: Diagnostic Efficacy of Apolipoprotein A1 and α-1Antitrypsin, Pilot Study

Drowning is one of the leading causes of death worldwide. The pathophysiology of drowning is complex and, sometimes, interpretation of the circumstances of death in the autopsy becomes the main source of information in its diagnosis. New advances in medical research, such as proteomics, especially in forensic pathology, are still in the development. We proposed to investigate the application of Mass Spectrometry-based technologies, to identify differentially expressed proteins that may act as potential biomarkers in the postmortem diagnosis of drowning. We performed a pilot proteomic experiment with the inclusion of two drowned and two control forensic cases. After applying restrictive parameters, we identified apolipoprotein A1 (ApoA1) and α-1 antitrypsin as differentially expressed between the two diagnostic groups. A validation experiment, with the determination of both proteins in 25 forensic cases (16 drowned and 9 controls) was performed, and we corroborated ApoA1 higher values in the drowning group, whereas α-1 antitrypsin showed lower levels. After adjusting by confounder factors, both remained as predictive independent factors for diagnosis of drowning (p = 0.010 and p = 0.022, respectively). We constructed ROC curves for biomarkers' levels attending at the origin of death and established an ApoA1 cut-off point of 100 mg/dL. Correct classification based on the diagnosis criteria was reached for 73.9% of the cases in a discriminant analysis. We propose apolipoprotein A1 (with our cutoff value for correct classification) and α-1 antitrypsin as valuable biomarkers of drowning. Our study, based on forensic cases, reveals our proteomic approach as a new complementary tool in the forensic diagnosis of drowning and, perhaps, in clinical future implications in drowned patients. However, this is a pilot approach, and future studies are necessary to consolidate our promising preliminary data.

Feasibility Study of MRI Muscles Molecular Imaging in Evaluation of Early Post-Mortem Interval

Estimating early postmortem interval (EPI) is a difficult task in daily forensic activity due to limitations of accurate and reliable methods. The aim of the present work is to describe a novel approach in the estimation of EPI based on quantitative magnetic resonance molecular imaging (qMRMI) using a pig phantom since post-mortem degradation of pig meat is similar to that of human muscles. On a pig phantom maintained at 20° degree, using a 1.5 T MRI scanner we performed 10 scans (every 4 hours) monitoring apparent diffusion coefficient (ADC), fractional anisotropy (FA) magnetization transfer ration (MTR), tractography and susceptibility weighted changes in muscles until 36 hours after death. Cooling of the phantom during the experiment was recorded. Histology was also obtained. Pearson’s Test was carried out for time correlation between post-mortem interval and MRI data. We found a significative inverse correlation between ADC, FA, MT values and PMI. Our preliminary data shows that post-mortem qMRMI is a potential powerful tool in accurately determining EPI and is worth of further investigation.

Postmortem proteomics to discover biomarkers for forensic PMI estimation

The assessment of postmortem degradation of skeletal muscle proteins has emerged as a novel approach to estimate the time since death in the early to mid-postmortem phase (approximately 24 h postmortem (hpm) to 120 hpm). Current protein-based methods are limited to a small number of skeletal muscle proteins, shown to undergo proteolysis after death. In this study, we investigated the usability of a target-based and unbiased system-wide protein analysis to gain further insights into systemic postmortem protein alterations and to identify additional markers for postmortem interval (PMI) delimitation. We performed proteomic profiling to globally analyze postmortem alterations of the rat and mouse skeletal muscle proteome at defined time points (0, 24, 48, 72, and 96 hpm), harnessing a mass spectrometry-based quantitative proteomics approach. Hierarchical clustering analysis for a total of 579 (rat) and 896 (mouse) quantified proteins revealed differentially expressed proteins during the investigated postmortem period. We further focused on two selected proteins (eEF1A2 and GAPDH), which were shown to consistently degrade postmortem in both rat and mouse, suggesting conserved intra- and interspecies degradation behavior, and thus preserved association with the PMI and possible transferability to humans. In turn, we validated the usefulness of these new markers by classical Western blot experiments in a rat model and in human autopsy cases. Our results demonstrate the feasibility of mass spectrometry-based analysis to discover novel protein markers for PMI estimation and show that the proteins eEF1A2 and GAPDH appear to be valuable markers for PMI estimation in humans.

Desmin and dystrophin abnormalities in upper airway muscles of snorers and patients with sleep apnea

BACKGROUND

The pathophysiology of obstruction and swallowing dysfunction in snores and sleep apnea patients remains unclear. Neuropathy and to some extent myopathy have been suggested as contributing causes. Recently we reported an absence and an abnormal isoform of two cytoskeletal proteins, desmin, and dystrophin, in upper airway muscles of healthy humans. These cytoskeletal proteins are considered vital for muscle function. We aimed to investigate for muscle cytoskeletal abnormalities in upper airways and its association with swallowing dysfunction and severity of sleep apnea.

METHODS

Cytoskeletal proteins desmin and dystrophin were morphologically evaluated in the uvula muscle of 22 patients undergoing soft palate surgery due to snoring and sleep apnea and in 10 healthy controls. The muscles were analysed with immunohistochemical methods, and swallowing function was assessed using videoradiography.

RESULTS

Desmin displayed a disorganized pattern in 21 ± 13% of the muscle fibres in patients, while these fibers were not present in controls. Muscle fibres lacking desmin were present in both patients and controls, but the proportion was higher in patients (25 ± 12% vs. 14 ± 7%, p = 0.009). The overall desmin abnormalities were significantly more frequent in patients than in controls (46 ± 18% vs. 14 ± 7%, p < 0.001). In patients, the C-terminus of the dystrophin molecule was absent in 19 ± 18% of the desmin-abnormal muscle fibres. Patients with swallowing dysfunction had 55 ± 10% desmin-abnormal muscle fibres vs. 22 ± 6% in patients without swallowing dysfunction, p = 0.002.

CONCLUSION

Cytoskeletal abnormalities in soft palate muscles most likely contribute to pharyngeal dysfunction in snorers and sleep apnea patients. Plausible causes for the presence of these abnormalities is traumatic snoring vibrations, tissue stretch or muscle overload.

Estimation of time since death based on light microscopic, electron microscopic, and electrolyte analysis in the gingival tissue

Background:

Estimation of time since death is an important parameter in forensic science. Although there are various methods available, precise estimation is still to be established.

Aim:

The present study aimed to evaluate the histological and ultrastructural changes in the gingival tissue along with the changes in electrolyte levels (sodium, potassium, calcium, and magnesium) among the three groups which included normal, 2, and 4 h since death.

Materials and Methods:

For light microscopic examination and electrolyte analysis, five normal gingival tissue samples were collected from patient following impaction procedure and five gingival tissue samples were obtained from postmortem specimen at 2 and 4 h since death. Each sample was divided into two parts. The first part was fixed in 10% formalin solution for the light microscopic analysis, and microscopic changes were observed between the groups. The second part was snap frozen at −80°C, until measurement of electrolyte using inductively coupled plasma-optical emission spectrometer, and the values were compared among the groups using Kruskal–Wallis test. For electron microscopic examination 2 and 4 h postmortem, gingival tissue samples were collected from the same individual and immediately fixed in 2.5% buffered glutaraldehyde, and the ultrastructural changes were compared with the normal gingival tissue.

Results:

The light microscopic changes were observed as early as 2 h since death, but there was no significant difference observed between 2 and 4 h postmortem samples whereas ultrastructurally significant difference in morphology was observed between 2 and 4 h postmortem gingival tissue. Our results can confirm histomorphological changes within 2 and 4 h since death.

Association of Inflammatory Status and Maxillary Sinus Schneiderian Membrane Thickness

OBJECTIVES

Certain Schneiderian membrane thicknesses (SMT) have shown to be more prone to tearing/perforation, and some pathologies might influence SMT. Henceforth, we aimed at studying the correlation of inflammatory status to SMT in human fresh cadaver heads.

MATERIAL AND METHODS

A total of 14 fresh cadaver heads including 27 Schneiderian membrane specimens were histologically collected. A 10-item inflammatory score was determined in the entire sample and also in the thinner and thicker areas of each sample. Data was analyzed by using the Wilcoxon rank test and the Spearman's rank correlation.

RESULTS

The mean measured SMT was 0.40 ± 0.12 mm and the median was 0.33 ± 0.12 mm. A weak positive correlation was found between the mean SMT and inflammation score without a statistical significance. (r = 0.385, p = 0.115). The Wilcoxon signed-rank test showed a statistical difference between the medians of the thinner and thicker areas (p < 0.001). The mean inflammation score of the thinner and thicker areas was 8.55 ± 2.57 and 11.61 ± 2.65, respectively. A moderate positive and statistically significant correlation was found between the inflammation score and the thickness of the thinner and thicker areas (r = 0.638, p = 0.000).

CONCLUSION

A moderate association between the Schneiderian membrane thickness and the level of inflammation exists.

Differential expression and localization of Ankrd2 isoforms in human skeletal and cardiac muscles

Four human Ankrd2 transcripts, reported in the Ensembl database, code for distinct protein isoforms (360, 333, 327 and 300 aa), and so far, their existence, specific expression and localization patterns have not been studied in detail. Ankrd2 is preferentially expressed in the slow fibers of skeletal muscle. It is found in both the nuclei and the cytoplasm of skeletal muscle cells, and its localization is prone to change during differentiation and upon stress. Ankrd2 has also been detected in the heart, in ventricular cardiomyocytes and in the intercalated disks (ICDs). The main objective of this study was to distinguish between the Ankrd2 isoforms and to determine the contribution of each one to the general profile of Ankrd2 expression in striated muscles. We demonstrated that the known expression and localization pattern of Ankrd2 in striated muscle can be attributed to the isoform of 333 aa which is dominant in both tissues, while the designated cardiac and canonical isoform of 360 aa was less expressed in both tissues. The 360 aa isoform has a distinct nuclear localization in human skeletal muscle, as well as in primary myoblasts and myotubes. In contrast to the isoform of 333 aa, it was not preferentially expressed in slow fibers and not localized to the ICDs of human cardiomyocytes. Regulation of the expression of both isoforms is achieved at the transcriptional level. Our results set the stage for investigation of the specific functions and interactions of the Ankrd2 isoforms in healthy and diseased human striated muscles.

Histopathologic evaluation of postmortem autolytic changes in bluegill (Lepomis macrohirus) and crappie (Pomoxis anularis) at varied time intervals and storage temperatures

Information is lacking on preserving fish carcasses to minimize postmortem autolysis artifacts when a necropsy cannot be performed immediately. The purpose of this study was to qualitatively identify and score histologic postmortem changes in two species of freshwater fish (bluegill—Lepomis macrochirus; crappie—Pomoxis annularis), at varied time intervals and storage temperatures, to assess the histologic quality of collected samples. A pooled sample of 36 mix sex individuals of healthy bluegill and crappie were euthanized, stored either at room temperature, refrigerated at 4 °C, or frozen at −20 °C, and then necropsied at 0, 4, 24, and 48 h intervals. Histologic specimens were evaluated by light microscopy. Data showed that immediate harvesting of fresh samples provides the best quality and refrigeration would be the preferred method of storage if sample collection had to be delayed for up to 24 h. When sample collection must be delayed more than 24 h, the preferred method of storage to minimize autolysis artifacts is freezing if evaluation of the gastrointestinal tract is most important, or refrigeration if gill histology is most important. The gill arch, intestinal tract, followed by the liver and kidney were the most sensitive organs to autolysis.

Histological Changes in Skeletal Muscle During Death by Drowning: An Experimental Study

A diagnosis of drowning is a challenge in legal medicine as there is generally a lack of pathognomonic findings indicative of drowning. This article investigates whether the skeletal muscle undergoes structural changes during death by drowning. Eighteen Wistar rats were divided into 3 equal groups according to the cause of death: drowning, exsanguination, and cervical dislocation. Immediately after death, samples of the masseter, sternohyoid, diaphragm, anterior tibial, soleus, and extensor digitorum longus muscles were obtained and examined by light and electron microscopy.In the drowning group, all muscles except the masseter displayed scattered evidence of fiber degeneration, and modified Gomori trichrome staining revealed structural changes in the form of abnormal clumps of red material and ragged red fibers. Under the electron microscope, there was myofibrillar disruption and large masses of abnormal mitochondria. In the exsanguination group, modified Gomori trichrome staining disclosed structural changes and mitochondrial abnormalities were apparent under light microscopy; however, there was no evidence of degeneration. No alterations were observed in the cervical dislocation group.As far as we know, this is the first time that these histological findings are described in death by drowning and are consistent with rhabdomyolysis and intense anoxia of skeletal muscle.

Translational Research in Pediatrics IV: Solid Tissue Collection and Processing

Solid tissues are critical for child-health research. Specimens are commonly obtained at the time of biopsy/surgery or postmortem. Research tissues can also be obtained at the time of organ retrieval for donation or from tissue that would otherwise have been discarded. Navigating the ethics of solid tissue collection from children is challenging, and optimal handling practices are imperative to maximize tissue quality. Fresh biopsy/surgical specimens can be affected by a variety of factors, including age, gender, BMI, relative humidity, freeze/thaw steps, and tissue fixation solutions. Postmortem tissues are also vulnerable to agonal factors, body storage temperature, and postmortem intervals. Nonoptimal tissue handling practices result in nucleotide degradation, decreased protein stability, artificial posttranslational protein modifications, and altered lipid concentrations. Tissue pH and tryptophan levels are 2 methods to judge the quality of solid tissue collected for research purposes; however, the RNA integrity number, together with analyses of housekeeping genes, is the new standard. A comprehensive clinical data set accompanying all tissue samples is imperative. In this review, we examined: the ethical standards relating to solid tissue procurement from children; potential sources of solid tissues; optimal practices for solid tissue processing, handling, and storage; and reliable markers of solid tissue quality.

Proteomic identification of biomarkers of skeletal muscle disorders

Disease-specific biomarkers play a central diagnostic and therapeutic role in muscle pathology. Serum levels of a variety of muscle-derived enzymes are routinely used for the detection of muscle damage in diagnostic procedures, as well as for the monitoring of physical training status in sports medicine. Over the last few years, the systematic application of mass spectrometry-based proteomics for studying skeletal muscle degeneration has greatly expanded the range of muscle biomarkers, including new fiber-associated proteins involved in muscle transformation, muscular atrophy, muscular dystrophy, motor neuron disease, inclusion body myositis, myotonia, hypoxia, diabetes, obesity and sarcopenia of old age. These mass spectrometric studies have clearly established skeletal muscle proteomics as a reliable method for the identification of novel indicators of neuromuscular diseases.

Postmortem cardiac tissue maintains gene expression profile even after late harvesting

Background

Gene expression studies can be used to help identify disease-associated genes by comparing the levels of expressed transcripts between cases and controls, and to identify functional genetic variants (expression quantitative loci or eQTLs) by comparing expression levels between individuals with different genotypes. While many of these studies are performed in blood or lymphoblastoid cell lines due to tissue accessibility, the relevance of expression differences in tissues that are not the primary site of disease is unclear. Further, many eQTLs are tissue specific. Thus, there is a clear and compelling need to conduct gene expression studies in tissues that are specifically relevant to the disease of interest. One major technical concern about using autopsy-derived tissue is how representative it is of physiologic conditions, given the effect of postmortem interval on tissue degradation.

Results

In this study, we monitored the gene expression of 13 tissue samples harvested from a rapid autopsy heart (non-failed heart) and 7 from a cardiac explant (failed heart) through 24 hours of autolysis. The 24 hour autopsy simulation was designed to reflect a typical autopsy scenario where a body may begin cooling to ambient temperature for ~12 hours, before transportation and storage in a refrigerated room in a morgue. In addition, we also simulated a scenario wherein the body was left at room temperature for up to 24 hours before being found. A small fraction (< 2.5%) of genes showed fluctuations in expression over the 24 hr period and largely belong to immune and signal response and energy metabolism-related processes. Global expression analysis suggests that RNA expression is reproducible over 24 hours of autolysis with 95% genes showing < 1.2 fold change. Comparing the rapid autopsy to the failed heart identified 480 differentially expressed genes, including several types of collagens, lumican (LUM), natriuretic peptide A (NPPA) and connective tissue growth factor (CTGF), which allows for the clear separation between failing and non-failing heart based on gene expression profiles.

Conclusions

Our results demonstrate that RNA from autopsy-derived tissue, even up to 24 hours of autolysis, can be used to identify biologically relevant expression pattern differences, thus serving as a practical source for gene expression experiments.