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Individual Case Analysis of Postmortem Interval Time on Brain Tissue Preservation
Jeffrey A Blair1, Chunyu Wang2,3, Damarys Hernandez2
1Department of Biological Sciences and School of Biomedical Sciences, Kent State University, Kent, Ohio, United States of America.
Abstract:
At autopsy, the time that has elapsed since the time of death is routinely documented and noted as the postmortem interval (PMI). The PMI of human tissue samples is a parameter often reported in research studies and comparable PMI is preferred when comparing different populations, i.e., disease versus control patients. In theory, a short PMI may alleviate non-experimental protein denaturation, enzyme activity, and other chemical changes such as the pH, which could affect protein and nucleic acid integrity. Previous studies have compared PMI en masse by looking at many different individual cases each with one unique PMI, which may be affected by individual variance. To overcome this obstacle, in this study human hippocampal segments from the same individuals were sampled at different time points after autopsy creating a series of PMIs for each case. Frozen and fixed tissue was then examined by Western blot, RT-PCR, and immunohistochemistry to evaluate the effect of extended PMI on proteins, nucleic acids, and tissue morphology. In our results, immunostaining profiles for most proteins remained unchanged even after PMI of over 50 h, yet by Western blot distinctive degradation patterns were observed in different protein species. Finally, RNA integrity was lower after extended PMI; however, RNA preservation was variable among cases suggesting antemortem factors may play a larger role than PMI in protein and nucleic acid integrity.
Insights
Postmortem interval (PMI) impacts tissue integrity. This study found most protein immunostaining remained stable over 50 hours, but RNA integrity decreased, with individual factors influencing preservation.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Postmortem interval (PMI) is crucial for human tissue sample integrity in research.
- Variability in PMI can confound comparisons between different patient groups.
- Previous studies often averaged diverse PMIs, masking individual case variations.
Purpose of the Study:
- To investigate the effect of extended postmortem intervals on protein and nucleic acid integrity in human hippocampal tissue.
- To establish a standardized method using serial sampling from the same individuals to control for inter-individual variance.
Main Methods:
- Human hippocampal tissue segments were sampled at multiple time points post-autopsy from the same individuals.
- Techniques included Western blot, RT-PCR, and immunohistochemistry.
- Evaluation of protein, nucleic acid, and tissue morphology changes over extended PMI.
Main Results:
- Immunostaining for most proteins remained consistent even after 50 hours postmortem.
- Distinct protein degradation patterns were observed using Western blot analysis.
- RNA integrity showed a decline with extended PMI, but with significant inter-case variability.
Conclusions:
- While some protein epitopes are stable, extended PMI can lead to protein degradation and reduced RNA integrity.
- Antemortem factors appear to play a more significant role in preserving protein and nucleic acid integrity than PMI.
- Standardized sampling from single cases with serial PMIs offers a more robust approach to studying tissue degradation.
