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Correlative analysis on the relationship between PMI and DNA degradation of cell nucleus in human different tissues
Xiji Shu1, Yaling Liu, Liang Ren
1Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Abstract:
To determining the postmortem interval (PMI) through quantitative analysis of the DNA degradation of cell nucleus in human brain and spleen by using image analysis technique (IAT). The brain and spleen tissues from 32 cadavers with known PMI were collected, subjected to cell smear every 1 h within the first 5-36 h after death, stained by Feulgen-Van's staining, Three indices reflecting DNA in brain cells (astrocytes) and splenic lymphocytes, including integral optical density (IOD), average optical density (AOD), average gray (AG) were measured by employing the mage analysis instrument. The results showed that IOD and AOD declined and AG increased with the prolongation of dead time within 5-36 h. A correlation between the PMI and gray parameters (IOD, AOD and AG) was identified and the corresponding regression equation was obtained. The parameters (IOD, AOD and AG) were proved to be effective quantitative indicators for accurate estimation of PMI within 5-36 h after death.
Insights
This study quantifies DNA degradation in brain and spleen cells to estimate the postmortem interval (PMI). Image analysis of DNA staining reveals reliable correlations for accurate PMI determination within 36 hours.
Area of Science:
- Forensic Science
- Molecular Biology
- Biotechnology
Background:
- Accurate postmortem interval (PMI) estimation is crucial in forensic investigations.
- Current methods for PMI determination have limitations in accuracy and applicability.
- Quantitative analysis of cellular changes offers a promising avenue for improved PMI estimation.
Purpose of the Study:
- To develop and validate a quantitative method for estimating the postmortem interval (PMI) using DNA degradation.
- To assess the efficacy of image analysis techniques (IAT) in measuring DNA changes in human brain and spleen tissues.
- To establish correlations between specific DNA degradation parameters and the time since death.
Main Methods:
- Human brain and spleen tissues from 32 cadavers with known PMI were analyzed.
- Cell smears were prepared hourly within the first 36 hours postmortem.
- Feulgen-Van's staining was employed, followed by image analysis to measure integral optical density (IOD), average optical density (AOD), and average gray (AG) of DNA in cell nuclei.
Main Results:
- DNA degradation parameters (IOD, AOD, AG) showed significant changes with increasing postmortem time (5-36 hours).
- Integral optical density (IOD) and average optical density (AOD) decreased, while average gray (AG) increased over time.
- A strong correlation was identified between these gray parameters and the known PMI, enabling the derivation of regression equations.
Conclusions:
- Quantitative image analysis of DNA degradation in brain astrocytes and splenic lymphocytes provides reliable indicators for PMI estimation.
- The developed method using IOD, AOD, and AG is effective for accurate PMI determination within the 5-36 hour postmortem window.
- This technique offers a valuable tool for forensic science, enhancing the accuracy of time-since-death investigations.
