Laboratory of Personal Identification and Forensic Morphology, Department of Health Sciences, University of Florence, Largo Brambilla 3, 50134 Florence, Italy.
Forensic Medical Sciences, Department of Health Science, University of Florence, Largo Brambilla 3, 50134 Florence, Italy.
Int J Mol Sci. 2024 Aug 14;25(16):8832. doi: 10.3390/ijms25168832.
Post-mortem interval (PMI) estimation remains one of the major challenges in forensic practice, especially for late PMIs beyond 7-10 days after the death of the subject. In 2022, an innovative method to investigate the occurrence of mutations induced by the death of a subject in the DNA of post-mortem dental pulps at different PMIs was developed, applying a next-generation sequencing (NGS) analysis. The present study aims to apply the same method of analysis to a small sample of teeth belonging to the same subject and analyzed at different PMIs/accumulated degree days (ADDs), and of teeth extracted from different subjects but analyzed at the same PMI/ADD to verify the repeatability of the results obtained in relation to the time elapsed since death. A total of 10 teeth were collected from 6 patients (3 males and 3 females) with PMI varying from 8 to 35 days, and ADD from 157.4 to 753.8. We found 1754 mutations in 56 genes, with more than 700 mutations having a prevalence > 5% and more than 300 variants considered of interest for the purposes of the study. Mutations that were not present at lower PMIs but manifested in later PMIs in pulps belonging to the same subject demonstrate that they can only have been acquired by the subject after death and according to the time elapsed since death. In total, 67 somatic mutations in 29 out of the 56 genes of the used panel occurred in a fashion that allows an association with specific PMI/ADD ranges (within 8 days, between 17 and 28, and beyond 30 days after death). The results suggest that temperature and humidity could influence the rate of DNA degeneration in dental pulps, thus PMI should be estimated in ADD more than days. The preliminary validation supports the hypothesis that the innovative method could be a useful tool for estimating the post-mortem interval even beyond the first week after death, but further analyses are needed to customize a specific genetic panel for forensic investigations and verify the influence of degenerative processes of soft tissues surrounding dental elements on DNA degeneration of pulps.
死后间隔时间（PMI）估计仍然是法医学实践中的主要挑战之一，特别是对于死后 7-10 天以上的晚期 PMI。2022 年，开发了一种创新方法，通过应用下一代测序（NGS）分析，研究死后牙髓 DNA 中由主体死亡引起的突变的发生情况。本研究旨在将相同的分析方法应用于属于同一主体且在不同 PMI/积累度天数（ADD）下分析的少量牙齿样本，以及从不同主体提取但在相同 PMI/ADD 下分析的牙齿样本，以验证与死亡时间相关的结果的可重复性。总共从 6 名患者（3 名男性和 3 名女性）中收集了 10 颗牙齿，PMI 从 8 天到 35 天不等，ADD 从 157.4 到 753.8。我们在 56 个基因中发现了 1754 个突变，其中超过 700 个突变的流行率>5%，超过 300 个变体被认为与研究目的相关。在属于同一主体的牙髓中，在较低的 PMI 中不存在但在较晚的 PMI 中出现的突变表明，它们只能在死后由主体获得，并且与死亡后经过的时间有关。总共，在所使用的面板的 56 个基因中的 29 个基因中，有 67 个体细胞突变以允许与特定的 PMI/ADD 范围（在死亡后 8 天内、在 17 到 28 天之间和超过 30 天后）相关联的方式发生。结果表明，温度和湿度可能会影响牙髓中 DNA 退化的速度，因此应该根据 ADD 而不是天数来估计 PMI。初步验证支持这样的假设，即创新方法可能是估计死后间隔时间的有用工具，即使在死后第一周之后，但是需要进一步的分析来为法医调查定制特定的遗传面板，并验证周围软组织的退化过程对牙髓 DNA 退化的影响牙齿元素。
