Date of Submission

5-2025

Document Type

Thesis

Degree Name

Master of Science in Forensic Science

Department

Forensic Science

Advisor

Devid San Pietro, Ph.D.

Committee Member

Heather M. Coyle, Ph.D.

Committee Member

Larry Quarino, Ph.D.

Keywords

Neuropeptides, Biomarkers, Gene Expression, Acute Pain, Chronic Pain, Postmortem

MeSH

Neuropeptides, Central Nervous System, Biomarkers, RNA, Pain, Gene Expression

LCSH

Neuropeptides, Central nervous system, RNA, Biochemical markers, Pain, Gene Expression

Abstract

Substance P (SP) and Met-Enkephalin (MET) are neuropeptides critical to the central nervous system (CNS) and are released as immediate responders to physical stressors like pain. In blood, SP and MET adapt based on an incident-death time interval to suggest the potential to use these as biomarkers in the assessment of pain prior to death. The mRNA and DNA manipulations of RNA isolation, cDNA synthesis, and RT-qPCR allowed for investigation into SP and MET gene expression (TACl, TACRl, OGFR) in those who experienced chronic tissue damage (e.g. domestic abuse) as compared to those who underwent an acute pain event (e.g. sudden traumatic event). Delta cycle threshold (L'.iCt) values were used as an inverse measure of gene expression to recognize SP and MET expression patterns as it relates to manner of death. Clear expression profiles were found in postmortem acute pain cases where the mean L'.iCt values for TACl and TACRl were 16.61 ± 1.93 and 15.56 ± 1.75 respectively with OGFR notably lower at 7.42 ± 1.13. This is compared to postmortem chronic cases where the mean L'.iCt values for TACl and TACRl were 18.85 ± 2.88 and 18.50 ± 2.86 respectively with OGFR again lower at 6.70 ± 2.38. The differential expression patterns observed in this study suggest acute pain is linked to raised OGFR expression where TAC1 and TACRl proved increasingly variable when compared to chronic pain samples. The results of this study supply preliminary support to the hypothesis that chronic pain conditions existent perimortem may lead to more unique biomarker profiles as compared to acute pain conditions perimortem. If there is ever uncertainty surrounding the circumstances of an individual's death, this study may therefore aid in the establishment of SP and MET as feasible biomarkers to understand the extent of suffering leading to death. Additional investigations constituting greater sample populations, with emphasis on chronic pain conditions, are required to further validate the study's results and to generate a well-established diagnostic criterion.

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