Immunohistochemical insights into hypothermia-related deaths: a systematic review

Mechanical asphyxia refers to the internal or external obstruction of the airways,resulting in the subsequent interruption of respiratory exchanges and hypoxia, whichmay be due to homicidal, suicidal, or accidental actions (1). From ahistomorphological perspective, the microscopic changes observable withhematoxylin-eosin staining in cases of mechanical asphyxia (such as acute pulmonaryemphysema, interalveolar hemorrhage, and vascular congestion) have been welldescribed and, if documented, can provide valuable support to macroscopic findings(2). Concurrently, in forensic medicine, there has been notable advancement in theapplication of immunohistochemical techniques, which are already widely used inclinical practice for diagnosing and characterizing neoplasms (3). Therefore, immunohistochemical techniques employed in forensic pathology todetermine the post-mortem interval and lesion dating have been complemented byadditional techniques used as valuable diagnostic aids in cases of natural or violentdeaths. Noteworthy are the numerous studies conducted on secondary deaths such assepsis or drowning (4,5). In the case of mechanical asphyxia, variations in several alveolar proteins have beendescribed, including surfactant protein-A (SP-A), P-selectin, E-selectin, Heat ShockProteins (HSPs), and hypoxia-inducible factor 1-α (HIF1-α) (6–8). This study aims to investigate immunohistochemical changes in alveolar proteins inindividuals who have died from mechanical asphyxia and compare these findings withthose in living subjects suffering from chronic obstructive pulmonary disease (COPD)or chronic hypoxia. It employs an observational cohort design with stratified clustersampling, categorizing subjects into two main groups: one consisting of individualswho have died from mechanical asphyxia (such as drowning, hanging, orstrangulation) and the other including living patients with COPD or other conditionsleading to chronic hypoxia. The primary objective of the study is to determine, by comparing the two groups,whether immunohistochemistry objectively reflects hypoxia induced by the asphyxialmechanism or if the expression of the markers is influenced by other factors such aspre-existing chronic hypoxia or modifications resulting from post-mortem changes. Itis essential to highlight that the use of immunohistochemistry on samples fromcadavers has been questioned due to the alterations that proteins undergo during post-mortem changes (9). The study employs an observational cohort design with stratified cluster sampling. Itcategorizes subjects into two main groups: one comprising individuals who have diedfrom mechanical asphyxia, including cases of drowning, hanging, or strangulation, andthe other including living patients with COPD or other conditions leading to chronichypoxia. The research will utilize hematoxylin-eosin staining and advancedimmunohistochemical techniques to evaluate the expression levels of the proteinsmentioned above in tissue samples. By comparing these protein expressions betweenthe two groups, the study aims to establish a reliable framework for understanding howpost-mortem changes and pre-existing conditions affect the immunohistochemicalmarkers used in forensic diagnostics. The anticipated outcomes of this research are twofold: first, to provide a solidfoundation for future studies in forensic pathology by elucidating the variations inprotein expression due to mechanical asphyxia and chronic hypoxia, and second, toenhance the diagnostic accuracy for asphyxial deaths by determining the impact ofpost-mortem changes and chronic conditions on protein expression.