Application of Intracerebral Aquaporin-4 Expression in Differential Diagnosis of Drowning: an Immunohistochemical Study Related to Timing of Autopsy.

Abstract

Background: The role of forensic pathologists is pivotal in definitively diagnosing drowning cases. Further differentiation becomes essential for distinguishing between freshwater drowning (FWD) and saltwater drowning (SWD). Aquaporins are small integral membrane proteins that serve as major water transport pathways in various cell types. AQP4 appears to be involved in mechanisms related to cerebral volume regulation. Our study aims to examine the expression of AQP4 in the brain as a potential marker for differentiating between FWD and SWD relating to autopsy-performing timing.

Materials and methods: A total of 23 cases were classified into three groups: FWD, SWD, and controls. All samples were classified upon autopsy-performing timing into two subgroups: within and after 72 hours of death. The samples were then processed for histological and immunohistochemical investigations.

Conclusion: For autopsies performed within 72 hours of death, we found a significantly higher value of AQP4-positive astrocytes in cases of FWD compared to SWD and control groups. We also found a significantly lower AQP4 expression in SWD cases compared to the control group. For autopsies conducted after 72 hours, the immunohistochemical staining does not reveal the peripheral terminations of astrocytes, which appear blurred and only recognizable as halos. In conclusion, the data aligns with existing literature about autopsies performed within 72 hours. However, in autopsies conducted after 72 hours, uncertain and even opposed results are observed. The difference can be ascribed to the post-mortem transformative processes that take place upon the cessation of vital functions.