Density of TMEM119-positive microglial cells in postmortem cerebrospinal fluid as a surrogate marker for assessing
Simone Bohnert1, Stefanie Trella2, Ulrich Preiß2
1Institute of Forensic Medicine, University of Wuerzburg, Versbacher Str. 3, 97078, Wuerzburg, Germany. simone.bohnert@uni-wuerzburg.de.
Abstract:
Routine coronal paraffin-sections through the dorsal frontal and parieto-occipital cortex of a total of sixty cases with divergent causes of death were immunohistochemically (IHC) stained with an antibody against TMEM119. Samples of cerebrospinal fluid (CSF) of the same cases were collected by suboccipital needle-puncture, subjected to centrifugation and processed as cytospin preparations stained with TMEM119. Both, cytospin preparations and sections were subjected to computer-assisted density measurements. The density of microglial TMEM119-positive cortical profiles correlated with that of cytospin results and with the density of TMEM119-positive microglial profiles in the medullary layer. There was no statistically significant correlation between the density of medullary TMEM119-positive profiles and the cytospin data. Cortical microglial cells were primarily encountered in supragranular layers I, II, and IIIa and in infragranular layers V and VI, the region of U-fibers and in circumscribed foci or spread in a diffuse manner and high density over the white matter. We have evidence that cortical microglia directly migrate into CSF without using the glympathic pathway. Microglia in the medullary layer shows a strong affinity to the adventitia of deep vessels in the myelin layer. Selected rapidly fatal cases including myocardial infarcts and drowning let us conclude that microglia in cortex and myelin layer can react rapidly and its reaction and migration is subject to pre-existing external and internal factors. Cytospin preparations proved to be a simple tool to analyze and assess complex changes in the CNS after rapid fatal damage. There is no statistically significant correlation between cytospin and postmortem interval. Therefore, the quantitative analyses of postmortem cytospins obviously reflect the neuropathology of the complete central nervous system. Cytospins provide forensic pathologists a rather simple and easy to perform method for the global assessment of CNS affliction.
Insights
This study shows that TMEM119 staining in cerebrospinal fluid (CSF) cytospins reflects microglial changes in the brain cortex. This method offers a simple way to assess central nervous system (CNS) damage, even after rapid death.
Area of Science:
- Neuroscience
- Immunohistochemistry
- Forensic Pathology
Background:
- Microglia are key immune cells in the central nervous system (CNS).
- TMEM119 is a specific marker for microglia.
- Assessing microglial changes in postmortem samples can be challenging.
Purpose of the Study:
- To investigate the utility of TMEM119 immunohistochemistry in postmortem cerebrospinal fluid (CSF) cytospins for evaluating CNS microglial status.
- To correlate CSF microglial findings with cortical microglial distribution and density.
- To explore the potential of cytospins as a simple diagnostic tool for rapid CNS damage assessment.
Main Methods:
- Immunohistochemical staining for TMEM119 on postmortem brain cortical sections and CSF cytospins from 60 cases.
- Computer-assisted density measurements of TMEM119-positive microglial profiles.
- Analysis of correlation between cortical and CSF microglial densities.
- Examination of microglial distribution in different cortical layers and white matter.
Main Results:
- Density of TMEM119-positive microglial profiles in cortical sections correlated with CSF cytospin results.
- Cortical microglia were found in specific layers (I, II, IIIa, V, VI) and white matter.
- Evidence suggests direct migration of cortical microglia into CSF, independent of the glymphatic pathway.
- Rapid reactivity and migration of microglia were observed in cases of sudden death.
Conclusions:
- Postmortem CSF cytospins stained with TMEM119 are a reliable indicator of cortical microglial changes.
- This method provides a simple and effective tool for forensic pathologists to assess global CNS pathology, especially after rapid fatal events.
- Microglial migration into CSF may occur directly from the cortex.
