Dados do Trabalho

Título

Tissue expression of glial markers in the white matter of the parahippocampal gyrus of individuals with hippocampal sclerosis

Introdução

Epilepsy (EPI) is the most common neurological disease. Hippocampal sclerosis (HS) is a frequent finding in surgical specimens of individuals with temporal lobe epilepsy (TLE). In MRI studies, white matter (WM) alterations may be observed in HS-TLE patients in topographies such as the parahippocampal gyrus (PHG).

Objetivo

Here, we investigated tissue expression of glial markers in the PHG WM of HS patients compared to autopsy controls. Our aim was to identify tissue changes that might cause neuroimaging alterations in the PHG of individuals with HS.

Método

Analysis of sections of EPI (HS; n=14) and control (n=7) specimens was made by means of immunohistochemistry for CNPase, GFAP and Iba-1 to evaluate oligodendrocyte, astrocyte and microglial populations, respectively. Microscopic fields (MFs; objective 40x) of the PHG WM were photodocumented and digitally analyzed with the ImageJ® software. The Threshold tool was used to semiquantitatively assess the staining by transforming each MF image into grayscale. A cutoff point was defined to convert the image into binary information (black/ white). The value of black pixels/total pixels of the field ratio was defined as “Mean” and mean values were compared between the groups (Mann-Whitney test; significance level p<0.05).

Resultados

GFAP and Iba1 highlighted astrocytic and microglial cytoplasmic processes, respectively. After semiquantitative evaluation, the EPI group presented lower and higher Mean values for GFAP and Iba-1 compared to controls, respectively (p<0.05). CNPase immunolabeling showed homogeneous myelin distribution in the WM and the corresponding Mean values were similar between the groups (p>0.05).

Conclusão

In a previous study by others, surgical samples of patients with TLE and mesial temporal sclerosis were assessed by stereology and showed less GFAP-positive cells in the PHG compared to controls. Possibly, corresponding to a lower ratio of GFAP-immunoreactive to total astrocytes. Moreover, studies with rodent-pilocarpine model of TLE showed higher expression of Iba-1 in the group with seizures, possibly associated with inflammation. Regarding CNPase staining, we found no previous data similar to ours, either in surgical or in experimental samples. Finally, MRI signal differences in extra-hippocampal areas were detected in patients with TLE and HS compared to controls, correlations between histopathological findings such as those found in the present investigation and those MRI alterations still require further investigation.

Palavras-chave

TEMPORAL LOBE EPILPESY, HISTOPATHOLOGY, GLIAL CELLS, WHITE MATTER, HIPPOCAMPAL SCLEROSIS