Aims: Epilepsy is one of the most prevalent neurological diseases. A third of patients with epilepsy remain drug-resistant. The exact aetiology of drug-resistant epilepsy (DRE) is still unknown. Neuronal tetraploidy has been associated with neuropathology. The aim of this study was to assess the presence of tetraploid neurons and astrocytes in DRE.Methods: For that purpose, cortex, hippocampus and amygdala samples were obtained from patients subjected to surgical resection of the epileptogenic zone. Post-mortem brain tissue of subjects without previous records of neurological, neurodegenerative or psychiatric diseases was used as control.Results: The percentage of tetraploid cells was measured by immunostaining of neurons (NeuN) or astrocytes (S100β) followed by flow cytometry analysis. The results were confirmed by image cytometry (ImageStream X Amnis System Cytometer) and with an alternative astrocyte biomarker (NDRG2). Statistical comparison was performed using univariate tests. A total of 22 patients and 10 controls were included. Tetraploid neurons and astrocytes were found both in healthy individuals and DRE patients in the three brain areas analysed: cortex, hippocampus and amygdala. DRE patients presented a higher number of tetraploid neurons (p = 0.020) and astrocytes (p = 0.002) in the hippocampus than controls. These results were validated by image cytometry. Conclusions:We demonstrated the presence of both tetraploid neurons and astrocytes in healthy subjects as well as increased levels of both cell populations in DRE patients.Herein, we describe for the first time the presence of tetraploid astrocytes in healthy subjects. Furthermore, these results provide new insights into epilepsy, opening new avenues for future treatment.
Background: Epilepsy is one of the most prevalent neurological diseases, a third of patients remain drug-resistant. The exact etiology of drug-resistant epilepsy (DRE) is still unknown. Neural tetraploidy has been associated with neuropathology. The aim of this study was to assess the presence of tetraploid neurons and astrocytes in DRE. Materials & methods: Cortex, hippocampus and amygdala samples were obtained from patients subjected to surgical resection of the epileptogenic zone. Postmortem brain tissue of subjects without previous records of neurological, neurodegenerative or psychiatric diseases were used as controls. The percentage of tetraploid cells was measured by immunostaining of neurons (NeuN) or astrocytes (S100β) followed by flow cytometry analysis. Results were confirmed by image cytometry (ImageStream X Amnis System Cytometer) and with an alternative astrocyte biomarker (NDRG2). Statistical comparison was performed using univariate tests. Results: A total of 22 patients and 10 controls were included. Tetraploid neurons and astrocytes were found both in healthy individuals and DRE patients in the three brain areas analyzed: cortex, hippocampus and amygdala. DRE patients presented a higher number of tetraploid neurons (p=0.020) and astrocytes (p=0.002) in the hippocampus compared to controls. These results were validated by image cytometry. Conclusion: We demonstrated the presence of both tetraploid neurons and astrocytes in healthy subjects and increased levels of both cell types in DRE patients. This is the first time that tetraploid astrocytes are described in healthy subjects. Furthermore, these results provide new insights into epilepsy, opening new avenues for future treatment.
Epilepsy is a disabling neurological disease that affects 2% of the population. Drug-resistant epilepsy (DRE) affects 25-30% of epilepsy patients. Understanding its underlying mechanisms is key to adequately manage this condition. To analyze the main epigenetic marks of DRE an epigenome-wide association study was carried out including samples from different regions of DRE patients brain and peripheral blood. An Illumina Infinium MethylationEPIC BeadChip array including cortex, hippocampus, amygdala, and peripheral blood from DRE subjected to neurosurgical resection of the epileptogenic zone was used. Overall, 32, 59, 3210, and 6 differentially methylated probes (DMPs) associated with DRE were found in the hippocampus, amygdala, cortex, and peripheral blood, respectively. These DMPs harbored 19, 28, 1574, and 7 genes, respectively, which play different roles in processes such as neurotrophic or calcium signaling. Three of the top DMPs observed in cortex were validated with methylation specific qPCR. Moreover, 163 DMPs associated with neurosurgery response at 6 months were found in the hippocampus. Genes located on these DMPs were involved in diverse processes such as synaptic signaling and central nervous system development. Besides 3 DMPs in blood samples were associated with response to neurosurgery at 12 months. In conclusion, the present study reports genome-wide DNA methylation changes across different regions of the DRE brain. These changes could be useful for further studies to disentangle the bases of DRE to search for therapeutic alternatives for this disease. Furthermore, they could also help identify patients likely to respond to neurosurgery.
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