Do the extracellular vesicles excreted during neuronal cell death play a neuron‐glia signalling role in neurodegeneration.

Abstract

AbstractBackgroundDuring neurodegeneration, dying neuronal cells may trigger neuroinflammatory responses or inform neighbouring glial cells of their dying status by releasing extracellular vesicles. Karyoptosis is a novel cell death caused by a block in autophagy which was first discovered in a dentatorubral‐pallidoluysian atrophy (DRPLA) mouse model. During karyoptosis cells exhibit signs of nucleophagy (nuclear breakdown) and vesicle expulsion. Understanding the molecular underpinnings of neurodegeneration is important for informing possible therapeutic intervention. Our hypothesis is that dying neurons release vesicles which are phagocytosed by microglia, and this leads to an inflammatory response.MethodUsing ex vivo samples from the DRPLA mouse model, immunofluorescence, and confocal imaging, we studied the phenotype of microglia pathologically. We used disease‐relevant brain regions with high levels of karyoptosis, such as the dentate nucleus. To further understand the microglial response and visualise the likely phagocytosis of these vesicles, we are also using a human neuroblastoma cell line to induce karyoptosis and purify the released vesicles for application to cultured BV2 microglia‐like cells.ResultOur initial data shows that more microglia are present in pathological areas with high karyoptosis activity in the DRPLA mice. Analysis of these microglia revealed an increased cell soma size, decreased branch length, and decreased intersections per microglia in the DRPLA model, all of which suggest the increased activation and de‐ramification of microglia in DRPLA mice.ConclusionThese findings indicate differences in the total number, activity, and overall phenotype of microglia in areas with high karyoptosis in this DRPLA model. This suggests that the vesicles released during this cell death process may be influencing microglia. Future work will focus on replicating these findings in vitro. Extracellular vesicles collected from human neuroblastoma will be applied to cultured microglia to visualise the uptake of vesicles, decode their contents, and further characterise any microglial response. This work will help further the understanding of how neuron‐glia signalling contributes to neurodegeneration.