Microgliosis In Brain Parenchyma After Acute Ischemia

It is widely accepted that microglia is the immune effector of central nervous system (CNS). Reactive microgliosis is characteristic of brain trauma as well as inflammatory and chronic neurodegenerative diseases. Microgliosis contains two major sources, one is the proliferation of resident microglia and the other is the migration of microglia from other brain regions. However, time course of microgliosis in brain parenchyma is still unrevealed after acute ischemia, In this study, we investigated the time windows of microgliosis in brain parenchyma by using a ptotothrombosis model and transgenic mice with brain microglia labeled by green fluorescent protein(GFP); and in order to understand what factors included in microgliosis after stroke,5-Bromo-2-deoxyuridine (BrdU) immunohistochemical staining was also implemented.We found that microglia were activated24h after stroke, during48h after stroke they are primarily activated, and clear boundary between the lesion area and the uninjured area is formed;3days after stroke microglia in nerve fibres along paracele and in thalamus nucleus area in the injured side becomes activated; during3-5days period after stroke, more and more GFP+cells gather at the boundary of lesion site and therefore an infract band is formed, at the same time several GFP+cells infiltrated into the infract core;7days after stroke, a large number of GFP+cells appear on the infract band, till15days after stroke the whole infract area is covered by GFP+cells gradually; the situation could last for a long time, at least for one month. We also found that microgliosis exists after acute stroke and it mainly happens in several brain areas including the infract area, cortex area near the infract area, nerve fibre area along paracele and thalamus nucleus area in the injured side. By using BrdU immunohistochemical staining, we found that microglia in the infract area and thalamus nucleus area could proliferate after acute stroke; and nerve fibre area along paracele may be one way along which microglia migrate to the lesion area. It may provide some reference data for stroke therapy.