Time - Dependent Study On Activation Of Microglia In Adult Mice After Stroke

Background and purpose:According to Epidemiological survey of China in2012, stroke becomes the highest morbility disease in China and the first disabled-leading cause worldwide. According to the causes of the stroke, it can be classified as ischemic stroke and hemorrhagic stroke, of which the previous accouts for the85%of total. The microglia is the cell which locates specifically in the brain. They are the residential immunity cells, whose number is nearly5%-10%of the total cells in the adult brain. They anticipate the processes like presentation of antigens, phagocytosis and production of different pro or anti inflammatory factors. Many scientists hold the same ideas that after the inflammatory events happen like stroke, the behaviors of the microglia are like a double-edge swords. About the research on the microglia after stroke, a lot of work has beend done. Now it is generally considered that the effects of microglia after stroke can be divided as two different stages, M1and M2. And the preliminary functions have been implemented. While the time-dependent activation of microglia after stroke is unclear yet. This work focused on the time-dependent activation of microglia through the expression of different markers on the cells in different time point after stroke in vivo or after OGD in vitro. The research on microglia activation time-dependently is the total innovation and it opens a window for the microglia-target therapy of strokeMethods:We used male C57/BL6mouse to undergo the ischemic stroke surgery (MCAO), testing the expression of different M1and M2markers of microglia in iplateral cortex, corpus callosum and hippocampus with RT-PCR and immunohistochemistry methods. In vitro, we used the medium of neurons after OGD1h to cultivate the microglia, testing the activation of microglia; we also coculture the neurons after OGD1h with the activated microglia with different inducers of M1or M2to test the effects of microglia on survival of neurons.Results:After stroke, microglia tended to be M2state from the d1-d2, peaked in d3-d5,then decreased in d7and came back to d14; while in the later time period after stroke, M1state prevailed, often increased in d3and remained in this state to d14after stroke. In vitro, the neurons after exposed to OGD could lead to the Ml state of the microglia which the ability of phagocytosis decreased and produced more pro-inflammatory factors; different polarized microglia had different effects on the survival of neurons, Mo (resting microglia) microglia could promote the suivival of the neurons after exposion to OGD and the M2microglia enhanced this effectConclusions:In vivo and in vitro experiments, all results showed that the early stage of microglia activation expressed mainly M2markers, acting as the neuroprotective role. Later on, there was a transforming from M2to Ml. The ability of phagocytosis of microglia in M1state would decrease and produce more pro-inflammatory factors.