| Objective: Observe the temporal and spatial changes of brain and retinal microglia in mice with chronic cerebral ischemia at different time points.Methods: Three-month-old C57BL/6J mouse was used to make a model of chronic cerebral ischemia with modified bilateral common carotid artery ligation(2VO).The sham operation group was used as a control,and the model was validated by perfusion with toluidine blue dye.7d,14 d,28d after modeling,HE staining was performed to observe the pathological changes of the hippocampus,cerebral cortex and retina.Immunohistochemical staining was used to observe the expression of IBA1,i NOS and TREM2 in hippocampus,cerebral cortex and retina.Results: The results of toluidine blue perfusion showed that the staining of brain tissue in mice immediately became lighter after 2VO.As the ischemic time increased,the staining of brain tissue deepened to a certain extent,but it was always lower than that of normal brain tissue.The results of HE staining showed that on the 7th day after 2VO,the cell volume increased and the cytoplasm was slightly stained in the hippocampal CA1.There were cell abnormalities in the hippocampal CA3;Vacuoles,increased cell volume,lightly stained cytoplasm,and abnormal cells in the DG area.Cells were loosely arranged and enlarged,and the cytoplasm was slightly stained or heavily stained in the cerebral cortex.The cell volume increased and the cytoplasm was lightly stained in retinal GCL.The intercellular space increased in the INL and ONL.On the 14 th day after 2VO,nuclear fragmentation appeared in the hippocampal CA1.Some cells were clustered together in the cerebral cortex.There were disordered cell arrangement and nuclear abnormality in the INL layer.On the 28 th day after 2VO,nuclear fragmentation occurred in the hippocampal CA3.The cells of INL were loosely arranged.Moreover,the number of cells in the GCL and INL decreased after 2VO,and gradually decreased over time.The immunohistochemical staining results showed that compared with the control group,on the 7th day after 2VO,the expression of IBA1 and i NOS increased and expression of TREM2 decreased in hippocampus CA1,CA3 and cerebral cortex.Expression of i NOS increased and expression of TREM2 decreased in DG area.The expression of IBA1,i NOS and TREM2 increased in GCL and IPL of the retina,and the expression of i NOS and TREM2 in INL increased.On the 14 th day after 2VO,the expression of IBA1 and i NOS in the hippocampus CA1,CA3,DG,and cortex increased,and the expression of TREM2 decreased.The expression of IBA1,i NOS,and TREM2 in GCL of the retina increased;the expression of IBA1,i NOS in IPL and INL increased.On the 28 th day after 2VO,the expression of IBA1 increased and the expression of TREM2 decreased in the hippocampal CA1.The expression of IBA1 and i NOS increased,and the expression of TREM2 decreased in hippocampal CA3,DG,and cortex.The expressions of IBA1,i NOS,and TREM2 in GCL,IPL,and INL of the retina increased.Moreover,the positive expression of IBA1 in CA1,and the positive expression of i NOS in DG,cortex and GCL increased with the prolonged ischemic time.Conclusion: 1.The modified 2VO can cause effective ischemia in the brain tissue of mice.2.After cerebral ischemia,the hippocampus,cortex and retina of mice showed certain degree of cell damage.3.After chronic cerebral ischemia,the positive expression of microglia d in hippocampus,cortex and retina increased.4.In general,the activation of MG in the hippocampus and cortex showed an increase in M1 type i NOS and a decrease in M2 type TREM2.In the contrat retinal MG activation showed an increase in both M1 type i NOS and M2 type TREM2.The above results suggest that the brain tissue and MG in the retina have a certain synergistic response to cerebral ischemia.The changes of MG in the retina may indicate inflammatory changes in the brain.But at the same time,there is a certain difference between the expression of M1 and M2 when the MG of the brain and the retina is activated,which requires further studies. |
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