Phagocytosis Assay of Microglia for Dead Neurons in Primary Rat Brain Cell Cultures

Clearance of dead brain tissue including the dead neurons through phagocytosis is an endogenous function of microglia in the brain, which is critical for inflammation resolution after ischemic stroke or head trauma. By regulating the function or polarization status of microglia, we may control their phagocytosis efficacy and therefore the cleanup process for the dead brain tissue. We cultured rat cortical neurons and microglia from the same litter of embryos. The cultured neurons are subjected to irradiation for inducing neuronal apoptosis. After labeling with propidium iodide (PI), the dead neurons (DNs) are exposed to the cultured microglia for phagocytosis assay. By counting the number of DNs in each microglia, we calculate the phagocytosis index to quantify the phagocytosis efficacy of microglia toward DNs. The protocol is divided into 4 sections: A) culturing rat cortical neurons from pre-natal rat embryos, B) preparing dead neurons as phagocytosis target, C) culturing rat brain microglia, D) quantifying phagocytosis index of microglia toward the dead neurons.