Comparison of Human Primary microglia and Human iPSC derived microglia cells as in vitro models for microglia activation

AbstractBackgroundMicroglia are resident immune effector cells in the CNS and play an essential role in neuroinflammation, ischemic and neurodegenerative disease. Therefore, microglia cells are considered a potential therapeutic target for neurodegenerative diseases. To fully understand the role of microglia, the preferred strategy would be to study primary human microglia isolated from post‐mortem human brain tissue. Microglia can be isolated from both control and diseased human brain tissue with confirmed neuropathology. However, the obvious limitation on brain collection and yield of isolated cells restricts the ability to perform screening studies. Induced pluripotent stem cells (iPSCs)‐derived microglia, may provide a suitable alternative for screening studies and large‐scale compound validation. Yet, to effectively use iPSC‐derived microglia, one must characterize the extent to which these cells faithfully represent biological processes in primary brain tissue.MethodHere, we compared the gene expression and cytokine release from primary human microglia cells obtained from tissue provided by the Netherlands Brain Bank and iPSC‐derived microglia.ResultExposure of primary and iPSC‐derived microglia to LPS resulted in increased TNF‐α secretion in a concentration and time dependent manner. LPS‐mediated TNF‐α secretion was strongly inhibited by dexamethasone. Priming of primary and iPSC‐derived microglia with LPS and treatment with nigericin, a potent inflammasome activator, resulted in robust secretion of IL‐1β and IL‐18. Furthermore, nigericin induced IL‐1β and IL‐18 release was blocked by the inflammasome inhibitor MCC950 in both cell types. In addition, similarly to in‐house differentiated microglia, commercially available iPSC‐derived microglia (Bit.bio) showed a strong expression of specific markers as well as cytokine response upon LPS treatment.ConclusionTaken together, we successfully demonstrated that primary and iPSC‐derived microglia respond similarly to LPS and nigericin treatment. For these reasons, these cell types could serve as a reliable tool for evaluating the potency and efficacy of prospective drugs for multiple neurological diseases associated with microglia activation, such as Alzheimer’s and Parkinson’s Disease.