Modeling microglial activation in Alzheimer’s disease with human postmortem microglial cultures

Alzheimer’s disease (AD) is a uniquely human disorder. Despite intense research, the lack of availability of model systems has hindered AD studies though in recent years transgenic mouse models have been produced, which develop AD-like amyloid beta peptide (Aβ) plaques. For the study of inflammatory changes in AD brains, these transgenic mice may have limitations due to differences in the innate immune system of humans and rodents. Many studies of inflammatory processes in AD have focused on the role of activated microglia. Over the last 8 years, our research has focused on the properties of human microglia cultured from brain tissues of AD and non-demented (ND) individuals. As these are the cells observed to be activated in AD tissues, they represent a useful system for modeling the inflammatory components of AD. In this review, we summarize data by our group and others on the use of microglia for AD-related inflammatory research, with emphasis on results using human postmortem brain microglia. A range of products have been shown to be produced by human postmortem microglia, both constitutively and in response to treatment with Aβ, including proinflammatory cytokines such as interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF) α, and macrophage colony stimulating factor (M-CSF), along with complement proteins, especially C1q, superoxide radicals and neurotoxic factors. In our studies, we have demonstrated that there was a significant difference between AD and ND microglia in terms of their secretion of M-CSF and C1q. We also discuss the role of putative Aβ microglial receptors, particular recent data showing a role for the receptor for advanced glycation endproducts (RAGE) in mediating the responses of human microglia to Aβ. Finally, our studies on the use of an Aβ spot paradigm to model microglia interactions with plaques demonstrated that many of the features of AD inflammation can be modeled with postmortem brain derived microglia.