Microglia Increase Inflammatory Responses in iPSC-Derived Human BrainSpheres.

Celina Monteiro Abreu,Helena T Hogberg,Thomas Hartung,Susanne Krasemann,Megan Chesnut,David Pamies,Shelly Odwin-Dacosta,Lucio Gama

doi:10.3389/fmicb.2018.02766

Abstract

Human induced pluripotent stem cells (iPSCs), together with 21st century cell culture methods, have the potential to better model human physiology with applications in toxicology, disease modeling, and the study of host-pathogen interactions. Several models of the human brain have been developed recently, demonstrating cell-cell interactions of multiple cell types with physiologically relevant 3D structures. Most current models, however, lack the ability to represent the inflammatory response in the brain because they do not include a microglial cell population. Microglia, the resident immunocompetent phagocytes in the central nervous system (CNS), are not only important in the inflammatory response and pathogenesis; they also function in normal brain development, strengthen neuronal connections through synaptic pruning, and are involved in oligodendrocyte and neuronal survival. Here, we have successfully introduced a population of human microglia into 3D human iPSC-derived brain spheres (BrainSpheres, BS) through co-culturing cells of the Immortalized Human Microglia – SV40 cell line with the BS model (μBS). We detected an inflammatory response to lipopolysaccharides (LPS) and flavivirus infection, which was only elicited in the model when microglial cells were present. A concentration of 20 ng/mL of LPS increased gene expression of the inflammatory cytokines interleukin-6 (IL-6), IL-10, and IL-1β, with maximum expression at 6–12 h post-exposure. Increased expression of the IL-6, IL-1β, tumor necrosis factor alpha (TNF-α), and chemokine (C-C motif) ligand 2 (CCL2) genes was observed in μBS following infection with Zika and Dengue Virus, suggesting a stronger inflammatory response in the model when microglia were present than when only astrocyte, oligodendrocyte, and neuronal populations were represented. Microglia innately develop within cerebral organoids (Nature communications)1, our findings suggest that the μBS model is more physiologically relevant and has potential applications in infectious disease and host-pathogen interactions research.

Highlights

Microphysiological systems and organotypic cell culture models are increasingly being used to model human physiology in vitro because these models better mimic the in vivo situation compared to traditional monolayer cell culture systems (Marx et al, 2016; Pamies and Hartung, 2017; Smirnova et al, 2018)
Microglia innately develop within cerebral organoids (Nature communications)1, our findings suggest that the μBS model is more physiologically relevant and has potential applications in infectious disease and host-pathogen interactions research
The basis for the majority of these models is a neural progenitor cell (NPC) population; microglia, arise from erythromyeloid precursor cells in the embryonic yolk sac, unlike the other cell types in the brain which arise from the neuroectoderm (Alliot et al, 1999; Ginhoux et al, 2013; Kierdorf et al, 2013; Sousa et al, 2017)

Summary

Introduction

Microphysiological systems and organotypic cell culture models are increasingly being used to model human physiology in vitro because these models better mimic the in vivo situation compared to traditional monolayer cell culture systems (Marx et al, 2016; Pamies and Hartung, 2017; Smirnova et al, 2018). Increased expression of the IL6, IL-1β, tumor necrosis factor alpha (TNF-α), and chemokine (C-C motif) ligand 2 (CCL2) genes was observed in μBS following infection with Zika and Dengue Virus, suggesting a stronger inflammatory response in the model when microglia were present than when only astrocyte, oligodendrocyte, and neuronal populations were represented.

Results

Conclusion