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High Resolution Dissection of Reactive Glial Nets in Alzheimer's Disease.

Bouvier DS, Jones EV, Quesseveur G, Davoli MA, A Ferreira T, Quirion R, Mechawar N, Murai KK - Sci Rep (2016)

Bottom Line: Applying the method to AD samples, we expose complex features of microglial cells and astrocytes in the disease.Through this methodology, we show that these cells form specialized 3D structures in AD that we refer to as reactive glial nets (RGNs).The method provided here will help reveal novel features of the healthy and diseased human brain, and aid experimental design in translational brain research.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.

ABSTRACT
Fixed human brain samples in tissue repositories hold great potential for unlocking complexities of the brain and its alteration with disease. However, current methodology for simultaneously resolving complex three-dimensional (3D) cellular anatomy and organization, as well as, intricate details of human brain cells in tissue has been limited due to weak labeling characteristics of the tissue and high background levels. To expose the potential of these samples, we developed a method to overcome these major limitations. This approach offers an unprecedented view of cytoarchitecture and subcellular detail of human brain cells, from cellular networks to individual synapses. Applying the method to AD samples, we expose complex features of microglial cells and astrocytes in the disease. Through this methodology, we show that these cells form specialized 3D structures in AD that we refer to as reactive glial nets (RGNs). RGNs are areas of concentrated neuronal injury, inflammation, and tauopathy and display unique features around β-amyloid plaque types. RGNs have conserved properties in an AD mouse model and display a developmental pattern coinciding with the progressive accumulation of neuropathology. The method provided here will help reveal novel features of the healthy and diseased human brain, and aid experimental design in translational brain research.

No MeSH data available.


Related in: MedlinePlus

Human RGNs are associated with inflammation in AD.(a–c) RGN astrocytes in AD tissue express the pro-inflammatory cytokines IL-6 and IL-1β and the IL-1β processing enzyme Caspase 1. (a) 3D projection showing IL-6-expressing GFAP+ astrocytes near an Aβ plaque in AD cortex (male, 87 years old). Overlay shows IL-6 (magenta), GFAP (green), and Thiazine red (cyan). (b) 3D projection showing IL-1β expression (magenta) in GFAP+ astrocytes (green) around an Thiazine red-labeled Aβ plaque (cyan). (c) Reactive astrocytes (magenta) close to Aβ plaques (blue; dotted ellipse) also express the IL-1β processing enzyme Caspase 1 (green; arrowhead) in the same AD patient. (d,e) Astrocyte are sources of pro-inflammatory cytokines inside and outside RGNs: Examples of astrocytic IL-6 (d, magenta) and IL-1β (e, magenta) expression inside and outside RGNs with the local astrocyte network (GFAP+, green) in AD cortex. Scale bars: 20 μm (a,b,d,e), 10 μm (c).
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f6: Human RGNs are associated with inflammation in AD.(a–c) RGN astrocytes in AD tissue express the pro-inflammatory cytokines IL-6 and IL-1β and the IL-1β processing enzyme Caspase 1. (a) 3D projection showing IL-6-expressing GFAP+ astrocytes near an Aβ plaque in AD cortex (male, 87 years old). Overlay shows IL-6 (magenta), GFAP (green), and Thiazine red (cyan). (b) 3D projection showing IL-1β expression (magenta) in GFAP+ astrocytes (green) around an Thiazine red-labeled Aβ plaque (cyan). (c) Reactive astrocytes (magenta) close to Aβ plaques (blue; dotted ellipse) also express the IL-1β processing enzyme Caspase 1 (green; arrowhead) in the same AD patient. (d,e) Astrocyte are sources of pro-inflammatory cytokines inside and outside RGNs: Examples of astrocytic IL-6 (d, magenta) and IL-1β (e, magenta) expression inside and outside RGNs with the local astrocyte network (GFAP+, green) in AD cortex. Scale bars: 20 μm (a,b,d,e), 10 μm (c).

Mentions: We next determined if the inflammatory features of mouse RGNs corresponded to those in AD. We observed that reactive human astrocytes, and not microglia, were also major source of IL-6 and IL-1β in AD, with highest levels of expression in RGN astrocytes around both dense-core and fibrillar plaques (Fig. 6a,b). Lower intensity staining of IL-6 and IL-1β was observed in neuronal-like structure around plaques and in some instances, both cytokines were localized in isolated reactive astrocytes beyond RGNs, potentially indicating a spread of expression of pro-inflammatory factors into adjacent areas (Fig. 6d,e) Along with IL-6 and IL-1β, caspase 1 (an enzyme that cleaves IL-1β into its mature form)42 was accumulated in RGN astrocytes, further demonstrating that astrocytes have detectable levels of molecular components needed for the processing and activation of IL-1β (Fig. 6c).


High Resolution Dissection of Reactive Glial Nets in Alzheimer's Disease.

Bouvier DS, Jones EV, Quesseveur G, Davoli MA, A Ferreira T, Quirion R, Mechawar N, Murai KK - Sci Rep (2016)

Human RGNs are associated with inflammation in AD.(a–c) RGN astrocytes in AD tissue express the pro-inflammatory cytokines IL-6 and IL-1β and the IL-1β processing enzyme Caspase 1. (a) 3D projection showing IL-6-expressing GFAP+ astrocytes near an Aβ plaque in AD cortex (male, 87 years old). Overlay shows IL-6 (magenta), GFAP (green), and Thiazine red (cyan). (b) 3D projection showing IL-1β expression (magenta) in GFAP+ astrocytes (green) around an Thiazine red-labeled Aβ plaque (cyan). (c) Reactive astrocytes (magenta) close to Aβ plaques (blue; dotted ellipse) also express the IL-1β processing enzyme Caspase 1 (green; arrowhead) in the same AD patient. (d,e) Astrocyte are sources of pro-inflammatory cytokines inside and outside RGNs: Examples of astrocytic IL-6 (d, magenta) and IL-1β (e, magenta) expression inside and outside RGNs with the local astrocyte network (GFAP+, green) in AD cortex. Scale bars: 20 μm (a,b,d,e), 10 μm (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835751&req=5

f6: Human RGNs are associated with inflammation in AD.(a–c) RGN astrocytes in AD tissue express the pro-inflammatory cytokines IL-6 and IL-1β and the IL-1β processing enzyme Caspase 1. (a) 3D projection showing IL-6-expressing GFAP+ astrocytes near an Aβ plaque in AD cortex (male, 87 years old). Overlay shows IL-6 (magenta), GFAP (green), and Thiazine red (cyan). (b) 3D projection showing IL-1β expression (magenta) in GFAP+ astrocytes (green) around an Thiazine red-labeled Aβ plaque (cyan). (c) Reactive astrocytes (magenta) close to Aβ plaques (blue; dotted ellipse) also express the IL-1β processing enzyme Caspase 1 (green; arrowhead) in the same AD patient. (d,e) Astrocyte are sources of pro-inflammatory cytokines inside and outside RGNs: Examples of astrocytic IL-6 (d, magenta) and IL-1β (e, magenta) expression inside and outside RGNs with the local astrocyte network (GFAP+, green) in AD cortex. Scale bars: 20 μm (a,b,d,e), 10 μm (c).
Mentions: We next determined if the inflammatory features of mouse RGNs corresponded to those in AD. We observed that reactive human astrocytes, and not microglia, were also major source of IL-6 and IL-1β in AD, with highest levels of expression in RGN astrocytes around both dense-core and fibrillar plaques (Fig. 6a,b). Lower intensity staining of IL-6 and IL-1β was observed in neuronal-like structure around plaques and in some instances, both cytokines were localized in isolated reactive astrocytes beyond RGNs, potentially indicating a spread of expression of pro-inflammatory factors into adjacent areas (Fig. 6d,e) Along with IL-6 and IL-1β, caspase 1 (an enzyme that cleaves IL-1β into its mature form)42 was accumulated in RGN astrocytes, further demonstrating that astrocytes have detectable levels of molecular components needed for the processing and activation of IL-1β (Fig. 6c).

Bottom Line: Applying the method to AD samples, we expose complex features of microglial cells and astrocytes in the disease.Through this methodology, we show that these cells form specialized 3D structures in AD that we refer to as reactive glial nets (RGNs).The method provided here will help reveal novel features of the healthy and diseased human brain, and aid experimental design in translational brain research.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.

ABSTRACT
Fixed human brain samples in tissue repositories hold great potential for unlocking complexities of the brain and its alteration with disease. However, current methodology for simultaneously resolving complex three-dimensional (3D) cellular anatomy and organization, as well as, intricate details of human brain cells in tissue has been limited due to weak labeling characteristics of the tissue and high background levels. To expose the potential of these samples, we developed a method to overcome these major limitations. This approach offers an unprecedented view of cytoarchitecture and subcellular detail of human brain cells, from cellular networks to individual synapses. Applying the method to AD samples, we expose complex features of microglial cells and astrocytes in the disease. Through this methodology, we show that these cells form specialized 3D structures in AD that we refer to as reactive glial nets (RGNs). RGNs are areas of concentrated neuronal injury, inflammation, and tauopathy and display unique features around β-amyloid plaque types. RGNs have conserved properties in an AD mouse model and display a developmental pattern coinciding with the progressive accumulation of neuropathology. The method provided here will help reveal novel features of the healthy and diseased human brain, and aid experimental design in translational brain research.

No MeSH data available.


Related in: MedlinePlus