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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

Specialized Reactive Glial Nets (RGNs) form around dense-core Aβ plaques in AD cortex.(a) 3-dimensional reconstruction of a confocal Z-stack showing GFAP+ reactive astrocytes (green) and Iba1+ microglia (magenta) surrounding a Thiazine red-labeled dense-core Aβ plaque (cyan) in an AD patient (female, 77 year old). Note the TR-labeled fibrils surrounding the core of the plaque. (b) 3D analysis of astrocyte and microglia position around a dense-core plaque. (c,d) Quantification of the positioning of astrocytes and microglia relative to plaques and the positive correlation between astrocyte and microglial cell number and plaque size (n = 39). (e) Sequence of 14 successive z- focal planes (1 μm step size) showing amoeboid Iba1+ cells (magenta) enveloping the core of the plaque (cyan) and reactive astrocytes circumscribing them with processes. Note GFAP+ astrocytic processes are excluded from the microglial cell territory. Scale bars: 20 μm.
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f3: Specialized Reactive Glial Nets (RGNs) form around dense-core Aβ plaques in AD cortex.(a) 3-dimensional reconstruction of a confocal Z-stack showing GFAP+ reactive astrocytes (green) and Iba1+ microglia (magenta) surrounding a Thiazine red-labeled dense-core Aβ plaque (cyan) in an AD patient (female, 77 year old). Note the TR-labeled fibrils surrounding the core of the plaque. (b) 3D analysis of astrocyte and microglia position around a dense-core plaque. (c,d) Quantification of the positioning of astrocytes and microglia relative to plaques and the positive correlation between astrocyte and microglial cell number and plaque size (n = 39). (e) Sequence of 14 successive z- focal planes (1 μm step size) showing amoeboid Iba1+ cells (magenta) enveloping the core of the plaque (cyan) and reactive astrocytes circumscribing them with processes. Note GFAP+ astrocytic processes are excluded from the microglial cell territory. Scale bars: 20 μm.

Mentions: Microglia and astrocytes are tightly interleaved among neurons in the healthy brain but undergo extensive structural and molecular changes in AD. However, the role of glial cells and their reorganization in AD is still actively debated5. This is due, in part, to the heterogeneity of their morphology and molecular profile1017303132. To decipher if microglia and astrocytes exhibit specific features around dense-core and fibrillar Aβ deposits and PHF/NFT aggregates, we performed detailed 3D analysis of their spatial organization. This revealed an elaborate 3D glial structure, with an inner sphere of dysmorphic/amoeboid microglia and an outer sphere of hypertrophic astrocytes around dense-core and fibrillar Aβ deposits. Abnormal and swollen axons were largely confined within these structures, being enveloped by microglial and astrocytic processes around both plaque types (Suppl. Fig. 3a,b). Labeling for phosphorylated tau using PS442 and AT8 revealed a strong enrichment of PHFs and NFTs in the vicinity of both dense-core and fibrillar Aβ plaques (Suppl. Fig. 4a) intermingled with microglia (Suppl. Fig. 4c,d) and astrocyte processes (Suppl. Fig. 4b,e), further demonstrating that microglia/astrocyte assemblies structurally define areas of degenerating neuronal processes around Aβ plaques. Together the microglia and astrocytes created a unified structure that we refer to as a reactive glial net (RGN) that is reminiscent of a glial scar but with conserved architecture (Figs 3 and 4).


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)

Specialized Reactive Glial Nets (RGNs) form around dense-core Aβ plaques in AD cortex.(a) 3-dimensional reconstruction of a confocal Z-stack showing GFAP+ reactive astrocytes (green) and Iba1+ microglia (magenta) surrounding a Thiazine red-labeled dense-core Aβ plaque (cyan) in an AD patient (female, 77 year old). Note the TR-labeled fibrils surrounding the core of the plaque. (b) 3D analysis of astrocyte and microglia position around a dense-core plaque. (c,d) Quantification of the positioning of astrocytes and microglia relative to plaques and the positive correlation between astrocyte and microglial cell number and plaque size (n = 39). (e) Sequence of 14 successive z- focal planes (1 μm step size) showing amoeboid Iba1+ cells (magenta) enveloping the core of the plaque (cyan) and reactive astrocytes circumscribing them with processes. Note GFAP+ astrocytic processes are excluded from the microglial cell territory. Scale bars: 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Specialized Reactive Glial Nets (RGNs) form around dense-core Aβ plaques in AD cortex.(a) 3-dimensional reconstruction of a confocal Z-stack showing GFAP+ reactive astrocytes (green) and Iba1+ microglia (magenta) surrounding a Thiazine red-labeled dense-core Aβ plaque (cyan) in an AD patient (female, 77 year old). Note the TR-labeled fibrils surrounding the core of the plaque. (b) 3D analysis of astrocyte and microglia position around a dense-core plaque. (c,d) Quantification of the positioning of astrocytes and microglia relative to plaques and the positive correlation between astrocyte and microglial cell number and plaque size (n = 39). (e) Sequence of 14 successive z- focal planes (1 μm step size) showing amoeboid Iba1+ cells (magenta) enveloping the core of the plaque (cyan) and reactive astrocytes circumscribing them with processes. Note GFAP+ astrocytic processes are excluded from the microglial cell territory. Scale bars: 20 μm.
Mentions: Microglia and astrocytes are tightly interleaved among neurons in the healthy brain but undergo extensive structural and molecular changes in AD. However, the role of glial cells and their reorganization in AD is still actively debated5. This is due, in part, to the heterogeneity of their morphology and molecular profile1017303132. To decipher if microglia and astrocytes exhibit specific features around dense-core and fibrillar Aβ deposits and PHF/NFT aggregates, we performed detailed 3D analysis of their spatial organization. This revealed an elaborate 3D glial structure, with an inner sphere of dysmorphic/amoeboid microglia and an outer sphere of hypertrophic astrocytes around dense-core and fibrillar Aβ deposits. Abnormal and swollen axons were largely confined within these structures, being enveloped by microglial and astrocytic processes around both plaque types (Suppl. Fig. 3a,b). Labeling for phosphorylated tau using PS442 and AT8 revealed a strong enrichment of PHFs and NFTs in the vicinity of both dense-core and fibrillar Aβ plaques (Suppl. Fig. 4a) intermingled with microglia (Suppl. Fig. 4c,d) and astrocyte processes (Suppl. Fig. 4b,e), further demonstrating that microglia/astrocyte assemblies structurally define areas of degenerating neuronal processes around Aβ plaques. Together the microglia and astrocytes created a unified structure that we refer to as a reactive glial net (RGN) that is reminiscent of a glial scar but with conserved architecture (Figs 3 and 4).

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