Quantifying Microglia Morphology from Photomicrographs of Immunohistochemistry Prepared Tissue Using ImageJ

Young, Kimberly; Morrison, Helena W.

doi:10.3791/57648-v

Cited by 131 publications

(97 citation statements)

References 14 publications

(17 reference statements)

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“…To further assess microglial morphology, 4–5 fields were taken per sample under confocal (Zeiss) at 20 × with a zoom factor 0.6. Images were processed to remove background and skeletonized followed by analysis of branch number, junction number and total branch length per microglia [ 34 ].…”

Section: Methodsmentioning

confidence: 99%

Trem2 H157Y increases soluble TREM2 production and reduces amyloid pathology

Qiao

Chen

Zhong

et al. 2023

Mol Neurodegeneration

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Background The rare p.H157Y variant of TREM2 (Triggering Receptor Expressed on Myeloid Cells 2) was found to increase Alzheimer’s disease (AD) risk. This mutation is located at the cleavage site of TREM2 extracellular domain. Ectopic expression of TREM2-H157Y in HEK293 cells resulted in increased TREM2 shedding. However, the physiological outcomes of the TREM2 H157Y mutation remain unknown in the absence and presence of AD related pathologies. Methods We generated a novel Trem2 H157Y knock-in mouse model through CRISPR/Cas9 technology and investigated the effects of Trem2 H157Y on TREM2 proteolytic processing, synaptic function, and AD-related amyloid pathologies by conducting biochemical assays, targeted mass spectrometry analysis of TREM2, hippocampal electrophysiology, immunofluorescent staining, in vivo micro-dialysis, and cortical bulk RNA sequencing. Results Consistent with previous in vitro findings, Trem2 H157Y increases TREM2 shedding with elevated soluble TREM2 levels in the brain and serum. Moreover, Trem2 H157Y enhances synaptic plasticity without affecting microglial density and morphology, or TREM2 signaling. In the presence of amyloid pathology, Trem2 H157Y accelerates amyloid-β (Aβ) clearance and reduces amyloid burden, dystrophic neurites, and gliosis in two independent founder lines. Targeted mass spectrometry analysis of TREM2 revealed higher ratios of soluble to full-length TREM2-H157Y compared to wild-type TREM2, indicating that the H157Y mutation promotes TREM2 shedding in the presence of Aβ. TREM2 signaling was further found reduced in Trem2 H157Y homozygous mice. Transcriptomic profiling revealed that Trem2 H157Y downregulates neuroinflammation-related genes and an immune module correlated with the amyloid pathology. Conclusion Taken together, our findings suggest beneficial effects of the Trem2 H157Y mutation in synaptic function and in mitigating amyloid pathology. Considering the genetic association of TREM2 p.H157Y with AD risk, we speculate TREM2 H157Y in humans might increase AD risk through an amyloid-independent pathway, such as its effects on tauopathy and neurodegeneration which merit further investigation.

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Section: Methodsmentioning

confidence: 99%

Trem2 H157Y increases soluble TREM2 production and reduces amyloid pathology

Qiao

Chen

Zhong

et al. 2023

Mol Neurodegeneration

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“…Z-stacks were z-projected and converted to grayscale. Skeleton analysis was performed in the z-stacks derived from the OPL using the ImageJ 1.52 h software according to a published protocol [ 46 ]. The total branch length and the total number of endpoints per image were divided by the number of Iba-1 pos cells in each image.…”

Section: Methodsmentioning

confidence: 99%

Endothelial Toll-like receptor 4 is required for microglia activation in the murine retina after systemic lipopolysaccharide exposure

Tsioti

Steiner

Escher

et al. 2023

J Neuroinflammation

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Background Clustering of microglia around the vasculature has been reported in the retina and the brain after systemic administration of lipopolysaccharides (LPS) in mice. LPS acts via activation of Toll-like receptor 4 (TRL4), which is expressed in several cell types including microglia, monocytes and vascular endothelial cells. The purpose of this study was to investigate the effect of systemic LPS in the pigmented mouse retina and the involvement of endothelial TLR4 in LPS-induced retinal microglia activation. Methods C57BL/6J, conditional knockout mice that lack Tlr4 expression selectively on endothelial cells (TekCre−posTlr4loxP/loxP) and TekCre−negTlr4loxP/loxP mice were used. The mice were injected with 1 mg/kg LPS via the tail vein once per day for a total of 4 days. Prior to initiation of LPS injections and approximately 5 h after the last injection, in vivo imaging using fluorescein angiography and spectral-domain optical coherence tomography was performed. Immunohistochemistry, flow cytometry, electroretinography and transmission electron microscopy were utilized to investigate the role of endothelial TLR4 in LPS-induced microglia activation and retinal function. Results Activation of microglia, infiltration of monocyte-derived macrophages, impaired ribbon synapse organization and retinal dysfunction were observed after the LPS exposure in C57BL/6J and TekCre−negTlr4loxP/loxP mice. None of these effects were observed in the retinas of conditional Tlr4 knockout mice after the LPS challenge. Conclusions The findings of the present study suggest that systemic LPS exposure can have detrimental effects in the healthy retina and that TLR4 expressed on endothelial cells is essential for retinal microglia activation and retinal dysfunction upon systemic LPS challenge. This important finding provides new insights into the role of microglia–endothelial cell interaction in inflammatory retinal disease.

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“…They can sense an inflammatory response and become reactive following infiltration into the site of injury [34]. Reactive microglia undergo several morphological changes based on their activity level [35]. In AD, excessive Aβ accumulation promotes microgliosis [36].…”

Section: Discussionmentioning

confidence: 99%

Severe histomorphological alterations in post‐mortem olfactory glomeruli in Alzheimer’s disease

et al. 2021

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Alzheimer's disease (AD) is the most prevalent form of dementia. Key AD symptoms include memory and cognitive decline; however, comorbid symptoms such as depression and sensory-perceptual dysfunction are often reported. Among these, a deterioration of olfactory sensation is observed in approximately 90% of AD patients. However, the precise pathophysiological basis underlying olfactory deficits because of AD remains elusive. The olfactory glomeruli in the olfactory bulb (OB) receive sensory information in the olfactory processing pathway. Maintaining the structural and functional integrity of the olfactory glomerulus is critical to olfactory signalling. Herein, we conducted an in-depth histopathological assessment to reveal detailed structural alterations in the olfactory glomeruli in AD patients. Fresh frozen post-mortem OB specimens obtained from six AD patients and seven healthy age-matched individuals were examined. We used combined immunohistochemistry and stereology to assess the gross morphology and histological alterations, such as those in the expression of Aβ protein, microglia, and neurotransmitters in the OB. Electron microscopy was employed to study the ultrastructural features in the glomeruli.Significant accumulation of Aβ, morphologic damage, altered neurotransmitter levels, and microgliosis in the olfactory glomeruli of AD patients suggests that glomerular damage could affect olfactory function. Moreover, greater neurodegeneration was observed in the ventral olfactory glomeruli of AD patients. The synaptic ultrastructure revealed distorted postsynaptic densities and a decline in presynaptic vesicles in AD specimens. These findings show that the primary K E Y W O R D S Alzheimer's disease, morphology, olfactory bulb, post-mortem histology, ultrastructure

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Quantifying Microglia Morphology from Photomicrographs of Immunohistochemistry Prepared Tissue Using ImageJ

Cited by 131 publications

References 14 publications

Trem2 H157Y increases soluble TREM2 production and reduces amyloid pathology

Trem2 H157Y increases soluble TREM2 production and reduces amyloid pathology

Endothelial Toll-like receptor 4 is required for microglia activation in the murine retina after systemic lipopolysaccharide exposure

Severe histomorphological alterations in post‐mortem olfactory glomeruli in Alzheimer’s disease

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