Tools and Approaches for Studying Microglia In vivo

Eme‐Scolan, Elisa; Dando, Samantha J.

doi:10.3389/fimmu.2020.583647

Cited by 42 publications

(40 citation statements)

References 97 publications

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“…Unfortunately, further investigation of reciprocal neuron-astrocyte interactions have long been hindered due to the lack of selective tools to modulate astrocytic GPCR signalling [ 34 , 35 ]. Designer receptors exclusively activated by designer drugs (DREADDs) are an interesting tool to tackle these issues as they use GPCR-mediated intracellular signal transduction pathways naturally present in astrocytes.…”

Section: Introductionmentioning

confidence: 99%

Side-by-side comparison of the effects of Gq- and Gi-DREADD-mediated astrocyte modulation on intracellular calcium dynamics and synaptic plasticity in the hippocampal CA1

et al. 2021

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Astrocytes express a plethora of G protein-coupled receptors (GPCRs) that are crucial for shaping synaptic activity. Upon GPCR activation, astrocytes can respond with transient variations in intracellular Ca2+. In addition, Ca2+-dependent and/or Ca2+-independent release of gliotransmitters can occur, allowing them to engage in bidirectional neuron-astrocyte communication. The development of designer receptors exclusively activated by designer drugs (DREADDs) has facilitated many new discoveries on the roles of astrocytes in both physiological and pathological conditions. They are an excellent tool, as they can target endogenous GPCR-mediated intracellular signal transduction pathways specifically in astrocytes. With increasing interest and accumulating research on this topic, several discrepancies on astrocytic Ca2+ signalling and astrocyte-mediated effects on synaptic plasticity have emerged, preventing a clear-cut consensus about the downstream effects of DREADDs in astrocytes. In the present study, we performed a side-by-side evaluation of the effects of bath application of the DREADD agonist, clozapine-N-oxide (10 µM), on Gq- and Gi-DREADD activation in mouse CA1 hippocampal astrocytes. In doing so, we aimed to avoid confounding factors, such as differences in experimental procedures, and to directly compare the actions of both DREADDs on astrocytic intracellular Ca2+ dynamics and synaptic plasticity in acute hippocampal slices. We used an adeno-associated viral vector approach to transduce dorsal hippocampi of male, 8-week-old C57BL6/J mice, to drive expression of either the Gq-DREADD or Gi-DREADD in CA1 astrocytes. A viral vector lacking the DREADD construct was used to generate controls. Here, we show that agonism of Gq-DREADDs, but not Gi-DREADDs, induced consistent increases in spontaneous astrocytic Ca2+ events. Moreover, we demonstrate that both Gq-DREADD as well as Gi-DREADD-mediated activation of CA1 astrocytes induces long-lasting synaptic potentiation in the hippocampal CA1 Schaffer collateral pathway in the absence of a high frequency stimulus. Moreover, we report for the first time that astrocytic Gi-DREADD activation is sufficient to elicit de novo potentiation. Our data demonstrate that activation of either Gq or Gi pathways drives synaptic potentiation through Ca2+-dependent and Ca2+-independent mechanisms, respectively.

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Section: Introductionmentioning

confidence: 99%

Side-by-side comparison of the effects of Gq- and Gi-DREADD-mediated astrocyte modulation on intracellular calcium dynamics and synaptic plasticity in the hippocampal CA1

et al. 2021

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“…A special group of tissue macrophages is microglial cells of the central nervous system (CNS) [78]. These cells have recently become a focus of interest, as they have an important function during CNS neuroinflammation and disease [79]. Different mouse reporter lines were used, and most of them bear the fractalkine receptor gene Cx3cr1 [80].…”

Section: Reporter Genesmentioning

confidence: 99%

“…Different mouse reporter lines were used, and most of them bear the fractalkine receptor gene Cx3cr1 [80]. However, this gene is expressed not only in microglia but also in other immune cells [79]. Nowadays, a new generation of microglial mouse reporter lines has been generated in which the reporter protein is mostly restricted to microglial cells [81][82][83].…”

Section: Reporter Genesmentioning

confidence: 99%

Macrophage Identification In Situ

Nikovics¹,

Favier²

2021

Biomedicines

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Understanding the processes of inflammation and tissue regeneration after injury is of great importance. For a long time, macrophages have been known to play a central role during different stages of inflammation and tissue regeneration. However, the molecular and cellular mechanisms by which they exert their effects are as yet mostly unknown. While in vitro macrophages have been characterized, recent progress in macrophage biology studies revealed that macrophages in vivo exhibited distinctive features. Actually, the precise characterization of the macrophages in vivo is essential to develop new healing treatments and can be approached via in situ analyses. Nowadays, the characterization of macrophages in situ has improved significantly using antigen surface markers and cytokine secretion identification resulting in specific patterns. This review aims for a comprehensive overview of different tools used for in situ macrophage identification, reporter genes, immunolabeling and in situ hybridization, discussing their advantages and limitations.

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“…In this context signature genes of microglia of the homoeostatic brain were identified, including Tmem119 , Sall1 , P2ry12 , Olfml3 , Hexb , Fcrls , Siglech , Tgfbr1, and Gpr34 [ 60 , 105 , 108 , 109 , 110 , 111 , 112 ]. A part of these genes was used to develop new reporter mice to label and/or genetically manipulate the microglia cell population [ 113 ]: Tmem119 eGFP and Tmem119 CreERT2 [ 114 ], Tmem119 TdTomato [ 115 ], Sall1 GFP , and Sall1 CreER [ 116 , 117 ], and Hexb TdTomato and Hexb CreERT2 [ 118 ], and P2ry12 CreER [ 119 ].…”

Section: Distinction Of Microglia and Macrophages In Gliomamentioning

confidence: 99%

Distinction of Microglia and Macrophages in Glioblastoma: Close Relatives, Different Tasks?

Brandenburg

Blank

Bungert

et al. 2020

IJMS

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For decades, it has been known that the tumor microenvironment is significant for glioma progression, namely the infiltration of myeloid cells like microglia and macrophages. Hence, these cell types and their specific tasks in tumor progression are subject to ongoing research. However, the distribution of the brain resident microglia and the peripheral macrophages within the tumor tissue and their functional activity are highly debated. Results depend on the method used to discriminate between microglia and macrophages, whereby this specification is already difficult due to limited options to distinguish between these both cell populations that show mostly the same surface markers and morphology. Moreover, there are indications about various functions of microglia and macrophages but again varying on the method of discrimination. In our review, we summarize the current literature to determine which methods have been applied to differentiate the brain resident microglia from tumor-infiltrated macrophages. Furthermore, we compiled data about the proportion of microglia and macrophages in glioma tissues and ascertained if pro- or anti-tumoral effects could be allocated to one or the other myeloid cell population. Recent research made tremendous efforts to distinguish microglia from recruited macrophages. For future studies, it could be essential to verify which role these cells play in brain tumor pathology to proceed with novel immunotherapeutic strategies.

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Tools and Approaches for Studying Microglia In vivo

Cited by 42 publications

References 97 publications

Side-by-side comparison of the effects of Gq- and Gi-DREADD-mediated astrocyte modulation on intracellular calcium dynamics and synaptic plasticity in the hippocampal CA1

Side-by-side comparison of the effects of Gq- and Gi-DREADD-mediated astrocyte modulation on intracellular calcium dynamics and synaptic plasticity in the hippocampal CA1

Macrophage Identification In Situ

Distinction of Microglia and Macrophages in Glioblastoma: Close Relatives, Different Tasks?

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