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A new approach for ratiometric in vivo calcium imaging of microglia

Brawek, Bianca; Liang, Yajie; Savitska, Daria; Li, Kaizhen; Fomin-Thunemann, Natalie; Kovalchuk, Yury; Zirdum, Elizabeta; Jakobsson, Johan LU and Garaschuk, Olga (2017) In Scientific Reports 7(1).
Abstract

Microglia, resident immune cells of the brain, react to the presence of pathogens/danger signals with a large repertoire of functional responses including morphological changes, proliferation, chemotaxis, production/release of cytokines, and phagocytosis. In vitro studies suggest that many of these effector functions are Ca2+-dependent, but our knowledge about in vivo Ca2+ signalling in microglia is rudimentary. This is mostly due to technical reasons, as microglia largely resisted all attempts of in vivo labelling with Ca2+ indicators. Here, we introduce a novel approach, utilizing a microglia-specific microRNA-9-regulated viral vector, enabling the expression of a genetically-encoded ratiometric... (More)

Microglia, resident immune cells of the brain, react to the presence of pathogens/danger signals with a large repertoire of functional responses including morphological changes, proliferation, chemotaxis, production/release of cytokines, and phagocytosis. In vitro studies suggest that many of these effector functions are Ca2+-dependent, but our knowledge about in vivo Ca2+ signalling in microglia is rudimentary. This is mostly due to technical reasons, as microglia largely resisted all attempts of in vivo labelling with Ca2+ indicators. Here, we introduce a novel approach, utilizing a microglia-specific microRNA-9-regulated viral vector, enabling the expression of a genetically-encoded ratiometric Ca2+ sensor Twitch-2B in microglia. The Twitch-2B-assisted in vivo imaging enables recording of spontaneous and evoked microglial Ca2+ signals and allows for the first time to monitor the steady state intracellular Ca2+ levels in microglia. Intact in vivo microglia show very homogenous and low steady state intracellular Ca2+ levels. However, the levels increase significantly after acute slice preparation and cell culturing along with an increase in the expression of activation markers CD68 and IL-1β. These data identify the steady state intracellular Ca2+ level as a versatile microglial activation marker, which is highly sensitive to the cell's environment.

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publication status
published
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in
Scientific Reports
volume
7
issue
1
publisher
Nature Publishing Group
external identifiers
  • scopus:85025445357
  • wos:000405907800084
ISSN
2045-2322
DOI
10.1038/s41598-017-05952-3
language
English
LU publication?
yes
id
9308d5f2-10ff-42e7-b0b9-dba61789eb7f
date added to LUP
2017-11-22 08:22:24
date last changed
2018-05-27 04:47:33
@article{9308d5f2-10ff-42e7-b0b9-dba61789eb7f,
  abstract     = {<p>Microglia, resident immune cells of the brain, react to the presence of pathogens/danger signals with a large repertoire of functional responses including morphological changes, proliferation, chemotaxis, production/release of cytokines, and phagocytosis. In vitro studies suggest that many of these effector functions are Ca<sup>2+</sup>-dependent, but our knowledge about in vivo Ca<sup>2+</sup> signalling in microglia is rudimentary. This is mostly due to technical reasons, as microglia largely resisted all attempts of in vivo labelling with Ca<sup>2+</sup> indicators. Here, we introduce a novel approach, utilizing a microglia-specific microRNA-9-regulated viral vector, enabling the expression of a genetically-encoded ratiometric Ca<sup>2+</sup> sensor Twitch-2B in microglia. The Twitch-2B-assisted in vivo imaging enables recording of spontaneous and evoked microglial Ca<sup>2+</sup> signals and allows for the first time to monitor the steady state intracellular Ca<sup>2+</sup> levels in microglia. Intact in vivo microglia show very homogenous and low steady state intracellular Ca<sup>2+</sup> levels. However, the levels increase significantly after acute slice preparation and cell culturing along with an increase in the expression of activation markers CD68 and IL-1β. These data identify the steady state intracellular Ca<sup>2+</sup> level as a versatile microglial activation marker, which is highly sensitive to the cell's environment.</p>},
  articleno    = {6030},
  author       = {Brawek, Bianca and Liang, Yajie and Savitska, Daria and Li, Kaizhen and Fomin-Thunemann, Natalie and Kovalchuk, Yury and Zirdum, Elizabeta and Jakobsson, Johan and Garaschuk, Olga},
  issn         = {2045-2322},
  language     = {eng},
  month        = {12},
  number       = {1},
  publisher    = {Nature Publishing Group},
  series       = {Scientific Reports},
  title        = {A new approach for ratiometric in vivo calcium imaging of microglia},
  url          = {http://dx.doi.org/10.1038/s41598-017-05952-3},
  volume       = {7},
  year         = {2017},
}