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M. Paques, M. Simonutti, J.-A. Sahel; In vivo Tracking of Microglial Cells in the Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5927.
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© ARVO (1962-2015); The Authors (2016-present)
Microglial cells (MCs) are active sensors of neural tissues that are rapidly mobilized upon disruption of homeostasis, whatever its cause. A characteristic feature of MCs is their capacity to promptly migrate upon areas of focal damage. Such trafficking of activated MCs has been observed in vitro and ex vivo. Yet, because of experimental constraints, limited in vivo data are available, especially concerning the tracking of individual MCs. Here, we documented the in vivo behavior of MCs in the basal state and following acute focal damage.
The behavior of green fluorescent protein-expressing MCs in the retina of CX3CR1gfp/+ and gfp/gfp mice was observed noninvasively using time-lapse confocal scanning laser ophthalmoscopy. Observations were made in the basal state and following focal laser damage.
In the basal state, permanent, extensive dendritic remodeling of all MCs, and random locomotion of a minor subset of MCs could be evidenced. Mobilization of MCs after focal laser damage, which started 1 hour after and lasted 48-72h, manifested by dendritic reorientation and convergent migration of proximal MCs, but also by nonconvergent migration of a subset of more distal MCs. Consequently, areas around damaged sites were continuously gone through by trafficking MCs. Such mobilization extended several hundred microns from the damaged area. Perivascular MCs showed less reactivity. The level of expression of CX3CR1 expression did not influence this process.
The retina is a privileged site for the in vivo observation of MCs. MCs showed a complex, heterogeneous trafficking, both in the basal state and following acute focal damage. Our procedure may help to decipher the molecular determinants of microglial migration.
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