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Toll-like Receptor 2 is Dispensable for an Immediate-early Microglial Reaction to Two-photon Laser-induced Cortical Injury In vivo.

Yoon H, Jang YH, Kim SJ, Lee SJ, Kim SK - Korean J. Physiol. Pharmacol. (2015)

Bottom Line: Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults.Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity.Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 130-701, Korea.

ABSTRACT
Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults. Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity. Although many previous studies have suggested that TLR2 contributes to microglial activation and subsequent pathogenesis following brain tissue injury, it is still unclear whether TLR2 has a role in microglia dynamics in the resting state or in immediate-early reaction to the injury in vivo. By using in vivo two-photon microscopy imaging and Cx3cr1 (GFP/+) mouse line, we first monitored the motility of microglial processes (i.e. the rate of extension and retraction) in the somatosensory cortex of living TLR2-KO and WT mice; Microglial processes in TLR2-KO mice show the similar motility to that of WT mice. We further found that microglia rapidly extend their processes to the site of local tissue injury induced by a two-photon laser ablation and that such microglial response to the brain injury was similar between WT and TLR2-KO mice. These results indicate that there are no differences in the behavior of microglial processes between TLR2-KO mice and WT mice when microglia is in the resting state or encounters local injury. Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

No MeSH data available.


Related in: MedlinePlus

The motility of microglial processes in TLR2-KO and WT mice. (A, B) Representative images for the maximum-intensity projections of an individual microglia from 0 min to 60 min after the starting of two-photon time series imaging in WT (A) and TLR2-KO (B) mice. Arrowheads indicate the extension (red) and retraction (white) of microglial processe (open: previous process; filled: extended or retracted one). (C) Length changes of microglial processes (extension and retraction) in TLR2-KO (n=87 processes/7 cells/3 mice) and WT (n=105 processes/9 cells/4 mice) mice. ns, no significant difference between the two groups. Data are presented as mean±SEM.
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Figure 1: The motility of microglial processes in TLR2-KO and WT mice. (A, B) Representative images for the maximum-intensity projections of an individual microglia from 0 min to 60 min after the starting of two-photon time series imaging in WT (A) and TLR2-KO (B) mice. Arrowheads indicate the extension (red) and retraction (white) of microglial processe (open: previous process; filled: extended or retracted one). (C) Length changes of microglial processes (extension and retraction) in TLR2-KO (n=87 processes/7 cells/3 mice) and WT (n=105 processes/9 cells/4 mice) mice. ns, no significant difference between the two groups. Data are presented as mean±SEM.

Mentions: By using in vivo two-photon microscopy imaging through a cranial window, we first observed the resting state dynamics of microglial processes for an hour in the intact somatosensory cortex of TLR2-KO or WT mice. As shown in Fig. 1A and 1B, the resting microglia in the both groups of mice had a small rod-shaped soma and ramified processes. Their processes continually extended and retracted, but microglial soma remained fixed (Fig. 1A and 1B). To quantify the motility (i.e. extension and retraction) of resting microglial processes, we measured the length changes of individual processes every five minutes. Fig. 1c shows that there was no significant difference in the motility of microglial processes between the TLR2-KO and WT mice (p>0.05). Imaging through a thinned-skull cranial window showed a similar shape and motility of microglia in WT mice to that obtained through an open-skull window (Fig. 2), indicating that our craniotomy procedure does not alter a physiological condition of microglia.


Toll-like Receptor 2 is Dispensable for an Immediate-early Microglial Reaction to Two-photon Laser-induced Cortical Injury In vivo.

Yoon H, Jang YH, Kim SJ, Lee SJ, Kim SK - Korean J. Physiol. Pharmacol. (2015)

The motility of microglial processes in TLR2-KO and WT mice. (A, B) Representative images for the maximum-intensity projections of an individual microglia from 0 min to 60 min after the starting of two-photon time series imaging in WT (A) and TLR2-KO (B) mice. Arrowheads indicate the extension (red) and retraction (white) of microglial processe (open: previous process; filled: extended or retracted one). (C) Length changes of microglial processes (extension and retraction) in TLR2-KO (n=87 processes/7 cells/3 mice) and WT (n=105 processes/9 cells/4 mice) mice. ns, no significant difference between the two groups. Data are presented as mean±SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4553406&req=5

Figure 1: The motility of microglial processes in TLR2-KO and WT mice. (A, B) Representative images for the maximum-intensity projections of an individual microglia from 0 min to 60 min after the starting of two-photon time series imaging in WT (A) and TLR2-KO (B) mice. Arrowheads indicate the extension (red) and retraction (white) of microglial processe (open: previous process; filled: extended or retracted one). (C) Length changes of microglial processes (extension and retraction) in TLR2-KO (n=87 processes/7 cells/3 mice) and WT (n=105 processes/9 cells/4 mice) mice. ns, no significant difference between the two groups. Data are presented as mean±SEM.
Mentions: By using in vivo two-photon microscopy imaging through a cranial window, we first observed the resting state dynamics of microglial processes for an hour in the intact somatosensory cortex of TLR2-KO or WT mice. As shown in Fig. 1A and 1B, the resting microglia in the both groups of mice had a small rod-shaped soma and ramified processes. Their processes continually extended and retracted, but microglial soma remained fixed (Fig. 1A and 1B). To quantify the motility (i.e. extension and retraction) of resting microglial processes, we measured the length changes of individual processes every five minutes. Fig. 1c shows that there was no significant difference in the motility of microglial processes between the TLR2-KO and WT mice (p>0.05). Imaging through a thinned-skull cranial window showed a similar shape and motility of microglia in WT mice to that obtained through an open-skull window (Fig. 2), indicating that our craniotomy procedure does not alter a physiological condition of microglia.

Bottom Line: Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults.Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity.Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 130-701, Korea.

ABSTRACT
Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults. Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity. Although many previous studies have suggested that TLR2 contributes to microglial activation and subsequent pathogenesis following brain tissue injury, it is still unclear whether TLR2 has a role in microglia dynamics in the resting state or in immediate-early reaction to the injury in vivo. By using in vivo two-photon microscopy imaging and Cx3cr1 (GFP/+) mouse line, we first monitored the motility of microglial processes (i.e. the rate of extension and retraction) in the somatosensory cortex of living TLR2-KO and WT mice; Microglial processes in TLR2-KO mice show the similar motility to that of WT mice. We further found that microglia rapidly extend their processes to the site of local tissue injury induced by a two-photon laser ablation and that such microglial response to the brain injury was similar between WT and TLR2-KO mice. These results indicate that there are no differences in the behavior of microglial processes between TLR2-KO mice and WT mice when microglia is in the resting state or encounters local injury. Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

No MeSH data available.


Related in: MedlinePlus