Toll-like Receptor 2 is Dispensable for an Immediate-early Microglial Reaction to Two-photon Laser-induced Cortical Injury In vivo.
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.
Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 130-701, Korea.
Heera
H
Yoon
Department of Oral Physiology and Neuroscience, School of Dentistry, Seoul National University, Seoul 110-749, Korea.
Yong Ho
YH
Jang
Department of Physiology, School of Medicine, Seoul National University, Seoul 110-799, Korea.
Sang Jeong
SJ
Kim
Department of Oral Physiology and Neuroscience, School of Dentistry, Seoul National University, Seoul 110-749, Korea.
Sung Joong
SJ
Lee
Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 130-701, Korea.
Sun Kwang
SK
Kim
Brain injury; In vivo two-photon microscopy imaging; Microglia; Toll-like receptor 2