&lt;i&gt;In vivo&lt;/i&gt; Chronic Two-Photon Imaging of Microglia in the Mouse Hippocampus

Kamei, Ryosuke; Urata, Shinji; Maruoka, Hisato; Okabe, Susumu

doi:10.3791/64104

Cited by 1 publication

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“…Despite the abundance of apoptotic newborn neurons in the hippocampus, there is limited information about the dynamic interaction between microglial processes and dying neurons, the time course of the engulfment process, and the digestion of phagolysosomal contents. This is partly attributed to the difficulty in visualizing unchallenged microglia in the deep subcortical regions, such as the DG (Kamei et al, 2022; Yang et al, 2010). Previous two‐photon imaging studies of adult cortical microglia successfully revealed the dynamic behavior of ramified microglia in physiological conditions (Kondo et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Previous two-photon imaging studies of adult cortical microglia successfully revealed the dynamic behavior of ramified microglia in physiological conditions (Kondo et al, 2011). However, the surgical procedures used for the implantation of an imaging window above the DG easily induce tissue injury and inflammation, which profoundly alter microglial behaviors (Kamei et al, 2022). Therefore, successful in vivo monitoring of phagocytosis by ramified microglia in the DG requires minimally invasive implantation techniques of imaging windows combined with genetically modified mice expressing distinct fluorescent proteins in newborn neurons and microglia.…”

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confidence: 99%

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In vivo imaging of the phagocytic dynamics underlying efficient clearance of adult‐born hippocampal granule cells by ramified microglia

Kamei

Okabe

2023

Glia

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The phagocytosis of dead cells by microglia is essential in brain development and homeostasis. However, the mechanism underlying the efficient removal of cell corpses by ramified microglia remains poorly understood. Here, we investigated the phagocytosis of dead cells by ramified microglia in the hippocampal dentate gyrus, where adult neurogenesis and homeostatic cell clearance occur. Two-color imaging of microglia and apoptotic newborn neurons revealed two important characteristics.Firstly, frequent environmental surveillance and rapid engulfment reduced the time required for dead cell clearance. The motile microglial processes frequently contacted and enwrapped apoptotic neurons at the protrusion tips and completely digested them within 3-6 h of the initial contact. Secondly, while a single microglial process engaged in phagocytosis, the remaining processes continued environmental surveillance and initiated the removal of other dead cells. The simultaneous removal of multiple dead cells increases the clearance capacity of a single microglial cell. These two characteristics of ramified microglia contributed to their phagocytic speed and capacity, respectively. Consistently, the cell clearance rate was estimated to be 8-20 dead cells/microglia/day, supporting the efficiency of removing apoptotic newborn neurons. We concluded that ramified microglia specialize in utilizing individual motile processes to detect stochastic cell death events and execute parallel phagocytoses.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%