Phagocytic response of astrocytes to damaged neighboring cells

Abstract

This study aims to understand the phagocytic response of astrocytes to the injury of neurons or other astrocytes at the single cell level. Laser nanosurgery was used to damage individual cells in both primary mouse cortical astrocytes and an established astrocyte cell line. In both cases, the release of material/substances from laser-irradiated astrocytes or neurons induced a phagocytic response in near-by astrocytes. Propidium iodide stained DNA originating from irradiated cells was visible in vesicles of neighboring cells, confirming phagocytosis of material from damaged cortical cells. In the presence of an intracellular pH indicator dye, newly formed vesicles correspond to acidic pH fluorescence, thus suggesting lysosome bound degradation of cellular debris. Cells with shared membrane connections prior to laser damage had a significantly higher frequency of induced phagocytosis compared to isolated cells with no shared membrane. The increase in phagocytic response of cells with a shared membrane occurred regardless of the extent of shared membrane (a thin filopodial connection vs. a cell cluster with significant shared membrane). In addition to the presence (or lack) of a membrane connection, variation in phagocytic ability was also observed with differences in injury location within the cell and distance separating isolated astrocytes. These results demonstrate the ability of an astrocyte to respond to the damage of a single cell, be it another astrocyte, or a neuron. This single-cell level of analysis results in a better understanding of the role of astrocytes to maintain homeostasis in the CNS, particularly in the sensing and removal of debris in damaged or pathologic nervous tissue.

Calcium Dynamics in Astrocytes During Cell Injury

“…This study establishes the involvement of Ca 2+ in the process of endocytosis of cellular debris described in our previous paper (Wakida et al, 2018). This observation is consistent with a role for astrocytes in removing cellular debris from the CNS following injury such as in traumatic brain injury (Sofroniew, 2009).…”

Microglia in the developing retina couple phagocytosis with the progression of apoptosis via P2RY12 signaling

“…Direct in vivo real‐time imaging in our work confirms the microglial clearance function in the developing zebrafish retina (Figures ). However, this does not exclude a possible phagocytic function for other cell types, such as Müller glia or possibly astrocytes in certain species, in the vertebrate retina. Indeed, Müller glial phagocytosis could occur at other developmental stages or in specific contexts of tissue damage or degeneration in zebrafish .…”

Fluid Shear Stress Enhances the Phagocytic Response of Astrocytes

“…Cells were dissociated by an 8 min incubation with 2 mg/mL papain (Sigma) in Hibernate E (without Calcium and B27, BrainBits) at 37 • C. Astrocytes were resuspended into Coculture media (BrainBits) and plated onto matrigel (Corning) coated u-Slide I 0.6 Luer (Ibidi, Inc.) at a concentration of 1 × 10 6 cells/mL. The channel of the U-slide was coated with polylysine and Matrigel (Wakida et al, 2018). Cells were incubated at 37 • C with 5% CO 2 under static conditions.…”

“…This is of critical importance to areas of research like traumatic brain injury and CNS repair. Our previous studies demonstrated the ability of astrocytes to respond to laser induced cell lysis via phagocytosis (Wakida et al, 2018(Wakida et al, , 2020. Membrane ruffling and subsequent vesicle formation in the responding astrocyte was associated with cellular debris from the targeted cell with the use of propidium iodide labeled DNA and pHrodo dye.…”