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Microglia, the resident immune cell of the brain, can be eliminated via pharmacological inhibition of the colony-stimulating factor 1 receptor (CSF1R). Withdrawal of CSF1R inhibition then stimulates microglial repopulation, effectively replacing the microglial compartment. In the aged brain, microglia take on a "primed" phenotype and studies indicate that this coincides with age-related cognitive decline. Here, we investigated the effects of replacing the aged microglial compartment with new microglia using CSF1R inhibitor-induced microglial repopulation. With 28 days of repopulation, replacement of resident microglia in aged mice (24 months) improved spatial memory and restored physical microglial tissue characteristics (cell densities and morphologies) to those found in young adult animals (4 months). However, inflammation-related gene expression was not broadly altered with repopulation nor the response to immune challenges. Instead, microglial repopulation resulted in a reversal of age-related changes in neuronal gene expression, including expression of genes associated with actin cytoskeleton remodeling and synaptogenesis. Age-related changes in hippocampal neuronal complexity were reversed with both microglial elimination and repopulation, while microglial elimination increased both neurogenesis and dendritic spine densities. These changes were accompanied by a full rescue of age-induced deficits in long-term potentiation with microglial repopulation. Thus, several key aspects of the aged brain can be reversed by acute noninvasive replacement of microglia.
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http://dx.doi.org/10.1111/acel.12832 | DOI Listing |
Brain Sci
July 2025
Department of Brain and Neuroscience, Tokyo Metropolitan Institute of Medical Science, Setagaya 156-8506, Japan.
Murine microglia exhibit rapid self-renewal upon removal from the postnatal brain. However, the signaling pathways that regulate microglial repopulation remain largely unclear. To address this knowledge gap, we depleted microglia from mixed glial cultures using anti-CD11b magnetic particles and cultured them for 4 weeks to monitor their repopulation ability in vitro.
View Article and Find Full Text PDFNeurobiol Dis
August 2025
Department of Neurology, First Hospital of China Medical University, Shenyang, Liaoning Province, China; Key Laboratory of Neurological Disease Big Data of Liaoning Province, Shenyang, China; Shenyang Clinical Medical Research Center for Difficult and Serious Diseases of the Nervous System, China. E
Microglia, as resident macrophages in the central nervous system (CNS), have been the focus of the scientific community. The pace of exploration in the origin and development of microglia, though tortuous, never stops. Since colony-stimulating factor receptor 1 (CSF1R) inhibitors can achieve effective depletion of microglia and the repopulated microglia can be comparable to the controls, the therapeutic potential of this repopulation has prompted increasing attention and investigation.
View Article and Find Full Text PDFFront Immunol
August 2025
Department of Neurology, Weihai Municipal Hospital, Cheeloo College of Medicine, Shandong University, Weihai, China.
Background: Myeloid cells, such as resident microglia (MG), infiltrating monocytes (Mo), macrophages (MΦ), and CNS border-associated macrophages (BAM) in the brain, participate in aged brain injury. Aged microglial replacement is protective against brain injury in aged mice; however, whether/how the molecular changes in myeloid cells are affected by this replacement in injured brains remains unclear.
Methods: Aged microglia in mice were eliminated by PLX3397 for 21 consecutive days and repopulated following withdrawal for 21 days; then, intracerebral hemorrhage (ICH) models were constructed.
Nature
August 2025
Institute for Stem Cell Biology and Regenerative Medicine, Department of Pathology, Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA.
Migration of transplanted allogeneic myeloid cells into the brain following systemic hematopoietic stem and progenitor cells transplantation (HCT) holds great promise as a therapeutic modality to correct genetic deficiencies in the brain such as lysosomal storage diseases. However, the toxic myeloablation required for allogeneic HCT can cause serious, life-threatening side effects limiting its applicability. Moreover, transplanted allogeneic myeloid cells are highly vulnerable to rejection even in an immune-privileged organ like the brain.
View Article and Find Full Text PDFNeurobiol Sleep Circadian Rhythms
May 2025
Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA.
Traumatic brain injury (TBI) causes persistent sleep disturbances, leading to long-term neurological consequences and reduced quality of life. We hypothesized that microglial depletion via PLX5622 (PLX), a colony-stimulating factor 1 receptor (CSFR1R) inhibitor, would exacerbate sleep disturbances and alter inflammatory profiles after TBI, and that microglial repopulation would ameliorate these effects. Male mice received PLX or control diets (21 days) followed by a midline fluid percussion injury (mFPI) or sham surgery.
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