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Updated: Jul 13, 2026
Identifying Microglia and Peripheral Infiltrating Macrophages in the Injured Spinal Cords Using Flow Cytometry
Published on: June 24, 2025
Characterization and modeling of monocyte-derived macrophages after spinal cord injury
Erin E Longbrake1, Wenmin Lai, Daniel P Ankeny
1Integrated Biomedical Science Graduate Studies Program, The Ohio State University College of Medicine, Columbus, Ohio, USA.
Abstract:
Spinal cord injury (SCI) elicits a neuroinflammatory reaction dominated by microglia and monocyte-derived macrophages (MDM). Because MDM do not infiltrate the spinal cord until days after injury, it may be possible to control whether they differentiate into neuroprotective or neurotoxic effector cells. However, doing so will require better understanding of the factors controlling MDM differentiation and activation. Our goal was to develop an in vitro model of MDM that is relevant in the context of SCI. This tool would allow future studies to define mechanisms and intracellular signaling pathways that are associated with MDM-mediated neuroprotection or neurotoxicity. We first characterized SCI-induced cytokine expression in MDM using laser capture microdissection and real-time PCR. Based on this data, we assessed which easily procurable primary macrophage subset would mimic this phenotype in vitro. We established the baseline and inductive potential of resident peritoneal, thioglycollate-elicited peritoneal and bone marrow-derived macrophages (BMDM) at the molecular, cellular and functional level. Of these cells, only BMDM retained the phenotypic, molecular and functional characteristics of MDM that infiltrate the injured spinal cord. Thus, peripheral macrophages should not be used interchangeably in vitro to model the functional consequences of the MDM response elicited by SCI.
Insights
Developing an accurate in vitro model for spinal cord injury (SCI) is crucial. Bone marrow-derived macrophages (BMDM) effectively mimic monocyte-derived macrophages (MDM) in SCI, unlike peripheral macrophages.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Spinal cord injury (SCI) triggers neuroinflammation involving microglia and monocyte-derived macrophages (MDM).
- MDM infiltration occurs days post-injury, presenting an opportunity to modulate their neuroprotective or neurotoxic functions.
- Understanding MDM differentiation and activation factors is key to controlling their response.
Purpose of the Study:
- To develop a relevant in vitro model of MDM for SCI research.
- To enable future studies on intracellular signaling pathways governing MDM neuroprotection or neurotoxicity.
Main Methods:
- Characterized SCI-induced cytokine expression in MDM via laser capture microdissection and real-time PCR.
- Assessed resident peritoneal, thioglycollate-elicited peritoneal, and bone marrow-derived macrophages (BMDM) for phenotypic, molecular, and functional mimicry of SCI-infiltrating MDM.
- Evaluated macrophages in vitro.
Main Results:
- Bone marrow-derived macrophages (BMDM) uniquely retained the phenotypic, molecular, and functional characteristics of MDM found in injured spinal cords.
- Resident peritoneal and thioglycollate-elicited peritoneal macrophages did not accurately model the SCI MDM response.
Conclusions:
- BMDM serve as a suitable in vitro model for studying MDM in the context of SCI.
- Peripheral macrophages are not interchangeable with SCI-infiltrating MDM for in vitro modeling.
- This model facilitates research into mechanisms controlling MDM function post-SCI.
