Macrophage polarization: a key event in the secondary phase of acute spinal cord injury

Journal of Cellular and Molecular Medicine, 2017 · DOI: 10.1111/jcmm.13034 · Published: May 1, 2017

Simple Explanation

Spinal cord injury (SCI) is a serious condition with two phases: acute and secondary. The secondary phase, influenced by inflammatory responses, is crucial for the outcome of SCI. Macrophages, a type of immune cell, play a significant role in this inflammation. Macrophages in the injured spinal cord can either worsen the damage or promote healing, depending on their type and activation status. Some treatments aim to shift macrophage activation towards benefiting SCI recovery, highlighting the importance of understanding the relationship between macrophages and SCI. This review provides an overview of the immunological aspects of acute SCI, focusing on the pathophysiology, the role of macrophage polarization, and new therapies that modulate macrophage polarization to protect the nervous system.

Study Duration

Not specified

Participants

Not specified

Evidence Level

Review

Key Findings

1
Macrophages in the injured spinal cord are heterogeneous, consisting of CNS-resident microglia-derived macrophages and bone marrow-derived macrophages, which differ in location and function.
2
Macrophages can be classified into M1 (classically activated, pro-inflammatory) and M2 (alternatively activated, anti-inflammatory) phenotypes, with M1s being predominant in the early stages of SCI.
3
The microenvironment of the injured spinal cord favors M1 polarization, and therapies aimed at shifting macrophage polarization towards M2 may promote tissue repair and functional recovery.

Research Summary

This review explores the immune pathophysiology of SCI, with a focus on inflammation dominated by macrophages in the secondary damage phase. The injured spinal cord microenvironment favors M1 polarization, with only a brief appearance of M2 macrophages early after SCI. M1 macrophages contribute to secondary tissue damage and axonal retraction, while M2 polarization has protective effects. Understanding how macrophage polarization influences secondary damage in spinal cord inflammation has led to the development of neuroprotective therapies targeting macrophage polarization in SCI.

Practical Implications

Therapeutic Target

Modulating macrophage polarization towards the M2 phenotype could be a promising therapeutic strategy for SCI.

Drug Development

Developing pharmacological interventions that alter macrophage responses to pro-inflammatory stimuli in SCI.

Clinical Intervention

Exploring cell transplantation (e.g., MSCs or M2 macrophages) to promote tissue repair and functional recovery after SCI.

Study Limitations

1
The timing and detailed conditions for the M1 to M2 phenotypic switch remain unknown.
2
Factors in the SCI tissue that lead to the phenotype switch are unclear.
3
Limitations with direct MSC transplantation methods preclude effective MSC infusions into post-SCI treatment protocols.

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