Elevated phagocytic capacity directs innate spinal cord repair

Area of Science:

• Neuroscience
• Immunology
• Regenerative Medicine

Background:

• Spinal cord injury (SCI) in mammals triggers chronic inflammation and poor debris clearance, hindering natural repair.
• Immune cells, particularly macrophages, play a complex role in SCI recovery, with both detrimental and beneficial functions.

Purpose of the Study:

• To investigate the immune response to SCI in zebrafish, a model known for regenerative capabilities.
• To identify key molecular mechanisms, especially within macrophages, that facilitate spinal cord repair.
• To compare immune responses and identify conserved regenerative genes between zebrafish and mammals.

Main Methods:

• Transcriptomic analysis of immune cells following SCI in zebrafish.
• Genetic ablation of specific immune cell populations, including macrophages.
• Comparative gene expression analysis between zebrafish and mouse macrophages.
• Functional assays to assess phagocytosis and regeneration.

Main Results:

• Zebrafish SCI induced transient immune activation and efficient debris clearance, unlike mammals.
• Zebrafish macrophages were identified as highly phagocytic and essential for spinal cord regeneration.
• The gene transcription and immune response regulator (tcim) was identified as crucial for macrophage phagocytosis and regeneration in zebrafish.
• Tcim promotes lipid metabolism and myeloid precursor reprogramming in both zebrafish and mouse macrophages, highlighting conserved function.

Conclusions:

• Efficient debris clearance by highly phagocytic macrophages is critical for innate spinal cord repair.
• The gene transcription and immune response regulator (tcim) is a conserved factor promoting macrophage phagocytosis and regeneration.
• Targeting tcim may offer a therapeutic strategy to enhance spinal cord repair in mammals.