Neutrophil immune profile guides spinal cord regeneration in zebrafish

Spinal cord injury triggers a strong innate inflammatory response in both non-regenerative mammals and regenerative zebrafish. Neutrophils are the first immune population to be recruited to the injury site. Yet, their role in the repair process, particularly in a regenerative context, remains largely unknown. Here, we show that, promoting neutrophil inflammation resolution by inhibiting Cxcr4 boosts cellular and functional regeneration. Neutrophil-specific RNA-seq analysis reveals an enhanced activation state that correlates with a transient increase in tnf-a expression in macrophage/microglia populations. Conversely, blocking neutrophil recruitment through Cxcr1/2 inhibition diminishes the presence of macrophage/microglia at the injury site and impairs spinal cord regeneration. Altogether, these findings provide new insights into the role of neutrophils in spinal cord regeneration, emphasizing the significant impact of their immune profile on the outcome of the repair process. Overall design: To understand the biological mechanisms promoted by neutrophils that improve spinal cord regeneration upon Cxcr4 inhibition, we sorted mpx:GFP+ cells from the injury site of lesioned larvae and from the same region of age-matched uninjured controls and performed Bulk RNA sequencing analysis in AMD3100- and DMSO-treated samples. Grant ID: 2022.02766.PTDC Grant title: Improving Spinal Cord Regeneration by modulating Neutrophil inflammation: lessons from a Zebrafish perspective Funding agency: Fundaçåo para a Ciência e Tecnologia (FCT), Portugal