Macrophages warrant Mauthner cell axon regrowth by preventing late-stage hyperglycemia in zebrafish

Axonal regeneration in the central nervous system is imperative for functional restoration following spinal cord injury (SCI). Myeloid cells are key regulators of axonal regeneration, yet their roles are not fully revealed. SCI perturbs glucose metabolism; however, its precise impact on axonal regeneration remains undefined. Moreover, whether myeloid cells orchestrate glucose metabolic responses to facilitate regeneration is unclear. Here, using the zebrafish Mauthner cell axon transection model, we demonstrate that following SCI, myeloid cell deficiency leads to a late-stage glucose surge, which leads to impaired axonal regeneration. We further identify glucagon signalling as a critical molecular determinant of this metabolic dysregulation and show that targeted mutations in gcga or its receptors (gcgra, gcgrb) rescue the axonal regeneration defects caused by myeloid cell deficiency. Finally, cell-depletion experiments demonstrated that macrophages are responsible for the late-stage hyperglycemia and defective axon regeneration of Mauthner cells. These findings suggest that glucose metabolism plays a critical role in macrophage-warranted axon regeneration in the spinal cord, positioning glucose homeostasis as a potential therapeutic target for enhancing axon regeneration and recovery.