Neonatal microglia-organized scar-free spinal cord repair

Spinal cord injury in adult mammals typically leads to scar formation and limited axon regeneration. This study found that neonatal mice, however, exhibit scar-free healing and axon regrowth after spinal cord injury. Microglia, a type of immune cell in the central nervous system, play a critical role in this scar-free healing process in neonates. Depleting microglia disrupts healing and stalls axon regrowth. Neonatal microglia transiently secrete fibronectin to form extracellular matrix bridges and express peptidase inhibitors that resolve inflammation, contributing to the scar-free healing. Transplantation of neonatal microglia or adult microglia treated with peptidase inhibitors into adult spinal cord lesions improves healing and axon regrowth.

• 1
  Neonatal mice exhibit scar-free healing and long projecting axon growth after spinal cord crush injury, unlike adult mice which form scars.
• 2
  Microglia depletion in neonatal mice disrupts scar-free healing and stalls axon regrowth, indicating their essential role in the injury response.
• 3
  Neonatal microglia transiently secrete fibronectin to form extracellular matrix bridges and express peptidase inhibitors for inflammatory resolution, while adult microglia exhibit persistent fibronectin expression and lack peptidase inhibitor induction.