Axon Regeneration and Functional Recovery after Spinal Cord Injury is Enhanced by Allele-Specific ApoE Neuronal Action through LRP8

Adult CNS trauma frequently causes neuronal disconnection and persistent deficits due to failed axon regeneration. While model system screening has identified multiple candidate neural repair pathways, ApoE-LRP8 signaling is unique in being implicated clinically. Here, we show that cortical axon regeneration requires LRP8 and is modified by APOE variants. ApoE2-expressing mice show reparative corticospinal and raphespinal axon growth with greater motor function than controls after spinal cord injury. Distinct from ApoE in other settings, there is no change in inflammation or scarring. After axotomy, ApoE exerts allele-specific effects on LRP8 localization and signaling in cortical neurons. APOE alleles regulate synaptic organization gene expression by cortical neurons after injury, with little effect on glial gene expression. AAV-mediated overexpression of ApoE2 in mice after spinal trauma increases locomotor recovery and reparative axon growth. Thus, ApoE-LRP8 signaling for axon regrowth following CNS trauma provides a potential therapeutic intervention site.