Inactivation of Rho signaling pathway promotes CNS axon regeneration

Regeneration in the CNS is blocked by many different growth inhibitory proteins. To foster regeneration, we have investigated a strategy to block the neuronal response to growth inhibitory signals. Here, we report that injured axons regrow directly on complex inhibitory substrates when Rho GTPase is inactivated. Treatment of PC12 cells with C3 enzyme to inactivate Rho and transfection with dominant negative Rho allowed neurite growth on inhibitory substrates. Primary retinal neurons treated with C3 extended neurites on myelin-associated glycoprotein and myelin substrates. To explore regeneration in vivo, we crushed optic nerves of adult rat. After C3 treatment, numerous cut axons traversed the lesion to regrow in the distal white matter of the optic nerve. These results indicate that targeting signaling mechanisms converging to Rho stimulates axon regeneration on inhibitory CNS substrates.