Figure 1. Sensory axons regeneration into the spinal cords of Nogo^−/−MAG^−/−OMgp^−/− tKO mice show modest if any enhancement with expression of NT-3.

The L4 and L5 dorsal roots of Nogo^−/−MAG^−/−OMgp^−/− tKO or C57Bl/6 control mice were crushed and analyzed in wholemounts (A, C, E) or in transverse sections (B, D, F), two weeks after rhizotomy. Regenerating axons were labeled by AAV-GFP injected into the DRG at the time of rhizotomy. The DREZ was identified by staining astrocytes with GFAP antibody (B’, D’, F’). A, B: In wildtype mice, almost all the labeled axons that regenerated along the L4 and L5 roots failed to cross the DREZ. C, D: Expression of NT-3 in the spinal cord of wildtype mice enabled some axons to penetrate the DREZ (e.g., arrow in D). E, F: Expression of NT-3 in the spinal cord of Nogo^−/−MAG^−/−OMgp^−/− tKO mice enhanced regeneration only modestly. Although some axons regenerated slightly deeper within the CNS (e.g., arrows in F), most of the axons terminate their regeneration at the DREZ, similar to NT-3 treated wildtype mice. G: Quantifications of the axons that regenerated into the CNS, counted at different distances from the DREZ and normalized against the number of labeled axons in the PNS. Three random sections from each L4 and L5 segment were quantified (n=3 mice/group). Error bars indicate SEM. * p< 0.05, Bar in F”, 200µm.