Figure 6: Establishment of an in vivo model of dorsal column axon regeneration.

(a) After in vivo electroporation of the L4 DRG, a dorsal column transection was performed at about the T12 level of the vertebrate. (b) The top panel shows peripheral axon sprouting in the peripheral nerve at a single axon level after a peripheral axotomy. Red arrow indicates the branching point. The bottom panel shows sprouting of the DRG central axon inside the spinal cord after dorsal column transection. Red, white and yellow arrow indicates primary, secondary and tertiary branching points, respectively. (c) A representative image from a control mouse showing that transection of the dorsal column axons (red line indicates the injury site) resulted in no axon regeneration into or beyond the injury site when observed at 2 weeks after the injury. (d) An enlarged image of the yellow square in panel c. (e) A representative image from a mouse that was subjected to peripheral axotomy (conditioning lesion) 1 week before the dorsal column transection (red line indicates the injury site). Note that many EGFP-labelled axons grew into and beyond the lesion site. (f) An enlarged image of the yellow square in panel e. Scale bars, b,d,f, 50 μm; c,e, 200 μm.