A comparison of the ability of GDA versus GRP transplants to promote axon growth across dorsal column injuries from adjacent microtransplanted adult sensory neurons at 8 days after injury and transplantation. (a) A montaged, confocal image scanned from a single 75-μm thick sagittally oriented section showing GFP+ axons (green) entering and exiting a dorsal column lesion bridged with hPAP+(red) GDAs. (b) In two cases in which GDA transplants did not adequately fill the injury site or migrate into lesion margins, GFP+sensory axons failed to cross the caudal lesion margin and instead formed dystrophic endings identical to those in control untreated injuries. LC, lesion center. (c) Confocal montage showing the complete failure of transplanted GRPs to support the growth of GFP axons across a dorsal column injury. Note that, despite the ability of transplanted GRPs to span the injury site, the majority of GFP+ axons have formed dystrophic endings within the caudal lesion margin. Scale bars: (a) 300 μm; (b) 100 μm; (c) 200 μm.