A surviving intact branch stabilizes remaining axon architecture after injury as revealed by in vivo imaging in the mouse spinal cord.
The complex morphology of axons presents a challenge in understanding axonal responses to injury and disease. By in vivo two-photon imaging of spinal dorsal column sensory axons, we systematically examined the effect of injury location relative to the main bifurcation point on axon degeneration and regeneration following highly localized laser injuries. Retrograde but not anterograde degeneration was strongly blocked at the bifurcation point at both the acute and subacute phases. Eliminating either the ascending or descending branch led to a poor regenerative response, while eliminating both led to a strong regenerative response. Thus, a surviving intact branch suppresses both retrograde degeneration and regeneration of the injured branch, thereby preserving the remaining axon architecture. Regenerating axons exhibited a dynamic pattern with alternating phases of regeneration and pruning over a chronic period. In vivo imaging continues to reveal new insights on axonal responses to injury in the mammalian spinal cord.
Department of Neurosciences, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA; Biomedical Sciences Graduate Program, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA.
Ariana O
AO
Lorenzana
Department of Neurosciences, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA.
Jae K
JK
Lee
Department of Neurosciences, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA.
Matthew
M
Mui
Department of Neurosciences, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA.
Amy
A
Chang
Department of Neurosciences, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA; Biomedical Sciences Graduate Program, University of California San Diego, School of Medicine, La Jolla, CA 92093-0691, USA. Electronic address: binhai@ucsd.edu.
Binhai
B
Zheng
D000818:Animals; D001369:Axons / Q000473:pathology*; D002470:Cell Survival; D004195:Disease Models, Animal; D051379:Mice; D009416:Nerve Regeneration / Q000502:physiology*; D055495:Neurogenesis; D013119:Spinal Cord Injuries / Q000473:pathology* / Q000503:physiopathology