title: Neuronal growth cones respond to laser-induced axonal damage.
abstract: Although it is well known that damage to neurons results in release of substances that inhibit axonal growth, release of chemical signals from damaged axons that attract axon growth cones has not been observed. In this study, a 532 nm 12 ns laser was focused to a diffraction-limited spot to produce site-specific damage to single goldfish axons in vitro. The axons underwent a localized decrease in thickness ('thinning') within seconds. Analysis by fluorescence and transmission electron microscopy indicated that there was no gross rupture of the cell membrane. Mitochondrial transport along the axonal cytoskeleton immediately stopped at the damage site, but recovered over several minutes. Within seconds of damage nearby growth cones extended filopodia towards the injury and were often observed to contact the damaged site. Turning of the growth cone towards the injured axon also was observed. Repair of the laser-induced damage was evidenced by recovery of the axon thickness as well as restoration of mitochondrial movement. We describe a new process of growth cone response to damaged axons. This has been possible through the interface of optics (laser subcellular surgery), fluorescence and electron microscopy, and a goldfish retinal ganglion cell culture model.
authors.affiliation: Beckman Laser Institute and Medical Clinic, University of California, Irvine, CA 92617, USA. wut2@uci.edu
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.forename: Samarendra
authors.initials: S
authors.lastname: Mohanty
authors.forename: Veronica
authors.initials: V
authors.lastname: Gomez-Godinez
authors.forename: Linda Z
authors.initials: LZ
authors.lastname: Shi
authors.forename: Lih-Huei
authors.initials: LH
authors.lastname: Liaw
authors.forename: Jill
authors.initials: J
authors.lastname: Miotke
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Meyer
authors.forename: Michael W
authors.initials: MW
authors.lastname: Berns
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D006054:Goldfish; D020439:Growth Cones / Q000502:physiology*; D007834:Lasers; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D012160:Retina / Q000166:cytology* / Q000293:injuries*