title: Effects of extracellular calcium and surgical techniques on restoration of axonal continuity by polyethylene glycol fusion following complete cut or crush severance of rat sciatic nerves.
abstract: Complete crush or cut severance of sciatic nerve axons in rats and other mammals produces immediate loss of axonal continuity. Loss of locomotor functions subserved by those axons is restored only after months, if ever, by outgrowths regenerating at ∼1 mm/day from the proximal stumps of severed axonal segments. The distal stump of a severed axon typically begins to degenerate in 1-3 days. We recently developed a polyethylene glycol (PEG) fusion technology, consisting of sequential exposure of severed axonal ends to hypotonic Ca(2+) -free saline, methylene blue, PEG in distilled water, and finally Ca(2+) -containing isotonic saline. This study examines factors that affect the PEG fusion restoration of axonal continuity within minutes, as measured by conduction of action potentials and diffusion of an intracellular fluorescent dye across the lesion site of rat sciatic nerves completely cut or crush severed in the midthigh. Also examined are factors that affect the longer-term PEG fusion restoration of lost behavioral functions within days to weeks, as measured by the sciatic functional index. We report that exposure of cut-severed axonal ends to Ca(2+) -containing saline prior to PEG fusion and stretch/tension of proximal or distal axonal segments of cut-severed axons decrease PEG fusion success. Conversely, trimming cut-severed ends in Ca(2+) -free saline just prior to PEG fusion increases PEG fusion success. PEG fusion prevents or retards the Wallerian degeneration of cut-severed axons, as assessed by measures of axon diameter and G ratio. PEG fusion may produce a paradigm shift in the treatment of peripheral nerve injuries. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Cameron L
authors.initials: CL
authors.lastname: Ghergherehchi
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: George D
authors.initials: GD
authors.lastname: Bittner
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Robert Louis
authors.initials: RL
authors.lastname: Hastings
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Michelle
authors.initials: M
authors.lastname: Mikesh
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.|Department of Plastic Surgery, Vanderbilt School of Medicine, Nashville, Tennessee.
authors.forename: D Colton
authors.initials: DC
authors.lastname: Riley
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Trevino
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, Texas.
authors.forename: Tim
authors.initials: T
authors.lastname: Schallert
authors.affiliation: Department of Plastic Surgery, Vanderbilt School of Medicine, Nashville, Tennessee.
authors.forename: Wesley P
authors.initials: WP
authors.lastname: Thayer
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Solomon Raju
authors.initials: SR
authors.lastname: Bhupanapadu Sunkesula
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Tu-Anh N
authors.initials: TA
authors.lastname: Ha
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Munoz
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Monika
authors.initials: M
authors.lastname: Pyarali
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Aakarshita
authors.initials: A
authors.lastname: Bansal
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Poon
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Mazal
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Tyler A
authors.initials: TA
authors.lastname: Smith
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Nicole S
authors.initials: NS
authors.lastname: Wong
authors.affiliation: Department of Neuroscience, University of Texas at Austin, Austin, Texas.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Dunne
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism* / Q000627:therapeutic use; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D008297:Male; D001523:Mental Disorders / Q000209:etiology / Q000628:therapy; D009416:Nerve Regeneration / Q000187:drug effects; D009431:Neural Conduction / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects / Q000473:pathology; D009493:Neurosurgery / Q000379:methods*; D011092:Polyethylene Glycols / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000187:drug effects*; D020426:Sciatic Neuropathy / Q000150:complications / Q000188:drug therapy* / Q000601:surgery*; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D011092:Polyethylene Glycols; D002118:Calcium
keywords: Wallerian degeneration; axonal regeneration; axotomy; nerve repair; polyethylene glycol; rat sciatic nerve