The Journal of Neuroscience, April 1, 1999, 19(7):2442-2454
Rapid Induction of Functional and Morphological Continuity
between Severed Ends of Mammalian or Earthworm Myelinated Axons
April B.
Lore1,
Jeffery
A.
Hubbell4,
David S.
Bobb Jr1,
Martis L.
Ballinger1,
Keisha L.
Loftin1,
Jeffory W.
Smith1,
Mark E.
Smyers1,
Habacuc D.
Garcia1, and
George D.
Bittner1, 2, 3, 5
1 Department of Zoology, 2 Institute for
Neuroscience, and 3 College of Pharmacy, University of
Texas at Austin, Austin, Texas 78712, 4 Institute for
Biomedical Engineering and Department of Materials, Swiss Federal
Institute of Technology and University of Zurich, CH-8044 Zurich,
Switzerland, and 5 Department of Physiology and Biophysics,
University of Texas Medical Branch, Galveston, TX 77555-0641
The inability to rapidly restore the loss of function that results
from severance (cutting or crushing) of PNS and CNS axons is a severe
clinical problem. As a novel strategy to help alleviate this problem,
we have developed in vitro procedures using
Ca2+-free solutions of polyethylene glycol (PEG
solutions), which within minutes induce functional and morphological
continuity (PEG-induced fusion) between the cut or crushed ends of
myelinated sciatic or spinal axons in rats. Using a PEG-based hydrogel
that binds to connective tissue to provide mechanical strength at the lesion site and is nontoxic to nerve tissues in earthworms and mammals,
we have also developed in vivo procedures that
permanently maintain earthworm myelinated medial giant axons
whose functional and morphological integrity has been restored by
PEG-induced fusion after axonal severance. In all these in
vitro or in vivo procedures, the success of
PEG-induced fusion of sciatic or spinal axons and myelinated medial
giant axons is measured by the restored conduction of action potentials
through the lesion site, the presence of intact axonal profiles in
electron micrographs taken at the lesion site, and/or the intra-axonal
diffusion of fluorescent dyes across the lesion site. These and other
data suggest that the application of polymeric fusiogens (such as our
PEG solutions), possibly combined with a tissue adherent (such as our
PEG hydrogels), could lead to in vivo treatments that
rapidly and permanently repair cut or crushed axons in the PNS and CNS
of adult mammals, including humans.
Key words:
axotomy; axonal regeneration; membrane fusion; neurotrauma; nerve repair; polyethylene glycol
Copyright © 1999 Society for Neuroscience 0270-6474/99/1972442-13$05.00/0