Neural Regeneration Research ›› 2018, Vol. 13 ›› Issue (1): 53-57.doi: 10.4103/1673-5374.224363

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Conundrums and confusions regarding how polyethylene glycol-fusion produces excellent behavioral recovery afer peripheral nerve injuries

George D. Bittner1, Dale R. Sengelaub2, Cameron L. Ghergherehchi3   

  1. 1 Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
    2 Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
    3 Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
  • Received:2017-09-30 Online:2018-01-15 Published:2018-01-15
  • Contact: George D. Bittner,bittner@austin.utexas.edu.

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Abstract:

Current Neuroscience dogma holds that transections or ablations of a segment of peripheral nerves produce: (1) Immediate loss of axonal continuity, sensory signaling, and motor control; (2) Wallerian rapid (1-3 days) degeneration of severed distal axons, muscle atrophy, and poor behavioral recovery after many months (if ever, after ablations) by slowly-regenerating (1 mm/d), proximal-stump outgrowths that must specifically reinnervate denervated targets; (3) Poor acceptance of microsutured nerve allografts, even if tissue-matched and immune-suppressed. Repair of transections/ablations by neurorrhaphy and well-specified-sequences of PEG-fusion solutions (one containing polyethylene glycol, PEG) successfully address these problems. However, conundrums and confusions regarding unorthodox and dramatic results of PEG-fusion repair in animal model systems often lead to misunderstandings. For example, (1) Axonal continuity and signaling is re-established within minutes by non-specifically PEG-fusing (connecting) severed motor and sensory axons across each lesion site, but remarkable behavioral recovery to near-unoperated levels takes several weeks; (2) Many distal stumps of inappropriately-reconnected, PEG-fused axons do not ever (Wallerian) degenerate and continuously innervate muscle fibers that undergo much less atrophy than otherwise-denervated muscle fibers; (3) Host rats do not reject PEG-fused donor nerve allografts in a non-immuno-privileged environment with no tissue matching or immunosuppression; (4) PEG fuses apposed open axonal ends or seals each shut (thereby preventing PEG-fusion), depending on the experimental protocol; (5) PEG-fusion protocols produce similar results in animal model systems and early human case studies. Hence, iconoclastic PEG-fusion data appropriately understood might provoke a re-thinking of some Neuroscience dogma and a paradigm shift in clinical treatment of peripheral nerve injuries.

Key words: axonal repair, axotomy, Wallerian degeneration, polyethylene glycol, allograft, autograft, nerve regeneration