Ultrastructural observations on the progress of nerve degeneration and regeneration at the suture site following vagal-hypoglossal nerve coaptation in cats

Ming E. Hu, Yeu Sheng Tyan, Peng Wei Hsu, Jee Ching Hsu, Hung Ming Chang, Eng Ang Ling, Chyn Tair Lan

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Nerve degeneration and regeneration have been investigated at the suture site following proximal-to-distal vagal-hypoglossal nerve coaptation (VHC) in cats at different time points (from 3 to 315 days postoperatively; dpo). Massive axonal degeneration and myelin breakdown and removal of degraded neural debris were observed during the first 2 weeks postoperatively. This was followed by active Schwann cell multiplication and inflammatory cell invasion at 14 dpo. Schwann cells appeared mobile, and were guided to the newly developed growth cones, dividing them into axonal sprout clusters. At 18 dpo, the migrating Schwann cells were confined to the preexisting basal lamina scaffolds, forming bands of Büngner. It is suggested that the latter may play a key role in navigating the regenerating axons to their newly acquired target organ at 22 dpo. Remyelination of axons was not observed till 46 dpo. Compared with the rapid axonal reaction in other models of nerve injury, the degeneration process in VHC was protracted and, furthermore, regeneration and remyelination were delayed. The subtle remodeling of the nerve in cross-coaptation may be far greater than previously recognized, and this may have clinical importance since patients undergoing nerve crossover microsurgery exhibit delayed motor rehabilitation, apparently as a direct result of a change in target innervation. Defining the mechanisms underlying the neuroplastic program could thus potentially improve the prognosis of crossover of two different peripheral nerves.

Original languageEnglish
Pages (from-to)230-245
Number of pages16
JournalCells Tissues Organs
Volume190
Issue number4
DOIs
Publication statusPublished - Sep 2009
Externally publishedYes

Keywords

  • Axonal sprouting
  • Growth cone
  • Hypoglossal nerve
  • Nerve cross-coaptation
  • Vagus nerve

ASJC Scopus subject areas

  • Anatomy
  • Histology

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