[The expression and distribution of ciliary neurotrophic factor in laryngeal nerve regeneration]

To explore the expression and distribution of ciliary neurotrophic factor(CNTF) mRNA and its protein in laryngeal nerve regeneration.

The recurrent laryngeal nerves were sectioned and then sutured in twelve dogs. Both proximal and distal stumps of sutured region were sectioned on different postoperative days and the sections were separately used for CNTF immunohistochemistry and CNTF mRNA in situ hybridization. The area and intensity of reactive product were measured by computer image processing system.

Strongly reactive product of CNTF mRNA and its protein deposited in myelin-related Schwann cells in normal laryngeal nerves. At week 2 following neurorrhaphy, there was very little hybridization signal and detectable CNTF immunoreactivity in distal stump and no regenerated nerve fibbers were found. At week 3, reactive product of CNTF mRNA and its protein was detected in thin Schwann cell processes ensheathing regenerated axons, while reactive product was not found in the proliferating Schwann cells which didn't ensheathe axons. CNTF immunoreactivity was also detected in the regenerated nerve axons. After long survival times, hybridization signal and the CNTF immunoreactivity in Schwamm cells became more widespread, and the area and intensity of reactive product significantly increased, but even at the longest survival time, they were still significantly less than those in intact nerve. The same change of CNTF mRNA and its protein was observed in a short segment proximal to the sutured region.

CNTF expression could depend on Schwann cell-axon regeneration. The level of CNTF expression stands in striking contrast to the up-regulation of nerve growth factor in peripheral nerve degeneration and regeneration. These suggest that the exogenous CNTF might provide a supportive environment for axonal regeneration.