J Korean Thyroid Assoc.  2015 May;8(1):88-97. 10.11106/cet.2015.8.1.88.

Regeneration of Recurrent Laryngeal Nerve using Polycaprolactone (PCL) Nerve Guide Conduit Coated with Conductive Materials

• Choi JS
• Kim H
• An HY
• Shim BS
• Lim JY

• KMID: 2149625
• DOI: http://doi.org/10.11106/cet.2015.8.1.88

Abstract

BACKGROUND AND OBJECTIVES
Recurrent laryngeal nerve (RLN) damage commonly occurs from a thyroid surgery and causes communication impairment, aspiration and dysphagia. The purpose of this study is to develop a polycaprolactone (PCL) nerve guide conduit (NGC) coated with conductive materials for facilitating regeneration from the RLN defects and to evaluate the usefulness of the PCL NGC coated with conductive materials in a rabbit model.
MATERIALS AND METHODS
The PCL NGCs coated with conductive materials were fabricated for this study. The types of conductive materials were single-walled carbon nanotubes (SWNTs) and poly (3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) which were coated on the PCL NGCs by layer-by-layer (LBL) assembly techniques. An 8-mm segment of left RLN was resected in 24 New Zealand white rabbits. Three different NGCs (PCL and PCL with two conductive materials) were interposed between both stumps and fixed with suture. For the assessment of functional regeneration, the vocal cord mobility was observed using endoscopic system after RLN stimulation, and the motion change was analyzed. The atrophies of thyroarytenoid muscle and nerve growth were evaluated by Hematoxylin-Eosin (H-E) and toluidine blue (T-B) staining, respectively. Immunohistochemical study using anti-neurofilament, S-100 staining was further performed to evaluate the nerve regeneration.
RESULTS
In endoscopic evaluation, the group with conductive PCL NGCs showed an improved tendency of vocal cord mobility compared to that of the other group. Nerve growth was observed with the time for 8 weeks in all groups and immunohistochemical staining revealed the expression of neurofilament and S-100 in regenerated nerve in all groups. The atrophies of thyroarytenoid muscle in the group with conductive PCL NGCs was also shown to be decreased compared to that of the nonconductive PCL NGC group.
CONCLUSION
The study shows that PCL NGC coated with conductive materials appears to be a good alternative option for the repair and regeneration of RNL damages.

Keyword

Recurrent laryngeal nerve; Regeneration; Nerve guide conduit

MeSH Terms

Atrophy
Deglutition Disorders
Laryngeal Muscles
Nanotubes, Carbon
Nerve Regeneration
Polystyrenes
Rabbits
Recurrent Laryngeal Nerve*
Regeneration*
Sutures
Thyroid Gland
Tolonium Chloride
Vocal Cords
Nanotubes, Carbon
Polystyrenes
Tolonium Chloride

Figure

• 

  Fig. 1. Fabrications of nerve guide conduits. (A) Micro- and nano- porous structured membrane template, (B) schematic illustration of coating process of conductive materials in membrane template, (C) application for nerve guide conduit with glue, (D) template NGC (left), conductive NGC coated with SWNTs (middle), conductive NGC coated with PEDOT:PSS (right).

• 

  Fig. 2. The animal operative procedure. (A) Careful dissection of left RLN, (B) 8 mm segmental resection of RLN, (C) NGC interposition, (D) schematic illustration of interposition of NGC between proximal and distal stumps. Asterisk: recurrent laryngeal nerve, arrow: resected nerve, arrowhead: interposed nerve guide conduit, respectively.

• 

  Fig. 3. Measurement of vocal fold movements. (A) Fully abducted position and fully adducted position were captured and measured the triangle area (angular points, abc), (B) The outcome of comparing the vocal cord movement among groups. The box and error bar denote means ± standard deviations. A: arytenoid, a: anterior commissure, b: fully abducted posterior commissure, c: fully adducted posterior commissure.

• 

  Fig. 4. Histologic evaluation of thyroarytenoid (TA) muscle atrophy. (A) The cross-sectional area of the TA muscles was measured by tracing outlines of the microscopic images, (B) the outcome of comparing the cross sectional area of the TA muscle among groups. The box and error bar denote means ± standard deviations. Arrowhead: atrophied TA muscle due to denervation of RLN, asterisk: compensated TA muscle due to reinnervation of RLN.

• 

  Fig. 5. Scanning electron microscope images of the template membrane and conductive materials coating membrane. (A) Micro-pore surface, (B) nano-pore surface, (C) cross section between inner and outer surface, (D) SWNT 3 layers membrane. (E) PEDOT:PSS 3 layers membrane.

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  Fig. 6. Histologic evaluation of regenerated RLN at 2, 4, 8 weeks after interposition. At 8 weeks, the regenerated nerve looked structurally normal in all groups. Arrows: regenerated RLNs.

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  Fig. 7. The expression of NF and S100 protein at 8 weeks. The NF and S100 protein in all groups were well expressed. DAPI (blue), NF, S100 protein (green).

Reference

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