Effects of a nerve-muscle pedicle on the denervated rat thyroarytenoid muscle.
OBJECTIVE
To evaluate the effects of the nerve-muscle pedicle (NMP) method on the rat thyroarytenoid (TA) muscle after transection of the recurrent laryngeal nerve (RLN).


METHODS
Quantitative histologic assessment of the TA muscle after NMP implantation.


METHODS
Thirty-six Wistar rats were divided into two groups: animals subjected to transection of the left RLN alone (DNV group) and animals subjected to transection of the left RLN followed by immediate transplantation of a NMP flap containing the sternohyoid (SH) muscle and ansa cervicalis nerve branch (NMP group). Animals were killed 2, 4, and 10 weeks after the treatments. The TA muscle stained with hematoxylin-eosin was evaluated quantitatively. The pre- and postsynaptic structures of the neuromuscular junction (NMJ) in the TA muscle were analyzed histochemically. The myosin heavy chain (MyHC) isoforms were evaluated using immunohistochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR).


RESULTS
In the NMP group, the TA muscle fiber recovered to almost normal at 10 weeks, and the ratio of the number of synaptophysin-positive nerve terminals to that of alpha-bungarotoxin-positive acetylcholine receptors recovered to 79.8 +/- 11.8% (P < .05, compared with the control). Immunohistochemistry and the RT-PCR method after laser capture microdissection revealed the expression of MyHC isoforms type 2B and type 2A; the latter was detected in the SH muscle but not in the normal or denervated TA muscle.


CONCLUSIONS
The NMP method was effective for recovering from the atrophic changes of the TA muscle after transection of the RLN. This was attributed to successful reinnervation by reconstruction of the NMJ, which might change MyHC isoform expression.
Kumai
Yoshihiko
Y
Department of Otolaryngology Head and Neck Surgery, Graduate School of Medicine, Kumamoto University, Kumamoto, Japan. 035r5120@med.stud.kumamoto-u.ac.jp
Ito
Takaaki
T
Udaka
Naoko
N
Yumoto
Eiji
E
D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D007821:Laryngeal Muscles / Q000502:physiology*; D009132:Muscles / Q000294:innervation* / Q000637:transplantation*; D018995:Myosin Heavy Chains / Q000032:analysis; D009469:Neuromuscular Junction / Q000737:chemistry; D010525:Peripheral Nerves / Q000637:transplantation*; D051381:Rats; D017208:Rats, Wistar; D012009:Recurrent Laryngeal Nerve / Q000601:surgery*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013524:Surgical Flaps
D018995:Myosin Heavy Chains