Expression of atrophy-related transcription factors in the process of intrinsic laryngeal muscle atrophy after denervation

We examined changes in the expressions of three atrophy-related transcription factors (FOXO3a, P-FOXO3a, and PGC-1α) in the process of intrinsic laryngeal muscle atrophy after denervation. In total, 51 Wistar rats were used. After transection of the unilateral recurrent laryngeal nerve, the thyroarytenoid (TA) muscle and the posterior cricoarytenoid (PCA) muscle were excised and subjected to histological and Western blot studies. Relationships between the expressions of transcription factors during atrophy of the intrinsic laryngeal muscles were investigated by comparing the results of the treated side (T) with those of the untreated side (U), and sequential changes in the T/U ratio after denervation were assessed. Loss of wet muscle weight, together with a decrease in muscle fiber cross-sectional area and increase in the number of muscle fibers/mm², occurred more quickly in TA muscle than in PCA muscle. Muscle atrophy progressed rapidly between 7 and 28 days after denervation, while expression of FOXO3a was maximal on day 7, in both TA and PCA muscles. By contrast, P-FOXO3a expression decreased gradually after denervation. Expression of PGC-1α increased slowly until day 7, and then it declined. Denervation-induced atrophy of the intrinsic laryngeal muscles was closely linked with the expression of FOXO3a and PGC-1α, suggesting that atrophy of these muscles may involve the actions of these transcription factors. In addition, muscle atrophy progressed faster in TA muscle than in PCA muscle, due mainly to differences in muscle fiber composition.