Effects of aging on thyroarytenoid muscle regeneration.

Abstract

OBJECTIVES/HYPOTHESIS: Regenerative properties of age-associated changes in the intrinsic laryngeal muscles following injury are unclear. The purpose of this study was to investigate the regenerative properties of the thyroarytenoid (TA) muscle in an aging rat model. The hypothesis was that following myotoxic injury, old animals would exhibit a decrease in mitotic activities of muscle satellite cells when compared with younger rats, suggesting reduced regenerative potential in the aging rat TA muscle. STUDY DESIGN: Animal group comparison. METHODS: Regeneration responses following injury to the TA muscle were examined in 18 young adult, middle-aged, and old Fischer 344/Brown Norway rats. TA muscle fiber cross-sectional area (CSA), satellite cell mitosis (number/fiber), and regeneration index (CSA injured side/CSA noninjured side) were measured and compared across age groups. RESULTS: Young adult animals had a significantly higher regeneration index than the middle-aged and old groups. Within the lateral region of the TA muscle (LTA), the regeneration index was significantly higher in the young adult animals than in the middle-aged and old animals. The regeneration index of the medial TA was significantly higher than the LTA across all age groups. CONCLUSIONS: The regenerative capacity of the TA muscle is impaired with increasing age.