Modulation of MyoD‐ and Ki‐67‐Positive Satellite Cells in the Short‐Term Denervated Rat Thyroarytenoid Muscle

Abstract

To evaluate the effects of short-term denervation on the kinetics of satellite cells (SCs) and myocytes in the rat thyroarytenoid (TA) muscle using immunohistochemistry for a myogenic regulatory factor, MyoD, and a cell proliferation marker, Ki-67. Quantitative immunohistochemical assessment of MyoD and Ki-67 expression in SCs and myocytes after denervation. The left recurrent laryngeal nerve (RLN) was transected in 15 adult Wistar rats, which were sacrificed 1, 3, or 7 days after the treatment (n = 5, each group). Fluorescein immunostaining was used to visualize the localization of MyoD+ and Ki-67+ SCs in combination with M-cadherin immunostaining for detection of SCs. We examined the temporal changes of the ratios of MyoD+ and Ki-67+ SCs for all of the counted muscle fibers and M-cadherin+ cells in both the denervated and the contralateral control TA muscle. On the denervated side, the TA muscle contained 3.8 +/- 0.4% MyoD+ SCs and 1.3 +/- 0.4% Ki-67+ SCs. Of the SCs, 22.6 +/- 2.2% were MyoD+, and 14.5 +/- 4.4% were Ki-67+, whereas SCs on the control side did not express these markers. In the rat TA muscle, denervation induces SC activation, and some SCs enter the cell cycle, whereas others are involved in the differentiation process. The number of activated SCs is relatively small compared with all M-cadherin+ SCs. Therefore, SCs might be good targets for a therapy to prevent TA muscle atrophy after RLN paralysis.