Tacrolimus enhances the recovery of normal laryngeal muscle fibre distribution after reinnervation

Objectives: To assess the recovery of various muscle fibre types in the posterior cricoarytenoid muscle after laryngeal reinnervation in the rat, and to determine the influence of tacrolimus on this process. Methods: Four groups of rats underwent resection and anastomosis of the left vagus nerve, and were administered either tacrolimus at a low dose or an immunosuppressive dose, or cyclosporin A at a low dose or an immunosuppressive dose. A fifth group received surgery alone, and a sixth group received neither surgery nor drug treatment (healthy group). Muscles were removed for immunohistochemical analysis 45 days after surgery. Results: There was no difference in the proportion of types 1, 2a and 2b muscle fibres, comparing the immunosuppressive tacrolimus group and the healthy group, whereas there were fewer type 1 fibres in the group receiving surgery alone, compared with the healthy group (7 vs 12.1 per cent, respectively; p=0.0303). Conclusion: Tacrolimus enhanced the recovery of normal laryngeal muscle fibres after reinnervation in the rat, indicating a possible role in laryngeal transplantation.