Objective: To investigate the morphological alteration and the protein expression of TGF-beta1 in long-term denervated posterior cricoarytenoid muscles (PCAMs) and to find the appropriate time point of reinnervation in long-term denervated PCAMs.
Method: Thirty-eight patients with vocal paralysis were recruited into four groups, the 6-12 months denervation group, the 1-2 years denervation group, the 2-3 years denervation group and the over 3 years denervation group. Twelve adults served as a control group. The morphological alteration was evaluated using Trichrome Masson staining and the change in expression of TGF-beta1, a fibrosis related factor, were observed using immunofluorescence stain and Western blot.
Result: The scars of myofibers were decreased, but the scars of collagen fibers were increased with the denervated time course extension. The ratio of scars of myofibers to scars of collagen fibers were progressively decrease with increased time course of denervation and more decrease within 2 years. There was still 48% scar of myofibers remained after 3 years of denervation. TGF-beta1 showed no staining in innervated, however, by 6-12 months and 1-2 years of muscle denervation there was a significant accumulation of TGF-beta1 protein in endochylema of myofiber. After 2 year of denervation, expression of TGF-beta1 protein in endochylema of myofiber, was decreased significantly, but after 3 year of denervation, there were no expression of TGF-beta1 protein in endochylema. In Western blot, the change in protein expression of TGF-beta1 was observed an 4.5-fold (P<0.01) increase from 6-12 months denervated muscles to innervated muscles, 11.4-fold (P<0.01) increase from 1-2 years denervated muscles to innervated muscles, 11.4-fold (P<0.01) increase from 2-3 years denervated muscles to innervated muscles (P<0.01). After 3 years, the protein expression of TGF-beta1 decreased, 0.5-fold to innervated muscles.
Conclusion: The morphological alteration and change in expression of TGF-beta1, a important factor of myelofibrosis, indicated there was a high amplitude of myelofibrosis within 2 years, but there is a morphological basis of muscles to regain their function within 3 years denervated muscles.