Biological changes of myoepithelial cells in atrophic glands after ligation of parotid duct

Objective: We investigated the proliferative changes of myoepithelial cells (MECs) in atrophic glands after ligation of the parotid duct in rats. Methods: Seventy-eight Wistar rats were used as experimental animals and the main duct of the right parotid gland of each rat was ligated. Tissue samples of the parotid gland were taken from each group after 0 (control), 1, 3, 5, 7, 14, 21, and 30 days; histological changes in the parotid gland were examined by hematoxylin and eosin staining (n = 6), and the proliferation and distribution of MECs at different time points after ligation were analyzed by immunohistochemical double-staining. Results: After ligation of the parotid duct, the hematoxylin and eosin staining results showed that alveolar cells gradually disappeared, while a large number of duct-like structures appeared; fibrous tissue in the parotid gland proliferated and was infiltrated with inflammatory cells. Quantitative analysis of immunohistochemical staining results indicated that MECs proliferated rapidly, reaching a peak on the 5th day, after which the proliferation rate of MECs decreased and was maintained at a low level after 30 days. At 180 days, few proliferating MECs were observed. Conclusions: After ligation of the parotid duct, the parotid gland gradually atrophied and MECs proliferated during the early stage; subsequently, the proliferation capacity of MECs decreased and eventually stopped.