OBJECTIVETo investigate the changes on the number and distribution of myoepithelial cells (MECs) during parotid gland regeneration.

METHODSA total of 54 Wistar rats were divided into eight experimental groups and one normal control group, with six rats in each group. The right parotid ducts of the rats in the experimental groups were ligated for 14 days and then reopened. The parotid tissue specimens were harvested at days 0, 1, 3, 5, 7, 10, 14, and 21. The histological changes of the regenerating gland were examined using hematoxylin-eosin staining. Immunohistochemical labeling was also performed to investigate the changes in the number and distribution of MECs at different time points of parotid regeneration. Both the histological and immunohistochemical changes observed in the experimental groups were compared with those in the normal control group.

RESULTSThe parotid gland showed marked atrophy 14 days after ligation. Most acinar cells disap- peared, but the number of duct-like structures obviously increased. MECs apparently increased in number and were mainly located at the periphery of the duct-like structures. Three days after duct reopening, the number of acinar cells significantly increased and the duct-like structures significantly reduced. Meanwhile, MECs also decreased in number and were mainly located at the periphery of the newly formed acini and duct-like structures. The number of MECs noticeably decreased 3 and 5 days after duct reopening. At 14 days after duct reopening, the glandular structures and the number and distribution of MECs returned to normal compared with those in the normal control group.

CONCLUSIONThe number and distribution of MECs returned to normal condition after parotid gland atrophy. Parotid regeneration mainly occurred within 5 days after duct reopening.