Apoptotic cell death during regressive changes in salivary glands: A morphological perspective

Apoptosis was initially identified through transmission electron microscopy. Subsequent advances in morphological techniques for apoptosis detection have revealed its involvement in multiple pathological conditions in various tissues. This review summarizes previous experimental studies on apoptotic cell death during regressive changes in the salivary glands, with a focus on morphological observations. Obstructive sialadenitis is histologically characterized by acinar cell loss and increased number of duct cells. Although acinar cells were previously believed to dedifferentiate into duct cells, there is evidence that they are eliminated by apoptosis. Animals fed a soft diet exhibited parotid gland atrophy, in which acinar cells decreased in size and disappeared because of apoptosis. Age-related changes in the salivary glands involved a reduced number of acinar cell through apoptosis. Additionally, apoptotic acinar cell death occurs in other pathological conditions, including the regression of hypertrophic and irradiated salivary glands. Apoptosis often eliminates acinar cells during atrophic alterations in the salivary glands. Unlike necrosis, apoptosis is an active form of cell death, thereby helping prevent the complete destruction of the salivary glands. However, the contribution of apoptosis to regressive changes in the salivary glands remains unclear and warrants further investigation. •Acinar cells are deleted by apoptosis in obstructive sialadenitis.•Apoptosis of acinar cells is involved in parotid gland atrophy induced by soft diet intake.•Decrease of acinar cells in salivary gland with aging is induced by apoptosis.•Further studies are necessary to clarify the significance of apoptosis in regressive changes of salivary glands.