Regeneration in chronic sialadenitis: an analysis of proliferation and apoptosis based on double immunohistochemical labelling

The understanding of regeneration in salivary glands as a finely tuned balance of cellular proliferation, differentiation and apoptosis has been limited by the difficulty of identifying proliferating cells. This has been overcome in the present investigation by double immunohistochemical labelling for the proliferation-associated antigen Ki67 and for different cell-type-specific antigens applied to 8 specimens of normal parotids and 16 specimens of chronic parotid sialadenitis with particular reference to acini and intercalated ducts. In comparison with low baseline rates of proliferation in normal parotids, proliferative indices were significantly increased in chronic sialadenitis in mature acinar cells, intercalated ductal cells and myoepithelial cells without evidence of proliferation by an additional population of cells. In accordance with findings in glands of experimental animals, the present data do not support the previously postulated concept of regeneration of acini and intercalated ducts by a hypothetical population of uncommitted ductal stem cells. The demonstration of a profound capacity for intrinsic glandular regeneration from differentiated cells represents a biological basis for the good results obtained from conservative therapy of chronic sialadenitis and offers hope for novel therapies designed to reconstitute impaired salivary flow.