Phenotype and cell proliferation activity of duct-like structures in human sublingual glands: a histological and immunohistochemical study

Abstract

There are several age-related microscopic changes in the salivary glands, including the increase in the number of duct-like structures (DLS). However, the true origin and the phenotype of the DLS are not known. Objective To evaluate the phenotype and the cell proliferation index of the DLS of human sublingual glands.Material and Methods Sixty sublingual glands obtained from human cadavers were divided into two groups - 0-30 and 61-90 years old. The phenotype was estimated by immunostaining for cytokeratin 19 (CK 19) and the S-100 protein as well as by the presence of mucin and glycogen. The cell proliferation index was determined by the Ki-67 antibody. The histochemical techniques used periodic acid-Schiff (PAS) and Alcian Blue. In each captured microscopic field, the DLS were counted to establish a percentage for the staining profile. The statistical analysis was accomplished using Student’s t-test, the Mann-Whitney test and Pearson’s correlation coefficient (p<0.05).Results Comparing both groups, only CK 19 showed a statistically significant difference (p=0.033), with the strongest expression in the elderly group. There was no significant difference between PAS and Alcian Blue (p=0.270). In both groups, the immunostaining for CK 19 was stronger than that for S-100 (p=0.004;p<0.001), but there was no correlation between the two immunomarkers (ρ=-0.163; p=0.315). There was no immunostaining for Ki-67.Conclusions DLS demonstrate a ductal phenotypic profile and do not present cell proliferation activity. DLS may represent a regressive process arising from acini or represent the result of metaplasia.

Acinar autolysis and mucous extravasation in human sublingual glands: a microscopic postmortem study

“…On the other hand, the opposite could also be considered. Extrapolating this data to the clinic, we understand that the junction of all age-related microscopic changes may explain the decrease in glandular function 19 .…”

“…It is known that many microscopic changes in SG occur with the aging process 2 , 8 , 19 . Autolysis and mucous extravasation are only mentioned in some postmortem 2 , 8 , 11 and in vivo studies 5 in human 2 , 5 , 8 , 19 and animal 11 SG as occasional findings. However, these phenomena are not clarified or even described in the literature.…”

“…Age-related microscopic changes have been reported for the major 2 , 5 , 6 , 8 , 11 , 19 and minor 15 , 18 , 21 , 22 salivary glands of humans 2 , 5 , 8 , 14 , 15 , 18 , 19 , 21 , 22 and rats 6 , 11 . Main microscopic aspects described were: replacement of parenchyma by fat and connective tissue 2 , 8 , 15 , 21 , acinar atrophy and increase in the number of duct/duct-like structures 2 , 6 , 8 , 15 , 19 , 21 , focal and diffuse mononuclear infiltration 2 , oncocytosis 2 , 8 , 15 , and congested blood vessels 2 . In a previous study of age-related changes in human sublingual glands (HSG) 2 , in addition to the main microscopic aspects described, occasional phenomena such as acinar autolysis and mucous extravasation were also observed.…”