Thymosin beta 10 expression in developing human salivary glands

Thymosin beta 10 (Tβ10) is a member of beta-thymosins (Tβs), a family of low molecular mass peptides abundant in many cell types. In previous studies, Tβs have been shown to play essential roles in many cellular functions, including cytokinesis, migration and endocytosis. Recently, Tβ10 has been found in high quantities in the saliva of human newborns, while it disappeared in the adults. On the basis of these data, it seemed of some interest to study the influence of Tβ10 during the development of the human salivary glands. To this end, we analyzed, using immunocytochemistry, the expression of Tβ10 in samples of the major and minor salivary glands obtained, at autopsy, from 2 human fetuses and 4 newborns, ranging from 13 up to 33 weeks of gestation. Tβ10 immunoreactivity was detected in all salivary glands examined, with marked differences from one gland to the next, the parotid glands showing the highest Tβ10 reactivity and minor salivary glands the lowest reactivity. Marked changes were observed in Tβ10 expression and localization during embryogenesis. Tβ10 was mainly localized extracellularly in the youngest human fetuses (13 weeks), in the cytoplasm of immature duct cells at 20 weeks, in acinar cells and in the duct lumen in 33 weeks old fetuses. Our data show, for the first time, a strong expression of Tβ10 in the human salivary glands during the initial phases of the physiological development, present at the 13th week of gestation, and suggesting a role for the peptide in the salivary glands' organogenesis.