Stereological and immunohistochemical study of development of human fetal labial salivary glands and their S-100 protein reactivity

Stereological and certain histochemical aspects of fetal growth and development of human labial salivary glands are reported. Stereological analysis showed a highly significant progressive increase in proportional gland volume occupied by acini from 27% at 20 weeks to 56% at 38 weeks ( P <0.0001), and a comparable halving of the relative gland volume occupied by connective tissue in the same period ( P <0.0001). Linear regression fitted the data well (r²= 0.59 and 0.47 respectively, n=46 ). The change in relative volume occupied by ducts or by vascular tissue was small and did not reach significance. S-100 protein reactivity was demonstrated in the cytoplasm of cells of the labial gland primordia from their origin. As gland differentiation progressed, the S-100 reactivity became localized in basophil acinar cells and in proximal (intercalated and intralobular), but not in distal, duct cells. A gradual increase in intensity of S-100 protein activity at these sites during salivary gland development was observed. Morphological maturity seems to be complete before 29 weeks but myocpithelial cells could not be identified with certainty.