| Objectives (1) To observe the histomorphologic development of human fetal major salivary (submandibular, parotid and sublingual) glands. (2) To observe the expression, distribution and developmental regularities of leptin and leptin receptor in fetal major salivary glands. (3) To approach the meaning and relationship of leptin and leptin receptor in fetal major salivary glands and the development of major salivary glands. (4) To approach the significance and relationship between leptin and the ontogeny of human fetus. Methods (1) Hematoxylin-Eosin (HE) staining. (2) Immuno-histochemical SABC method. Results (1) In tissue sections with HE staining, branched cellular twigs and terminal buds which cell arranged densely were seen in major salivary glands of the 13-week fetus, and some of the cellular twigs had a lumen. At 14th week, terminal buds had a lumen too. With the growth of fetus from 17 to 23 weeks, ducts mainly differentiated into interlobular and striated ducts as their number increased, but it wasn't easy to identify intercalated ducts; acini appeared and acinar cells differentiated into serous and mucous cells when their number increased; glands were divided into lobules by connective tissues. From 24 to 35 weeks, the ducts and acini of every salivary gland were chubbier and more exuberant. (2) After using histochemical method, the epithelial cells of ducts in fetal submandibular, parotid and sublingual glands showed leptin-immunoreactivity weak positive at 13th week. The immunoreactive materials distributed in the epithelial cytoplasm of the ducts. Nuclei were negative. The staining intensity increased with increasing gestational age. It increased to intense positive in submandibular gland of the 24-week fetus, and increased tomoderate positive in parotid and sublingual glands of the 17-week fetus when it seemed to be stabilized thereafter. (3) At 13th week, the epithelial cells of ducts in fetal submandibular, parotid and sublingual glands showed leptin receptor-immunoreactivity weak positive too. With the growth of gestational age, the immunoreactive intensity increased. At 22th week, it increased to intense positive, and weaker after 23 weeks. The immunoreactive materials also distributed in the epithelial cytoplasm of the ducts. Nuclei showed negative. Conclusion (1) In developing human fetal major salivary glands, branched cellular twigs and terminal buds were found at first, then they developed into the formation of ducts which had a lumen and differentiated successively into interlobular, striated and intercalated ducts and acini. (2) Leptin and leptin receptor were present in fetal major salivary glands, they were localized principally in the epithelial cytoplasm of the ducts and showed a certain developmental regularity. (3) Leptin and leptin receptor may be involved in fetal major salivary glands and gastrointestinal development and the functional regulation. |
