The Histological And Ultrastructural Observation Of Development Of Miniature Pig Salivary Glands

BACKGROUND:Salivary glands are classic models for studying developmental events such as organ development, branching morphogenesis,epithelial-mesenchymal interaction because they have relative simple structures.Salivary glands development involves many interplay events which include cell migration,proliferation,differentiation and morphogenesis.Underlying these cellular processes are complex changes in gene expression.The research of the salivary gland development and the gene regulation mechanism can provide basic and useful information for the future research of salivary gland gene therapy,tissue engineering and salivary gland function restoration.The most popular animal models for studying salivary gland development are Drosophlia and rodents,such as mouse.The advantages of these models are that they are affordable and easy to manage. However the disadvantages of these models are also obvious.The gross anatomical, morphological and physiological features of salivary glands of these models are different from those of human salivary gland.The miniature pig is increasingly used as a large animal model for variety of biomedical and pre-clinical investigations.Previous studies demonstrated that the volume,weight,anatomy and histology of miniature pig salivary glands are more similar to those of human than Drosophlia and mouse,so the miniature pig may be a better animal model for salivary gland development research.Unfortunately there is little information about the histological and ultrastructural observation of miniature pig salivary gland development.OBJECTIVE:1.To observe the sequential histological features of different development stages of miniature pig salivary glands(parotid gland and submandibular gland)and identify the embryonic day of the different development stages of salivary glands.2.To observe the sequential ultrastructural feathers of different development stages of miniature pig salivary glands(parotid gland and submandibular gland)and discuss the correlation of histological and ultrastructural observations.MATERIALS AND METHODS:1.Select the E40,E60,E80,E95 miniature pig embryo and the P0 miniature pig,3 embryos/stage,the parotid gland and submandibular gland were removed from the E60,E80, E95 miniature pig embryo and the P0 miniature pig,the whole head were cut from the E40 embryo.2.Get the salivary gland samples of different development stages,3samples/stage.Serial section were made for all the samples.The sections were stained with Hematoxylin and Eosin,and the histological features are observed and described.3.Ultrastructural study,Ultrastructural features of different salivary gland development stages by using transmission electron microscope.RESULTS:1 The development process of miniature pig salivary gland(parotid gland and submandibular gland)were divided into 5 stages based on the features of development,including Initial Bud stage(E40),Pseudoglandual stage(E60),Canalicular stage(ES0),Terminal Bud stage(E95), Mature stage(P0).In the same embryonic day,the submandibular gland develops earlier than parotid gland.2 Verify the histological features in the ultrastructural level and observe the ultrastructural features of different cells and structures.CONCLUSION:This is the first study presenting dynamic morphological changes of salivary gland in the miniature pig.Observe the sequential histological and ultrastructural features of different development stages of miniature pig salivary gland(parotid gland and submandibular gland)and identify the embryonic day of the different development stage of salivary gland.Observe the ultrastructural features of different cells and structures.Find that in the same embryonic day,the submandibular gland develops earlier than parotid gland.