The Morphology Of Miniature Pig’s Inner Ear Development

With the dramatic development of life science, pigs play a more and more important role in the experiments and applications of life science research. Pigs show unique advantages in the aspects of animal models about human diseases, the effectiveness and security evaluation of new drugs and the donation of xenotransplantation. Comparative medicine has demonstrated that pigs share a lot of similarities with human beings in cardiovascular and digestive system, skin structure, bone development, nutritional demands as well as mineral metabolism. As a kind of animal model, pig is superior to other experimental animals in various research areas. They are widely used experimental animals in medical biology research with growing importance. Extensively utilized in medical and scientific research, miniature pigs are studied by most branches of life science. China possess special and abundant resources of experimental miniature pigs. In their original place, those pigs are included in isolated groups formed by long-term inbreeding. For example, there are some selected distinctive species of miniature pigs in the areas such as Guizhou Province, Xishangbanna, Bama County, Wuzhishan and Tibet. When compared to the large size, high rearing expense and inconvenience of experimental operation and postoperative management of ordinary pigs, the miniature pigs are easier to be used in experiments, convenient for microbial control and have low rearing costs due to their relative small size. Because of these advantage, miniature pigs gradually become important experimental animal of life science. Affected by some factors as popularity of animal protection and "3R" principle, the number of miniature pigs used in experiments increases rapidly. It is expected to substitute monkeys and dogs to become a new type of experimental animals which can be used extensively. Therefore, as animal models, miniature pigs have broad application prospects and significant position in the biomedical research field with incomparable superiority. Choosing miniature pigs as animal models for otological research and studying the morphological changes of miniature pigs’ inner ear development can provide morphological support for further research. Part one:The Morphology of Miniature Pig’s Cochlear DevelopmentObjective:Studying the developing process of domestic Guizhou miniature pig’s inner ear can provide morphological support for gene regulation and immunohistochemistry during the cochlear development of miniature pig and for the further research which use miniature pig as animal model.Materials and Methods:Pregnant Guizhou miniature pigs, E21(embryo21), E28, E32, E35, E42, E49, E56, E63,E70,E77,E84,E91, E98,E107were chosen as animal models. The heads of embryos were taken within49days and the cochleas were taken under the microscope after56days. The collodion-embedded frozen section technique was applied to slice the embryonic heads horizontally and the cochlea according to the parallels of modiolus, then made serial sections. At the same time, we used the HE staining method to observe the morphological evolution process of cochlear development of Guizhou miniature pigs.Results:The otic vesicles of Guizhou miniature pigs appeared at the21st day of the embryonic developing period, followed with the development of cochlea. Enormous changes of morphological evolution took place during the49th day and56th day. The cochlea showed primary mature appearance by the end of the56th days of embryonic development. During the process of embryonic development, the mesenchyme filled in the cochlea of the pigs could be observed between the56th and63rd day. In the70th day, three rows of outer hair cells and a row of inner hair cells could be perceived clearly together with the cochlear duct which had developed to3.5laps. And finally, in the91st day, the hair cells and supporting cells had became mature and the structure of Corti’s organ achieved its complete appearance.Conclusion:The development of hearing organs contains certain regularities. Requiring longer time to develop and achieving mature appearance during embryonic period, the inner ear developing process of Guizhou miniature pigs has a lot of similarities with the process of humans. Part two:The Morphology of Stria Vascularis Development of Miniature PigObjective:Stria vascularis, the metabolically active epithelial tissue, which is located on the outer sidewall of cochlear tube, has the function of producing K+, absorbing the electrolytes of endolymph and generating endolymphatic positive potential. The high concentration of K+in endolymph and the circulation of K+in both endolymph and perilymph are the basis of maintaining cochlear function and homeostasis. Through observing the development of stria vascularis of Guizhou miniature pigs, morphological support is provided to study the gene regulation, immunohistochemistry and situ hybridization during the stria vascularis developing process.Results:At the49th day of embryonic period, the stria vascularis began to develop and its epithelium emerged at the56th day. The structure maturation of stria vascularis was accomplished in the91st day, at this time, three layers of typical cells, which were marginal cells, intermediate cells and basal cells, could be observed.Materials and Methods:The cochlea of E63、E77、E84、E98were chosen as examples and the structure of their stria vascularis were observed under transmission electron microscope.Conclusion:The development of the stria vascularis of Guizhou miniature pigs follows the order of basal turn to apical turn and its maturation can be achieved during the embryonic period. Both of the characteristics are very similar to humans.