The Research On The Morphology, The Expression Of Na~+-k~+-ATPase Of Endolymphatic Sac, Stria Vascularis And Mesenchymal Stem Cells In Cochlea During Mice Embryo Development

Part Ⅰ The study on the dissection of endolymphatic sac via cranium of guinea pigObjective: To demonstrate the effect of endolymphatic sac on the function of inner ear, we detect a new way to dissect the endolymphatic sac.Method: Healthy adult guinea pig was intracranial vivisected under the microscope and the anatomy of the process to was recorded by the camera system and results of histological verification results.Result: Accurate positioning endolymphatic sac on the guinea pig skulls Specimen and vivisect endolymphatic sac of guinea pig successfully under the microscope, the endolymphatic sac was confirmed by the histological results.Conclusion: It is a simple and easy method to dissect endolymphatic sac via cranium of guinea pig.Part Ⅱ The research on the morphology, the expression of Na~+-K~+-ATPase of endolymphatic sac, stria vascularis during mice embryo developmentObjective: To detect both the morphology and the expression of Na~+-K~+-ATPase of endolymphatic sac, stria vascularis during mice embryo development.Method: A. Kun Ming mice with normal pinna reflex was choosed to mate with a ratio of 2:1(female:male). Embryos at E12-E2,P1-P3 were obtained from healthy. B. Paraffin sections and HE staining for E12-E20 and P1-P3 mouse embryonic temporal bone specimens were carried out to observe the morphological of every stages under a microscope. C. Immunohistochemistry was used to determine the expression level of the Na~+-K~+-ATPase in endolymphatic sac and stria vascularis at E13-E20.Results: The endolymphatic sac primordial formed from the expansion of endolymphatic duct tip at E13, and then developed into cystic structure at E14 and papillary structures formed at E18. The lateral wall of cochlear duct formed stria vascularis primordial from basal turn to apex turn from E15 to E19, developing into mature stria vascularis( three-cell structure)from basal turn to apex turn from P1 to P3. The Na~+-K~+-ATPase expression of endolymphatic sac epithelium was weak at E13. However, it’s expression level gradually increased from E14 to E20. There is no expression in cochlear duct at every embryo stages.Conclusion: Endolymphatic sac derived from the vestibule and stria vascularis evolved from the lateral wall of the cochlear duct. Development and maturation of endolymphatic sac were earlier than the stria vascularis which was gradually mature from cochlear duct basal turn to apex turn. Whole cochlear duct only develop into mature cochlear Scala media. The Na~+-K~+-ATPase expression in endolymphatic sac during embryo development speculate high K+ in endolymph,which plays an important role in the development of inner ear hair cells. We estimate that endolymphatic sac epithelium began to absorb endolymph since the endolymphatic sac express AQP2 at E18.Part Ⅲ Mesenchymal stem cells in mouse development embryonic cochleaObjective: The area surrounding the mouse cochlear duct contains many mesenchymal cells during embryonic development. In this study we investigate whether these mesenchymal cells are stem cells.Methods: Embryos at various embryonic stages were obtained from healthy and normal mice with sensitive pinna reflex. Frozen sections at each period of embryonic development were used for immunohistochemistry to determine the expression of the stem cell markers cadherin and SSEA4.Results: The mice cochlear volute appeared at embryonic day 14(E14). Cadherin and SSEA4 were expressed in mesenchymal cells beyond the cochlear duct cells and spiral ganglion-like cells at E15. The expression of cadherin and SSEA4 in mesenchymal cells were weaken or even disappeared at E16.Conclusion: During embryonic development, the mesenchymal cells in mouse cochlea were similar to stem cells and may disappear gradually at E16.