The development of rat palatal shelves in vitro: An ultrastructural analysis of the inhibition of epithelial cell death and palate fusion by the epidermal growth factor

[摘要] Unfusedpalatalshelvesfromday-15ratembryoswereculturedwiththeirmedialedgesincontact.Duringthenext20hrepithelialsurfacesofapposingshelvesadhered,andtheepithelialcellsinthisareadegeneratedandwerereplacedbymesenchymalcellsinamannersimilartothatreportedforpalatefusioninvivointheratandinvitrointhemouse.Fourhoursaftercontactthesuperficialcellsofapposingpalatesadheredwitha10–25-nmdistanceseparatingcellmembraneswhileafter20hrthesecellswereeithereliminatedorhadlosttheirflattenedappearanceandbecomeindistinguishablefromthecuboidal-shapedcellsadjacenttothebasementmembrane.Theratioofcytoplasmtonucleoplasmwasreduced,anddegeneratedcellswereeliminatedbymacrophages.Additionofepidermalgrowthfactor(EGF)totheculturemediuminhibitedepithelialadhesionanddegeneration.Basalandsuperficialcellsretainedtheiroriginalappearance,whiletheratioofcytoplasmtonucleoplasmwasincreased.Numerousdesmosomesandtonofilamentswereevidentaswellaselaboratemembranefoldings.Theappearanceofthesecellularelementsissimilartothatobservedinkeratinizingpalatalepithelialcellsfromtheoralregion.TheseresultssuggestthatEGFinducestheepithelialcellstokeratinize,andasaconsequencethenormalsequenceofstepsofpalatefusionareinhibited.

[学科分类] 生物科学（综合）