Organ specificity in mesenchymal induction demonstrated in the embryonic development of the mammary gland of the mouse☆

[摘要] Mammaryglandrudimentsof12-to14-daymouseembryosdevelopedtypicallyinorganculture,forminganipplewithanipplesheath,aramifyingductsystem,andadiposetissue.Bycontrast,rudimentstakenfrom16-dayembryosfailedtodevelopunderthesamecultureconditions.Thecharacteristic“restingphase”intheearlydevelopmentoftheglandwasalsoobservedinvitro,anditslengthwasfoundtodependontheageoftheepithelialcomponent.Trypsin-isolatedepithelialrudimentsdidnotdevelopintheabsenceofmesenchymebutspreadonthesubstrate.Epithelialspreadingalsooccurredwhentheamountofaccompanyingmesenchymewasverysmall.Trypsin-isolatedmammaryepitheliaof12-to16-dayembryoscouldsuccessfullyberecombinedwith12-daymammarymesenchyme,butwhensalivarymesenchymewasusedinstead,only16-dayepitheliawereabletocontinuedevelopment.Trypsin-isolated16-daymammaryepitheliaand12-dayepithelialrudiments,mechanicallydeprivedofmostoftheiradheringmesenchymalcells,werecombinedwithmesenchymeofthesubmandibularsalivaryglandof13-dayembryos.Themorphogeneticpatternoftheresultingglandularstructurewassimilartothatofthesalivarygland.Epithelialgrowthandbranchingwasgreatlystimulated,thebranchingpatternshiftedfrommonopodialtodichotomous,andevenadenomereformationoccurred.Whenmammaryorsalivaryglandepitheliawereexposedtothesimultaneouspresenceofbothtypesofmesenchymetheirmorphogenesiswasstronglyinhibitedandtypicalofneitherorgan.Thisisinterpretedasamutualinterferenceofthemorphogeneticinfluencesofmammaryandofsalivarymesenchyme.Theobviousorganspecificityof(salivary)mesenchymalinduction,andtheepitheliomesenchymalinterfaceasapossiblesiteofitsactionarediscussed.

[学科分类] 生物科学（综合）