Mammary gland morphogenesis in vitro: Formation of branched tubules in collagen gels by a cloned rat mammary cell line

[摘要] Thethree-dimensionalgrowthinvitroofclonedratmammarycelllinesonfloatingtypeIcollagengelshasbeeninvestigated.Multicellularoutgrowthsformedbythevariouscelltypesshowmorphologicaldifferencesonserialhistologicalsectioningandelectronmicroscopy.Onecellline,Rama25,anepithelialcelllinederivedfromadimethylbenz(a)anthracene(DMBA)-inducedmammaryadenocarcinomacanformbranchedtubuleswithinthematrix.Theamountofcollageninthematrixmodifiedthestructureofthepredominantoutgrowthsformedbythiscellline.High-concentration(0.6%w/v)collagengelssupportthegrowthoftubulesupto0.5mminlengthwhichhaveanextensivelumensurroundedbyringsofupto26cells.Absenceofdifferentiatedmyoepithelialelementsaroundtheringsuggestsaresemblencetoprimitiveductsfoundinthemammaryglandsofneonatalrats.Thespectrumofcellularpolaritytowardthelumenseenthroughoutthetubulesandtheoccasionalirregulararrangementofepithelialcellsarefeaturesofadenocarcinoma.Lumenformationoccursbycentralcellnecrosisandseparationoftheexternallayersofinitiallysolidcords.Thetubulesbrancheitherdichotomously,bybifurcationatthedistalendsormonopodially,bybuddingatthesidesoftheoutgrowths.Rama25grownongelscontaininglowerconcentrationsofcollagen(0.1or0.3%w/v)producenarrowbranchingstructureswithincompleteluminaandspikesofelongatedcells.TubularstructuresarenotformedbyRama25grownonnonfloatinggels.Atthelightmicroscopiclevelthelayerofspindlecellsformedbeneaththesurfacemonolayeronnonfloatedgelsresemblesthesarcomatousregionsoftumors,howeverattheultrastructurallevelthespindlecellsshowsomeevidenceofbeingmyoepithelial-likeratherthanfibroblast-like.Sandwichingtheepithelialcellsheetbetweentwolayersofcollagengelresultsinlossofcontactwiththemediaandtheformationofspindlecells.Themyoepithelial-likecelllinesRama29andRama401formspikedbranchesofelongatedcellsandsolidbranchingcordsofcells,respectively.However,nolumenformationisobserved.Thefibroblast-likecelllineRama27showsextensivemigrationofeithersinglecellsorchainsofcellsintothegel.Thusonlyonecelltype(Rama25)isnecessarytoformbranchedtubulesinvitroandthestructureofthetubulescanbemodifiedbycollagen,acomponentoftheextracellularmatrix.

[学科分类] 生物科学（综合）