简介：Withtheexceptionofmatureerythrocytes,cellswithinthehumanhematopoieticsystemarecharacterizedbythecellsurfaceexpressionofthepan-leukocytereceptorCD45.Here,weidentifyanovelsubsetamongmononuclearcordbloodcellsdepletedoflineagecommitmentmarkers(Lin-)thataredevoidofCD45expression.Surprisingly,functionalexaminationofLin-CD45-cellsalsolackingcellsurfaceCD34revealedtheywerecapableofmultipotentialhematopoieticprogenitorcapacity.Co-culturewithmouseembryoniclimbbudcellsdemonstratedthatLin-CD45-CD34-cellswerecapableofcontributingtocartilagenodulesanddifferentiatingintohumanchondrocytes.BMP-4,amesodermalfactorknowntopromotechondrogenesis,significantlyaugmentedLin-CD45-CD34-differentiationintochondrocytes.Moreover,unlikeCD34+humanhematopoieticstemcells,Lin-CD45-CD34-cellswereunabletoproliferateorsurviveinliquidcultures,whereassingleLin-CD45-CD34-cellswereabletochimerizetheinnercellmass(ICM)ofmurineblastocystsandproliferateinthisembryonicenvironment.OurstudyidentifiesanovelpopulationofLin-CD45-CD34-cellscapableofcommitmentintobothhematopoieticandchondrocyticlineages,suggestingthathumancordbloodmayprovideamoreubiquitoussourceoftissuewithbroaderdevelopmentalpotentialthanpreviouslyappreciated.

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简介：Humanplacenta-derivedmononuclearcells(MNC)wereisolatedbyaPercolldensitygradientandculturedinmesenchymalstemcell(MSC)maintenancemedium.Thehomogenouslayerofadherentcellsexhibitedatypicalfibroblastlikemorphology,alargeexpansivepotential,andcellcyclecharacteristicsincludingasubsetofquiescentcells.Invitrodifferentiationassaysshowedthetripotentialdifferentiationcapacityofthesecellstowardadipogenic,osteogenicandchondrogeniclineages.FlowcytometryanalysesandimmunocytochemistrystainshowedthatplacentalMSCwasahomogeneouscellpopulationdevoidofhematopoieticcells,whichuniformlyexpressedCD29,CD44,CD73,CD105,CD166,laminin,fibronectinandvimentinwhilebeingnegativeforexpressionofCD31,CD34,CD45andα-smoothmuscleactin.Mostimportantly,immuno-phenotypicanalysesdemonstratedthatthesecellsexpressedclassImajorhistocompatibilitycomplex(MHC-Ⅰ),buttheydidnotexpressMHC-Ⅱmolecules.Additionallythesecellscouldsuppressumbilicalcordblood(UCB)lymphocytesproliferationinducedbycellularornonspecificmitogenicstimuli.Thisstronglyimpliesthattheymayhavepotentialapplicationinallografttransplantation.SinceplacentaandUCBarehomogeneous,theMSCderivedfromhumanplacentacanbetransplantedcombinedwithhematopoieticstemcells(HSC)fromUCBtoreducethepotentialgraft-versus-hostdisease(GVHD)inrecipients.