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.
