The Important Role of Flt3-L in Ex Vivo Expansion of Hematopoietic Stem Cells Following Co-Culture With Mesenchymal Stem Cells

Objective: hematopoietic stem cells (hscs) transplantation using umbilical cord blood(ucb) has improved during the last decade. because of cell limitations, several studies focusedon the ex vivo expansion of hscs. numerous investigations were performed to introducethe best cytokine cocktails for hsc expansion the majority used the fms-relatedtyrosine kinase 3 ligand (flt3-l) as a critical component. according to flt3-l biology, inthis study we have investigated the hypothesis that flt3-l only effectively induces hscsexpansion in the presence of a mesenchymal stem cell (msc) feeder.materials and methods: in this experimental study, hscs and mscs were isolated fromucb and placenta, respectively. hscs were cultured in different culture conditions in thepresence and absence of msc feeder and cytokines. after ten days of culture, total nucleatedcell count (tnc), cluster of differentiation 34+ (cd34+) cell count, colony formingunit assay (cfu), long-term culture initiating cell (ltc-ic), homeobox protein b4 (hoxb4)mrna and surface cd49d expression were evaluated. the fold increase for some cultureconditions was compared by the t test.results: hscs expanded in the presence of cytokines and mscs feeder. the rate of expansionin the co-culture condition was two-fold more than culture with cytokines (p < 0.05).flt3-l could expand hscs in the co-culture condition at a level of 20-fold equal to thepresence of stem cell factor (scf), thrombopoietin (tpo) and flt3-l without feeder cells.the number of extracted colonies from ltc-ic and cd49d expression compared with acytokine cocktail condition meaningfully increased (p < 0.05).conclusion: flt3-l co-culture with mscs can induce high yield expansion of hscs andbe a substitute for the universal cocktail of scf, tpo and flt3-l in feeder-free culture.