title: The Important Role of FLT3-L in Ex Vivo Expansion of Hematopoietic Stem Cells following Co-Culture with Mesenchymal Stem Cells.
abstract: OBJECTIVE
  Hematopoietic stem cells (HSCs) transplantation using umbilical cord blood (UCB) has improved during the last decade. Because of cell limitations, several studies focused on the ex vivo expansion of HSCs. Numerous investigations were performed to introduce the best cytokine cocktails for HSC expansion The majority used the Fms-related tyrosine kinase 3 ligand (FLT3-L) as a critical component. According to FLT3-L biology, in this study we have investigated the hypothesis that FLT3-L only effectively induces HSCs expansion in the presence of a mesenchymal stem cell (MSC) feeder.
  
  
  METHODS
  In this experimental study, HSCs and MSCs were isolated from UCB and placenta, respectively. HSCs were cultured in different culture conditions in the presence and absence of MSC feeder and cytokines. After ten days of culture, total nucleated cell count (TNC), cluster of differentiation 34+(CD34(+)) cell count, colony forming unit 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 culture conditions was compared by the t test.
  
  
  RESULTS
  HSCs expanded in the presence of cytokines and MSCs feeder. The rate of expansion in 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 the presence 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 a cytokine cocktail condition meaningfully increased (P<0.05).
  
  
  CONCLUSIONS
  FLT3-L co-culture with MSCs can induce high yield expansion of HSCs and be a substitute for the universal cocktail of SCF, TPO and FLT3-L in feeder-free culture.
authors.affiliation: Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran ; Faulty of Paramedics, Kermanshah University of Medical Science, Kermanshah, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Oubari
authors.affiliation: Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran.
authors.forename: Naser
authors.initials: N
authors.lastname: Amirizade
authors.affiliation: Department of Medical Immunology, Faculty of Medical Science, Tarbiat Modares University, Tehran, Iran.
authors.forename: Hemn
authors.initials: H
authors.lastname: Mohammadpour
authors.affiliation: Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran.
authors.forename: Mozhdeh
authors.initials: M
authors.lastname: Nakhlestani
authors.affiliation: Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran.
authors.forename: Mahin Nikougoftar
authors.initials: MN
authors.lastname: Zarif
keywords: Expansion; Fms-Related Tyrosine Kinase 3 Ligand; Hematopoietic Stem Cells; Mesenchymal Stem Cells