title: Ex vivo expansion of cord blood progenitors impairs their short-term and long-term repopulating activity associated with transcriptional dysregulation of signalling networks.
abstract: OBJECTIVE
  Cord blood (CB) has been established to be an alternative source of haematopoietic stem/progenitor cells (HPC) for transplantation. The number of HPC per CB unit is limited, which results in engraftment delay. Ex vivo expansion of HPC improvement must overcome this.
  
  
  METHODS
  Flow cytometry was used to extensively phenotype HPC pre- and post-expansion and CFDA-SE staining was used to track cell divisions. The NSG mouse model was employed in transplantation studies to determine long and short term repopulation in human cells. Gene array analysis was used to evaluate signalling pathways regulated following ex vivo expansion of HPC.
  
  
  RESULTS
  expansion of CD34(+) HPC impaired their regenerative function. In this xenograft transplantation model we showed that repopulating activity of CB cells declined following expansion. Expanded HPC had delayed engraftment at early and late stages post-transplant. High resolution division tracking revealed that the cultured HPC had reduced expansion and self-renewal probability and increased differentiation rate compared to non-expanded cells. Gene expression analysis exposed significant modulation of a complex network of genes and pathways that normally maintain HPC proliferation and limit their differentiation.
  
  
  CONCLUSIONS
  The decline in short-term engraftment is consistent with the loss of rapid SCID repopulating ability r(SRA) by expanded CD34(+) CD38(+) cells recently reported. Our data raise concerns for future clinical applications of expanded HPC alone in transplantation.
authors.affiliation: Sydney Cord & Marrow Transplant Facility, Sydney Children's Hospital, Sydney, NSW, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Holmes
authors.forename: F
authors.initials: F
authors.lastname: Yan
authors.forename: K-H
authors.initials: KH
authors.lastname: Ko
authors.forename: R
authors.initials: R
authors.lastname: Nordon
authors.forename: E
authors.initials: E
authors.lastname: Song
authors.forename: T A
authors.initials: TA
authors.lastname: O'Brien
authors.forename: A
authors.initials: A
authors.lastname: Dolnikov
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D005312:Fetal Blood / Q000166:cytology*; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D016130:Immunophenotyping; D051379:Mice; D015398:Signal Transduction; D013997:Time Factors; D014183:Transplantation, Heterologous
chemical_list: D018952:Antigens, CD34; D018797:Cell Cycle Proteins