title: Hematopoietic stem cell (CD34+) uptake of superparamagnetic iron oxide is enhanced by but not dependent on a transfection agent.
abstract: OBJECTIVE
  Tracking the fate of cells after infusion would be a valuable asset for many stem cell therapies, but very few (cell) labels are approved for human therapeutic use. Superparamagnetic iron oxide particles (SPIO) can be internalized into stem cells in vitro to allow real-time tracking with gradient echo magnetic resonance imaging, but SPIO are approved for (diagnostic) imaging and not for (therapeutic) cell labeling in vivo. In this study, we investigated the possibility of labeling stem cells with an SPIO approved for patient use, albeit in a novel manner by enhancing uptake with the use of a transfection agent, also approved for patient use. Although there are many reports of hematopoietic stem cells being labeled with SPIO, there is some controversy regarding the efficiency of this and whether undifferentiated CD34+ progenitor (stem) cells are able to take up iron in the absence of a transfection agent to enhance the process.
  
  
  METHODS
  Human CD34+ cells were treated in vitro as follows: incubation with (i) medium only (control), (ii) ferumoxide (Endorem) and (iii) ferumoxide (Endorem) plus exposure to a transfection agent (protamine sulfate). Cells were incubated for 2, 4 and 24 hours and assessed for viability, differentiation capacity and visualized in vitro with 3-T magnetic resonance imaging. The cells were also analyzed by means of flow cytometry and morphology examined by electron microscopy.
  
  
  RESULTS
  CD34+ hematopoietic progenitor cells can internalize ferumoxide (Endorem) independently of a transfection agent. However, uptake of ferumoxide is enhanced after exposure to protamine sulfate. Iron labeling of CD34+ cells in this manner does not affect cell viability and does not appear to affect the potential of the cells to grow in culture. Iron-labeled CD34+ cells can be visualized in vitro on 3-T magnetic resonance image scanning.
  
  
  CONCLUSIONS
  Endorem and protamine sulfate can be combined to promote iron oxide nanoparticle uptake by CD34+ cells, and this methodology can potentially be used to track the fate of cells in a clinical trial setting because both compounds are (separately) approved for clinical use.
authors.affiliation: Stroke Trials Unit, University of Nottingham, Nottingham, UK.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: England
authors.forename: Philip M W
authors.initials: PM
authors.lastname: Bath
authors.forename: Maryam
authors.initials: M
authors.lastname: Abaei
authors.forename: Dorothee
authors.initials: D
authors.lastname: Auer
authors.forename: D Rhodri E
authors.initials: DR
authors.lastname: Jones
mesh_terms: D018952:Antigens, CD34 / Q000235:genetics; D002454:Cell Differentiation; D058948:Cell Tracking; D003287:Contrast Media; D052203:Ferrosoferric Oxide; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles / Q000008:administration & dosage; D059630:Mesenchymal Stem Cells / Q000166:cytology; D014162:Transfection / Q000379:methods
chemical_list: D018952:Antigens, CD34; D003287:Contrast Media; D058185:Magnetite Nanoparticles; D052203:Ferrosoferric Oxide