Intracytoplasmic tagging of cells with ferumoxides and transfection agent for cellular magnetic resonance imaging after cell transplantation: methods and techniques.
BACKGROUND
Superparamagnetic iron oxides (SPIO) are being used to label cells for in vivo monitoring by magnetic resonance imaging (MRI). The purpose of this study is to present protocols using SPIO and a polycationic transfection agent for magnetic labeling of cells as a basis for cellular MRI.


METHODS
Various concentrations of ferumoxides (FE)-poly-l-lysine (PLL) complexes were used to magnetically label cells. Iron incorporation into cells along with cell viability and short- and long-term toxicity were evaluated.


RESULTS
Rapidly growing cell suspension and adherent cells were effectively labeled by means of endocytosis into endosomes at low concentrations of FE (25 microg/mL media) and PLL (0.75 microg/mL media). Hematopoietic stem cells and lymphocytes required higher concentrations of PLL (1.5 microg/mL) in serum-free media during initial FE-PLL complex formation before labeling the cells in culture. Total iron concentration in cells depended on the cell type, concentration of FE-PLL complexes in media, cellular density, and incubation time. Iron concentrations after overnight incubation with given FE at 25 microg/mL media resulted in, for example, T cells being labeled with 1 to 3 pg/cell of intracytoplasmic endosomal iron and 15 to 20 pg/cell of intracytoplasmic iron in mesenchymal stem cells compared with 0.01 to 0.1 pg/cell for unlabeled cells. Protocols developed for this study demonstrated no adverse effect on the cell viability, functional capacity, or toxicity.


CONCLUSIONS
This technique can be used to label cells for in vivo MRI tracking of stem cells and lymphocytes. FE at a concentration of 25 to 50 microg/mL with a ratio of SPIO to PLL of 1:0.03 to 1:0.06 would be sufficient to label cells for cellular MRI.
Arbab
Ali S
AS
Experimental Neuroimaging Section, Laboratory of Diagnostic Radiology Research, National Institutes of Health, Bethesda, MD 20892, USA. saali@cc.nih.gov.
Bashaw
Lindsey A
LA
Miller
Bradley R
BR
Jordan
Elaine K
EK
Bulte
Jeff W M
JW
Frank
Joseph A
JA
D000818:Animals; D002454:Cell Differentiation; D002470:Cell Survival / Q000187:drug effects*; D017690:Cell Transplantation; D004396:Coloring Agents; D003593:Cytoplasm / Q000378:metabolism; D003911:Dextrans; D004338:Drug Combinations; D005295:Ferrocyanides; D052203:Ferrosoferric Oxide; D006801:Humans; D007202:Indicators and Reagents; D007501:Iron / Q000378:metabolism / Q000493:pharmacokinetics; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D009369:Neoplasms / Q000175:diagnosis; D009994:Osmolar Concentration; D010087:Oxides / Q000493:pharmacokinetics; D011107:Polylysine / Q000493:pharmacokinetics; D013997:Time Factors
D004396:Coloring Agents; D003911:Dextrans; D004338:Drug Combinations; D005295:Ferrocyanides; D007202:Indicators and Reagents; D058185:Magnetite Nanoparticles; D010087:Oxides; D011107:Polylysine; D007501:Iron; C065507:ferumoxides; C000170:ferric ferrocyanide; D052203:Ferrosoferric Oxide