title: Effects of EdU labeling on mesenchymal stem cells.
abstract: BACKGROUND
  Thymidine analog 5-ethynyl-2-deoxyuridine (EdU) has recently been used for tracking mesenchymal stem cells (MSCs). In the present study, we tested whether EdU was cytotoxic and whether it interfered with differentiation, cytokine secretion and migration of MSCs.
  
  
  METHODS
  EdU labeling was performed by incubating adipose-derived stem cells (ADSCs) with 10(-8) mol/L of EdU for 48 h. Incorporation of EdU was detected by reaction with azide-conjugated Alexa594. The labeled and unlabeled ADSCs were compared for proliferation and apoptosis as determined by CellTiter and comet assays, respectively. They were also compared for neuron-like and endothelial differentiation as determined by morphology, marker expression and function. Comparison of their secreted cytokine profile was performed by cytokine antibody array. Comparison of their response to homing factor SDF-1 was performed by migration assay.
  
  
  RESULTS
  EdU was incorporated into the nucleus in approximately 70% of ADSCs. No significant differences in proliferation and apoptosis rates were observed between EdU-labeled and unlabeled ADSCs. Isobutylmethylxanthine induced both EdU-labeled and unlabeled ADSCs to assume a neuron-like morphology and to express β-III tubulin. Endothelial growth medium-2 (EGM2) induced endothelial differentiation in both EdU-labeled and unlabeled ADSCs, including the ability to uptake low-density lipoprotein and to form capillary-like structures as well as the expression of vWF, eNOS and CD31. EdU-labeled and unlabeled ADSCs exhibited identical secreted cytokine profile and identical migratory response to SDF-1.
  
  
  CONCLUSIONS
  At the recommended dosage of 10(-8) mol/L, EdU is non-toxic to ADSCs. EdU label did not interfere with differentiation, cytokine secretion or migratory response to SDF-1 by ADSCs.
authors.affiliation: Knuppe Molecular Urology Laboratory, Department of Urology, School of Medicine, University of California, San Francisco, CA 94143, USA.
authors.forename: Hongxiu
authors.initials: H
authors.lastname: Ning
authors.forename: Maarten
authors.initials: M
authors.lastname: Albersen
authors.forename: Guiting
authors.initials: G
authors.lastname: Lin
authors.forename: Tom F
authors.initials: TF
authors.lastname: Lue
authors.forename: Ching-Shwun
authors.initials: CS
authors.lastname: Lin
mesh_terms: D017667:Adipocytes / Q000166:cytology*; D000273:Adipose Tissue / Q000166:cytology; D017209:Apoptosis / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D003857:Deoxyuridine / Q000009:adverse effects / Q000031:analogs & derivatives*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology*
chemical_list: D016207:Cytokines; C031086:5-ethynyl-2'-deoxyuridine; D003857:Deoxyuridine