Characterization of 18F-FDG uptake in human endothelial cells in vitro.
The contribution of (18)F-FDG uptake by endothelial cells to uptake values measured by PET in various tissues is as yet unclear. We therefore sought to characterize (18)F-FDG uptake in an in vitro model of human endothelial cells.


METHODS
Commercially obtained human umbilical vein endothelial cells (HUVECs) were seeded in 6-multiwell plates 48-96 h before incubation with 1-2 MBq (18)F-FDG per well. Radioactivity measurements were performed after washing and mechanical dissolvation of the cellular monolayers. Cellular (18)F-FDG uptake was referred to protein concentration. This experimental protocol was subsequently varied to study the effect of different parameters of interest. Furthermore, radio-thin-layer chromatography was used to identify intracellular (18)F-FDG metabolites. (18)F-FDG uptake in HUVECs was compared with that by a human monocyte-macrophage (HMM) preparation and by glioblastoma cells (GLIOs) under identical experimental conditions.


RESULTS
(18)F-FDG accumulated in HUVECs in a time-dependent manner and was trapped mainly as (18)F-FDG-6-phosphate and (18)F-FDG-1,6-diphosphate. Unlabeled glucose and cytochalasin B competitively inhibited (18)F-FDG uptake, whereas phlorizin had no significant effect. Glucose deprivation significantly enhanced (18)F-FDG uptake by a factor of 2.7, whereas sodium depletion had no significant influence. HUVECs treated with vascular endothelial growth factor (VEGF) showed a significant 82% increase in (18)F-FDG accumulation after a 2-h exposure to 50 ng/mL VEGF. (18)F-FDG uptake in HUVECs was significantly higher than that in HMMs and in the range of the uptake values measured in GLIOs.


CONCLUSIONS
(18)F-FDG accumulates in HUVECs by mechanisms analogous to those in neoplastic cells or neurons. VEGF significantly stimulates endothelial (18)F-FDG uptake. The observed differences in (18)F-FDG uptake between HUVECs, HMMs, and GLIOs are difficult to extrapolate to in vivo conditions but stimulate further studies on the contribution of endothelial (18)F-FDG uptake to the overall uptake of that tracer in neoplastic or vascular lesions.
Maschauer
Simone
S
Department of Nuclear Medicine, Laboratory of Molecular Imaging, Friedrich-Alexander University, Erlangen, Germany.
Prante
Olaf
O
Hoffmann
Markus
M
Deichen
J Thiess
JT
Kuwert
Torsten
T
D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging* / Q000378:metabolism*; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D005909:Glioblastoma / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D009000:Monocytes / Q000000981:diagnostic imaging* / Q000378:metabolism*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism; D014471:Umbilical Veins / Q000000981:diagnostic imaging / Q000378:metabolism
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D012964:Sodium; D005947:Glucose