J Korean Soc Magn Reson Med.  2013 Sep;17(3):181-191. 10.13104/jksmrm.2013.17.3.181.

Serial MR Imaging of Magnetically Labeled Humen Umbilical Vein Endothelial Cells in Acute Renal Failure Rat Model

• Lee SJ
• Lee SY
• Kang KP
• Kim W
• Park SK

• KMID: 2206916
• DOI: http://doi.org/10.13104/jksmrm.2013.17.3.181

Abstract

PURPOSE
To evaluate the usefulness of in vivo magnetic resonance (MR) imaging for tracking intravenously injected superparamagnetic iron oxide (SPIO)-labeled human umbilical vein endothelial cells (HUVECs) in an acute renal failure (ARF) rat model.
MATERIALS AND METHODS
HUVECs were labeled with SPIO and poly-L-lysine (PLL) complex. Relaxation rates at 1.5-T MR, cell viability, and labeling stability were assessed. HUVECs were injected into the tail vein of ARF rats (labeled cells in 10 rats, unlabeled cells in 2 rats). Follow-up serial T2*-weighted gradient-echo MR imaging was performed at 1, 3, 5 and 7 days after injection, and the MR findings were compared with histologic findings.
RESULTS
There was an average of 98.4+/-2.4% Prussian blue stain-positive cells after labeling with SPIO-PLL complex. Relaxation rates (R2*) of all cultured HUVECs at day 3 and 5 were not markedly decreased compared with that at day 1. The stability of SPIO in HUVECs was maintained during the proliferation of HUVECs in culture media. In the presence of left unilateral renal artery ischemia, T2*-weighted MR imaging performed 1 day after the intravenous injection of labeled HUVECs revealed a significant signal intensity (SI) loss exclusively in the left renal outer medulla regions, but not in the right kidney. The MR imaging findings at days 3, 5 and 7 after intravenous injection of HUVECs showed a SI loss in the outer medulla regions of the ischemically injured kidney, but the SI progressively recovered with time and the right kidney did not have a significant change in SI in the same period. Upon histologic analysis, the SI loss on MR images was correspondent to the presence of Prussian blue stained cells, primarily in the renal outer medulla.
CONCLUSION
MR imaging appears to be useful for in vivo monitoring of intravenously injected SPIO-labeled HUVECs in an ischemically injured rat kidney.

Keyword

Magnetic resonance imaging (MRI); Superparamagnetic iron oxide (SPIO); Human umbilical vein endothelial cells (HUVECs); Cell tracking

MeSH Terms

Acute Kidney Injury
Animals
Cell Survival
Cell Tracking
Culture Media
Endothelial Cells
Ferric Compounds
Ferrocyanides
Follow-Up Studies
Human Umbilical Vein Endothelial Cells
Injections, Intravenous
Iron
Ischemia
Kidney
Magnetic Resonance Spectroscopy
Magnets
Rats
Relaxation
Renal Artery
Track and Field
Umbilical Veins
Veins
Culture Media
Ferric Compounds
Ferrocyanides
Iron

Figure

• 

  Fig. 1 Light, fluorescent and electron microscopic findings for labeled and unlabeled HUVECs. a. Light micrograph of Prussian blue-stained HUVECs. Unlabeled cells (upper panel) show no iron staining after a Prussian blue stain and cells labeled with ferumoxides-PLL complex (lower panel) show blue/iron staining (arrows) in the cytoplasm. Bar = 50 µm. b. Fluorescent micrograph of HUVECs unlabeled (upper panel) and labeled (lower panel) with CellTracker. HUVECs were incubated with Celltracker for 15 minutes. Essentially all HUVECs labeled with CellTracker appear green fluorescent. Bar = 50 µm. c. Electron micrograph of SPIO labeled HUVECs showed electron dense SPIO particles in the cytoplasmic endosomal vesicles (×12,000).

• 

  Fig. 2 Labeling stability. Relaxation rates (R2*) of all HUVECs (the number of cells, 1 × 106 cells) after labeling with SPIO at days 1, 3, and 5 were similar to each other. However, the relaxation rate (R2*) of HUVECs at day 1 was increased by over 50% in comparison with that of unlabeled HUVECs (the number of cells, 1 × 106).

• 

  Fig. 3 Coronal T2*-weighted MR images of rat kidney. a-d. Serial images obtained after 1, 3, 5, and 7 days, respectively. a. Finding at the T2*-weighted postinjection MR image showed a signal intensity loss exclusively in the left renal outer medulla regions (arrow), but the right kidney did not show a significant change in signal intensity at 1 day in a kidney with unilateral renal artery ischemia. b-d. MR images at 3, 5, and 7 days after intravenous injection of HUVECs into rats with unilateral renal artery ischemia showed a signal intensity loss in the left renal outer medulla regions that progressively faded (arrow), and the right kidney showed no significant change of signal intensity.

• 

  Fig. 4 Graph of serial T2*-ROI measurements of the renal cortex and medulla after HUVECs injection. After injection of the labeled cells, an increase in the T2* ROI was observed. Serial T2*-ROI was gradually decreased at 3, 5, and 7 days after SPIO-labeled HUVECs injection.

• 

  Fig. 5 Light and fluorescent microscopic findings 1 day after unilateral renal artery ischemia. a, b. Light microscopic examination showed that the control right kidney was normal (a) but, tubular dilatation, loss of brush border and tubular cell loss were concentrated in the outer medulla of the left kidney (b). c, d. Light micrograph of Prussian blue stain shows that blue colored cells were found at the outer medulla of the left kidney 1 day after unilateral renal artery ischemia (d) but not in the right kidney (c). e, f. Fluorescent microscopy showed that CellTracker-positive HUVECs were found in the outer medulla of left kidney (f) but not in the right kidney (e). (H & E stain, Bar = 50 µm.)

• 

  Fig. 6 MR images and light and fluorescent microscopic findings of an ischemically injured kidney after injection of SPIO-labeled HUVECs at days 1 and 5. MR imaging examination on day 1 showed a signal intensity loss in the left renal outer medulla regions (a). Prussian blue stain-positive cells were found at the outer medulla of the left kidney (c). By fluorescent microscopic examination, the CellTracker-positive HUVECs were found in the outer medulla of the left kidney (e). There was a strong correlation between signal intensity loss area and the location of Prussian blue stain-positive cells and CellTracker-positive HUVECs. MR imaging 5 days after injection of HUVECs showed a decreased signal intensity loss in the left renal outer medulla region (b). Prussian blue stain-positive cells and CellTracker-positive HUVECs were found in the same area, but slightly decreased in numbers compared to day 1 (d and f).

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