In vitro labeling and MRI of mesenchymal stem cells from human umbilical cord blood

Ju, Shenghong; Teng, Gaojun; Zhang, Yu; Ma, Ming; Chen, Feng; Ni, Yicheng

doi:10.1016/j.mri.2005.12.017

« Previous Next »Magnetic Resonance Imaging
Volume 24, Issue 5 , Pages 611-617, June 2006

In vitro labeling and MRI of mesenchymal stem cells from human umbilical cord blood☆

Shenghong Ju
- Laboratory of Molecular Imaging, Department of Radiology, Zhongda Hospital, Southeast University, Nanjing 210009, China
Gaojun Teng
- Laboratory of Molecular Imaging, Department of Radiology, Zhongda Hospital, Southeast University, Nanjing 210009, China
- Corresponding author. Tel.: +86 25 83272121; fax: +86 25 83311083.
Yu Zhang
- Laboratory of Molecular and Boimolecular Electronics, Southeast University, Nanjing 210009, China
Ming Ma
- Laboratory of Molecular and Boimolecular Electronics, Southeast University, Nanjing 210009, China
Feng Chen
- Laboratory of Molecular Imaging, Department of Radiology, Zhongda Hospital, Southeast University, Nanjing 210009, China
- Department of Radiology, University Hospitals, K.U.LEUVEN, B-3000 Leuven, Belgium
Yicheng Ni
- Department of Radiology, University Hospitals, K.U.LEUVEN, B-3000 Leuven, Belgium

Received 16 September 2005; accepted 17 December 2005. published online 16 February 2006.

Abstract

Objective

The aim of this study was to label human umbilical cord blood mesenchymal stem cells (MSCs) with poly-l-lysine (PLL)-conjugated superparamagnetic iron oxide particles and to obtain magnetic resonance (MR) images of the labeled MSCs' suspension at 1.5 T.

Material and Methods

PLL was conjugated with iron oxide to form superparamagnetic particles called Fe₂O₃-PLL. Human umbilical cord blood MSCs were isolated, purified, expanded and incubated with Fe₂O₃-PLL. Prussian blue stain was performed to show intracellular iron; spectrometry was used to quantify iron uptake within cells. Tetrazolium salt (MTT) assay was applied to evaluate toxicity and proliferation of MSCs labeled with various concentrations of Fe₂O₃-PLL. The cell apoptosis rate was determined by annexin V/propichium iodide (PI) double staining method. Vials containing cells underwent MR imaging (MRI) with T₁, T₂ and T₂* weighted MRI.

Results

Iron-containing intracytoplasmatic vesicles could be observed clearly with Prussian blue staining in all samples except the unlabeled control. The iron content per cell determined by spectrometry was 64.51±10.32 pg. Among MSCs with and without labeling of various concentrations of Fe₂O₃-PLL, MTT values of light absorption had no statistically significant difference (Kruskal–Wallis test, χ²=10.35, P=.17). A concentration at 20 μg/ml of iron appeared most suitable for incubating cells. Of labeled and unlabeled MSCs, the early [annexin V-fluorescein isothiocyanate (FITC)-positive/PI-negative] and late (annexin V-FITC-positive/PI-positive) apoptotic cells were 10.34±0.43%/11.36±1.30% and 4.01±1.76%/2.98±1.37%, respectively, and there were no significant differences between them (P>.05). T₂ weighted image (WI) and T₂*WI demonstrated significant decrease of signal intensity (SI) in vials containing 1×10⁶ (1 day), 1×10⁶ (8 days) and 5×10⁵ labeled cells, in comparison with unlabeled cells (P<.05). The percentage change of SI (ΔSI) was significantly higher in 10⁶ labeled cells after 1-day culture than that in the same number of labeled cells after 8-day culture and that in 5×10⁵ labeled cells, particularly on T₂*WI (P<.05). Among pulse sequences, T₂*WI demonstrated the highest ΔSI (P<.05).

Conclusion

The human umbilical cord blood MSCs can be labeled with Fe₂O₃-PLL without significant change in viability and apoptosis. The suspension of labeled MSCs can be imaged with standard 1.5-T MR equipment.

Keywords: Mesenchymal stem cells, Magnetic resonance, Cell labeling, Iron oxide particles