Novel (89)Zr cell labeling approach for PET-based cell trafficking studies - PubMed (original) (raw)

Novel (89)Zr cell labeling approach for PET-based cell trafficking studies

Aditya Bansal et al. EJNMMI Res. 2015.

Abstract

Background: With the recent growth of interest in cell-based therapies and radiolabeled cell products, there is a need to develop more robust cell labeling and imaging methods for in vivo tracking of living cells. This study describes evaluation of a novel cell labeling approach with the positron emission tomography (PET) isotope (89)Zr (T 1/2 = 78.4 h). (89)Zr may allow PET imaging measurements for several weeks and take advantage of the high sensitivity of PET imaging.

Methods: A novel cell labeling agent, (89)Zr-desferrioxamine-NCS ((89)Zr-DBN), was synthesized. Mouse-derived melanoma cells (mMCs), dendritic cells (mDCs), and human mesenchymal stem cells (hMSCs) were covalently labeled with (89)Zr-DBN via the reaction between the NCS group on (89)Zr-DBN and primary amine groups present on cell surface membrane protein. The stability of the label on the cell was tested by cell efflux studies for 7 days. The effect of labeling on cellular viability was tested by proliferation, trypan blue, and cytotoxicity/apoptosis assays. The stability of label was also studied in in vivo mouse models by serial PET scans and ex vivo biodistribution following intravenous and intramyocardial injection of (89)Zr-labeled hMSCs. For comparison, imaging experiments were performed after intravenous injections of (89)Zr hydrogen phosphate ((89)Zr(HPO4)2).

Results: The labeling agent, (89)Zr-DBN, was prepared in 55% ± 5% decay-corrected radiochemical yield measured by silica gel iTLC. The cell labeling efficiency was 30% to 50% after 30 min labeling depending on cell type. Radioactivity concentrations of labeled cells of up to 0.5 MBq/10(6) cells were achieved without a negative effect on cellular viability. Cell efflux studies showed high stability of the radiolabel out to 7 days. Myocardially delivered (89)Zr-labeled hMSCs showed retention in the myocardium, as well as redistribution to the lung, liver, and bone. Intravenously administered (89)Zr-labeled hMSCs also distributed primarily to the lung, liver, and bone, whereas intravenous (89)Zr(HPO4)2 distributed to the liver and bone with no activity in the lung. Thus, the in vivo stability of the radiolabel on the hMSCs was evidenced.

Conclusions: We have developed a robust, general, and biostable (89)Zr-DBN-based cell labeling strategy with promise for wide applications of PET-based non-invasive in vivo cell trafficking.

Keywords: Cell labeling; In vivo cell tracking; Zirconium-89, PET.

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Figures

Figure 1

Figure 1

Scheme for synthesis of 89 Zr-DBN and cell labeling.

Figure 2

Figure 2

Comparison of cell population doubling times for 89 Zr-labeled and unlabeled mMCs, hMSCs and mDCs. The cells were plated at appropriate cell number at day 3, and CyQUANT assay was performed at day 7 post-labeling. No significant differences were observed between radiolabeled and unlabeled cells. Values are shown as mean ± standard deviation, n = 3.

Figure 3

Figure 3

Assessment of (A) viability, (B) cytotoxicity, and (C) apoptosis in 89 Zr-labeled and unlabeled cells. No statistically significant differences were observed between 89Zr-labeled and unlabeled cells after 7 days of culture with regard to viability, cytotoxicity, or apoptosis. As positive controls, 30 μg/mL digitonin was used for assays (A) and (B), and 2 μΜ staurosporine for (C). *p < 0.05 versus assessments in 89Zr-labeled and unlabeled cells using unpaired _t_-test. Values are shown as mean ± standard deviation, n = 3.

Figure 4

Figure 4

Retention of 89 Zr in 89 Zr-labeled cells expressed as radioactivity in MBq in the cell population. The retention value is representing total radioactivity/106 cells in the proliferating cell population. No significant change was observed in retention of 89Zr in radiolabeled cells. Values are shown as mean ± standard deviation, n = 3.

Figure 5

Figure 5

Representative PET images and biodistribution data of 89 Zr-labeled hMSCs and 89 Zr(HPO 4 ) 2 following intravenous injection. 89Zr-labeled human MSCs (2 × 105 cells with radioactivity concentration approximately 0.37 MBq/106 cells) and 89Zr(HPO4)2 (approximately 0.074 MBq radioactivity) were intravenously injected in athymic mice. Most of the radioactivity was distributed in the lung, liver, and bones following injection of 89Zr-labeled hMSCs whereas most of the radioactivity was distributed in the liver and bones following injection of 89Zr(HPO4)2. Values in graphs are shown as mean ± standard deviation, n = 3.

Figure 6

Figure 6

Representative PET images and biodistribution data of 89 Zr-labeled hMSCs following myocardial delivery. 89Zr-labeled hMSCs (2 × 105 cells with radioactivity concentration approximately 0.37 MBq/106 cells) were delivered to myocardium of an ischemia/reperfusion mouse model. Most of the radioactivity was distributed in the heart (arrow), lung, liver, and bones following myocardial delivery of 89Zr-labeled hMSCs. Values in graph are shown as mean ± standard deviation, n = 5.

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