Ectopic Expression of the Sodium-Iodide Symporter Enables Imaging of Transplanted Cardiac Stem Cells In Vivo by Single-Photon Emission Computed Tomography or Positron Emission Tomography
John Terrovitis, MD*,
Keng Fai Kwok, BS ,
Riikka Lautamäki, MD, PhD ,
James M. Engles, MS, MBA,
Andreas S. Barth, MD, PhD*,
Eddy Kizana, MBBS, PhD*,
Junichiro Miake, MD, PhD*,
Michelle K. Leppo, BS*,
James Fox, BS,
Jurgen Seidel, PhD,
Martin Pomper, MD, PhD ,
Richard L. Wahl, MD,
Benjamin Tsui, PhD,
Frank Bengel, MD,
Eduardo Marbán, MD, PhD* and
M. Roselle Abraham, MD*,*
* Department of Cardiology, Johns Hopkins University, Baltimore, Maryland
Department of Diagnostic Imaging Physics, Johns Hopkins University, Baltimore, Maryland
Department of Nuclear Medicine, Johns Hopkins University, Baltimore, Maryland
Department of Radiology, Johns Hopkins University, Baltimore, Maryland
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Figure 1 Confirmation of hNIS-Expression
(A) Immunostaining confirmed the expression of human sodium-iodide symporter (hNIS) (green) in rat cardiac-derived stem cells after lentiviral transduction (nuclei were counterstained by blue Hoechst dye). (B) hNIS messenger ribonucleic acid was detected by reverse transcription-polymerase chain reaction in rat hearts after transplantation of sodium-iodide symporter (NIS)+ rat cardiac-derived stem cells (band at 353 base pairs [bp] white arrow, I). The white arrow for II indicates the lack of a specific band in a rat heart injected with the same number of NIS– cells. (C) Confirmation of hNIS activity in transduced cells. NIS transduction promoted in vitro technetium 99m (pertechnetate) uptake by NIS+ rat cardiac-derived stem cells; this uptake was abolished by the specific NIS blocker sodium perchlorate (100 µmol/l) (2 independent experiments, each condition tested in triplicate). ctr = control.
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Figure 2 Effect of hNIS Overexpression on Cell Viability, Proliferation, and Function
(A) There was no difference in viability and proliferation of NIS+ versus nontransduced rat cardiac-derived stem cells. (B) Additional transduction with a lentiviral construct expressing firefly luciferase under the transcriptional control of a cardiac-specific promoter (NCX1, cardiac sodium-calcium exchanger) indicated no decrease in the cardiogenic potential of hNIS-expressing cells compared with control cells. (C to E) Angiogenesis and vascular tube formation assays. Representative images of human vascular endothelial cells as positive control cells (C), nontransduced rat cardiac-derived stem cells (D), and rat cardiac-derived stem cells transduced with hNIS (E). The ability to form vascular structures was preserved after transduction with hNIS. Abbreviations as in Figure 1.
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Figure 3 Dual Isotope SPECT/CT of an Animal Injected With hNIS-Expressing Cells
(Red) Technetium 99m uptake; (green) thallium 201 (201Tl) uptake. There is a clear intramyocardial region (yellow arrows) corresponding to the rat cardiac-derived stem cell injection site within a perfusion deficit. Noninfarcted myocardium appears green due to 201Tl uptake. The liver was also visualized due to uptake of 201Tl. (A) Transverse, (B) coronal, and (C) sagittal slice orientation. CT = computed tomography; hNIS = human sodium-iodide symporter; SPECT = single-photon emission computed tomography.
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Figure 4 Dual Isotope SPECT/CT of an Animal Injected With Nontransduced Cells
(Red) Technetium 99m uptake; (green) thallium 201 uptake. The only Tc signal in the cardiac region is derived from the blood pool (atrial and ventricular cavities). (A) Transverse, (B) coronal, and (C) sagittal slice orientation. Abbreviations as in Figure 3.
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Figure 5 Longitudinal Tracking of hNIS-Expressing Cell by SPECT
(Upper panel) Day 1 after cell injection; (middle panel) day 3 after cell injection; (lower panel) day 6 after cell injection. Arrows point to signal from engrafted cells. Display settings are identical in all images. Abbreviations as in Figure 3.
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Figure 6 SPECT and PET Imaging of an Animal Injected With hNIS-Expressing Cells
(A to C) SPECT/computed tomography 24 h after cell injection. Red: technetium 99m uptake; green: thalium 201 uptake. White arrows point to signal from hNIS expressing rat cardiac-derived stem cells. (A) Transverse, (B) coronal, and (C) sagittal slice orientation. (D to F) PET of the same animal at 48 h after cell injection. Red: iodine 124 uptake; green: ammonia 13 uptake. White arrows point to signal from hNIS-expressing cells. (D) Transverse, (E) coronal, and (F) sagittal slice orientation. PET = positron emission tomography; other abbreviations as in Figure 3.
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Figure 7 Successful PET/CT Coregistration Based on the 18Fluoride PET Images
Red: iodine 124 (124I) uptake. White arrows point to signal from hNIS-expressing rat cardiac-derived stem cells. The stomach takes up 124I and is visualized in the image (yellow arrows). Noninfarcted myocardium and liver (black arrows) take up ammonia 13 and appear green in the perfusion scan. (A) Transverse, (B) coronal, and (C) sagittal slice orientation. CT = computed tomography; other abbreviations as in Figures 3 and 6.
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Figure 8 CDC Engraftment by Quantitative PCR
Column histogram reveals percentage cell engraftment on days 1 and 8 relative to baseline. Rapid cell loss occurs within 8 days after intramyocardial cell delivery. CDC = cardiac-derived stem cell; PCR = polymerase chain reaction.
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