Abstract 565: Messenger RNA Transfection of Human Sodium Iodide Symporter Reporter Gene Into Mesenchymal Progenitor Cells for Nuclear Imaging
Background: Optimization of stem cell therapy for ischemic heart disease requires clinically-applicable imaging technology to enable monitoring of cell distribution, engraftment and viability following transplantation. We sought to determine the feasibility of mRNA transfection as a method to induce functional human sodium iodide (hNIS) reporter gene expression without using viral vectors in adult human bone marrow-derived mesenchymal progenitor cells (hMPCs) for nuclear imaging following administration.
Methods and Results: Polyadenylated hNIS mRNA was synthesized in vitro and transfected into hMPCs with Lipofectamine 2000. hNIS mRNA was detectable in transfected hMPCs for up to 7 d. Flow cytometric analysis of hMPCs transfected with hNIS mRNA confirmed cell-surface expression of hNIS protein at 48 h (38.7%), 72 h (39.8%) and 7 days (40.4%). hNIS was not detected in non-transfected hMPC controls. 99mTc-pulse of hNIS+ hMPCs resulted in cell number-dependent activity: 125,000 hMPCs: 865.1±85.2 cpm; 50,000 hMPCs: 506.5±184.4 cpm; 10,000 hMPCs: 374.3±5.2 cpm. Sodium perchlorate suppressed all activity. To determine the feasibility of imaging hNIS+ hMPCs in vivo, hMPCs (2.5×106 or 5×106) were embedded into Matrigel patches and implanted in the abdominal wall of nude rats. After 3 d, transplanted hNIS+ hMPCs were detectable by nanoSPECT/CT imaging using 99mTc as tracer. % injected dose and ex vivo counts of excised Matrigel patches were consistent with the number of hNIS+ hMPCs delivered (Table 1⇓).
Conclusions: hNIS mRNA transfection is a feasible approach to expressing functional hNIS protein at the cell surface of hMPCs for up to 7 days. Pilot animal studies provide encouraging data on the feasibility of quantitative imaging of hNIS+ hMPCs in vivo. mRNA transfection of hNIS reporter gene into hMPCs may represent a clinically-applicable method to enable tracking of hMPC distribution, engraftment and viability by nuclear imaging following transplantation.