%0 Journal Article
%T Optimal Labeling Dose, Labeling Time, and Magnetic Resonance Imaging Detection Limits of Ultrasmall Superparamagnetic Iron-Oxide Nanoparticle Labeled Mesenchymal Stromal Cells
%A Anders Bruun Mathiasen
%A Louise Hansen
%A Tina Friis
%A Carsten Thomsen
%A Kishore Bhakoo
%A Jens Kastrup
%J Stem Cells International
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/353105
%X Background. Regenerative therapy is an emerging treatment modality. To determine migration and retention of implanted cells, it is crucial to develop noninvasive tracking methods. The aim was to determine ex vivo magnetic resonance imaging (MRI) detection limits of ultrasmall superparamagnetic iron-oxide (USPIO) labeled mesenchymal stromal cells (MSCs). Materials and Methods. 248 gel-phantoms were constructed and scanned on a 1.5T MRI-scanner. Phantoms contained human MSCs preincubated with USPIO nanoparticles for 2, 6, or 21 hours using 5 or 10£¿¦Ìg£¿USPIO/105 MSCs. In addition, porcine hearts were scanned after injection of USPIO labeled MSCs. Results. Using 21£¿h incubation time and 10£¿¦Ìg£¿USPIO/105 MSCs, labeled cells were clearly separated from unlabeled cells on MRI using 250.000 ( ), 500.000 ( ), and 1.000.000 MSCs ( ). At lower incubation times and doses, neither labeled nor unlabeled cells could be separated. In porcine hearts labeled, but not unlabeled, MSCs were identified on MRI. Conclusions. As few as 250.000 MSCs can be detected on MRI using 21£¿h incubation time and 10£¿¦Ìg£¿USPIO/105 MSCs. At lower incubation times and doses, several million cells are needed for MRI detection. USPIO labeled cells can be visualized by MRI in porcine myocardial tissue. 1. Introduction Stem cell therapy with potential to regenerate damaged myocardium is an emerging treatment modality for ischemic heart disease [1¨C3]. For future success of cardiac stem cell therapy, it is crucial to develop noninvasive tracking methods for determining the biodistribution and fate of the stem cells after delivery. Thus far, tracking of cardiovascular delivered stem cells in a clinical setting has been limited to direct cell labeling with radioisotopes and tracking with gamma-cameras, single-photon emission computed tomography, or positron emission tomography [4]. Although providing highly sensitive visualization, these methods are limited by low spatial resolution and short half-lives of radioisotopes from minutes to hours, thus only permitting short-term tracking of the cells. Other drawbacks are exposure to ionizing radiation and nontarget signal leakage. Tracking of cells labeled with superparamagnetic iron-oxide (SPIO) or ultrasmall superparamagnetic iron-oxide (USPIO) nanoparticles using magnetic resonance imaging (MRI) offers high spatial resolution in combination with high soft tissue detail, without exposing the patient to ionizing radiation. Furthermore, the cells can be tracked for months. Cellular labeling methods with SPIO or USPIO are relatively simple, fast and
%U http://www.hindawi.com/journals/sci/2013/353105/