In Vivo Magnetic Resonance Imaging of Mesenchymal Stem Cells in Myocardial Infarction

Abstract

Background-We investigated the potential of magnetic resonance imaging (MRI) to track magnetically labeled mesenchymal stem cells (MR-MSCs) in a swine myocardial infarction (MI) model. Methods and Results-Adult farm pigs (nϭ5) were subjected to closed-chest experimental MI. MR-MSCs (2.8 to 16ϫ10 Key Words: magnetic resonance imaging Ⅲ myocardial infarction Ⅲ cells Ⅲ contrast media B ecause of the limited regenerative capacity of the heart muscle, mesenchymal stem cells (MSCs), found in bone marrow, may have enormous therapeutic potential for limiting infarct size and restoring cardiac function after irreversible ischemic injury. Most techniques for the study of stem cell transplantation in animal models require histological analysis to determine the fate and migration of cells. [1][2][3][4][5] Thus, the number and location of MSCs delivered using intramyocardial delivery techniques can only be estimated postmortem. The recent ability to label MSCs 6 with magnetic resonance imaging (MRI)-visible contrast agents should enable serial tracking and quantification of MSC transplantation noninvasively with high spatial resolution. Thus, the purpose of this study was to determine whether magnetically labeled MSCs injected intramyocardially could be detected and tracked noninvasively by MRI in a swine model of myocardial infarction. Methods Animal ModelAnimal studies were approved by the Institutional Animal Care and Use Committee. The evening before creation of a myocardial infarction (MI), 5 farm pigs (25 to 35 kg; Archer Farms, Belcamp, Md) received aspirin (325 mg) and diltiazem (180 mg sustained release) orally. Animals were sedated with acepromazine, ketamine, and atropine; induced with thiopental; and then intubated and mechanically ventilated with oxygen and isoflurane. To create MI, cardiac catheterization was performed via a 9F carotid sheath, and a 2.0 or 2.5ϫ20-mm coronary angioplasty balloon (Cordis, Inc) was inflated in the left anterior descending (LAD) artery beyond the first diagonal branch to occlude LAD flow for 60 minutes, followed by reperfusion. After allowing for stabilization, allogeneic MSCs were given by intramyocardial injection using a deflectable guiding catheter and a helical needle (Biocardia, Inc). In 4 animals, MRMSCs were injected; 1 control animal received nonlabeled MSCs. Magnetically Labeled MSCsSwine mesenchymal stem cells were isolated and cultured as previously described. 7 The MSCs were culture-expanded 2 or 3 passages in vitro, yielding up to 400 million cells, which were frozen and thawed for use. In two studies, before freezing, the MSCs were fluorescently labeled with DiI (1,1Ј-dioctadecyl-3,3,3Ј3Ј-testramethylindocarbocyanine perchlorate) and DAPI (4Ј,6-Diamidino-2-phenylindole), which preferentially stain cells membranes and nuclei, respectively.The swine MSCs were magnetically labeled by incubation with ferumoxides injectable solution (25 g Fe/mL, Feridex, Berlex Laboratories) in culture medium for 24 to 48 hours with 375 ng/mL poly-L-lysine (PLL; average MWϭ275 kDa) added ...

The cell labeling efficacy, cytotoxicity and relaxivity of copper-activated MRI/PET imaging contrast agents

“…. This observation may be attributed to the fact that under the physiological conditions (pH 7.4), the carboxylic acid group mostly remain in the deprotonated form, i.e., negatively charged and as reported earlier the negatively charged surface of the nanoparticles facilitate the phagocytosis of the nanoparticles and hence the cell labeling [72]. When Cu 2+ ions are coordinated to the DOTA on the surface of the nanoparticles, the carboxylate groups of DOTA moiety would no longer remain free resulting in a significant change in surface charges.…”

“…The differential behavior concerning the uptake into the stem cells between the two surface modified nanoparticles and Feridex was established. The cell labeling efficiencies were evaluated by following the standard method [70], [71] and [72]. A strong Prussian blue staining was observed when the cells were incubated with the Feridex plus transfecting agent.…”

Magnetic Resonance Imaging of Single Co-Labeled Mesenchymal Stromal Cells after Intracardial Injection in Mice

“…The efficacy of such therapies could be in part monitored by cellular MRI. Cell tracking of large cohorts of magnetically labeled MSC has been demonstrated in rat models of nephropathy after intravenous [32] and intraarterial [33] injection and after intramyocardial cell injection in a porcine model of myocardial infarction [34]. Furthermore, at least four clinical trials using MRI cell tracking with superparamagnetic iron oxides have been performed with promising results and it is most likely that MSC-based therapies will become more and more popular over the next decades [35,36] This study investigates the possibility of in-vivo single cell detection of MSC by MRI, which would be a valuable technique to track the migration of even small numbers of MSC in living animals and may help to improve the understanding of the timeline of cell-based therapies, the cells immediate and long-term fate as well as the exclusion of graft failure or tumor formation at the injection side [37].…”

Isolation, Characterization and Differentiation Potential of Cardiac Progenitor Cells in Adult Pigs

“…These include BM-derived mononuclear cells (BM-MNCs) (Kamihata et al 2001;Bhakta et al 2006;Makela et al 2007), peripheral blood mononuclear cells (PB-MNCs) (Kamihata et al 2002;Doyle et al 2008) and BM-derived mesenchymal stem cells (Pak et al 2003). Bone marrow-derived MSC have been magnetically Introduction 57 labeled in order to develop non-invasive methods for studying the engraftment based on magnetic resonance imaging (MRI) (Kraitchman et al 2003;He et al 2007). Pig MSC were used also to explore new delivery methods like a patch of a fibrin matrix seeded with autologous cells (Liu et al 2004).…”