JUNE 2003

MRI monitors stem cell myocardial implantation

By: Charles Bankhead

CONTEXT: Most cellular transplantation techniques designed to repair damaged myocardium require histologic analysis to determine cell status. The ability to label mesenchymal stem cells with an MR contrast medium and nuclear tracers has created the potential for noninvasive serial tracking and quantification of transplanted cells.

RESULTS: Dara Kraitchman, Ph.D., an assistant professor of radiology at Johns Hopkins University, tracked the progress of Feridex-labeled mesenchymal stem cells injected intramyocardially and peripherally into pigs after experimental myocardial infarction and reperfusion. The stem cells were colabeled with indium-111 oxine. Serial whole-body SPECT imaging was performed in the first 48 hours after injection to track cell distribution. Contrast-enhanced MRI and SPECT were performed again a week after stem cell delivery. Contrast-enhanced MRI demonstrated successful localization of the labeled mesenchymal stem cells in the areas of infarction a week after intramyocardial delivery. Intravenous delivery was unsuccessful. Imaging revealed that most of the peripherally delivered cells ended up in the lungs.

IMAGE: Real-time MR fluoroscopic image of a dog's heart with induced infarction was acquired after two injections of Feridex-labeled mesenchymal stem cells in the left ventricular septum. The top arrow identifies a region where 100% of the injected cells were labeled with contrast; the bottom arrow indicates a site where about 50% of the cells were tagged. (Provided by D. Kraitchman)

IMPLICATIONS: "We know that the infarct gets smaller over time and that the stem cells remain viable. We are now trying to determine whether the cells are differentiating into the cardiac myocyte phenotype when they are delivered by MR," Kraitchman said.