Researchers from the Johns Hopkins Department of Radiology and Institute of Cell Engineering have used a non-invasive imaging technique, called SPECT/CT, to successfully trace stem cells’ destinations after being injected into the body to treat animal hearts damaged by myocardial infarction.

In the study, researchers surgically induced acute myocardial infarctions in seven dogs, six of which later received canine mesenchymal stem cells ( MSCs ) labeled with a radioactive tracer and magnetic resonance imaging ( MRI ) contrast agent to enhance image quality.

The internal distribution of the injected stem cells was tracked with SPECT/CT and MRI scanners immediately after injection as well as at multiple time points over seven days to assess whether the MSCs preferentially migrated or “homed” in on damaged cardiac tissue.
Previous studies in animals were only able to demonstrate homing by examining the tissue microscopically after death.

The results, reported in the Circulation, revealed redistribution of the radiolabeled mesenchymal stem cells from the initial localization in the lungs to the target organ, the heart, at 24 hours post-injection. Moreover, the cells remained visible in SPECT/CT images until seven days after the injection.

SPECT/CT also found redistribution of the mesenchymal stem cells to non-target organs, such as the liver, kidney and spleen. Measuring the radiation levels in tissues obtained from the animals after their death validated these findings.

MRI, because of its lower sensitivity, was unable to demonstrate targeted cardiac localization of mesenchymal stem cells.

“ Our study demonstrates that SPECT/CT imaging is well suited to dynamically track the biodistribution and movement of stem cells to both target and non-target organs,” says lead investigator Dara L. Kraitchman, at the Johns Hopkins Russell H. Morgan Department of Radiology and Radiological Science. “ uch a non-invasive means of studying stem cell movement could be very helpful in monitoring therapeutic safety and efficacy in clinical trials.”

Source: Johns Hopkins Medical Institutions, 2005


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