Researchers from the Johns Hopkins Department of had discovered a new way to test the stem cells journey in the heart after a heart attack.
The researchers had 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, or heart attack.
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. Both the tracer and contrast agent are widely used in research and routine clinical practice.
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 team's results, reported in the latest issue of Circulation, revealed redistribution of the radio-labeled MSCs 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 MSCs 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 MSCs.