Dynamic Tracking of Injected Mesenchymal Stem Cells after Myocardial Infarction in Rats: A Serial 7T MRI Study

Area of Science:

• Cardiovascular Research
• Regenerative Medicine
• Biomedical Imaging

Background:

• Myocardial infarction (MI) leads to adverse cardiac remodeling.
• Mesenchymal stem cells (MSCs) show therapeutic potential for MI.
• Tracking transplanted MSCs in vivo is crucial for understanding their efficacy.

Purpose of the Study:

• To evaluate micron-sized particles of iron oxide (MPIO) for tracking MPIO-labeled MSCs in a rat MI model using 7T MRI.
• To assess the impact of MSC transplantation on cardiac function and remodeling post-MI.

Main Methods:

• MSCs dual-labeled with MPIO and CM-DiI were injected into the infarct periphery of rats 7 days post-MI.
• 7T MRI was used to dynamically assess stem cell location, signal intensity, and cardiac function at multiple time points.
• Histological analysis and real-time PCR were performed to evaluate cell fate, inflammation, and tissue repair.

Main Results:

• MPIOs caused observable hypointensities on T2*-weighted MRI, indicating their presence.
• MSCs transplantation moderated left ventricular remodeling and improved cardiac function.
• Most iron-positive cells were identified as macrophages, and MSC survival decreased significantly over time.
• MSC treatment increased capillary density and reduced cardiomyocyte apoptosis and fibrosis in the peri-infarct region.

Conclusions:

• MPIOs are not a reliable marker for long-term in vivo tracking of MSC engraftment.
• Despite limited cell retention, MSCs demonstrate significant therapeutic benefits in mitigating adverse cardiac remodeling after MI.