Ho's novel approach investigates transplant rejection non-invasively by observing macrophage accumulation in heart tissues using MRI.
"We were able to use MRI to visualize individual macrophages. By tracking individual cells, we also were able to observe, for the first time, that rejection progresses from the outside of the heart to the inside," said Ho. "Up to now, this phenomenon hasn't been observed in pre-clinical or clinical research because biopsy samples are very limited in location and size."
The reported findings also have broader implications for biology and medicine, according to Ho.
"We now have the ability to visualize non-invasively and with sensitivity individual cells and their movement to targeted sites. Our new approach offers almost unlimited potential for monitoring cell therapies, such as those using stem cells, and for tracking cellular and developmental processes," Ho said.
For the research reported in PNAS, Yijen Wu, research biologist at the Pittsburgh NMR Center for Biomedical Research, tagged macrophages with nanometer (USPIO)- or micrometer (MPIO)-sized paramagnetic iron oxide particles, which are very sensitive to the magnetic fields used during MRI. Wu injected the MPIO or USPIO particles into rats that had received heart transplants three days earlier. Macrophages, which typically ingest foreign materials inside the body (bacteria, for example), incorporated the particles. Using MRI, the researchers then track tagged macrophages that infiltrate transplanted hearts. The locations of the tagged macrophages are highly defined and appear circular in shape, said Wu. This finding indicates that the
Source:Carnegie Mellon University