At Johns Hopkins Medicine, scientists have developed a way to watch therapeutic cells as they travel through the body in real time — a breakthrough that could transform how doctors tailor cell therapy treatments for individual patients. Using a technique called magnetic particle imaging (MPI), researchers tracked injected cells in mice and discovered which delivery routes get more healing cells to where they're needed most, a finding that could reshape cancer and autoimmune disease treatment.
The problem with current cell therapies is frustratingly simple: doctors can't see where the cells actually go. CAR-T cell therapy, for instance, involves engineering a patient's own immune cells to hunt down and destroy cancer cells, yet existing imaging tools like conventional MRI and CT scanners reveal nothing about how many cells were successfully delivered or whether they're reaching the tumor. "Using MPI, we can visualize where therapeutic cells end up in the body," says Jeff Bulte, professor of radiology at Johns Hopkins and director of cellular imaging for the Institute for Cell Engineering. This visibility could help determine the right dose of cell therapy for each person, rather than relying on one-size-fits-all approaches.
In their study, published in Science Advances, Bulte's team led by first author Ali Shakeri-Zadeh compared two types of therapeutic cells: larger mesenchymal stem cells (about 25 micrometers) commonly studied for fighting autoimmune diseases and cancer, and smaller neural precursor cells (about 10 micrometers) derived from induced pluripotent stem cells. The scientists labeled both cell types with specialized ultra-tiny nanoparticles called superparamagnetic iron oxide nanoparticles, then injected them into normal mice and mice with experimental autoimmune encephalomyelitis (EAE), a standard model for studying multiple sclerosis.
The results revealed something critical: injecting cells directly into an artery proved far more effective than other routes. When delivered this way, therapeutic cells accumulated in key target organs — particularly the brain and spleen — where they could address disease. The team also observed cells traveling to the lungs and liver. In mice without autoimmune disease, cells similarly moved to the lungs, liver, and brain, but didn't accumulate noticeably in the spleen.
This distinction matters enormously for MS and related conditions. "In autoimmune diseases, particularly MS, it's thought that harmful immune cells, or T cells, are released from the spleen," Shakeri-Zadeh explains. "Our experiments in EAE mice show that therapeutic cells could subdue harmful immune cells right at the source, in the spleen." By visualizing this journey, researchers can now see whether their treatment is actually reaching the organ where disease originates.
The scientists acknowledge that while artery injection proved effective in their mouse model, the optimal delivery method will likely vary from person to person — which is precisely why personalized imaging matters. Rather than guessing whether a patient received enough cells in the right place, doctors could use MPI to confirm treatment success before moving forward.
Bulte and his team plan to expand these experiments to cancer and other neurological diseases like ALS, exploring how MPI can improve cell therapy delivery across multiple conditions. If the technique scales to humans, it could fundamentally change how personalized medicine works, transforming cell therapy from a hope-and-monitor approach into a precisely guided, individually tailored treatment.