Bradley Hann1,2, Kevin S. Tang3, Kevin M. Bennett2, Erik M. Shapiro, 3,4
1Biological Health System Engineering, Arizona State College, Tempe, AZ, United States; 2School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States; 3Department of Biomedical Engineering, Yale University, New Haven, CT, United States; 4Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT, United States
The accumulation and presence of MPIOs in bone marrow was studied over seven days. High-resolution, serial in-vivo MRI was performed on mice injected with various quantities of MPIOs. MRI signal changes were monitored in bone marrow and muscle to study MPIO trafficking. In vivo labeling efficiency of bone marrow-resident monocytes was then quantified using flow cytometry. Unexpected results were obtained. It was found that MPIOs did not label monocytes in marrow. An alternative explanation for the success of MPIOs in immune cell trafficking is presented, centered around re-entrance of MPIOs into the circulation long after initial clearance from the vasculature.