Magnetic resonance imaging of gadolinium-labeled pancreatic islets for experimental transplantation

New imaging techniques that couple anatomical resolution to sensitivity may greatly contribute to improving islet transplantation. In the present work, a report is given of the direct detection of islets by magnetic resonance imaging (MRI) after ex vivo cell labeling with the MRI T₁ contrast agent GdHPD03A. Experiments on mouse and human islets demonstrated well-tolerated uptake of GdHPD03A, based on morphology, viability, glucose-dependent insulin response and apoptosis/ toxicity gene array profile. GdHPD03A loading was sufficient for in vitro MRI cell detection. In vivo isotransplanted mouse islets into the kidney capsule and xenotransplanted human islets within the mouse liver were detected. Imaging specificity was supported by the absence of signal in unlabeled islet transplants, its persistence upon using fat-suppression MRI protocols and the colocalization with the transplanted islets. In conclusion, direct islet imaging with high spatial and contrast resolution after labeling with GdHPD03A is demonstrated, allowing visualization of kidney subcapsular mouse islet grafts and intrahepatic human islet xenografts.