Functional MRI characterization of isolated human islet activation.

The noninvasive assessment of pancreatic islets would be an invaluable tool in advancing the treatment of type I diabetes and in understanding its pathophysiology. As shown previously in rodents, manganese-enhanced MRI (MEMRI) can be successfully used to quantify β-cell function. In this study, we successfully applied this technique to isolated human pancreatic islets in both a static and, more significantly, MRI-compatible perfusion set-up. Unlike rodent islets, which produced a significant increase in the signal-to-noise ratio (SNR) when treated with 25 µM MnCl(2) or less, human islets demonstrated significant manganese uptake when exposed to an extracellular concentration of 50 µM MnCl(2). Nonspecific passive manganese uptake was present and quantified in a 15% SNR increase over the control group. However, glucose-induced manganese uptake caused an SNR increase equal to 45% over nonactivated islets. This corresponds to a statistically significant decrease in the T(1) relaxation time from 1501 ms for untreated islets to 1362 ms following passive uptake, and to 861 ms following glucose stimulation. As expected, no manganese cytotoxicity was measured, as shown by normal insulin secretion profiles. These data confirm the viability of MEMRI to assess isolated human islet functionality in vitro, and this technique shows promise for the monitoring of their performance in vivo following transplantation.