Islet of Langerhans Graft Monitoring by Magnetic Resonance Imaging

• Semi-quantitative assessment of intrahepatic MRI signal on T2*-weighted sequences, at 6 days, 6 weeks, 6 months and 1 year after transplantation [ Time Frame: 2005-2009 ] [ Designated as safety issue: No ]
  

• Islet graft function assessed by exogenous insulin requirements, HbA1c, mean amplitude of glucose excursions (MAGE) and fasting C-peptide. [ Time Frame: 2005-2009 ] [ Designated as safety issue: No ]
  

Drug: ferucarbotran (iron-based MRI contrast agent)
islets will be incubated with ferucarbotran prior to transplantation, for imaging after transplantation
Procedure: Islet transplantation
intraportal percutaneous islet transplantation
Procedure: Magnetic resonance imaging
Magnetic resonance imaging of the liver before and after islet transplantation (6 days, 6 weeks, 6 months, 1 year)

The objectives will be addressed in a pilot study. We plan to enroll 15 patients over 3 years in islet transplantation alone (ITA), islet-after-kidney transplantation (IAK) or simultaneous islet-kidney transplantation (SIK) procedures. Patients will be followed-up for 1 year after transplantation.

Islet isolation and transplantation Islets will be isolated and purified from pancreata harvested from multiorgan donors, according to the automated method described by Ricordi, with local modifications. After isolation, islets will be cultured overnight at 37°C in CMRL medium. After overnight culture, islets will be changed to fresh medium containing carbodextran-coated iron oxide nanoparticles (Resovist; Schering, Baar, Switzerland), at a target concentration of 5ul/ml, with a total dose not exceeding 0.08 ml/kg body weight, and further cultured for a total of 48-72 hours at 25°C until transplantation. Islet transplantation will be performed by intraportal infusion of the islet preparation, using a transhepatic percutaneous approach. Patients will receive infusions of at least 5,000 IEQ/kg. A second islet infusion will be administered to patients who have not reached insulin independence after the first transplant.

Graft monitoring and follow-up Patients will be followed for 1 year after last islet infusion. MRI will be performed prior to, 6 days, 6 weeks, 6 months and 1 year after islet infusion. A standard MRI protocol will be adapted. Since transplanted islets are already iron-labeled, no injection of contrast media will be done during MRI examination, and MRI sequences will not be repeated. After a scout image, axial views of the liver will be acquired with a fast gradient echo T2* weighted sequence, a fast spin echo T2* weighted sequence, ultrashort echo time T2* weighted sequences, a spin echo T1 weighted sequence and in/out of phase fast gradient echo T1 weighted sequences. Iron-labeled islets will be visualized as a loss of signal on fast gradient echo T2* weighted sequence, and the islet mass will be assessed in a semi-quantitative fashion using a visual scale. Finally, ultrashort echo time sequences will be used to generate a T2 map. The amount of iron contained inside the transplanted islets will be quantified based on the T2 map and the correction for the distribution of the iron particles inside the liver.

Monitoring results will be compared to islet function assessed by routine tests: exogenous insulin requirement, C-peptide, HbA1c, fructosamine, arginine stimulation test. Results will be analyzed retrospectively for the first 2 years. According to results of the analysis, the investigators may decide to intervene proactively (i.e. administer antirejection therapy) in the last year of the study, whenever results suggestive of a dysfunction are observed.