Instant Blood-Mediated Inflammatory Reaction (IBMIR) is a major cause of graft loss during pancreatic islet transplantation, leading to a low efficiency of this treatment method and significantly limiting its broader clinical use. Within the procedure, transplanted islets obstruct intrahepatic portal vein branches and consequently restrict blood supply of downstream lying liver tissue, resulting typically in ischemic necrosis. The extent of ischemic lesions is influenced by mechanical obstruction and inflammation, as well as subsequent recanalization and regeneration capacity of recipient liver tissue. Monitoring of immediate liver perfusion impairment, which is directly related to the intensity of post-transplant inflammation and thrombosis (IBMIR), is essential for improving therapeutic and preventive strategies to improve overall islet graft survival. In this study, we present a new experimental model enabling direct quantification of liver perfusion impairment after pancreatic islet transplantation using ligation of hepatic arteries followed by contrast-enhanced magnetic resonance imaging (MRI). The ligation of hepatic arteries prevents the contrast agent from circumventing the portal vein obstruction and enables to discriminate between well-perfused and non-perfused liver tissue. Here we demonstrate that the extent of liver ischemia reliably reflects the number of transplanted islets. This model represents a useful tool for in vivo monitoring of biological effect of IBMIR-alleviating interventions as well as other experiments related to liver ischemia. This technical paper introduces a novel technique and its first application in experimental animals.

• Keywords
• IBMIR, MRI, Pancreatic islet transplantation, instant blood-mediated inflammatory reaction, liver ischemia, magnetic resonance imaging,
• MeSH
• Embolism * complications   diagnosis   MeSH
• Ischemia * diagnostic imaging   etiology   MeSH
• Liver * blood supply   diagnostic imaging   pathology   MeSH
• Rats MeSH
• Magnetic Resonance Angiography methods   MeSH
• Graft Survival MeSH
• Reproducibility of Results MeSH
• Models, Theoretical MeSH
• Islets of Langerhans Transplantation adverse effects   MeSH
• Portal Vein * MeSH
• Image Enhancement methods   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

AIM: Assessment of islet mass before islet transplantation requires a reliable technique to enable exact analysis of islet volume. This study aimed to test the applicability of digital image analysis (DIA) for evaluation of samples of purified and non-purified islets. METHODS: Pancreatic islets were isolated from 10 Lewis rats. Samples of purified (n = 10) and non-purified islets (n = 30) were counted conventionally and by using a computerized method. The equipment for the computerized counting consisted of a digital camera installed on a stereomicroscope and connected to a personal computer. Images of 2272x1704 pixels were processed using a previously described non-commercial program originally developed for this purpose. Islets were converted to equivalents using globe and ellipsoid models. The insulin content of purified islets was assessed using radioimmunoassay and was correlated to the absolute and standardized islet number. RESULTS: Mean absolute numbers of purified islets +/- SD were 908 +/- 130 and 1049 +/- 230 (manually and DIA respectively). Mean insulin content +/- SD obtained from purified islets was 161 +/- 45 mU. The mean equivalents of purified islets (1589 +/- 555 for globe and 1219 +/- 452 for ellipsoid) significantly correlated with insulin content. However, this correlation was not significant when absolute islet numbers were used, counted using either method. There was no significant difference in absolute non-purified islet numbers assessed by manual and computerized methods (average +/- SD in 50 microl samples; 12.6 +/- 4.1 and 13.3 +/- 5.3 respectively; p = 0.22). The manual method showed a significantly higher yield of islet equivalents (IE; p < 0.001 for both globe and ellipsoid). CONCLUSION: The computer-based system for islet counting correlated better to insulin content than conventional islet estimation and prevented overestimation. Reproducibility and ease of assessment make it potentially applicable to clinical islet transplantation.

• Publication type
• Journal Article MeSH

Diabetes is a disorder characterized by beta-cell loss or exhaustion and insulin deficiency. At present, knowledge is lacking on the underlying causes and for the therapeutic recovery of the beta-cell mass. A better understanding of diabetes pathogenesis could be obtained through exact monitoring of the fate of beta-cells under disease and therapy conditions. This could pave the way for a new era of intervention by islet replacement and regeneration regimens. Monitoring the beta-cell mass requires a reliable method for noninvasive in vivo imaging. Such a method is not available at present due to the lack of a beta-cell-specific contrast agent. The only existing method to monitor islet cells in vivo consists of labeling islet transplants with iron nanoparticles prior to transplantation and visualization of the transplanted islets by magnetic resonance imaging (MRI). Therefore, accurate assessment of the native beta-cell mass is still limited to autopsy studies. Endeavors to find a biological structure specific for beta-cells led to the discovery of potential candidates that have been tested for noninvasive imaging. Among them are the ligand to the vesicular monoamine transporter type 2 (VMAT-2), which is called dihydrotetrabenazine (DTBZ), antibodies to zinc transporter (ZnT-8) and the monoclonal antibody IC2. While DTBZ and antibodies to ZnT-8 showed binding activities to more than beta-cells, the anti-IC2 monoclonal antibody showed binding properties exclusively to insulin-producing beta-cells. This effect was demonstrated in many previous investigations, and has been further substantiated more recently. Thus, at present, IC2 seems to be the only useful marker for noninvasive functional imaging of native beta-cells. Experiments with a radioisotope-chelated IC2 structure on pancreas ex vivo showed that the tracer specifically bound to the beta-cell surface and could be detected by nuclear imaging. In the near future, these promising findings may offer a new way to monitor the beta-cell mass in vivo under disease and therapy conditions so that we can learn more about diabetes pathogenesis and options for disease prevention.

• Publication type
• Journal Article MeSH