We describe an automated method for the isolation of human pancreatic islets. The procedure meets the following requirements: 1) minimal traumatic action on the islets, 2) continuous digestion in which the islets that are progressively liberated can be saved from further enzymatic action, 3) minimal human intervention in the digestion process, and 4) high yield and purity of the isolated islets. After purification on Ficoll gradients, an average of 164,600 islets/pancreas was obtained (2279 islets/g), with an average purity of 78.5% islets. The average volume and average insulin content of the final islet preparation were 348 mm3 and 93.4 U, respectively. The islets were morphologically intact with a normal degree of beta-granulation and responded to glucose stimulation with a fivefold increase of insulin secretion over basal levels. The procedure is now being used for the initiation of the second phase of clinical trials on human islet transplants.

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Patient selection based on sensitization to donor HLA may be one of the factors crucial for the success of islet transplant. Further, in some patients, rejection of islets can be associated with sensitization to mismatched donor histocompatibility antigens.

Background Quantification of islet mass is a crucial criterion for defining the quality of the islet product ensuring a potent islet transplant when used as a therapeutic intervention for select patients with type I diabetes. Methods This multi-center study involved all 8 member institutions of the National Institutes of Health-supported Islet Cell Resources (ICR) consortium. The study was designed to validate the standard counting procedure for quantifying isolated, dithizone-stained human islets as a reliable methodology by ascertaining the accuracy, repeatability (intra-observer variability), and intermediate precision (inter-observer variability). The secondary aim of the study was to evaluate a new software-assisted digital image analysis method as a supplement for islet quantification. Results The study demonstrated the accuracy, repeatability and intermediate precision of the standard counting procedure for isolated human islets. This study also demonstrated that software-assisted digital image analysis as a supplemental method for islet quantification was more accurate and consistent than the standard manual counting method. Conclusions Standard counting procedures for enumerating isolated stained human islets is a valid methodology, but computer-assisted digital image analysis assessment of islet mass has the added benefit of providing a permanent record of the isolated islet product being evaluated that improves quality assurance operations of current good manufacturing practice (cGMP).

This study demonstrates that HLA antibodies present in the sera of sensitized individuals can cross-react with SLA. Thus, xenotransplantation of porcine organs into HLA-sensitized patients has the potential to be rejected by humoral mechanisms. Testing to avoid such cross-reactive antibodies should be considered.

Fluorescence-activated cell sorting (FACS) is an essential tool for studies requiring isolation of distinct intestinal epithelial cell populations. Inconsistent or lack of reporting of the critical parameters associated with FACS methodologies has complicated interpretation, comparison, and reproduction of important findings. To address this problem a comprehensive multicenter study was designed to develop guidelines that limit experimental and data reporting variability and provide a foundation for accurate comparison of data between studies. Common methodologies and data reporting protocols for tissue dissociation, cell yield, cell viability, FACS, and postsort purity were established. Seven centers tested the standardized methods by FACS-isolating a specific crypt-based epithelial population (EpCAM+/CD44+) from murine small intestine. Genetic biomarkers for stem/progenitor (Lgr5 and Atoh 1) and differentiated cell lineages (lysozyme, mucin2, chromogranin A, and sucrase isomaltase) were interrogated in target and control populations to assess intra- and intercenter variability. Wilcoxon's rank sum test on gene expression levels showed limited intracenter variability between biological replicates. Principal component analysis demonstrated significant intercenter reproducibility among four centers. Analysis of data collected by standardized cell isolation methods and data reporting requirements readily identified methodological problems, indicating that standard reporting parameters facilitate post hoc error identification. These results indicate that the complexity of FACS isolation of target intestinal epithelial populations can be highly reproducible between biological replicates and different institutions by adherence to common cell isolation methods and FACS gating strategies. This study can be considered a foundation for continued method development and a starting point for investigators that are developing cell isolation expertise to study physiology and pathophysiology of the intestinal epithelium.

Islet transplantation is a treatment option for type I diabetic patients. Preservation of human pancreata prior to islet isolation using two-layer method with perfluorocarbon (PFC) and University of Wisconsin solution (UW) results in twofold increase in islet yields. The objective of this study was to determine the mechanism by which islets undergo apoptosis and determine PFC's effects on this process. Gene array analysis was used to analyze the expression of pro-and antiapoptotic genes in islets isolated from pancreata preserved under varying conditions. A 12-fold increase in the expression of inhibitor of apoptosis (IAP) and survivin was observed in islets isolated from pancreata preserved in PFC. This was accompanied by decreased expression of BAD (3.7-fold), BAX (2.7-fold) and caspases (5.2-fold). Levels of activated caspase-9 (77.98%), caspase-2 (61.5%), caspase-3 (68.3%) and caspase-8 (37.2%) were also reduced. 'Rescue' of pancreata after storage (12 h) in UW by preservation using PFC also resulted in a down-regulation of pro-apoptotic genes and inhibition of caspase activation. Apoptosis observed in islets from all groups was mainly mitochondriadependent, mediated by change in redox potential initiated by hypoxia. We demonstrate that reduction in hypoxia of pancreata preserved using PFC leads to significant up-regulation of anti-apoptotic and inhibition of pro-apoptotic genes.

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