A.M.J Shapiro

Islet Transplantation in Seven Patients with Type 1 Diabetes Mellitus Using a Glucocorticoid-Free Immunosuppressive Regimen

BACKGROUND Registry data on patients with type 1 diabetes mellitus who undergo pancreatic islet transplantation indicate that only 8 percent are free of the need for insulin therapy at one year. METHODS Seven consecutive patients with type 1 diabetes and a history of severe hypoglycemia and metabolic instability underwent islet transplantation in conjunction with a glucocorticoid-free immunosuppressive regimen consisting of sirolimus, tacrolimus, and daclizumab. Islets were isolated by ductal perfusion with cold, purified collagenase, digested and purified in xenoprotein-free medium, and transplanted immediately by means of a percutaneous transhepatic portal embolization. RESULTS All seven patients quickly attained sustained insulin independence after transplantation of a mean (+/-SD) islet mass of 11,547+/-1604 islet equivalents per kilogram of body weight (median follow-up, 11.9 months; range, 4.4 to 14.9). All recipients required islets from two donor pancreases, and one required a third transplant from two donors to achieve sustained insulin independence. The mean glycosylated hemoglobin values were normal after transplantation in all recipients. The mean amplitude of glycemic excursions (a measure of fluctuations in blood glucose concentrations) was significantly decreased after the attainment of insulin independence (from 198+/-32 mg per deciliter [11.1+/-1.8 mmol per liter] before transplantation to 119+/-37 mg per deciliter [6.7+/-2.1 mmol per liter] after the first transplantation and 51+/-30 mg per deciliter [2.8+/-1.7 mmol per liter] after the attainment of insulin independence; P<0.001). There were no further episodes of hypoglycemic coma. Complications were minor, and there were no significant increases in lipid concentrations during follow-up. CONCLUSIONS Our observations in patients with type 1 diabetes indicate that islet transplantation can result in insulin independence with excellent metabolic control when glucocorticoid-free immunosuppression is combined with the infusion of an adequate islet mass.

Intraductal collagenase delivery into the human pancreas using syringe loading or controlled perfusion.

Effective intraductal delivery of the enzyme collagenase into the pancreas is crucial to the subsequent ability to isolate viable islets. Most clinical islet transplant centers load the enzyme into the pancreas by retrograde injection using a syringe following cannulation of the pancreatic duct. An alternative approach is to perfuse the pancreas via the pancreatic duct with collagenase solution using a recirculating perfusion device system. This provides control over perfusion pressures and collagenase temperature. This study reports on our evaluation of the delivery of Liberase™-HI into the pancreas of 14 consecutive adult multiorgan cadaveric donors. Alternate glands were procured and processed using an identical protocol with the exception of collagenase delivery. The first group of pancreases was loaded using the perfusion technique where cold (4°C) Liberase™-HI was perfused at 80 mmHg for 5 min after which the pressure was increased to 180 mmHg. The collagenase solution was then slowly warmed to 35°C, transferred to the dissociation chamber and mechanically dissociated, and then purified using discontinuous gradients of Ficoll. Pancreases in the second group were loaded with collagenase (28–32°C) using the syringe technique before mechanical dissociation and purification. There were no significant differences in pancreas cold ischemia, donor age, body mass index, maximum blood glucose, or serum amylase of the donors between the two groups. Mean collagenase digestion time in the digestion chamber was not different between the two groups; however, the amount of undigested tissue remaining after dissociation was significantly higher in the syringe-loaded group (15.3 ± 2.6 g vs. 4.6 ±2.1 g, mean ± SEM, p < 0.05). Postdigestion recovery of islets was 471 ± 83 × 103 IE in the perfusion group compared with 391 ± 57 × 103 IE for the syringe-loaded group. Postpurification recovery was higher in the perfused group (379 ± 45 vs. 251 ± 28 × 103 IE, p < 0.05, two-tailed paired t-test). No difference in in vitro islet viability was observed between the two groups following glucose perifusion with the calculated stimulation index of 4.6 ± 0.6 for the perfusion group and 4.2 ± 0.7 for the syringe-loaded group. Controlled perfusion via the pancreatic duct allows the effective delivery of the enzyme achieving maximal distension to all regions of the pancreas leading to an increased recovery of the islets with no detrimental effect on subsequent in vitro islet function.

Expansion of mesenchymal stem cells from human pancreatic ductal epithelium

Fibroblast-like cells emerging from cultured human pancreatic endocrine and exocrine tissue have been reported. Although a thorough phenotypic characterization of these cells has not yet been carried out, these cells have been hypothesized to be contaminating fibroblasts, mesenchyme and/or possibly beta-cell progenitors. In this study, we expanded fibroblast-like cells from adult human exocrine pancreas following islet isolation and characterized these cells as mesenchymal stem cells (MSCs) based on their cell surface antigen expression and ability to differentiate into mesoderm. Analysis by flow cytometry demonstrated that pancreatic MSCs express cell surface antigens used to define MSCs isolated from bone marrow such as CD13, CD29, CD44, CD49b, CD54, CD90 and CD105. In addition, utilizing protocols used to differentiate MSCs isolated from other somatic tissues, we successfully differentiated pancreatic MSCs into: (1) osteocytes that stained positive for alkaline phosphatase, collagen, mineralization (calcification) and expressed osteocalcin, (2) adipocytes that contained lipid inclusions and expressed fatty acid binding protein 4 and (3) chondrocytes that expressed aggrecan. We also demonstrated that pancreatic MSCs are multipotent and capable of deriving cells of endodermal origin. Pancreatic MSCs were differentiated into hepatocytes that stained positive for human serum albumin and expressed endoderm and liver-specific genes such as GATA 4 and tyrosine aminotransferase. In addition, preliminary protocols used to differentiate these cells into insulin-producing cells resulted in the expression of genes necessary for islet and beta-cell development such as Pax4 and neurogenin 3. Therefore, multipotent MSCs residing within the adult exocrine pancreas could represent a progenitor cell, which when further manipulated could result in the production of functional islet beta-cells.

Factors influencing the loss of beta-cell mass in islet transplantation.

Recent advances in clinical islet transplantation have clearly demonstrated that this procedure can provide excellent glycemic control and often insulin independence in a population of patients with type 1 diabetes. A key limitation in the widespread application of clinical islet transplantation is the requirement of 10,000 islet equivalents/kg in most recipients, generally derived from two or more cadaveric donors. It has been determined that a majority of the transplanted islets fail to engraft and become fully functional. In this review article, the factors that contribute to this early loss of islets following transplantation are discussed in depth.

Risk factors for islet loss during culture prior to transplantation

Culturing islets can add great flexibility to a clinical islet transplant program. However, a reduction in the islet mass has been frequently observed during culture and its degree varies. The aim of this study was to identify the risk factors associated with a significant islet loss during culture. One‐hundred and four islet preparations cultured in an attempt to use for transplantation constituted this study. After culture for 20 h (median), islet yield significantly decreased from 363 309 ± 12 647 to 313 035 ± 10 862 islet equivalent yield (IE) (mean ± SE), accompanied by a reduction in packed tissue volume from 3.9 ± 0.1 to 3.0 ± 0.1 ml and islet index (IE/islet particle count) from 1.20 ± 0.04 to 1.05 ± 0.04. Culture did not markedly alter islet purity or percent of trapped islet. Morphology score and viability were significantly improved after culture. Of 104 islet preparations, 37 suffered a substantial islet loss (>20%) over culture. Factors significantly associated with risk of islet loss identified by univariate analysis were longer cold ischemia time, two‐layer method (TLM) preservation, lower islet purity, and higher islet index. Multivariate analysis revealed that independent predictors of islet loss were higher islet index and the use of TLM. This study provides novel information on the link between donor‐ isolation factors and islet loss during culture.

Pretransplant HLA antibodies are associated with reduced graft survival after clinical islet transplantation.

Despite significant improvements in islet transplantation, long‐term graft function is still not optimal. It is likely that both immune and nonimmune factors are involved in the deterioration of islet function over time. Historically, the pretransplant T‐cell crossmatch and antibody screening were done by anti‐human globulin—complement‐dependent cytotoxicity (AHG‐CDC). Class II antibodies were not evaluated. In 2003, we introduced solid‐phase antibody screening using flow‐based beads and flow crossmatching. We were interested to know whether pretransplant human leukocyte antigen (HLA) antibodies or a positive flow crossmatch impacted islet function post‐transplant. A total of 152 islet transplants was performed in 81 patients. Islet function was determined by a positive C‐peptide. Results were analyzed by procedure. Class I and class II panel reactive antibody (PRA) > 15% and donor‐specific antibodies (DSA) were associated with a reduced C‐peptide survival (p < 0.0001 and p < 0.0001, respectively). A positive T‐ and or B‐cell crossmatch alone was not. Pretransplant HLA antibodies detectable by flow beads are associated with reduced graft survival. This suggests that the sirolimus and low‐dose tacrolimus‐based immunosuppression may not control the alloimmune response in this presensitized population and individuals with a PRA > 15% may require more aggressive inductive and maintenance immunosuppression, or represent a group that may not benefit from islet transplantation.

Variation in Human Islet Viability Based on Different Membrane Integrity Stains

Membrane integrity fluorescent staining is used routinely to evaluate islet viability. Results are used as one of the determining factors in islet product release criteria, and are used to assess the efficacy of different culture conditions. Recently, it has been observed that there is variation in the viability staining of freshly isolated islets based on which viability assay is used. This investigation compares three membrane integrity stains for the viability assessment of isolated human islets. Fluorescein diacetate/propidium iodide (FDA/PI), the current standard method for assessing islet viability, demonstrates intense extracellular fluorescence, reducing the differential staining of intact islets. We further evaluated SYTO-13/ethidium bromide (SYTO/EB) and calcein AM/ethidium homodimer (C/EthD) as alternative viability assays, and found considerable variation between FDA/PI and either SYTO/EB or C/EthD staining. Preparations of human islets were obtained from cadaveric pancreata after collagenase digestion, mechanical separation, and purification by continuous Ficoll gradient centrifugation. For each preparation, two replicate samples of 50 islets were counted for each stain, and the percent viability calculated. The results for SYTO/EB and C/EthD were nearly identical [57.6 ± 7.3% and 57.9 ± 7.2%, respectively (mean ± SEM), N = 11]. FDA/PI-stained islets, however, showed consistently elevated values when compared to SYTO/EB. Accurate assessment of islet viability remains a critical determinant of islet product release. The discrepancies found between FDA/PI scoring and visual quality, compared with alternative stains, suggests that the FDA/PI stain may not be the optimal approach to assess islet viability.

Methods of Human Islet Culture for Transplantation

The ability to maintain isolated human islet preparations in tissue culture has recently been adopted by most islet transplant centers, and improves the safety as well as the practicality of islet transplantation. Maintaining islet viability and recovery, however, remains challenging in a clinical setting, due to stringent conditions required for culture. Islet culture is further complicated by the fact that islets do not form a monolayer. This review aims to clarify media, supplementation, and conditions that have been shown to be relevant to human islets, as well as to offer avenues of future research. Factors examined that may influence islet survival include base medium, glucose concentration, vitamin, inorganic ion, lipid, hormone, growth factor, amino acid, and binding protein composition and concentration, as well as culture temperature and seeding density. In addition, this article reviews novel techniques, such as coculture and matrices, that have been employed in an attempt to improve islet survival and functional viability.

Long‐Term Follow‐Up of the Edmonton Protocol of Islet Transplantation in the United States

We report the long‐term follow‐up of the efficacy and safety of islet transplantation in seven type 1 diabetic subjects from the United States enrolled in the multicenter international Edmonton Protocol who had persistent islet function after completion of the Edmonton Protocol. Subjects were followed up to 12 years with serial testing for sustained islet allograft function as measured by C‐peptide. All seven subjects demonstrated continued islet function longer than a decade from the time of first islet transplantation. One subject remained insulin independent without the need for diabetic medications or supplemental transplants. One subject who was insulin‐independent for over 8 years experienced graft failure 10.9 years after the first islet transplant. The remaining six subjects demonstrated continued islet function upon trial completion, although three had received a supplemental islet transplant each. At trial completion, five subjects were receiving insulin and two remained insulin independent, although one was treated with liraglutide. The median hemoglobin A1c was 6.3% (45 mmol/mol). All subjects experienced progressive decline in the C‐peptide/glucose ratio. No patients experienced severe hypoglycemia, opportunistic infection, or lymphoma. Thus, although the rate and duration of insulin independence was low, the Edmonton Protocol was safe in the long term. Alternative approaches to islet transplantation are under investigation.

Detrimental effect of excessive collagenase class II on human islet isolation outcome

Commercially available purified collagenases, derived from Clostridium histolyticum, contain two different classes of collagenase: class I collagenase (CI) and class II collagenase (CII) at a predetermined ratio. In this study, using purified CI and CII in separate vials, we had a unique opportunity to investigate the effect of the proportion between two collagenase classes on clinical human islet isolation. Pancreas organs derived from deceased donors were prospectively assigned to one of three different enzyme protocols: group A – CII:CI = 1:1 vial; group B – 1:2; group C – 1.5:1. As a result, their total collagenase activities were 2116, 2230, and 3117 Wunsch units/pancreas in groups A, B, and C, respectively but thermolysin dosage was adjusted to 624–988 Units/g pancreas. The pancreas was not efficiently digested in group C in spite of a relatively longer digestion time and significantly higher Wunsch activity, resulting in the poorest islet isolation outcome among the three groups. Additional retrospective analysis revealed that this suboptimal outcome in group C was not because of the absolute excessive amount of collagenase activity but as a result of the relatively high proportion of CII (i.e., unbalanced CII/CI ratio). Our study suggests that an excessive CII is ineffective in releasing islets from human pancreas, and rather a balanced CII/CI ratio is of paramount importance.