Iodixanol-controlled density gradient during islet purification improves recovery rate in human islet isolation

Quality of life after total pancreatectomy with islet autotransplantation for chronic pancreatitis in Japan

BACKGROUND

Patients with chronic pancreatitis (CP) often have severe and intractable abdominal pain, leading to decreased quality of life (QOL), inability to work or attend school, and increased health care costs due to repeated emergency room visits and hospitalizations.

METHODS

We evaluated the efficacy of total pancreatectomy and islet autotransplantation (TPIAT) in terms of pain control and QOL in CP patients treated at our center in Japan. To evaluate QOL, we used the Short-Form 36 Health Survey version 2 (SF-36v2_® Standard, Japanese), European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30), and Quality of Life Questionnaire-Pancreatic Modification (QLQ-PAN28).

RESULTS

Between August 2016 and June 2019, we performed this procedure in 5 patients. All patients were followed up for 12 months and all transplanted islets were still functioning at the 1-year follow-up. The major adverse events were abdominal wall hemorrhage, intestinal obstruction, intra-abdominal abscess, and abdominal pain requiring hospitalization; no case had sequelae. No major complications were due to islet transplantation. Pain scores improved postoperatively in all patients. Three QOL item dimensions role-physical (p = 0.03125), general health perception (p = 0.03125) and vitality (p = 0.03125) in the SF-36 were significantly improved 12 months after TPIAT. Mean values of many other QOL items improved, though not significantly.

CONCLUSION

The QOL improvement after TPIAT for CP suggests its effectiveness in the Japanese population.

Pancreas Preservation in Modified Histidine-lactobionate Solution Is Superior to That in University of Wisconsin Solution for Porcine Islet Isolation

BACKGROUND

We previously reported that modified extracellular-type trehalose-containing Kyoto (MK) solution, which contains a trypsin inhibitor (ulinastatin), significantly improved the islet yield compared with University of Wisconsin (UW) preservation, which is the gold standard for organ preservation for islet isolation. In this study, we evaluated the efficiency of a modified histidine-lactobionate (MHL) solution in addition to UW or MK solution. The MHL solution has a high sodium-low potassium composition with low viscosity compared with the UW solution. Moreover, similar to MK solution, MHL solution also contains ulinastatin.

METHODS

Porcine pancreata were preserved in UW, MK, or MHL solution, followed by islet isolation. An optimized number (1500 IE) of isolated islets from each group were then transplanted into streptozotocin-induced diabetic mice.

RESULTS

The islet yield before and after purification was significantly higher in the MHL group than in the UW group. On the contrary, the islet yield before and after purification was not significantly different between the MHL and MK groups. Preserving the porcine pancreata in MHL solution improved the outcome of islet transplantation in streptozotocin-induced diabetic mice compared with that in UW solution.

CONCLUSIONS

Pancreas preservation with MHL solution preserves islet function better than UW solution. The effect of MHL solution is similar to that of MK solution, suggesting that MHL solution can be used as an alternative to MK solution for pancreatic islet transplantation.

Clinical Islet Transplantation Covered by Health Insurance in Japan

Pancreatic islet transplantation is a treatment option for patients with type 1 diabetes mellitus and has been performed in various countries [1–5].  [...]

PRISM: A Novel Human Islet Isolation Technique

BACKGROUND

Successful pancreatic islet isolations are a key requirement for islet transplantation in selected patients with type 1 diabetes. However, islet isolation is a technically complex, time-consuming, and manual process. Optimization and simplification of the islet isolation procedure could increase islet yield and quality, require fewer operators, and thus reduce cost.

METHODS

We developed a new, closed system of tissue collection, washing, buffer change, and islet purification termed PancReatic Islet Separation Method (PRISM). In the developmental phase, pump and centrifuge speed was tested using microspheres with a similar size, shape, and density as digested pancreatic tissue. After optimization, PRISM was used to isolate islets from 10 human pancreases.

RESULTS

Islet equivalents viability (fluorescein diacetate/propidium iodide), morphology, and dynamic glucose-stimulated insulin secretion were evaluated. PRISM could be performed by 1 operator in 1 flow cabinet. A similar islet yield was obtained using PRISM compared to the traditional islet isolation method (431 234 ± 292 833 versus 285 276 ± 197 392 islet equivalents, P = 0.105). PRISM islets had similar morphology and functionality.

CONCLUSIONS

PRISM is a novel islet isolation technique that can significantly improve islet isolation efficiency using fewer operators.

Pancreatic Islet Purification from Large Mammals and Humans Using a COBE 2991 Cell Processor versus Large Plastic Bottles

The islet purification step in clinical islet isolation is important for minimizing the risks associated with intraportal infusion. Continuous density gradient with a COBE 2991 cell processor is commonly used for clinical islet purification. However, the high shear force involved in the purification method using the COBE 2991 cell processor causes mechanical damage to the islets. We and other groups have shown human/porcine islet purification using large cylindrical plastic bottles. Shear stress can be minimized or eliminated using large cylindrical plastic bottles because the bottles do not have a narrow segment and no centrifugation is required during tissue loading and the collection processes of islet purification. This review describes current advances in islet purification from large mammals and humans using a COBE 2991 cell processor versus large cylindrical plastic bottles.

Recombinant collagenase from Grimontia hollisae as a tissue dissociation enzyme for isolating primary cells

Collagenase products are crucial to isolate primary cells in basic research and clinical therapies, where their stability in collagenolytic activity is required. However, currently standard collagenase products from Clostridium histolyticum lack such stability. Previously, we produced a recombinant 74-kDa collagenase from Grimontia hollisae, which spontaneously became truncated to ~60 kDa and possessed no stability. In this study, to generate G. hollisae collagenase useful as a collagenase product, we designed recombinant 62-kDa collagenase consisting only of the catalytic domain, which exhibits high production efficiency. We demonstrated that this recombinant collagenase is stable and active under physiological conditions. Moreover, it possesses higher specific activity against collagen and cleaves a wider variety of collagens than a standard collagenase product from C. histolyticum. Furthermore, it dissociated murine pancreata by digesting the collagens within the pancreata in a dose-dependent manner, and this dissociation facilitated isolation of pancreatic islets with masses and numbers comparable to those isolated using the standard collagenase from C. histolyticum. Implantation of these isolated islets into five diabetic mice led to normalisation of the blood glucose concentrations of all the recipients. These findings suggest that recombinant 62-kDa collagenase from G. hollisae can be used as a collagenase product to isolate primary cells.

"Old School" Islet Purification Based on the Unit Gravity Sedimentation as a Rescue Technique for Intraportal Islet Transplantation-A Case Report

Here, we present a case that required a supplemental "old school" islet purification for a safe intraportal infusion. Following pancreas procurement from a brain-dead 26-year-old male donor (body mass index: 21.9), 24.6 ml of islet tissue was isolated after continuous density gradient centrifugation. The islet yield was 504,000 islet equivalent (IEQ), distributed among the following three fractions: 64,161 IEQ in 0.6 ml of pellet, 182,058 IEQ in 10 ml, and 258,010 IEQ in 14 ml with 95%, 20%, and 10% purity, respectively. After a 23-h culture, we applied supplemental islet purification, based on the separation of tissue subfractions during unit gravity sedimentation, a technique developed over 60 years ago ("old school"). This method enabled the reduction of the total pellet volume to 11.6 ml, while retaining 374,940 IEQ with a viability of over 90%. The final islet product was prepared in three infusion bags, containing 130,926 IEQ in 2.6 ml of pellet, 108,079 IEQ in 4 ml of pellet, and 135,935 IEQ in 5 ml of pellet with 65%, 40%, and 30% purity, respectively, and with the addition of unfractionated heparin (70 units/kg body weight). Upon the islet infusion from all three bags, portal pressure increased from 7 to 16 mmHg. Antithrombotic prophylaxis with heparin was continued for 48 h after the infusion, with target activated partial thromboplastin time 50-60 s, followed by fractionated heparin subcutaneous injections for 2 weeks. β-Cell graft function assessed on day 75 post-transplantation was good, according to Igls criteria, with complete elimination of severe hypoglycemic episodes and 50% reduction in insulin requirements. Time spent within the target glucose range (70-180 mg/dl) improved from 42% to 98% and HbA1c declined from 8.7% to 6.7%. Supplemental "old school" islet purification allowed for the safe and successful utilization of a robust and high-quality islet preparation, which otherwise would have been discarded.

Excellent Islet Yields after 18-h Porcine Pancreas Preservation by Ductal Injection, Pancreas Preservation with MK Solution, Bottle Purification, and Islet Purification Using Iodixanol with UW Solution and Iodixanol with MK Solution

Successful islet isolation is the key to successful islet transplantation. Our group recently modified the islet isolation protocol to include pancreatic ductal injection of the preservation solution, pancreas storage in modified extracellular-type trehalose-containing Kyoto (MK) solution, and use of an iodixanol-based purification solution and bottle purification. In this study, we applied these methods to porcine islet isolation after 18-h pancreas preservation and compared two solutions with different compositions in bottle purification. Islet yield before purification was 651,661 ± 157,719 islet equivalents (IE) and 5576 ± 1538 IE/g pancreas weight. An IU solution was made by adding iodixanol to University of Wisconsin solution and an IK solution was made by adding iodixanol to MK solution. The efficacy of the two solutions for islet isolation was compared. There were no significant differences between the two purification methods with regard to islet yield, survival rate, purity, score, or stimulation index. These results indicate that our isolation protocol produces efficient islet yields from prolonged cold-stored pancreas and that IU and IK solutions are equally useful for islet purification.

In vitro and in vivo effects of insulin-producing cells generated by xeno-antigen free 3D culture with RCP piece

To establish widespread cell therapy for type 1 diabetes mellitus, we aimed to develop an effective protocol for generating insulin-producing cells (IPCs) from adipose-derived stem cells (ADSCs). We established a 3D culture using a human recombinant peptide (RCP) petaloid μ-piece with xeno-antigen free reagents. Briefly, we employed our two-step protocol to differentiate ADSCs in 96-well dishes and cultured cells in xeno-antigen free reagents with 0.1 mg/mL RCP μ-piece for 7 days (step 1), followed by addition of histone deacetylase inhibitor for 14 days (step 2). Generated IPCs were strongly stained with dithizone, anti-insulin antibody at day 21, and microstructures resembling insulin secretory granules were detected by electron microscopy. Glucose stimulation index (maximum value, 4.9) and MAFA mRNA expression were significantly higher in 3D cultured cells compared with conventionally cultured cells (P < 0.01 and P < 0.05, respectively). The hyperglycaemic state of streptozotocin-induced diabetic nude mice converted to normoglycaemic state around 14 days after transplantation of 96 IPCs under kidney capsule or intra-mesentery. Histological evaluation revealed that insulin and C-peptide positive structures existed at day 120. Our established xeno-antigen free and RCP petaloid μ-piece 3D culture method for generating IPCs may be suitable for clinical application, due to the proven effectiveness in vitro and in vivo.

Comparison of Tissue Loading Before and After the Creation of a Continuous Density Gradient in Porcine Islet Purification

The purification step is one of the most important and difficult procedures in islet isolation for pancreatic islet transplantation. We previously reported that a purification method using large plastic bottles effectively achieved a high yield of islets from the porcine pancreas. In this study, we evaluated the impact of the timing of tissue loading on porcine islet purification using large plastic bottles. One method involved loading digested tissue after creating a continuous density gradient (tissue after gradient [TAG]). The other method involved loading digested tissue before creating a continuous density gradient (tissue before gradient [TBG]). There were no significant differences between TAG and TBG in terms of the islet yield, rates of viability and purity, score, and in the stimulation index after purification. Furthermore, there were no marked differences in the attainability or suitability of post-transplantation normoglycemia. Our study shows the equivalency of these two methods of islet purification.

A Comparison of Pancreatic Islet Purification using Iodixanol with University of Wisconsin Solution and with Na-Lactobionate and Histidine Solution

Purification of pancreatic islets is an important step in islet isolation for islet transplantation. In this study, to investigate how a solution composed mainly of Na-lactobionate and histidine (HL) influences the purification of islets, iodixanol was added to a purified solution for porcine islet isolation. A solution (IU) made by adding iodixanol to University of Wisconsin solution and a solution (IHL) made by adding iodixanol to HL solution were used to evaluate the islet isolation performance. We noted no significant differences between the two purification methods with regard to the islet yield, survival rate or purity, score, or stimulation index. These results show that IHL solution is as useful as IU solution for islet purification.

Evaluation of Islet Purification Methods for Making a Continuous Density Gradient and Loading Tissue

Islet purification is one of the most important steps of islet isolation for pancreatic islet transplantation. We previously reported that a purification method using large plastic bottles effectively achieved a high yield of islets from porcine pancreas. In this study, we evaluated the methods for making a continuous density gradient and loading tissue. One method involved loading digested tissue on top of a continuous density gradient (top loading). The other method involved mixing digested tissue with low-density solution and then making a continuous gradient (mixed loading). There were no significant differences between the 2 purification methods in terms of the islet yield, rate of viability or purity, score, or in the stimulation index after purification. Furthermore, there were no marked differences in the attainability or suitability of posttransplantation normoglycemia. Our study shows the equivalency of these 2 methods of islet purification.

Adhesion characteristics of porcine pancreatic islets and exocrine tissue to coating materials

Since the report of the Edmonton protocol in 2000, islet transplantation has been implemented worldwide, and xenotransplantation using porcine islets has also been reported. In addition, many basic experiments using pancreatic islets and exocrine tissue after isolation have been reported. Recently, exocrine cells have been found to be essential for inducing the differentiation of pancreatic islets. Therefore, the importance of the culture conditions for pancreatic tissue when conducting experiments using pancreatic tissue is also increasing. In this study, we focused on the coat material and examined the adhesive properties of porcine pancreatic islets and exocrine tissue after isolation. Porcine islet isolation was performed, and isolated islets (purity ≥95%) and exocrine tissue (purity ≥99%) were used to achieve adhesion to several extracellular matrixes, fibronectin, collagen type I, collagen type IV, laminin I, fibrinogen, and bovine serum albumin (BSA). DMEM with 0.5% FBS was used as the assay medium. For exocrine tissue, the adhesion was promoted in fibronectin, collagen type I, laminin I, and fibrinogen. The adhesive ability to fibronectin was more than twice that to BSA, while the adhesive ability to collagen type I, laminin I, and fibrinogen was less than twice that to BSA. For islets, the adhesive ability to fibronectin was weaker than that of exocrine tissue. Furthermore, the adhesion effect in fibronectin was obtained within 30 minutes and in medium containing little serum for both islets and exocrine tissues. These data suggest that fibronectin may be useful for the adhesion of pancreatic tissue.

Current issues in allogeneic islet transplantation

PURPOSE OF REVIEW

Transplantation of allogenic pancreatic islets is a minimally invasive treatment option to control severe hypoglycemia and dependence on exogenous insulin among type 1 diabetes (T1D) patients. This overview summarizes the current issues and progress in islet transplantation outcomes and research.

RECENT FINDINGS

Several clinical trials from North America and other countries have documented the safety and efficacy of clinical islet transplantation for T1D patients with impaired hypoglycemia awareness. A recently completed phase 3 clinical trial allows centres in the United States to apply for a Food and Drug Administration Biologics License for the procedure. Introduction of anti-inflammatory drugs along with T-cell depleting induction therapy has significantly improved long-term function of transplanted islets. Research into islet biomarkers, immunosuppression, extrahepatic transplant sites and potential alternative beta cell sources is driving further progress.

SUMMARY

Allogeneic islet transplantation has vastly improved over the past two decades. Success in restoration of glycemic control and hypoglycemic awareness after islet transplantation has been further highlighted by clinical trials. However, lack of effective strategies to maintain long-term islet function and insufficient sources of donor tissue still impose limitations to the widespread use of islet transplantation. In the United States, wide adoption of this technology still awaits regulatory approval and, importantly, a financial mechanism to support the use of this technology.

A proteome analysis of pig pancreatic islets and exocrine tissue by liquid chromatography with tandem mass spectrometry

Liquid chromatography with tandem mass spectrometry (LC-MS/MS) is a proteome analysis method, and the shotgun analysis by LC-MS/MS comprehensively identifies proteins from tissues and cells with high resolving power. In this study, we analyzed the protein expression in pancreatic tissue by LC-MS/MS. Islets isolated from porcine pancreata (purity ≥95%) and exocrine tissue (purity ≥99%) were used in this study. LC-MS/MS showed that 13 proteins were expressed in pancreatic islets only (Group I), 43 proteins were expressed in both islets and exocrine tissue (Group I&E), and 102 proteins were expressed in exocrine tissue only (Group E). Proteins involved in islet differentiation and cell proliferation were identified in Group I (e.g. CLUS, CMGA, MIF). In addition, various functional proteins (e.g. SCG2, TBA1A) were identified in islet by using the new method of 'principal component analysis (PCA)'. However, the function of such proteins on islets remains unclear. EPCAM was identified in Group E. Group E was found to include proteins involved in clinical inflammatory diseases such as pancreatitis (e.g. CBPA1, CGL, CYTB, ISK1 and PA21B). Many of these identified proteins were reported less frequently in previous studies, and HS71B, NEC2, PRAF3 and SCG1 were newly detected in Group I while CPNS1, DPEP1, GANAB, GDIB, GGT1, HSPB1, ICTL, VILI, MUTA, NDKB, PTGR1, UCHL3, VAPB and VINC were newly detected in Group E. These results show that comprehensive expression analysis of proteins by LC-MS/MS is useful as a method to investigate new factors constructing cellular component, biological process, and molecular function.

Improved yield of canine islet isolation from deceased donors

BACKGROUND

Canine diabetes is a strikingly prevalent and growing disease, and yet the standard treatment of a twice-daily insulin injection is both cumbersome to pet owners and only moderately effective. Islet transplantation has been performed with repeated success in canine research models, but has unfortunately not been made available to companion animals. Standard protocols for islet isolation, developed primarily for human islet transplantation, include beating-heart organ donation, vascular perfusion of preservation solutions, specialized equipment. Unfortunately, these processes are prohibitively complex and expensive for veterinary use. The aim of the study was to develop a simplified approach for isolating canine islets that is compatible with the financial and logistical restrictions inherent to veterinary medicine for the purpose of translating islet transplantation to a clinical treatment for canine diabetes.

RESULTS

Here, we describe simplified strategies for isolating quality islets from deceased canine donors without vascular preservation and with up to 90 min of cold ischemia time. An average of more than 1500 islet equivalents per kg of donor bodyweight was obtained with a purity of 70% (N = 6 animals). Islets were 95% viable and responsive to glucose stimulation for a week. We found that processing only the body and tail of the pancreas increased isolation efficiency without sacrificing islet total yield. Islet yield per gram of tissue increased from 773 to 1868 islet equivalents when the head of the pancreas was discarded (N = 3/group).

CONCLUSIONS

In summary, this study resulted in the development of an efficient and readily accessible method for obtaining viable and functional canine islets from deceased donors. These strategies provide an ethical means for obtaining donor islets.

Comparison of Purification Solutions With Different Osmolality for Porcine Islet Purification

The osmolality of the purification solution is one of the most critical variables in human islet purification during islet isolation. We previously reported the effectiveness of a combined continuous density/osmolality gradient for the supplemental purification of human islets. We herein applied a combined continuous density/osmolality gradient for regular purification. The islets were purified with a continuous density gradient without osmolality preparation [continuous density/normal osmolality (CD/NO)] or continuous density/osmolality solution with osmolality preparation by 10× Hank's balanced salt solution (HBSS) [continuous density/continuous osmolality (CD/CO)]. The osmolality of the low-density solution was 400 mOsm/kg in both groups and that of the high-density solution was 410 mOsm/kg in the CD/NO group and 500 mOsm/kg in the CD/CO group. Unexpectedly, we noted no significant differences between the two solutions in terms of the islet yield, rate of viability and purity, score, stimulation index, or the attainability and suitability of posttransplantation normoglycemia. Despite reports that the endocrine and exocrine tissues of pancreata have distinct osmotic sensitivities and that high-osmolality solutions result in greater purification efficiency, the isolation and transplant outcomes did not markedly differ between the two purification solutions with different osmolalities in this study.

The Evaluation of Islet Purification Methods That Use Large Bottles to Create a Continuous Density Gradient

Islet purification is one of the most important steps of islet isolation for pancreatic islet transplantation. The most common method of islet purification is density gradient centrifugation using a COBE 2991 cell processor. However, this method can damage islets mechanically through its high shearing force. We recently reported that a new purification method using large plastic bottles effectively achieves a high yield of islets from the porcine pancreas. In the present study, we evaluated the methods of making a continuous density gradient. The gradient was produced with a gradient maker and two types of candy cane-shaped stainless steel pipes. One method was to use a "bent-tipped" stainless steel pipe and to load from a high-density solution to a low-density solution, uploading the stainless steel pipe. The other method was to use a regular stainless steel pipe and to load from a low-density solution to a high-density solution, leaving the stainless steel pipe in place. There were no significant differences between the two solutions in terms of the islet yield, rate of viability or purity, score, or the stimulation index after purification. Furthermore, there were no differences in the attainability or suitability of posttransplantation normoglycemia. Our study shows the equivalency of these two methods of islet purification.

β-Cell regeneration through the transdifferentiation of pancreatic cells: Pancreatic progenitor cells in the pancreas

Pancreatic progenitor cell research has been in the spotlight, as these cells have the potential to replace pancreatic β‐cells for the treatment of type 1 and 2 diabetic patients with the absence or reduction of pancreatic β‐cells. During the past few decades, the successful treatment of diabetes through transplantation of the whole pancreas or isolated islets has nearly been achieved. However, novel sources of pancreatic islets or insulin‐producing cells are required to provide sufficient amounts of donor tissues. To overcome this limitation, the use of pancreatic progenitor cells is gaining more attention. In particular, pancreatic exocrine cells, such as duct epithelial cells and acinar cells, are attractive candidates for β‐cell regeneration because of their differentiation potential and pancreatic lineage characteristics. It has been assumed that β‐cell neogenesis from pancreatic progenitor cells could occur in pancreatic ducts in the postnatal stage. Several studies have shown that insulin‐producing cells can arise in the duct tissue of the adult pancreas. Acinar cells also might have the potential to differentiate into insulin‐producing cells. The present review summarizes recent progress in research on the transdifferentiation of pancreatic exocrine cells into insulin‐producing cells, especially duct and acinar cells.

Pancreatic Islets: Methods for Isolation and Purification of Juvenile and Adult Pig Islets

The current situation of organ transplantation is mainly determined by the disbalance between the number of available organs and the number of patients on the waiting list. This obvious dilemma might be solved by the transplantation of porcine organs into human patients. The metabolic similarities which exist between both species made pancreatic islets of Langerhans to that donor tissue which will be most likely transplanted in human recipients. Nevertheless, the successful isolation of significant yields of viable porcine islets is extremely difficult and requires extensive experiences in the field. This review is focussing on the technical challenges, pitfalls and particularities that are associated with the isolation of islets from juvenile and adult pigs considering donor variables that can affect porcine islet isolation outcome.

Clinical Islet Isolation

The overarching success of islet transplantation relies on the success in the laboratory to isolate the islets. This chapter focuses on the processes of human islet cell isolation and the ways to optimally provide islet cells for transplantation. The major improvements in regards to the choice of enzyme type, way the digested pancreas tissue is handled to best separate islets from the acinar and surrounding tissues, the various methods of purification of the islets, their subsequent culture and quality assurance to improve outcomes to culminate in safe and effective islet transplantation will be discussed. After decades of improvements, islet cell isolation and transplantation now clearly offer a safe, effective and feasible therapeutic treatment option for an increasing number of patients suffering from type 1 diabetes specifically for those with severe hypoglycaemic unawareness.

Adult porcine islet isolation using a ductal preservation method and purification with a density gradient composed of histidine-tryptophan-ketoglutarate solution and iodixanol

BACKGROUND

Given the fragility of adult porcine islets, reduction of shearing stress in islet purification using histidine-tryptophan-ketoglutarate (HTK) solution and iodixanol could be an effective strategy. We examined the effect of ductal preservation with HTK solution and an islet purification protocol that utilizes HTK solution and iodixanol in adult porcine islet isolation.

METHODS

Islets were isolated with a modified Ricordi method using adult Prestige World Genetics (PWG) and Yucatan pigs. The discontinuous density gradient was composed of either HTK solution/iodixanol (n = 23, iodixanol group) or Hank's balanced salt solution (HBSS)/Ficoll (n = 17, Ficoll group). In the iodixanol group, ductal injection of HTK solution was performed before purification.

RESULTS

In PWG pigs, significantly higher islet yield after purification (3480 ± 214.2 islet equivalent [IEQ]/g, P = .003) and higher recovery rate (85.45% ± 3.49%, P = .0043) were obtained from the HTK/iodixanol group as compared to the HBSS/Ficoll group (1905 ± 323.2 IEQ/g, and 67.22% ± 4.77%, respectively). Similar results were obtained in Yucatan pigs with greater body weight.

CONCLUSION

Ductal preservation and iodixanol-based islet purification using HTK solution improved the yield of adult porcine islet isolation compared to the conventional method using HBSS and Ficoll. The results of this study support the feasibility of an adult porcine islet isolation protocol using HTK solution and iodixanol, which have the favorable physical properties.

An effective method to release human islets from surrounding acinar cells with agitation in high osmolality solution

INTRODUCTION

Islet purification is mainly performed by the density gradient method. However, purification of the embedded islets that are surrounded by exocrine tissue should be difficult, because their density is similar to exocrine tissue. In this study, we performed chart review to assess the relationship between the ratio of embedded islets and efficacy of purification. Then, we tested several conditions of a new method to free the islets from surrounded exocrine tissues using high osmolality solution with gentle agitation.

MATERIALS AND METHODS

First, we performed chart review of our human islet isolation. Second, embedded islet-enriched human islet fractions (embedded islets >50%) were suspended in University of Wisconsin (UW) solution (UW group, 320 mOsm/kg/H(2)0) or osmolality-adjusted UW solution (400, 500, and 600 mOsm/kg/H(2)0; 400 group, 500 group, and 600 group, respectively). Each tube was gently shaken at 4°C. The tissue samples were taken before shaking and after 15, 30, and 60 minutes. Islet yield, percentage of embedded islets, and viabilities were assessed.

RESULTS

The chart review revealed that high ratio of embedded islets deteriorated the efficacy of islet purification. The islet yield in all groups except for the 600 group did not change at 15 minutes, but it decreased in all groups at 60 minutes. The average percentage of embedded islets before shaking was 62.6%. Although percentage of embedded islets were decreasing in all groups, it was < 20% at 15 minutes in the 500 and 600 groups whereas it was >44% in the UW group, which indicated that higher osmolality would have a greater effect. Viability was >95% in all groups at 30 minutes.

CONCLUSIONS

The embedded islets deteriorated the efficacy of islet purification. Gentle agitation of embedded islets in high osmolality (500 mOsm/kg/H(2)O, 15 minutes) could release islets from surrounded exocrine tissue.

Usefulness of the secretory unit of islet transplant objects (SUITO) index for evaluation of clinical autologous islet transplantation

BACKGROUND

Assessing the engrafted islet mass is important in evaluating the efficacy of islet transplantation. We previously demonstrated that the average secretory unit of islet transplant objects (SUITO) index within 1 month of allogeneic islet transplantation was an excellent predictor of insulin independence. However, the usefulness of the SUITO index for evaluating autologous islet transplantation has not been explored. The purpose of the present study was to assess the relationship between the SUITO index and clinical outcomes after total pancreatectomy followed by autologous islet transplantation.

METHODS

We performed 27 total pancreatectomies followed by autologous islet transplantation from October 2006 to January 2011. Cases were divided into an insulin-independent group (IIG; n = 12) and an insulin-dependent group (lDG; n = 15). The SUITO index was calculated by the formula [fasting C-peptide (ng/mL)/fasting glucose (mg/dL) -63] × 1,500. The average SUITO index within the first month of transplantation except for days 0, 1, and 2, maximum SUITO index, and most recent SUITO index were calculated in each case, and values were compared between the IIG and the IDG.

RESULTS

The average SUITO index within 1 month was significantly higher in the IIG than in the IDG (24.6 ± 3.4 vs 14.9 ± 2.0, respectively; P < .02). The maximum SUITO indices were 45.7 ± 7.7 in the IIG and 30.1 ± 8.1 in the IDG (not significant), and the recent SUITO indices were 36.9 ± 6.7 in the IIG and 22.8 ± 6.1 in the IDG (not significant).

CONCLUSIONS

The average SUITO index within 1 month was an excellent predictor of insulin independence after total pancreatectomy followed by autologous islet transplantation.

A new method for generating insulin-secreting cells from human pancreatic epithelial cells after islet isolation transformed by NeuroD1

The generation of insulin-secreting cells from nonendocrine pancreatic epithelial cells (NEPEC) has been demonstrated for potential clinical use in the treatment of diabetes. However, previous methods either had limited efficacy or required viral vectors, which hinder clinical application. In this study, we aimed to establish an efficient method of insulin-secreting cell generation from NEPEC without viral vectors. We used nonislet fractions from both research-grade human pancreata from brain-dead donors and clinical pancreata after total pancreatectomy with autologous islet transplantation to treat chronic pancreatitis. It is of note that a few islets could be mingled in the nonislet fractions, but their influence could be limited. The NeuroD1 gene was induced into NEPEC using an effective triple lipofection method without viral vectors to generate insulin-secreting cells. The differentiation was promoted by adding a growth factor cocktail into the culture medium. Using the research-grade human pancreata, the effective method showed high efficacy in the differentiation of NEPEC into insulin-positive cells that secreted insulin in response to a glucose challenge and improved diabetes after being transplanted into diabetic athymic mice. Using the clinical pancreata, similar efficacy was obtained, even though those pancreata suffered chronic pancreatitis. In conclusion, our effective differentiation protocol with triple lipofection method enabled us to achieve very efficient insulin-secreting cell generation from human NEPEC without viral vectors. This method offers the potential for supplemental insulin-secreting cell transplantation for both allogeneic and autologous islet transplantation.

Comparison of New Preservation Solutions, HN-1 and University of Wisconsin Solution, in Pancreas Preservation for Porcine Islet Isolation

For pancreatic islet transplantation, maintaining organ viability after pancreas procurement is critical and a major determinant for better graft function and survival. University of Wisconsin (UW) solution is currently the gold standard for abdominal organ preservation and the pancreas in particular. However, in the use of UW preservation solution for islet transplantation, there are disadvantages to be overcome, such as the inhibition of collagenase activity during pancreatic digestion. In this study, we compared UW solution with HN-1 solution in pancreas preservation for islet isolation. Islet yield was significantly greater in the HN-1 group than the UW group both before and after purification. In the in vitro assay, the adenosine triphosphate content in cultured islets was significantly higher in the HN-1 group than in the UW group. Furthermore, in streptozotocin-induced diabetic nude mice, the islet graft function of the HN-1 group was superior to that of the UW group. We concluded that the use of HN-1 solution is a promising approach for optimal pancreas preservation in islet transplantation.

Comparison of Incubation Solutions Prior to the Purification of Porcine Islet Cells

For pancreatic islet transplantation, one of the most important steps of islet isolation is islet purification. The most common method of islet purification is density gradient centrifugation because there are differences in density between islets and acinar tissue. However, the density of islets/acinar tissue depends on several conditions, such as the incubation time before purification and the osmolality of the preincubation solution. In this study, we evaluated the impact of using two different preincubation solutions before purification. We used the University of Wisconsin (UW) solution and a new preservation solution (HN-1), which we recently developed. There were no significant differences between the two solutions in terms of the islet yield, rate of viability, and purity or stimulation index after purification. There were also no differences in the attainability and suitability of posttransplantation normoglycemia. Our study shows that the HN-1 solution is equivalent to the UW solution for preincubation before islet purification.

Diabetes-free survival in patients who underwent islet autotransplantation after 50% to 60% distal partial pancreatectomy for benign pancreatic tumors

BACKGROUND

Several retrospective studies with short-term follow-up have demonstrated a low rate of new-onset diabetes after distal pancreatectomy for benign pancreatic tumors. We sought to determine the long-term diabetes-free survival of patients who underwent islet autotransplantation (IAT) after distal pancreatectomy and to identify any associations between the isolation parameters of autologous islets and diabetes-free survival.

METHODS

Among the 37 nondiabetic patients who underwent 50% to 60% partial pancreatectomy, 20 underwent IAT (IAT group; median follow-up period, 61 months). In the IAT group, diabetes-free survival was determined based on annual oral glucose tolerance tests, fasting blood glucose, and hemoglobin A1C.

RESULTS

The 7-year diabetes-free survival rate was 51% in the IAT group (median follow-up period, 61 months) and 45% in the 37 study subjects. Diabetes-free survival was significantly prolonged when islet yield per gram of pancreas weight was more than 5154 islet equivalents (IEQ)/g, even in patients with prediabetes and high insulin resistance who had a markedly high rate of diabetes development. The proportion of patients with impaired glucose tolerance at 2 years after distal pancreatectomy was 12 of 16 in the control group, 6 of 7 in patients with islet yields of less than 5154 IEQ/g, and 3 of 11 in patients with islet yields of more than 5154 IEQ/g (P=0.019).

CONCLUSIONS

Partial (50%-60%) pancreatectomy for benign pancreatic tumors had a major metabolic consequence, especially in patients with prediabetes and high insulin resistance. In this setting, prolonged diabetes-free survival was observed in patients who underwent IAT when a high islet yield per gram of pancreas was achieved.

Alternative immunomodulatory strategies for xenotransplantation: CD80/CD86-CTLA4 pathway-modified immature dendritic cells promote xenograft survival

Background

Xenotransplantation is a promising approach to circumventing the current organ shortage. However, T-cell-dependent anti-xenoresponses are a major challenge to successful xenografts. Given the advantages of the use of CTLA4-Ig in the survival of allografts, the purpose of the study was to investigate the therapeutic potential of CTLA4-IgG4 modified immature dendritic cells (imDCs) in the prevention of islets xenograft rejection.

Methods

CTLA4-IgG4 was constructed by the fusion of the extracellular regions of porcine CTLA4 to human the hIgG4 Fc region. The imDCs were induced and cultured from porcine peripheral blood mononuclear cells (PBMC). The CTLA4-IgG4 modified imDCs were delivered via the portal vein to the liver of diabetic mice (insulin-dependent diabetes mellitus) before islet xenografting, and mCTLA4-Ig was administered intravenously after xenotransplantation.

Results

The xenograft survival of mice receiving unmodified imDCs was approximately 30 days. However, following administration of CTLA4-IgG4 modified imDCs before grafting and mCTLA4-Ig after grafting, xenografts survived for more than 100 days. Flow cytometric analysis showed that the CD4⁺CD25⁺Foxp3⁺ Treg population was increased in spleens. The efficacy of donor CTLA4-IgG4 modified imDCs correlated partially with the amplification of Tregs.

Conclusions

These results confirm that selective inhibition of the direct and indirect pathways of T-cell activation by donor CTLA4-IgG4 modified imDCs and receptor CTLA4-Ig is a highly effective strategy to promote survival of xenografts.

Update on islet transplantation

Clinical islet transplantation has progressed considerably over the past 12 years, and >750 patients with type 1 diabetes have received islet transplants internationally over this time. Many countries are beginning to accept the transition from research to accepted and funded clinical care, especially for patients with brittle control that cannot be stabilized by more conventional means. Major challenges remain, including the need for more than one donor, and the requirement for potent, chronic immunosuppression. Combining immunological tolerance both to allo- and autoantigens, and a limitless expandable source of stem cell- or xenograft-derived insulin-secreting cells represent remaining hurdles in moving this effective treatment to a potential cure for all those with type 1 or 2 diabetes.

Fresh islets are more effective for islet transplantation than cultured islets

For clinical islet transplantation, isolated islets deteriorate rapidly in culture, although culturing islets prior to transplantation provides flexibility for evaluation of isolated islets and pretreatment of patients. In the present study, we compared human fresh islets to cultured islets with in vitro and in vivo assays. After culture for 24, 48, and 72 h, islet yield significantly decreased from 2,000 to 1,738 ± 26 (13% loss), 1,525 ± 30 (24% loss), or 1,298 ± 18 IEQ (35% loss), respectively. The ATP contents were significantly higher in the 6-h cultured group (near fresh group) than in 48-h culture groups. The stimulation index was relatively higher in the 6-h cultured group than in 48-h cultured group. Human islets with or without culture were transplanted into diabetic nude mice. The attainability of posttransplantation normoglycemia was significantly higher in fresh group than in the culture groups. Intraperitoneal glucose tolerance testing (IPGTT) showed that the blood glucose levels of mice transplanted with fresh islets were significantly lower than with cultured islets at 30, 60, 90, and 120 min after injection. These data suggest that human islet transplantation without culture could avoid the deterioration of islets during culture and improve the outcome of islet transplantation. Based on these data, we have transplanted fresh islets without culture for our current clinical islet transplantation protocol.

Evaluation of osmolality of density gradient for human islet purification

For pancreatic islet transplantation, the most common method of islet purification is density gradient centrifugation because of the differences in density between islets and acinar tissue. The density of islets/acinar tissue depends on several conditions, such as osmolality of purification solution. In this study, we evaluated the osmolality of iodixanol-controlled density gradients (400, 450, and 500 mOsm/kg) on the islet purification step. The density of the purification solutions was controlled by changing the volumetric ratio of iodixanol and the purification solutions (iodixanol-Kyoto solutions; IK solutions). The osmolality of density gradients was controlled by addition of 10× Hanks balanced salt solution (HBSS) solution. Density of both islets and acinar tissue increased relative to increase of the osmolality of purification solutions. There were no significant differences among the three groups on islet yield after density-adjusted purification and the rate of postpurification recovery. In vitro and in vivo assays suggest that the quality of islets was similar among the three groups. Our data suggest that efficacy of purification and quality of isolated islets is similar when the osmolality of purification solutions is between 400 and 500 mOsm/kg and density adjustment is applied. Since the density of islet and acinar tissue is changed according to osmolality, the density adjustment is important when using several osmolality solutions.

Improvement of porcine islet isolation by inhibition of trypsin activity during pancreas preservation and digestion using α1-antitrypsin

Porcine islets are considered to be a promising resource for xenotransplantation. However, it is difficult to isolate porcine islets because of the marked fragility and rapid dissociation. Endogenous trypsin is one of the main factors to damage islets during the isolation procedure. Recent studies have suggested that trypsin inhibitors during the preservation of pancreas or the collagenase digestion can improve the result of islet isolation. In this study, we examined whether α1-antitrypsin (Aralast™), which inhibits several endogenous proteases and has immunomodulatory properties, can protect islets from the proteases and improve the results of porcine islet isolation. Twelve porcine pancreata were divided into three groups: without Aralast group (standard, n = 5), preserved with Aralast using the ductal injection (DI) method (DI, n = 3), and with Aralast using the DI method and in the collagenase solution (DI+C, n = 4). Efficacy of islet isolation was assessed by islet yields, purity, and viability. The trypsin activity of the preservation and the digestion solution during the isolation procedure was measured. During islet isolation, the trypsin activity in DI+C group was significantly inhibited compared to the standard group, whereas DI group showed less effect than DI+C group. The average of postpurification islet equivalents (IEQ) per pancreas weight in the DI+C group was significantly higher than the standard group (standard: 3516 ± 497 IEQ/g, DI: 4607 ± 1090 IEQ/g, DI+C: 7097 ± 995 IEQ/g; p = 0.017 between standard and DI+C). In the DI+C group, stimulation index was higher than in other groups, although there was no significant difference. The presence of Aralast in both DI solution and collagenase solution markedly inhibited trypsin activity during pancreas digestion procedure and improved the porcine islet isolation. Inhibition of trypsin activity by Aralast could improve porcine islet isolation.

Islet purification method using large bottles effectively achieves high islet yield from pig pancreas

Porcine islets are a promising resource for xenotransplantation. However, low efficacy of islet isolation because of their marked fragility remains a problem. Recently we found that the standard purification method using COBE 2991 cell processor (COBE) with Ficoll density gradient solution damaged islets mechanically by high shearing force. In this study, we evaluated our new purification method using large plastic bottles for the efficacy of islet purification. Ten porcine pancreata were used. The average warm ischemic time was over 40 min; therefore, these pancreata were considered to be in a marginal condition. After digestion, the digested tissue was divided into three groups. Each group was purified using either top loading method with bottle (top group) or bottom loading method with bottle (bottom group) or standard COBE method (COBE group). Islet yield per pancreas weight (IEQ/g) and the rate of postpurification recovery in the top group were significantly higher than the COBE group (top: 8060 ± 1652 IEQ/g, bottom: 4572 ± 614 IE/g, COBE: 3900 ± 734 IE/g. p < 0.02 in top vs. COBE; top percentage of recovery: 99.3 ± 12.3%, bottom: 62.6 ± 8.8%, COBE: 49.5 ± 6.7%, p < 0.02 in top vs. bottom and COBE). The average sizes of purified islets in the top and bottom groups were significantly larger than COBE group (Average diameter top: 156 ± 8 μm, bottom: 147 ± 6 μm, COBE: 119 ± 6 μm, p < 0.01 in top vs. COBE and in bottom vs. COBE), which indicated that bottle method can reduce shear force during purification. Our new purification using top loading bottle method enabled us to obtain a high yield of porcine islets from marginal pancreata.

Comparison of ulinastatin, gabexate mesilate, and nafamostat mesilate in preservation solution for islet isolation

For islet transplantation, maintaining organ viability after pancreas procurement is critically important for optimal graft function and survival. We recently reported that islet yield was significantly higher in the modified ET-Kyoto (MK) solution, which includes a trypsin inhibitor (ulinastatin), compared with the UW solution, and that the advantages of MK solution are trypsin inhibition and less collagenase inhibition. In this study, we compared ulinastatin with other trypsin inhibitors, gabexate mesilate, and nafamostat mesilate, in preservation solution for islet isolation. Ulinastatin was easily dissolved in ET-Kyoto solution, while ET-Kyoto with gabexate mesilate and nafamostat mesilate became cloudy immediately after addition. Although there were no significant differences in islet yield among the three groups, viability was significantly higher for the MK group than for the GK group or the NK group. The stimulation index was significantly higher for the MK group than for the GK group. In summary, there are no other trypsin inhibitors that are more effective than ulinastatin. Based on these data, we now use ET-Kyoto solution with ulinastatin for clinical islet transplantation.

An effective purification method using large bottles for human pancreatic islet isolation

The purification process is one of the most difficult procedures in pancreatic islet isolation. It was demonstrated that the standard purification method using a COBE 2991 cell processor with Ficoll density gradient solution harmed islets mechanically by high shear force. We reported that purification using large bottles with a lower viscosity gradient solution could improve the efficacy of porcine islet purification. In this study, we examined whether the new bottle purification method could improve the purification of human islets. Nine human pancreata from brain-dead donors were used. After pancreas digestion, the digested tissue was divided into three groups. Each group was purified by continuous density gradient using ET-Kyoto and iodixanol gradient solution with either the standard COBE method (COBE group) or the top loading (top group) or bottom loading (bottom group) bottle purification methods. Islet yield, purity, recovery rate after purification, and in vitro and in vivo viability were compared. Islet yield per pancreas weight (IE/g) and the recovery rate in the top group were significantly higher than in the COBE and bottom groups. Furthermore, the average size of purified islets in the top group was significantly larger than in the COBE group, which indicated that the bottle method could reduce the shear force to the islets. In vivo viability was also significantly higher in the top group compared with the COBE group. In conclusion, the top-loading bottle method could improve the quality and quantity of human islets after purification.

A Combined Continuous Density/Osmolality Gradient for Supplemental Purification of Human Islets

For islet transplantation, islet purification minimizes the risks associated with islet infusion through the portal vein. However, islet purification may result in decreased numbers of islets recovered from digested tissue. In this study, we evaluated the effectiveness of performing supplemental purification (SP) after regular purification (RP). We designed the densities of low- and high-density solutions based on the outcome of RP. Moreover, a combined continuous osmolality/continuous density gradient for the SP was used in this study. Low-density/osmolality (1.075-1.110 g/cm³/400-410 mOsm/kg) and high-density/osmolality (1.090-1.125 g/cm³/495-505 mOsm/kg) solutions were produced by changing the volumetric ratio of iodixanol, 10 × HBSS, and RP solutions. The percentage of islet recovery (postpurification IE/prepurification IE × 100) after RP was 77.3 ± 5.6%, and the percentage of islet recovery after addition of SP was 85.3 ± 5.4%. In vitro and in vivo assessments showed that islet viability and function were not altered by the additional purification step. These data suggest that the addition of SP could contribute approximately 8% to islet recovery with viability and potency comparable to that obtained by RP and, therefore, that usage of the combined continuous density and continuous osmolality gradient for SP could efficiently improve islet equivalents in the final preparation.

Encapsulated islets transplantation: Past, present and future

Islet transplantation could become an ideal treatment for severe diabetes to prevent hypoglycemia shock and irreversible diabetic complications, once some of the major and unresolved obstacles are overcome, including limited donor supplies and side effects caused by permanent immunosuppressant use. Approximately 30 years ago, some groups succeeded in improving the blood glucose of diabetic animals by transplanting encapsulated islets with semi-permeable membranes consisting of polymer. A semi-permeable membrane protects both the inner islets from mechanical stress and the recipient's immune system (both cellular and humoral immunities), while allowing bidirectional diffusion of nutrients, oxygen, glucose, hormones and wastes, i.e., immune-isolation. This device, which enables immune-isolation, is called encapsulated islets or bio-artificial pancreas. Encapsulation with a semi-permeable membrane can provide some advantages: (1) this device protects transplanted cells from the recipient's immunity even if the xenogeneic islets (from large animals such as pig) or insulin-producing cells are derived from cells that have the potential for differentiation (some kinds of stem cells). In other words, the encapsulation technique can resolve the problem of limited donor supplies; and (2) encapsulation can reduce or prevent chronic administration of immunosuppressants and, therefore, important side effects otherwise induced by immunosuppressants. And now, many novel encapsulated islet systems have been developed and are being prepared for testing in a clinical setting.

Impact of tissue volume and purification on clinical autologous islet transplantation for the treatment of chronic pancreatitis

Autologous islet transplantation after total pancreatectomy is an excellent treatment for painful chronic pancreatitis. Traditionally, islets have been isolated without purification; however, purification is applied when the tissue volume is large. Nevertheless, the impact of tissue volume and islet purification on clinical outcomes of autologous islet transplantation has not been well examined. We analyzed 27 cases of autologous islet transplantation performed from October 2006 to January 2011. After examining the relationship between tissue volume and portal pressure at various time points, we compared islet characteristics and clinical outcomes between cases with complications (complication group) and without (noncomplication group), as well as cases with purification (purification group) and without (nonpurification group). Tissue volume significantly correlated with maximum (R = 0.61), final (R = 0.53), and delta (i.e., difference between base and maximum; R = 0.71) portal pressure. The complication group had a significantly higher body mass index, tissue volume, islet yield, and portal pressure (maximum, final, delta), suggesting that complications were associated with high tissue volume and high portal pressure. Only one of four patients (25%) in the complication group became insulin free, whereas 11 of 23 patients (49%) in the noncomplication group became insulin free with smaller islet yields. The purification group had a higher islet yield and insulin independence rate but had similar final tissue volume, portal pressure, and complication rates compared with the nonpurification group. In conclusion, high tissue volume was associated with high portal pressure and complications in autologous islet transplantation. Islet purification effectively reduced tissue volume and had no negative impact on islet characteristics. Therefore, islet purification can reduce the risk of complications and may improve clinical outcome for autologous islet transplantation when tissue volume is large.

Recent progress in pancreatic islet transplantation

Diabetes mellitus remains a major burden. More than 200 million people are affected worldwide, which represents 6% of the world’s population. Type 1 diabetes mellitus is an autoimmune disease, which induces the permanent destruction of the β-cells of the pancreatic islets of Langerhans. Although intensive insulin therapy has proven effective to delay and sometimes prevent the progression of complications such as nephropathy, neuropathy or retinopathy, it is difficult to achieve and maintain long term in most subjects. The successes achieved over the last few decades by the transplantation of whole pancreas and isolated islets suggest that diabetes can be cured by the replenishment of deficient β cells. However, islet transplantation efforts have various limitations, including the limited supply of donor pancreata, the paucity of experienced islet isolation teams, side effects of immunosuppressants and poor long term results. The purpose of this article is to review the recent progress in clinical islet transplantation for the treatment of diabetes and to describe the recent progress on pancreatic stem/progenitor cell research, which has opened up several possibilities for the development of new treatments for diabetes.

Autologous islet cell transplantation to prevent surgical diabetes

Autologous islet transplantation (AIT) is performed to prevent surgical diabetes after total or semi-total pancreatectomy for the treatment of chronic pancreatitis with severe abdominal pain. In addition, AIT is used in cases of benign pancreatic tumors and pancreatic trauma. It has been shown that AIT results in better outcomes in terms of glycemic control compared with allogeneic islet transplantation. The reasons for the favorable outcomes of AIT are thought to be: (i) patients have no autoimmune diseases; (ii) the transplanted islets do not suffer allogeneic rejection; (iii) diabetogenic antirejection drugs are not required; (iv) pancreata do not undergo a cytokine storm as a result of periods of brain death; (v) the period of cold preservation of retrieved pancreata is short; (vi) the isolated islets are immediately transplanted without culture; and (vii) pancreata with pancreatitis may contain more progenitor cells. Further research into AIT would help improve the results of allogeneic islet transplantation. Conversely, the technical difficulties associated with islet isolation appear to be the largest hurdle for AIT; therefore, remote center islet isolation may prove to be key in the promotion of this treatment.

Evolution of β-Cell Replacement Therapy in Diabetes Mellitus: Islet Cell Transplantation

Diabetes mellitus remains one of the leading causes of morbidity and mortality worldwide. According to the Centers for Disease Control and Prevention, approximately 23.6 million people in the United States are affected. Of these individuals, 5 to 10% have been diagnosed with Type 1 diabetes mellitus (T1DM), an autoimmune disease. Although it often appears in childhood, T1DM may manifest at any age, leading to significant morbidity and decreased quality of life. Since the 1960s, the surgical treatment for diabetes mellitus has evolved to become a viable alternative to insulin administration, beginning with pancreatic transplantation. While islet cell transplantation has emerged as another potential alternative, its role in the treatment of T1DM remains to be solidified as research continues to establish it as a truly viable alternative for achieving insulin independence. In this paper, the historical evolution, procurement, current status, benefits, risks, and ongoing research of islet cell transplantation are explored.

Pancreas procurement and preservation for islet transplantation: personal considerations

Pancreatic islet transplantation is a promising option for the treatment of type 1 diabetic patients. After the successful demonstration of the Edmonton protocol, islet transplantation has advanced significantly on several fronts, including improved pancreas procurement and preservation systems. Since we frequently use pancreata from donors after cardiac death in Japan,we have applied the in situ regional organ cooling system for pancreas procurement to reduce the warm ischemic time. To reduce the apoptosis of pancreatic tissue during cold preservation, we have applied the ductal injection of preservation solution. For pancreas preservation, we use modified Kyoto solution, which is advantageous at trypsin inhibition and less collagenase inhibition. In this paper, we show pancreas procurement and preservation in our group for islet transplantation.

Clinical allogeneic and autologous islet cell transplantation: update

Islet cell transplantation is categorized as a β-cell replacement therapy for diabetic patients who lack the ability to secrete insulin. Allogeneic islet cell transplantation is for the treatment of type 1 diabetes, and autologous islet cell transplantation is for the prevention of surgical diabetes after a total pancreatectomy. The issues of allogeneic islet cell transplantation include poor efficacy of islet isolation, the need for multiple donor pancreata, difficulty maintaining insulin independence and undesirable side effects of immunosuppressive drugs. Those issues have been solved step by step and allogeneic islet cell transplantation is almost ready to be the standard therapy. The donor shortage will be the next issue and marginal and/or living donor islet cell transplantation might alleviate the issue. Xeno-islet cell transplantation, β-cell regeneration from human stem cells and gene induction of the naïve pancreas represent the next generation of β-cell replacement therapy. Autologous islet cell transplantation after total pancreatectomy for the treatment of chronic pancreatitis with severe abdominal pain is the standard therapy, even though only limited centers are able to perform this treatment. Remote center autologous islet cell transplantation is an attractive option for hospitals performing total pancreatectomies without the proper islet isolation facilities.

Prediction of pancreatic tissue densities by an analytical test gradient system before purification maximizes human islet recovery for islet autotransplantation/allotransplantation

BACKGROUND

Using standard density gradient (SDG) ranges for human islet purification frequently results in islet loss and transplantation of lower islet mass. Measuring the densities of islet and acinar tissue beforehand to customize the gradient range for the actual COBE 2991 cell processor (COBE) purification is likely to maximize the recovery of islets. We developed an analytical test gradient system (ATGS) for predicting pancreatic tissue densities before COBE purification to minimize islet loss during purification.

METHODS

Human islets were isolated from deceased donor (n=30) and chronic pancreatitis pancreata (n=30). Pancreatic tissue densities were measured before purification by the ATGS, and the density gradient range for islet purification in a COBE was customized based on density profiles determined by the ATGS. The efficiency of custom density gradients (CDGs) to recover high islet yield was compared with predefined SDGs.

RESULTS

Pancreatic tissue densities from autografts were significantly higher than in allograft preparations. In allograft purifications, a higher proportion of islets were recovered using ATGS-guided CDGs (85.9%±18.0%) compared with the SDG method (69.2%±27.0%; P=0.048). Acinar contamination at 60%, 70%, and 80% cumulative islet yield for allografts was significantly lower in the CDG group. In autograft purifications, more islets were recovered with CDGs (81.9%±28.0%) than SDGs (55.8%±22.8%; P=0.03). CDGs effectively reduced islet loss by minimizing islet sedimentation in the COBE bag.

CONCLUSIONS

Using ATGS-guided CDGs maximizes the islet recovery for successful transplantations by reducing acinar contamination in allograft preparations and by reducing sedimentation of islets in the COBE bag in autograft preparations.

Improving efficacy of clinical islet transplantation with iodixanol-based islet purification, thymoglobulin induction, and blockage of IL-1β and TNF-α

Poor efficacy is one of the issues for clinical islet transplantation. Recently, we demonstrated that pancreatic ductal preservation significantly improved the success rate of islet isolation; however, two transplants were necessary to achieve insulin independence. In this study, we introduced iodixanol-based purification, thymoglobulin induction, and double blockage of IL-1β and TNF-α as well as sirolimus-free immunosuppression to improve the efficacy of clinical islet transplantation. Nine clinical-grade human pancreata were procured. Pancreatic ductal preservation was performed using ET-Kyoto solution in all cases. When the isolated islets met the clinical criteria, they were transplanted. We utilized two methods of immunosuppression and anti-inflammation. The first protocol prescribed daclizumab for induction, then sirolimus and tacrolimus to maintain immunosuppression. The second protocol used thymoglobulin for induction and tacrolimus and mycophenolate mofetil to maintain immunosuppression. Eternacept and anakinra were administered as anti-inflammatory drugs. The total amount of insulin required, HbA1c, and the SUITO index were determined to analyze and compare the results of transplantation. All isolated islet preparations (9/9) met the criteria for clinical transplantation, and they were transplanted into six type 1 diabetic patients. All patients achieved insulin independence with normal HbA1c levels; however, the first protocol required two islet infusions (N = 3) and the second protocol only required a single infusion (N = 3). The average SUITO index, at 1 month after a single-donor islet transplantation, was significantly higher in the second protocol (49.6 ± 8.3 vs. 19.3 ± 6.3, p < 0.05). Pancreatic ductal preservation, iodixanol-based purification combined with thymoglobulin induction, and blockage of IL-1β and TNF-α as well as sirolimus-free immunosuppression dramatically improved the efficacy of clinical islet transplantations. This protocol enabled us to perform successful single-donor islet transplantations. Further large-scale studies are necessary to confirm these results and clarify the mechanism of each component.

Assessment of human islet isolation with four different collagenases

BACKGROUND

The isolation of islets from the human pancreas critically depends on the efficiency of the digestive enzymes. Liberase HI had been used as a standard preparation until the issues concerning bovine spongiform encephalopathy. Thus, we must now use other collagenases for clinical islet transplantation, four of which we have evaluated herein.

METHODS

The digestion of each of 17 pancreata from brain-dead donors was performed using the following collagenases: Liberase HI (HI; Roche, n = 9); Liberase MTF C/T (MTF; Roche, n = 4); Collagenase NB1 Premium Grade (NB1; Serva, n = 7); or Clzyme Collagenase HA (CI, VitaCyte, n = 4). Islet isolations were based on the Edmonton protocol for HI, whereas our modified islet isolation method was used for the three new enzymes (MTF, NB1, and CI).

RESULTS

There were no significant differences in donor age, body mass index, pancreas size, and cold ischemic time among the four groups. The phase I time in the NB1 group was significantly shorter than in the CI group (P = .0014). The prepurification IEQ/g in the HI group was significantly lower than the others (P = .0003 vs MTF, .0007 vs NB1, and .0009 vs CI, respectively). The postpurification IEQ/g in the MTF group was significantly higher than in the HI group (P = .006). The viability in the NB1 group was significantly greater than the HI group (P = .003).

CONCLUSION

Three new enzymes (MTF, NB1, and CI) may enable us to obtain higher islet yields than with HI.