Fresh human islet transplantation to replace pancreatic endocrine function in type 1 diabetic patients. Report of six cases

Considerations and challenges of islet transplantation and future therapies on the horizon

Islet transplantation is a treatment for selected adults with type 1 diabetes and severe hypoglycemia. Islets from two or more donor pancreases, a scarce resource, are usually required to impact glycemic control, but the treatment falls short of a cure. Islets are avascular when transplanted into the hypoxic liver environment and subjected to inflammatory insults, immune attack, and toxicity from systemic immunosuppression. The Collaborative Islet Transplant Registry, with outcome data on over 1,000 islet transplant recipients, has demonstrated that larger islet numbers transplanted and older age of recipients are associated with better outcomes. Induction with T-cell depleting agents and the TNF-α inhibitor etanercept and maintenance systemic immunosuppression with mTOR inhibitors in combination with calcineurin inhibitors also appear advantageous, but concerns remain over immunosuppressive toxicity. We discuss strategies and therapeutics that address specific challenges of islet transplantation, many of which are at the preclinical stage of development. On the horizon are adjuvant cell therapies with mesenchymal stromal cells and regulatory T cells that have been used in preclinical models and in humans in other contexts; such a strategy may enable reductions in immunosuppression in the early peri-transplant period when the islets are vulnerable to apoptosis. Human embryonic stem cell-derived islets are in early-phase clinical trials and hold the promise of an inexhaustible supply of insulin-producing cells; effective encapsulation of such cells or, silencing of the human leukocyte antigen (HLA) complex would eliminate the need for immunosuppression, enabling this therapy to be used in all those with type 1 diabetes.

A Stem Cell Approach to Cure Type 1 Diabetes

Treatment of type 1 diabetes with insulin injection is expensive, complicated, and insufficient. While cadaveric islet transplantations coupled with immunosuppressants can cure diabetes, the scarcity of acceptable islets is problematic. Developmental research on pancreas formation has informed in vitro differentiation of human pluripotent stem cells into functional islets. Although generating β cells from stem cells offers a potential cure for type 1 diabetes, several challenges remain, including protecting the cells from the immune system.

The Future of Islet Transplantation Is Now

Milestones in the history of diabetes therapy include the discovery of insulin and successful methods of beta cell replacement including whole pancreas and islet cell transplantation options. While pancreas transplantation remains the gold standard for patients who have difficulty controlling their symptoms with exogenous insulin, islet allotransplantation is now able to provide similar results with some advantages that make it an attractive potential alternative. The Edmonton Protocol, which incorporated a large dose of islets from multiple donors with steroid-free immunosuppression helped to establish the modern era of islet transplantation almost 20 years ago. While islet allotransplantation is recognized around the world as a powerful clinical therapy for type 1 diabetes it is not yet recognized by the Federal Drug Administration of the United States. Large-scale clinical trials administered by the Clinical Islet Transplantation Consortium have recently demonstrated that the well-regulated manufacture of a human islet product transplanted into patients with difficult to control type 1 diabetes and with a history of severe hyperglycemic episodes can safely and efficaciously maintain glycemic balance and eliminate the most severe complications associated with diabetes. The results of these clinical trials have established a strong basis for licensure of clinical islet allotransplantation in the US. Recognition by the Federal Drug Administration would likely lead to third party reimbursement for islet allotransplantation as a therapeutic option in the United States and would make the treatment available to many more patients. The high costs of rampant diabetes justify the expense of the treatment, which is in-line with the costs of clinical pancreas transplantation. While much enthusiasm and hope is raised toward the development and optimization of stem cell therapy, the islet transplantation community should push toward licensure, if that means broader access of this procedure to patients who may benefit from it. Even as we prepare to take the first steps in that direction, we must acknowledge the new challenges that a shift from the experimental to clinical will bring. Clinical islet allotransplantation in the United States would be a game-changing event in the treatment of type 1 diabetes and also generate enthusiasm for continued research.

Collagenase Lot Selection and Purification for Adipose Tissue Digestion

Crude Clostridial collagenase (CCC) remains the most widely used enzyme for the digestion of tissues prior to cell isolation and culture. CCC contains numerous components in addition to specific collagenases and proteases. A chronic problem associated with CCC is significant lot variability which occurs with respect to the ability of different lots of CCC to digest tissue. We have evaluated numerous commercially available samples of CCC for their ability to digest human liposuction-derived SC fat. Digestion capacity was evaluated as the ability to release endothelial cells from fat as well as the ability of isolated cells to adhere to tissue culture plastic. A significant variation in digestion efficacy between lots of collagenase was observed. We subsequently purified CCC using a partial purification method with dialysis and centrifugation as well as a complete purification, using liquid chromatography, to remove all nonspecific proteases. While partially purified collagenase retained digestion capacity, pure collagenase exhibited reduced digestion capacity. Maximum digestion was achieved with pure collagenase when trypsin was added. The use of completely purified collagenase with trypsin is advantageous where all components in the enzyme digestion mixture must be known.

Clinical pancreatic islet transplantation

Clinical pancreatic islet transplantation can be considered one of the safest and least invasive transplant procedures. Remarkable progress has occurred in both the technical aspects of islet cell processing and the outcomes of clinical islet transplantation. With >1,500 patients treated since 2000, this therapeutic strategy has moved from a curiosity to a realistic treatment option for selected patients with type 1 diabetes mellitus (that is, those with hypoglycaemia unawareness, severe hypoglycaemic episodes and glycaemic lability). This Review outlines the techniques required for human islet isolation, in vitro culture before the transplant and clinical islet transplantation, and discusses indications, optimization of recipient immunosuppression and management of adjunctive immunomodulatory and anti-inflammatory strategies. The potential risks, long-term outcomes and advances in treatment after the transplant are also discussed to further move this treatment towards becoming a more widely available option for patients with type 1 diabetes mellitus and eventually a potential cure.

Progress in islet transplantation in patients with type 1 diabetes mellitus

More than 500 patients with type 1 diabetes mellitus have now received islet transplants at over 50 institutions worldwide in the past 5 years. Rates of insulin independence at 1 year with current protocols are impressive. However, inexorable decay of islet function over time indicates that there are many opportunities for improvement. Improved control of glycosylated hemoglobin and reduced risk of recurrent hypoglycemia are seen as important benefits of islet transplantation, irrespective of the status regarding insulin independence. For the use of islet transplantation to expand it is essential that the donor-to-recipient ratio be reliably reduced to 1 : 1. Enormous opportunities lie ahead for the development of successful living donor islet transplantation, single donor protocols, improved engraftment, islet proliferation in vitro and in the recipient, alternative islet sources, and novel tolerizing drugs. With these emerging opportunities, islet transplantation may expand to include more patients with type 1 diabetes, including children, and will not be restricted to the most unstable forms of the disease, as it is today.

Islet cell transplantation

Islet transplantation has become a promising treatment for selected patients with type 1 diabetes. Here we provide an overview of the procedure including its history, the process of donor selection, and the techniques and procedures involved in a successful transplant. A brief overview of the current immunosuppressive regimens, the long-term follow-up and the reported outcomes will also be discussed. While islet transplantation is currently generally reserved for adults with type 1 diabetes with severe hypoglycemia or glycemic lability, we herein consider the possibility of its application to the pediatric population.

Assessing the effect of immunosuppression on engraftment of pancreatic islets

BACKGROUND

In addition to ischemia and immunologic factors, immunosuppressive drugs have been suggested as a possible contributing factor to the loss of functional islets after allogeneic islet cell transplantation. Using our previously described islet-kidney (IK) transplantation model in miniature swine, we studied whether an islet-toxic triple-drug immunosuppressive regimen (cyclosporine+azathioprine+prednisone) affects the islet engraftment process and thus long-term islet function.

METHODS

Donor animals underwent partial pancreatectomy, autologous islet preparation, and injection of these islets under the autologous kidney capsule to prepare an IK. Experimental animals received daily triple-drug immunosuppression during the islet engraftment period. Control animals did not receive any immunosuppression during this period. Four to 8 weeks later, these engrafted IK were transplanted across a minor histocompatibility mismatched barrier into pancreatectomized, nephrectomized recipient animals at an islet dose of approximately 4500 islet equivalents/kg recipient weight. Cyclosporine was administered for 12 days to the recipients to induce tolerance of the IK grafts and the animals were followed long-term.

RESULTS

Diabetes was corrected by IK transplantation in all pancreatectomized recipients on both the control arm (n=3) and the experimental arm (n=4) of the study and all animals showed normal glucose regulation over the follow-up period. Intravenous glucose tolerance tests performed at 1, 2, and 3 or more months after IK transplantation showed essentially equivalent glycemic control in both control and experimental animals.

CONCLUSION

In this preclinical in vivo large animal model of islet transplantation, the effect of triple-drug immunosuppression on islet function does not negatively affect islet engraftment as assessed by the long-term function of engrafted islets.

Regeneration and bioengineering of transplantable abdominal organs: current status and future challenges

INTRODUCTION

The most critical issue to organ transplantation is the identification of new sources of organs. The present manuscript illustrates the state-of-the-art regenerative medicine (RM) investigations aiming to manufacturing abdominal organs for transplant purposes.

AREAS COVERED

This manuscript focuses on research in the bioengineering and regeneration of kidneys, insulin-producing cells, livers and small bowel. The main technology currently under development exploits the seeding of cells on supporting scaffolding material. Despite favorable preliminary results obtained with relatively simple, hollow organs, when more complex organs are considered, the scenario changes dramatically. Investigations are still in early stages, and clinical translation is not yet foreseeable based on current knowledge and information. Obstacles are numerous but we believe the critical factor hampering success is lack of in-depth understanding of the extracellular matrix (ECM) and cell-ECM interactions, as well as the mechanisms with which organs develop in utero.

EXPERT OPINION

The success of RM to generate transplantable abdominal organs relies heavily on progress in (stem) cell therapies, developmental and ECM biology, and in the thorough understanding of the intricate relationship and interplay between cells and the ECM. This will require enormous investments in financial and medical resources, which ideally should be embarked upon by governments, the private sector and academia.

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.

Simultaneous islet and kidney transplantation in seven patients with type 1 diabetes and end-stage renal disease using a glucocorticoid-free immunosuppressive regimen with alemtuzumab induction

OBJECTIVE

The aim of this study was to evaluate the efficiency and safety of simultaneous islet and kidney transplantation in patients with type 1 diabetes and end-stage renal disease using a glucocorticoid-free immunosuppressive regimen with alemtuzumab induction.

RESEARCH DESIGN AND METHODS

Seven patients with type 1 diabetes and end-stage renal failure were transplanted with allogenic islets and kidneys procured from brain-dead donors. To prevent organ rejection, patients received alemtuzumab for induction immunosuppression, followed by sirolimus and tacrolimus. No glucocorticoids were given at any time.

RESULTS

The median duration of follow-up was 18.3 months (range 13-31). Kidney survival was 100%. Four patients became insulin independent at 1 year. The other three reduced insulin use to less than 25% of the amount required before transplantation. Serum C-peptide levels were significantly greater posttransplant in all patients, indicating continued islet function. No major procedure-related complications were observed.

CONCLUSIONS

Our results demonstrate that a steroid-free immunosuppressive regimen consisting of alemtuzumab, sirolimus, and tacrolimus is feasible for simultaneous islet and kidney transplantation. The question of whether this induction regimen is superior to more standard induction deserves large studies.

Minimization and withdrawal of steroids in pancreas and islet transplantation

For reducing the corticosteroid (CS)-related side-effects, especially cardiovascular events, CS-sparing protocols have become increasingly common in pancreas transplantation (PT). Lympho-depleting induction antibodies, such as rabbit anti-thymocyte globulin (rATG) or alemtuzumab, have been widely used in successful trials. The results of various CS-sparing protocols combining calcineurin inhibitors (CNI) and mycophenolate or sirolimus, have been mixed for rejection and survival rates. Most of the studies were uncontrolled trials of low-risk patients, therefore the grade of evidence is limited. Large-scale prospective studies with long-term follow up are necessary to assess risks and benefits of CS-sparing regimens in PT before recommending such strategies as standard practice. Islet allo-transplantation for patients with brittle type 1 diabetes mellitus, less invasive and safer procedure than PT, has been attempted since late 1980s, but diabetogenic immunosuppressants at maintenance, mainly CS and high-dose CNI, prevented satisfactory results (10% insulin-independence at 1-year post-transplant). Since 2000, CS-free and CNI-reducing protocols, including more potent induction [daclizumab, OKT3gamma1(ala-ala) anti-CD3 antibody, rATG] and maintenance (sirolimus, mycophenolate) agents, have significantly improved short-term outcomes whereas long-term are still inadequate (from 80% to 20% insulin-independence from 1- to 5-year post-transplant). Main limitations are allo- and autoimmunity, immunosuppression-related islet and systemic toxicity and transplant site unsuitability, which tolerogenic protocols and biotechnological solutions may solve.

Allogeneic islet transplantation

Significant progress has been made in the field of beta-cell replacement therapies by islet transplantation in patients with unstable Type 1 diabetes mellitus (T1DM). Recent clinical trials have shown that islet transplantation can reproducibly lead to insulin independence when adequate islet numbers are implanted. Benefits include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. Numerous challenges still limit this therapeutic option from becoming the treatment of choice for T1DM. The limitations are primarily associated with the low islet yield of human pancreas isolations and the need for chronic immunosuppressive therapies. Herein the authors present an overview of the historical progress of islet transplantation and outline the recent advances of the field. Cellular therapies offer the potential for a cure for patients with T1DM. The progress in beta-cell replacement treatment by islet transplantation as well as those of emerging immune interventions for the restoration of self tolerance justify great optimism for years to come.

Islet cell transplantation today

INTRODUCTION

Long-term studies strongly suggest that tight control of blood glucose can prevent the development and retard the progression of chronic complications of type 1 diabetes mellitus. In contrast to conventional insulin treatment, replacement of a patient's islets of Langerhans either by pancreas organ transplantation or by isolated islet transplantation is the only treatment to achieve a constant normoglycemic state and avoiding hypoglycemic episodes, a typical adverse event of multiple daily insulin injections. However, the cost of this benefit is still the need for immunosuppressive treatment of the recipient with all its potential risks.

MATERIALS AND METHODS

Islet cell transplantation offers the advantage of being performed as a minimally invasive procedure in which islets can be perfused percutaneously into the liver via the portal vein. Between January 1990 and December 2004, 458 pancreatic islet transplants worldwide have been reported to the International Islet Transplant Registry (ITR) at our Third Medical Department, University of Giessen/Germany.

RESULTS

Data analysis of islet cell transplants performed in the last 5 years (1999-2004) shows at 1 year after adult islet transplantation a patient survival rate of 97%, a functioning islet graft in 82% of the cases, whereas insulin independence was meanwhile achieved in 43% of the cases. However, using a novel protocol established by the Edmonton Center/Canada, the insulin independence rates have improved significantly reaching meanwhile a 50-80% level.

CONCLUSION

Finally, the concept of islet cell or stem cell transplantation is most attractive, as it offers many perspectives: islet cell availability could become unlimited and islet or stem cells my be transplanted without life-long immunosuppressive treatment of the recipient, just to mention two of them.

Technique, complications, and therapeutic efficacy of percutaneous transplantation of human pancreatic islet cells in type 1 diabetes: the role of US

PURPOSE

To retrospectively evaluate the role of ultrasonography (US) with regard to the technique, complications, and therapeutic efficacy of percutaneous intrahepatic transplantation of human pancreatic islet cells with combined US and fluoroscopic guidance.

MATERIALS AND METHODS

The institutional review board approved the study, and informed consent was obtained from all patients. After kidney transplantation, 34 uremic diabetic patients (20 men, 14 women; mean age, 40.9 years; age range, 29-61 years) underwent percutaneous intrahepatic transplantation of islet cells. Portal vein patency and liver echotexture were preliminarily assessed with color Doppler US. US also was used to identify early complications and presence (group A patients) or absence (group B patients) of hepatic parenchymal changes. Differences between the two groups in C peptide serum level and range were analyzed (Mann-Whitney test). Therapeutic efficacy of transplantation was assessed with regard to insulin independence period (rate and duration), exogenous insulin requirement, glycated hemoglobin, and C peptide level. A C peptide level of more than 0.5 ng/mL was considered to indicate well-functioning islet cells.

RESULTS

Fifty-eight procedures were technically successful, with a single puncture used in 51 of 58 patients. Complications occurred in three of 58 patients (hemoperitoneum, hemothorax, and thrombosis in one patient each) and were conservatively treated and resolved. Duration of insulin independence in 12 patients was more than 3 months (mean, 21 months). Well-functioning islet cells at 6 years were found in 19 of 34 patients. Hyperechoic parenchymal changes were evident at US in 12 of 34. No statistically significant difference in C peptide level was found between groups (P > .05), but a wider range of values was recorded in group B.

CONCLUSION

Complication rate of transplantation with US and fluoroscopic guidance was low. Well-functioning islet cells were found in about 50% of patients at 6 years of follow-up. Hepatic implantation of islet cells was evident on US images in more than one-third of patients.

Islet transplantation improves vascular diabetic complications in patients with diabetes who underwent kidney transplantation: a comparison between kidney-pancreas and kidney-alone transplantation

BACKGROUND

The aim of this study was to evaluate the effects of islet transplantation on patient survival and diabetic vascular complications.

METHODS

Thirty-seven type 1 uremic diabetic kidney transplant patients underwent islet transplantation (KI group). Uremic type 1 diabetic kidney-pancreas (KP group, n=162), kidney-alone (KD group, n=42) transplant patients, and uremic type 1 diabetic patients still on hemodialysis (HD+DM group, n=196) constituted the control groups for survival and endothelial morphology.

RESULTS

Patient survival was similar in the KI and KP groups and higher than in the HD+DM group (P<0.05). Patients experiencing long-term islet function (KI-successful [KI-s], n=24) showed a better survival (100%, 100%, and 90%) than those in the KI group who lost islet function (KI-unsuccessful [KI-u], n=13) (84%, 75%, and 45%) at 1, 4 and 7 years, respectively (P=0.02). The cardiovascular death rate for the KI group (18%) was similar to the KD group (19%) but lower when the KI-s group is considered alone (5%), and showed a cardiovascular death rate similar to the KP group (8%). The KI-s group showed a good metabolic profile, with reduction of exogenous insulin requirement and persistent C-peptide secretion, as compared with the KI-u group. The endothelial morphology was evaluated with a skin biopsy obtained in all groups. The KI-s and the KP groups demonstrated decreased signs of endothelial injury compared with the KI-u and HD+DM groups. The KI group showed a better atherothrombotic profile than the HD+DM group, with higher levels of natural anticoagulant protein.

CONCLUSIONS

Successful islet transplantation improves survival, atherothrombotic profile, and endothelial morphology in uremic type 1 diabetic kidney transplant patients.

Induction of islet allotolerance in nonhuman primates

Recent clinical trials have pioneered the successful use of a nonsteroidal immunosuppressive regimen and established a basis for application in a routine clinical setting. In this study, a single islet transplant was not sufficient to regulate blood glucose levels, and a second transplant became necessary. A similar observation was made in our macaque islet transplant study, where animals after the second transplantation have shown trends towards normoglycemia in the presence of mycophenolate mofetil. All five animals that received the second transplant have shown an initial rise in C peptide levels, which rapidly decreased as we tapered the MMF dose from 20 mg/kg BID to 5 mg/kg SID. Two animals of the five that were preconditioned with MMF one week prior to transplantation have shown significantly higher C peptide levels. We believe that it is very important to understand the relationship between the first graft failure and subsequent islet allograft success. Since graft success did not correlate with number of transplanted islets, the correction of blood glucose levels toward normoglycemia after the second transplantation suggests a mechanism by which the allotolerance to second transplant is facilitated by the first islet transplantation. These initial observations suggest approaches to "tolerize" the recipient to accept the second-transplant islets (a) through preconditioning the animal to improve the rate of success for the first transplant or (b) through tolerization to islets in the first transplant to facilitate better engraftment of the second-transplant islets.

High-dosed nicotinamide decreases early graft failure after pig to nude rat intraportal islet transplantation

BACKGROUND

Clinical and experimental data indicate that early failure of intraportally grafted islets is mediated by inflammation. Although nicotinamide (NA) has the potential to protect rodent islets it is unknown whether large mammalian islets can be protected in an inflammatory environment. Therefore, we investigated NA-mediated protection of pig islets intraportally transplanted into diabetic nude rats characterized by involvement of NO in intrahepatic graft failure.

METHODS

Nonfasting serum glucose levels were evaluated after intraportal transplantation (TX) of 4000 pig islets or intraportal sham-TX in diabetic nude rats infused for 7 days with saline (0 mg), 500 mg, or 1000 mg NA/kg/day. The nitrate/nitrite serum levels were colorimetrically quantified 0, 24, and 48 hr posttransplant.

RESULTS

Graft survival after 21 days was not improved (2/13) by 500 mg NA compared to 0 mg NA (1/22) and 500 mg sham-TX (0/7). A total of 1000 mg NA promoted sustained normoglycemia in transplanted rats (10/18, P<0.001 vs. 0 mg NA, P<0.05 vs. 500 mg NA) but deteriorated hyperglycemia in 1000 mg NA sham-TX (P<0.01 vs. 0 mg sham-TX). Regeneration of endogenous islets determined as pancreatic insulin content was only measured in islet recipients receiving 1000 mg NA (P<0.001). Posttransplant NO levels were not affected by NA and increased in all recipients two-fold (P<0.05 vs. day 0).

CONCLUSIONS

Compared with efficient administration in syngeneic rodent models NA has to be applied in significant higher doses for protection of xenografted pig islets implying that protection of islets from large mammalians after transplantation into a proinflammatory organ seems feasible. In contrast to other observations graft survival was not mediated by interference of NA with hepatic NO generation.

Autoantibody response to islet transplantation in type 1 diabetes

Islet allotransplantation into patients with autoimmune type 1 diabetes represents a reexposure to autoantigen. Here, measurement of antibodies to GAD and IA-2 autoantigens before and after islet transplantation in 36 patients (33 receiving islet plus kidney grafts with cyclosporin and steroid-based immunosuppression, and 3 receiving solitary islet transplants with mycophenolate but cyclosporin-free immunosuppression) demonstrated marked rises in GAD antibodies within 7 days posttransplantation in 5 patients (3 receiving islet after kidney transplants, and 2 receiving solitary islet transplants) and within 30 days in the third patient receiving solitary islet transplantation. GAD antibodies were of the IgG1 subclass, against major autoantigenic epitopes, and in cases of islet after kidney transplants, the responses were short-lived and not accompanied by HLA antibodies. Two of these patients had subsequent marked rises of IA-2 antibodies, and an additional patient had a marked rise in IgM-GAD antibodies 3 years after transplantation. Insulin independence was not achieved in patients with autoantibody elevations and was significantly less frequent in these patients. These data are consistent with a reactivation of autoimmunity that may be dependent on immunosuppression therapy and is associated with impaired graft function.

Prevention of early islet graft failure by selective inducible nitric oxide synthase inhibitors after pig to nude rat intraportal islet transplantation

BACKGROUND

Clinical and experimental data indicate that early failure of intraportally grafted islets is caused by inflammation including secretion of cytokines and nitric oxide. Direct inducible nitric oxide synthase suppression may avoid detrimental effects associated with steroid administration. We compared the efficiency of selective and unselective inducible nitric oxide synthase inhibitors with dexamethasone to suppress nitric oxide generation after intraportal islet xenotransplantation into nude rats.

METHODS

Nonfasting serum glucose levels were daily evaluated after intraportal transplantation of 4000 freshly isolated pig islets into diabetic nude rats (85 mg/kg streptozotocin) either sham-treated with saline (n=21) or continuously infused for 7 days with L-NG-monomethyl-arginine (n=7), S-methyl-isothiourea (n=15), or S-(2-aminoethyl)-isothiourea (n=19) in a dosage of 240, 100, or 50 mg/kg/day, respectively. Dexamethasone was injected i.p. twice as a daily bolus of 20 mg/kg (n=10) starting 1 day pretransplant. The nitrate/nitrite serum level was quantified colorimetrically 0, 24, and 48 hr posttransplant.

RESULTS

Saline treatment partially resulted in graft function (4/21) throughout the observation period (21 days). L-NG-monomethyl-arginine-treated rats showed sustained hyperglycemia (0/7) not different from diabetic controls. Normoglycemia was observed after treatment with dexamethasone (6/10, P<0.05 versus saline and L-NG-monomethyl-arginine), S-methyl-isothiourea (10/15, P<0.01), or S-(2-aminoethyl)-isothiourea (15/19, P<0.001). Graft function was associated with complete suppression of nitric oxide generation after S-methyl-isothiourea and S-(2-aminoethyl)-isothiourea treatment (P<0.001 versus saline) and partial suppression after dexamethasone treatment (P<0.05).

CONCLUSIONS

Our observation of long-term function of xenogeneic islets in an inflammatory environment without interference of reactive T cells revealed the potency of highly selective isothioureas to completely suppress inducible nitric oxide synthase making reduction of islet-toxic immunosuppression feasible.

Insights from a successful case of intrahepatic islet transplantation into a type 1 diabetic patient

We report a case of long-term (>4 yr) successful intrahepatic islet transplantation into a type 1 diabetic patient chronically immunosuppressed for a prior kidney graft. The exogenous insulin requirement decreased progressively after transplantation, and insulin treatment was withdrawn at 6 months. Glycosylated hemoglobin levels were in the normal range at 1 and 2 yr (5.3%) and increased slightly above the upper normal limit at 3 and 4 yr (6.3% and 6.4%). Fasting C peptide levels remained stable during the entire follow-up, but the proinsulin to insulin ratios increased dramatically at yr 3. Glycemic levels after an oral glucose tolerance test showed a diabetic profile at 1 yr, a normal profile at 2 yr, and an impaired glucose tolerance profile at 3 yr. Intravenous glucose tolerance test-induced first phase insulin release, present at 1 and 2 yr, disappeared at 3 yr. Diabetes-related autoantibodies (islet cell antibodies, glutamic acid decarboxylase antibodies, and tyrosine phosphatase-like protein antibodies) were undetectable before transplantation and remained so during the entire follow-up. The patient died of myocardial infarction 50 months after transplantation while she was still in good metabolic control (glycosylated hemoglobin, <6.8%) in the absence of exogenous insulin administration. The autoptic liver showed well granulated islets, richly vascularized and without evidence of lympho-mononuclear cell infiltration. The morphometrically extrapolated intrahepatic beta-cell mass was 99.9 mg. In conclusion, this successful islet graft showed a bell-shaped clinical effect, maximal at 2 yr after transplantation, followed by a slow progressive decline. The absence of allo- and autoreactivities against the transplanted islets points to a nonimmune-mediated beta-cell loss as the cause of graft functional deterioration.

Effects of prolonged exposure to pancreatic glucagon on the function, antigenicity and survival of isolated human islets

BACKGROUND

Certain clinical conditions are associated with inappropriately high levels of circulating glucagon. To date, little information is available about the direct effects of prolonged exposure of human islet cells to pancreatic glucagon. In the present study we evaluated the function, antigenicity and survival of human islets exposed for 24 h to human pancreatic glucagon.

METHODS

We prepared human islets of Langerhans by collagenase digestion and density-gradient purification, incubated them for 24 h with 44 or 430 pmol/l pancreatic glucagon at physiological (5.5 mmol/l) glucose level, and evaluated their insulin release function, which was then compared with that obtained from islets kept at high (11.1 mmol/l) glucose concentration. In addition, aliquots of the islets were evaluated to assess their chemotactic properties towards human monocyte-macrophage cells, and their potency to induce cytokine release from human lymphocytes. Finally, survival of the islet cells cultured under varying conditions was evaluated, and an assessment was performed of mRNA expression of Bcl-2 and Bax proteins.

RESULTS

The insulin secretion results demonstrated that, compared to the control islets, the islets previously exposed to either 44 or 430 pmol/l glucagon exhibited changes in insulin release in response to glucose, consisting of augmented secretion at low glucose challenge, and no further significant increase at high glucose stimulation, similar to the effects observed with islets pre-cultured with high glucose. These effects were reversible, as documented by the recovery of normal islet sensitivity to glucose after an additional 24-h culture in medium lacking glucagon. Compared to control islets, the culture medium from islets pre-cultured with high glucagon or high glucose showed an increased chemotactic potency towards human monocyte-macrophage cells. In addition, human lymphocytes released a greater amount of tumour necrosis factor alpha when co-cultured with the islets pre-exposed to high glucagon or high glucose, whereas no significant difference was observed (in comparison with control islets) as regards the release of gamma-interferon, interleukin-2 and interleukin-10. The TUNEL technique and RT-PCR showed, respectively, no major difference in cell survival and expression of mRNA encoding for Bcl-2 and Bax protein between control islets and islets kept for 24 h in the presence of high glucagon or high glucose.

CONCLUSIONS

Our results show that in vitro exposure of human islets to pancreatic glucagon for 24 h causes changes in the function and antigenicity of isolated human islets that are similar to the changes observed after pre-culture with increased glucose levels. Under our experimental conditions, these changes were not accompanied by any evidence of cytotoxicity.

Pancreatic and islet transplantation

Diabetes mellitus is the most devastating chronic disease of all time. This review discusses the current therapies for type 1 diabetes that are predicated on the restoration of insulin secretion by transplantation. Recent developments in vascularized pancreas transplantation have led to a dramatic increase in the number of these procedures performed worldwide, with over 10,000 cases reported currently to the International Pancreas Transplant Registry. Although the procedure contributes to a significant improvement in quality of life, compared with traditional insulin therapy, it still suffers from a number of shortcomings, including a persistently high postoperative morbidity rate and the requirement of long-term immunosuppression. Islet transplantation is therefore being pursued actively as an equally efficient means of restoring normoglycemia, but without the attendant morbidity of the whole-organ procedure, and hopefully with a significantly reduced need for immunosuppression.

Improved quality and yield of islets isolated from human pancreata using a two-step digestion method

A new approach, involving a two-step digestion process and Los Angeles preservation solution #1 (LAP-1), a cold storage solution, was developed for isolation of high-quality islets from human pancreata for transplantation. This approach markedly improves the islet yield, purity and viability, and the isolation success rate. In this method, the pancreas was digested first in warm collagenase solution for up to 20 minutes. After decanting the enzyme solution, partially digested tissue was dissociated by gentle agitation in cold LAP-1 solution without additional collagenase. The digested tissues were stored in cold LAP-1 solution until islet purification on Euro-Ficoll. Forty-six islet isolations were performed consecutively by the new method (group 1). These results were compared to those obtained earlier with 46 consecutive isolations, using our previous method that had been used before development of the new method (group 2). Our old method was a modification of Ricordi's method involving only warm collagenase digestion and the storage of digested tissues in cold Hanks balanced salt solution. All pancreata were partial, containing the body and tail. There were no significant differences in both groups with regard to the donor age, cold ischemic time, harvesting conditions, and pancreatic weight. Pancreas digestion was completed in approximately 1 hour in both groups. The isolation success rate as determined by viable islets after 2 days in culture was 93.5% (43 of 46 cases) in group 1, and 56.5% (26 of the 46) in group 2. Immediately after isolation, the new method yielded a total of 335,739 +/- 36,244 islets equivalent to 150 microm (IEQ) and 6,233 +/- 681 IEQ/g of pancreas with 83 +/- 2.5% purity, whereas the old method yielded a total of 195,587 +/- 25,242 IEQ and 3,763 +/- 5,509 IEQ/g with 69.2 +/- 4.7% purity. Isolated islets in group 1 maintained a good three-dimensional structure, displayed normal insulin release to high glucose stimulation in vitro, and restored euglycemia after transplantation into streptozotocin-diabetic athymic mice. The two-step digestion method provides a sufficient number of islets for transplantation from a single pancreas.

Lessons from in vitro perifusion of pancreatic islets isolated from 80 human pancreases

We report the average insulin response to acute glucose measured by in vitro perifusion of pancreatic islets isolated from 80 consecutive human organs. Different perifusion parameters were considered [basal release, stimulation index (SI), time to peak, incremental area under the curve delta-AUC alpha)], and the correlation among them was determined. SI positively correlated with delta-AUC alpha (p < 0.001, r = 0.80) while negatively with time to peak (p < 0.05, r = -0.23). We also evaluated several variables of the isolation procedure that might affect responsiveness to glucose by human islets. Sex and age of pancreas donors, cold ischemia time, duration of the digestion, collagenase concentration, and lot characteristics (collagenase, trypsin, clostripain, and proteases activity), and final islet yield were considered. Multivariate regression analysis showed only an independent association between SI and the concentration of collagenase (p = 0.01).

Long-term survival and function of intrahepatic islet allografts in rhesus monkeys treated with humanized anti-CD154

Reported effects of anti-CD154 treatment on autoimmunity, alloreactivity, and inflammatory events mediated by macrophages and endothelial cells indicated that it might be an ideal agent for the prevention of intrahepatic islet allograft failure. This hypothesis was tested in MHC-mismatched rhesus monkeys. Transplantation of an adequate number of viable islets resulted in engraftment and insulin independence in six of six recipients treated with anti-CD154 (hu5c8) induction plus monthly maintenance therapy (post-operative day >125, >246, >266, >405, >419, >476). Anti-CD154 (hu5c8) displayed no inhibitory effect on islet cell function. For monkeys followed for >100 days, continued improvement in graft function, as determined by first phase insulin release in response to intravenous glucose, was observed after the first 100 days post-transplant. No evidence of toxicity or infectious complications has been observed. All recipients treated with anti-CD154 became specifically nonresponsive to donor cells in mixed lymphocyte reactions. Furthermore, three monkeys are now off therapy (>113, >67, and >54 days off anti-CD154), with continued insulin independence and donor-specific mixed lymphocyte reaction hyporeactivity. In striking contrast to all previously tested strategies, transplantation of an adequate number of functional islets under the cover of anti-CD154 (hu5c8) monotherapy consistently allows for allogeneic islet engraftment and long-term insulin independence in this highly relevant preclinical model.

Potential application of neonatal porcine islets as treatment for type 1 diabetes: a review

Islet transplantation has been shown to be a viable option for treating patients with type 1 diabetes. However, widespread clinical application of this treatment will necessitate an alternative source of insulin-producing tissue. Porcine pancreata may be a potential source of islets since pigs are inexpensive, readily available, and exhibit morphological and physiological characteristics comparable to humans. Recently, we developed a simple, standardized procedure for isolating large numbers of neonatal porcine islets with a reproducible and defined cellular composition. Following nine days of in vitro culture, tissue from one neonatal pig pancreas yielded approximately 50,000 islet cell aggregates, consisting of primarily epithelial cells (57%) and pancreatic endocrine cells (35%). In addition, neonatal porcine islets were responsive to glucose challenge in vitro and were capable of correcting hyperglycemia in alloxan-induced diabetic nude mice. Although neonatal porcine islets constitute an attractive alternative source of insulin-producing tissue for clinical transplantation, many aspects such as the immunological responses to these tissue and the latent period (2 to 8 weeks) between transplantation of these islets and the reversal of hyperglycemia need further investigation. This article discusses these issues and presents possible solutions to problems that may hinder the potential application of neonatal porcine islets for transplantation into patients with type 1 diabetes.

Clinical islet cell transplantation. Are we there yet?

Diabetes mellitus is perhaps the most devastating chronic disease of all time. A brief history of the evolution of treatment modalities is provided, culminating in the rationale for the physiologic replacement of a functioning beta-cell mass by transplantation. Vascularized pancreas transplantation is discussed briefly as an introduction to the transplantation of the isolated islet. A detailed review of the current state of human islet transplantation for the cure of diabetes is then described. Finally, areas for future development are highlighted.

Cryopreservation of rat pancreatic islets: effect of ethylene glycol on islet function and cellular composition

BACKGROUND

Inasmuch as cryopreservation can facilitate clinical islet transplantation by providing a means of storing supplemental islets in order to augment marginally adequate grafts, protocols are needed to allow for a minimal loss in viable beta cells. By replacing the cryoprotectant dimethyl sulfoxide (DMSO) with ethylene glycol (EG), a more simplified cryopreservation protocol was developed, which resulted in improved survival and function of rat pancreatic islets.

METHODS

Nonfrozen islets, islets cryopreserved in DMSO, and EG-cryopreserved islets were compared for percent recovery, cellular composition, in vitro viability, and metabolic function after transplantation.

RESULTS

After cryopreservation in DMSO or EG, islet yield was similar to that of nonfrozen controls; however, islets cryopreserved in DMSO exhibited lower cellular DNA, insulin, and glucagon content, as well as an impaired insulin secretory capacity in vitro than the nonfrozen controls. When compared with controls, islets cryopreserved in DMSO contained a higher proportion of beta cells but a lower number of glucagon-positive cells, whereas cryopreservation with EG resulted in similar DNA/hormone contents, in vitro viability, and cellular composition. Transplantation of islet grafts composed of comparable numbers of beta cells (2.1-2.3 million) corrected diabetes in 100% (6/6; nonfrozen controls), 92% (10/11; DMSO), and 100% (14/14; EG) of the recipients; however, those who received DMSO-treated islets took longer to achieve euglycemia and remained glucose-intolerant.

CONCLUSIONS

These results demonstrate that EG allows for the successful cryopreservation of rat islet beta and a cells with the same yield and quality as nonfrozen islets. The observation that alpha-cell survival was better after cryopreservation with EG may explain the improved functional viability of these grafts. Further studies are needed to assess whether this protocol provides any advantage for cryopreserving large numbers of human islets.

A comparison of the use of two immunomagnetic microspheres for secondary purification of pancreatic islets

Immunomagnetic cell separation has been shown to be a highly attractive alternative to density-dependent methods for islet purification. There are two types of beads, magnetic inducible microspheres (MIMS) and Dynabeads, in this context. The aim of this study was to compare the two beads and ligands using the same method of purification. Two batches of collagenase were used. Using either monoclonal antibodies or lectins with a specificity for rat acinar tissue, the beads were used to immunomagnetically label pancreatic digest before magnetic separation. The results showed that both MIMS coated with a lectin and Dynabeads coated with an antibody removed 80% of the acinar contamination with a 70% islet yield. However, the MIMS were significantly less effective with the second enzyme, which produced larger acinar particles. In this study, although the MIMS produced the least nonspecific islet trapping, the Dynabeads coated with Leicester Department of Surgery no. 10 antibody were found to be the most efficient particle for immunomagnetic islet purification.

Normalization of diabetes in spontaneously diabetic cynomologus monkeys by xenografts of microencapsulated porcine islets without immunosuppression

Porcine pancreatic islets were microencapsulated in alginate-polylysine-alginate capsules and transplanted intraperitoneally into nine spontaneously diabetic monkeys. After one, two, or three transplants of 3-7 x 10(4) islets per recipient, seven of the monkeys became insulin independent for periods ranging from 120 to 804 d with fasting blood glucose levels in the normoglycemic range. Glucose clearance rates in the transplant recipients were significantly higher than before the graft administration and the insulin secretion during glucose tolerance tests was significantly higher compared with pretransplant tests. Porcine C-peptide was detected in all transplant recipients throughout their period of normoglycemia while none was found before the graft administration. Hemoglobin A1C levels dropped significantly within 2 mo after transplantation. While ketones were detected in the urine of all recipients before the graft administration, all experimental animals became ketone free 2 wk after transplantation. Capsules recovered from two recipients 3 mo after the restoration of normoglycemia were found physically intact with enclosed islets clearly visible. The capsules were free of cellular overgrowth. Examination of internal organs of two of the animals involved in our transplantation studies for the duration of 2 yr revealed no untoward effect of the extended presence of the microcapsules.

Porcine islet cells of Langerhans are destroyed by human complement and not by antibody-dependent cell-mediated mechanisms

In the near future, xenotransplantation of porcine islets of Langerhans might be an alternative in the treatment of patients with diabetes mellitus. However, xenotransplantation of islets of Langerhans in large animals has been shown to result in an exceedingly short graft survival, which suggests that a humoral immune response might play a major role in islet demise. This study was performed to assess binding human preformed antibodies to isolated porcine islet cells (PIC) and to determine the lysis of PIC using human sera in complement-mediated cytotoxicity (CMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Ten Dutch Landrace pigs were used for the isolation of PIC. Sera from 30 healthy blood donors (1/10 diluted) were used in a 51Cr release assay to assess CMC. Heat-inactivated normal human sera and fresh sera from patients with agammaglobulinemia were used as controls. Binding of human IgM IgG, and IgA antibodies to PIC was tested in an ELISA using isotype-specific secondary monoclonal antibodies ADCC was tested in a 51Cr release assay using normal human sera and sera from newly diagnosed type I diabetics with peripheral blood mononuclear cells as effector cells and PIC as targets. It was found that PIC were recognized by human IgM and IgG preformed antibodies and that fresh human sera had strong CMC activity inducing a percentage-specific PIC lysis of 61 +/- 10% (mean +/- SD) within 60 min. Agammaglobulinemic sera killed 42 +/- 12% of PIC. No significant cytotoxic activity was found in ADCC assays using normal sera or sera from diabetic patients. These results show that all tested human sera lyse PIC via CMC, even in the absence of human antibodies, as concluded from the use of agammaglobulinemic sera. In pig-to-human transplantation, islets may be hyperacutely rejected by antibody-dependent and antibody-independent activation of complement and not by antibody-dependent cell-mediated mechanisms.

Lymphokine release during co-culture of human lympho-mononuclear cells and fresh or cultured human, porcine and bovine pancreatic islets

In this study we evaluated whether isolated human (HI), porcine (PI) and bovine (BI) islets, either fresh (Fr) or cultured for 4 weeks (4 w) affect cytokine release from human lymphomononuclear cells (LMC) differently. We prepared LMC from peripheral blood by density gradient purification and co-cultured 1 x 10(6) LMC for 24 h with 100 hand-picked islets, either within 48 h of isolation or after culture for 4 weeks. Soluble interleukin-2 receptor (IL-2R), interferon-gamma (IFN), interleukin-4 (IL-4) and interleukin-10 (IL-10) were measured by sandwich enzyme-linked immunoadsorbent assay. Compared with controls (Ctrl, LMC without islets), Fr-HI, Fr-PI and Fr-BI caused a similar increase of IL-2R and IFN release, whereas 4 w-HI and 4 w-BI did not lead to any significant production of these two cytokines. IL-10 concentrations increased with Fr-PI and Fr-BI, but not with Fr-HI, and no major effect of the 4-week culture was seen. IL-4 levels were below the detection limit of the method used in these experiments. Thus, fresh allo- and xeno-islets caused a similar increase of the release of cytokines known to be markers of Th1 activation, whereas the release of IL-10, a marker of Th2 activation, increased with xeno-, but not with allo-islets; culturing the islets for 4 weeks decreased Th1, but not Th2 activation.

Large scale isolation, growth, and function of porcine neonatal islet cells

Based upon existing methods of isolating fetal porcine islet tissue, a simple, reliable procedure was developed for the preparation of porcine neonatal islet cell aggregates with a reproducible and defined cellular composition. After 9 d of in vitro culture, tissue from one neonatal pig pancreas yielded approximately 50,000 islet cell aggregates, consisting of primarily epithelial cells (57%) and pancreatic endocrine cells (35%). During the culture period, the total beta cell mass decreased initially, but subsequently increased 1.5-fold between days 3 and 9. Transplantation of grafts consisting of 3 x 10(5) beta cells (1,000 aggregated) under the kidney capsule of alloxan-diabetic nude mice corrected hyperglycemia in 75% (10/13) of the animals, whereas, 100% (20/20) of recipients implanted with 6 x 10(5) beta cells (2,000 aggregates) achieved euglycemia within 8 wk posttransplantation. Nephrectomy of the graft bearing kidney at 14 wk posttransplantation resulted in hyperglycemia in all recipients, and examination of the grafts revealed the presence of numerous well-granulated insulin- and glucagon-containing cells. The cellular insulin content of these grafts was 20 to 30-fold higher than at the time of transplantation. These results indicate that the neonatal porcine pancrease can be used as a source of large numbers of viable islet cells, which have the potential for growth both in vitro and in vivo, and exhibit the metabolic capacity to correct diabetes in nude mice.

Determinants of a normal (versus impaired) oral glucose tolerance after combined pancreas-kidney transplantation in IDDM patients

After successful pancreas transplantation, insulin-dependent diabetic patients are characterized by a normal or at worst impaired oral glucose tolerance (World Health Organisation criteria). It is not known which pathophysiological mechanisms cause the difference between normal and impaired oral glucose tolerance. Therefore, we studied 41 patients after successful combined pancreas-kidney transplantation using stimulation in the fasting state with oral glucose (75 g), intravenous glucose (0.33 g/kg) and glucagon bolus injection (1 mg i.v.). Glucose (glucose oxidase), insulin and C-peptide (immunoassay) were measured. Repeated-measures analysis of variance and multiple regression analysis were used to analyse the results which showed: 28 patients had a normal, and 13 patients had an impaired oral glucose tolerance. Impaired oral glucose tolerance was associated with a greatly reduced early phase insulin secretory response (insulin p < 0.0001; C-peptide p = 0.037). Age (p = 0.65), body mass index (p = 0.94), immunosuppressive therapy (cyclosporin A p = 0.84; predniso(lo)ne p = 0.91; azathioprine p = 0.60) and additional clinical parameters were not different. Reduced insulin secretory responses in patients with impaired oral glucose tolerance were also found with intravenous glucose or glucagon stimulations. Exocrine secretion (alpha-amylase in 24-h urine collections) also demonstrated reduced pancreatic function in these patients (-46%; p = 0.04). Multiple regression analysis showed a significant correlation of 120-min glucose with ischaemia time (p = 0.003) and the number of HLA-DR mismatches (p = 0.026), but not with HLA-AB-mismatches (p = 0.084). In conclusion, the pathophysiological basis of impaired oral glucose tolerance after pancreas transplantation is a reduced insulin secretory capacity. Transplant damage is most likely caused by perioperative influences (ischaemia) and by the extent of rejection damage related, for example, to DR-mis-matches.

Intercellular Ca2+ waves sustain coordinate insulin secretion in pig islets of Langerhans

Insulin release was investigated in parallel with changes in cytosolic calcium concentration, [Ca2+]i, in pig islets stimulated by glucose. After two days in culture, glucose stimulation failed to induce insulin release, and caused limited [Ca2+]i changes in few cells. After ten days, insulin response was partially restored and [Ca2+]i recordings revealed a slow oscillatory activity of the whole islet. Slow oscillations appeared to be due to the average [Ca2+]i variations resulting from the spreading of waves throughout the islet. These waves demonstrate the reestablishment of functional cell coupling, which appears to play a critical role in insulin release.

The long-term metabolic function of intraportal and renal subcapsular islet isografts and the effect on glomerular basement membrane thickness in rats

Previous studies of intraportal islet autotransplantation in large animals have reported graft failure after months or years. In the rat it has been reported that intraportal islet isografts eventually failed whilst islets transplanted to the renal subcapsule functioned up to a year. We made Dark Agouti (DA) rats severely diabetic with streptozotocin, then 1000 or 3000 DA islets were transplanted beneath the renal capsule or into the liver. One set of transplanted rats and untreated diabetic and normal non-diabetic littermates were monitored lifelong by measurement of plasma glucose, others were killed at 6, 12 and 18 months for measurement of haemoglobin A1c, intravenous glucose tolerance test, pancreas insulin content and histology of the kidney. Renal glomerular basement membrane thickness was measured by the orthogonal intercept method. The results showed that intraportal isografts reversed hyperglycaemia significantly faster than renal subcapsular isografts. In the renal subcapsular site, consistent reversal of diabetes was achieved with 3000 islets but not with 1000 islets. Furthermore, intraportal islet grafts with 3000 islets led to lower, normal random glucose level than renal subcapsular grafts for the first 13 months. Normoglycaemia was maintained lifelong in all rats that achieved early normoglycaemia after transplantation of 3000 islets, irrespective of the site of islet transplantation. The fasting glucose, haemoglobin A1c levels, K value and glomerular basement membrane thickness of the recipients of 3000 islets to either the intraportal and subcapsular site were not significantly different from each other and the normal controls up to 18 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Transplantation of islets of Langerhans in patients with insulin-dependent diabetes mellitus

From 1974 to December, 1992, as reported by the International Islet Transplant Registry, there have been 175 adult islet allografts worldwide. Ninety-eight of these transplants have been performed since 1989. Eleven patients with Type I diabetes mellitus who have received islet allografts since 1989 have achieved insulin-independence for variable periods of time. As of June, 1993, four patients remain insulin-independent (from > 127 to > 326 days). Insulin-independence after human islet cell transplantation is not yet a consistent achievement. Several key issues in pancreas procurement, islet cell isolation, islet preservation, islet engraftment and the prevention of islet allograft rejection still need to be addressed. The expansion of current clinical trials should be limited to patients who are taking or who require immunosuppressive drugs for other reasons (kidney or liver transplant recipient) since the risks of chronic immunosuppression probably outweight the risks from chronic diabetes, although as we are able to induce a more specific state of immunosuppression this rationale may become debatable.

Cell preservation in University of Wisconsin solution during isolation of canine islets of Langerhans

Allogeneic islet transplantation in Type I diabetic patients is considerably hampered by the variable outcome of islet isolation and purification. After collagenase digestion of the pancreas, islet isolation is traditionally performed under hypothermic conditions in physiological solutions such as Hanks and RPMI. The University of Wisconsin solution (UWS) has been shown superior for hypothermic preservation of the pancreas. We, therefore, compared the UWS and RPMI for canine islet isolation and subsequent purification in either a conventional hyperosmotic density gradient of dextran in Hanks, or a novel normosmotic density gradient of Percoll in UWS. The isolation solution did not affect islet yield before purification (51% of the native islet mass). Loss of amylase (30%) and swelling of the acinar cells were observed in RPMI. In contrast, no loss of amylase and slight shrinkage of the acinar cells were observed in the UWS. Cell swelling affected the density separation and viability of the cells. Dextran density separation resulted in a 15% purity and 41% recovery of the islets isolated in RPMI, as compared to a 93% purity and 52% recovery of islets isolated in UWS. Percoll density separation improved the purity (99%) and recovery (74%) of islets isolated in UWS. Islets isolated in UWS demonstrated a superior basal and glucose stimulated insulin release during perifusion. Electron microscopy demonstrated a well-preserved islet ultrastructure after isolation in both solutions--except for slightly swollen mitochondria after isolation in RPMI. Autotransplantation of islets in pancreatectomised dogs was successful both after isolation in UWS and RPMI. We conclude that prevention of cell swelling during isolation and purification in the UWS resulted in an improved yield of viable and consistent virtually pure islets. Prevention of cell swelling during islet isolation should facilitate the analysis and control of other factors affecting outcome in man.

Transplanted beta cell response to increased metabolic demand. Changes in beta cell replication and mass

We determined the capacity of transplanted beta cells to modify their replication and mass when stimulated by changes in metabolic demand. Five groups of Lewis rats were studied: group 1 (Tx-Px) had a 95% pancreatectomy 14 d after transplantation of 500 islets; group 2 (Px-Tx) had a 95% pancreatectomy 14 d before transplantation of 500 islets; group 3 (Tx) was transplanted with 500 islets; group 4 (Px) had a 95% pancreatectomy; and group 5 (normal) was neither transplanted nor pancreatectomized. Blood glucose was normal in Tx-Px and Tx groups at all times. Px-Tx and Px groups developed severe hyperglycemia after pancreatectomy that was corrected in Px-Tx group in 83% of rats 28 d after transplantation. Replication of transplanted beta cells increased in Tx-Px (1.15 +/- 0.12%) and Px-Tx (0.85 +/- 0.12%) groups, but not in Tx group (0.64 +/- 0.07%) compared with normal pancreatic beta cells (0.38 +/- 0.05%) (P < 0.001). Mean beta cell size increased in Tx-Px (311 +/- 14 microns2) and Px-Tx (328 +/- 13 microns2) groups compared with Tx (252 +/- 12 microns2) and normal (239 +/- 9 microns2) groups (P < 0.001). Transplanted beta cell mass increased in Tx-Px (1.87 +/- 0.51 mg) and Px-Tx (1.55 +/- 0.21 mg) groups compared with Tx group (0.78 +/- 0.17 mg) (P < 0.05). In summary, changes in transplanted beta cells prevented the development of hyperglycemia in Tx-Px rats. Transplanted beta cells responded to increased metabolic demand increasing their beta cell mass.

Assessment of islet isolation efficacy in dogs

The outcome of islet isolation is considered uncertain because of the large variability of islet and insulin yield, but comparison of the isolated and native islet population has not been attempted. We therefore addressed the efficacy of collagenase digestion, and density gradient purification of islets from the splenic dog pancreas (n = 31) by morphometry of the islet volume and size distribution, and by extraction of insulin and amylase, in samples from the pancreas, the digest, and gradient fractions. In contrast to a approximately 90% recovery of pancreatic insulin and amylase after digestion, islet yield amounted to 50% of the islet content of the pancreas. After density separation, islets were mainly found in the purified fractions, while half of the recovered insulin was located in the acinar fraction of the gradients-indicating a substantial proportion of islets entrapped in acinar fragments. The islet and insulin content of the pancreas correlated well with islet and insulin yield after digestion (r = 0.7, p < .0001). The insulin content of digest suspensions did neither correlate with islet nor insulin recovery in the purified fraction of the gradients (r = 0.4) as opposed to the islet content of digest suspensions, which correlated with both (r = 0.7, p < .0001). After density separation near 100% purity was obtained, and no loss of insulin from isolated islets was demonstrated by extraction and microscopy. Size distributions of native and isolated islets demonstrated no fragmentation. We conclude that the variability of isolation outcome may be attributed to a large extent to the variability of the native endocrine pancreas. Isolation efficacy was best documented by morphometry, because insulin extraction did not discriminate between free and entrapped islets. However, assessment by both morphometry and extraction allowed the quantitation of entrapped islets, and demonstrated preservation of beta-cell granulation. Similar studies should facilitate the analysis of other factors affecting islet isolation in man.

Evolution of kidney, pancreas, and islet transplantation for patients with diabetes at the University of Minnesota

Transplantation began at the University of Minnesota in 1963. Treatment of diabetes and its complications has been emphasized since 1966, when the first pancreas-kidney transplant was done. Of 3,640 kidneys transplanted by 1992, 1,373 were for diabetic recipients, including 658 from living donors and 715 from cadaver donors. The results progressively improved; since 1984, survival rates of kidney grafts have been similar for diabetic and nondiabetic recipients, with three fourths of the grafts functioning at 4 years. As of 1992, 501 pancreas transplants had been done, including 170 simultaneous with a kidney, 142 after a kidney, and 188 alone for nonuremic diabetic patients; again, the results have improved: by the 1990s, graft survival rates were similar in the 3 recipient categories. Successful pancreas transplants have been shown by our coworkers to stabilize or improve neuropathy and prevent recurrence of diabetic nephropathy in kidney grafts. In an attempt to simplify endocrine replacement therapy, we have done 63 human islet transplants, 34 as allografts for patients with type I diabetes and 29 as autografts after total pancreatectomy to treat chronic pancreatitis. Insulin independence occurs for about 50% of islet autograft recipients. Two recent islet allograft recipients treated with 15-deoxyspergualin have had sustained insulin independence. We anticipate that endocrine replacement therapy by transplantation will become routine for diabetic patients as methods to prevent rejection are refined.